TPG 4140 Natural Gas. West African Gas Pipeline: Development and Prospects for the Oil and Gas Industry in Ghana

Transcription

1 NTNU Norges teknisk-naturvitenskapelige universitet TPG 4140 Natural Gas West African Gas Pipeline: Development and Prospects for the Oil and Gas Industry in Ghana Supervisor Prof. Jon Steinar Gudmundsson Written by: Sreedhar Subramanian Ebenezer Hayfron-Benjamin Trondheim Norway, 2012

2 Contents Abstract... vii 1. Introduction Background of West African Gas Pipeline Energy Situation in Nigeria Objectives of the WAGP project Benefits of WAGP Source of natural gas for WAGP and the gas specifications Scope of Project Report Technical Parameters of Pipeline and Simple Pressure Drop calculation Energy demand in Ghana History of Electrical Power in Ghana Combined Cycle Power Plant at Takoradi T Simple Cycle Thermal Power plant at Takoradi T Fuel supply to thermal plants and Challenges Electricity demand forecast in Ghana Energy Utilization in Ghana State of Oil and Gas Industry in Ghana Oil and Gas Resources Technology used for exploration Challenges WAGP Technical integrity of the pipeline Gas composition and conditioning challenges Regulatory framework Environmental Challenges Project Cost and Delays Current Challenges Environmental Impact of WAGP Conclusion References Appendices ii

3 9.1. Appendix-A: Daily Oil and Gas production in Jubilee Field, Ghana Appendix-B: Pressure Drop Calculations Appendix-C: z-factor calculations Appendix-D: Pressure Drop Calculation List of Tables Table 1: WAGP data... 2 Table 2 : WAGP Ownership... 3 Table 3: Composition of flared associated gas in Niger Delta basin... 7 Table 4: WAGP Gas Pipeline Receipt Gas Quality Specification... 7 Table 5: Typical natural gas composition for WAGP... 8 Table 6: Grid power generation capacity available for Table 7: Ongoing Power plant projects in Ghana Table 8: Tariff for gas delivered through WAGP Table 9: Natural gas demand forecast for Ghana Table 10: Station capacity Table 11: Breakup of Electricity demand in Ghana List of Figures Figure 1 : WAGP pipeline... 2 Figure 2: Nigeria s dry natural gas production and consumption... 4 Figure 3: Annual natural gas production in Nigeria... 4 Figure 4: Combined Cycle Power Plant Figure 5: Simple Cycle thermal plant Figure 6: Oil fields in Ghana Figure 7 : FPSO Figure 8: Typical crude oil processing iii

4 Figure 9: Subsea flow lines Figure 10: Daily Associated Gas Production Figure 11: Daily Oil Production Figure 12: Associated gas production Figure 13 : Fuel for FPSO Figure 14: Flared gas for the month iv

5 Nomenclature d = internal diameter of pipe, m f = Darcy friction coefficient, dimensionless g = gravitational acceleration, m/s 2 K = constant, dimensionless L = pipe length, m M = molecular mass, kg/kmol n = exponent for the gas flow rate (range of values between 1.74 and 2) P = absolute pressure, Pa P 1 = absolute pressure at pipe entrance, Pa P 2 = absolute pressure at pipe exit, Pa P avg = flow average pressure, Pa P st = standard pressure, x 10 5 Pa Q o = volume gas flow rate at standard conditions, m 3 /s R = universal gas constant, J/(kmol K) Re = Reynolds number of the gas flow, dimensionless T = absolute temperature, K T avg = flow average temperature, K T st = standard temperature, K z = gas compressibility factor, dimensionless m = Mass flow rate (kg/s) Greek Symbols = coefficient, dimensionless = coefficient, dimensionless max = maximum variation of the friction factor, dimensionless P = pressure drop, Pa = wall roughness, m = efficiency factor, dimensionless µ = gas dynamic viscosity, Pa s v

6 = gas cinematic viscosity, m 2 /s = gas density, kg/m 3 Abbreviations WAGP West African Gas Pipeline ECOWAS Economic Community of West African States WAGPA West African Gas Pipeline Authority WAPCo West African Pipeline Company VRA Volta River Authority (VRA) VALCO Volta Aluminum Company Units mmscfd tcf bcf scf/stb bbls MW MMBtu GWh million standard cubic feet per day trillion cubic feet billion cubic feet standard cubic feet/standard barrels barrels of oil Megawatts Million British Thermal Units Gigawatts hour Prefixes Giga Mega Conversion factors 1 sm 3 = scf vi

7 Abstract West African Gas Pipeline (WAGP) is a 678 km pipeline starting from Nigeria and supplying natural gas to Benin, Togo and Ghana. The pipeline was commissioned in 2008 and can carry up to a maximum capacity of 474 MMscf/day (or MSm 3 ) of natural gas. In this report we have looked at the technical parameters (pressure drop along the length of the pipeline), socioeconomic factors and the environmental impact of the project on the participating countries. Nigeria, which has estimated natural gas reserves of trillion cubic feet (tcf), supplies the gas to the WAGP. Before the commencement of the project, most of the gas was being flared. The participating countries are expected to save over USD 500 million dollars on fuels cost for electricity generation. The pressure drop across the pipeline was calculated to be 22 bar and a pressure gradient of approximately bar/100 km. Ghana has been a major beneficiary, using the supplied gas, as well as recent oil and gas discoveries to generate thermal power and feeding many of her industries like the Aluminum Company, VALCO. The WAGP, though plagued with many challenges has delivered on most of the socio and economic benefits for all the four countries involved in the project. Keywords: WAGP, pressure drop, thermal power, associated and non-associated gas, electricity, environmental impact. vii

8 1. Introduction West African Gas Pipeline (WAGP) is a 678 km pipeline starting from Nigeria and supplying natural gas to Benin, Togo and Ghana. The pipeline was commissioned in 2008 and built to carry a maximum capacity of 474 MMscf/day of natural gas. As per the terms of agreement, Nigeria will initially supply 170 MMscf/day of gas through WAGP. Considerable delay in construction of pipeline resulted in the construction cost exceeding the initial budget. The supply of gas by Nigeria has also been erratic and well below the amount pledged. Political instabilities, pipeline vandalism and poor quality of gas supply from Nigeria pose a serious challenge to the gas transportation through WAGP. Ghana is looking at other alternatives to meet its increasing energy demands for the future including development of its own Jubilee field. In this report the technical parameters (pressure drop along the length of the pipeline), socio-economic factors and the environmental impact of the project on the participating countries related to the West African Gas Pipeline will be assessed Background of West African Gas Pipeline Energy plays a very important role in the economic development of a country. The idea of constructing the West African Gas Pipeline (WAGP) was initially proposed by Economic Community of West African States (ECOWAS) in The studies done by World Bank in 1991 confirmed the commercial feasibility of supplying Nigerian gas to Ghana. There was an increased interest in the pipeline due to the severe energy shortage in Ghana, Benin and Togo in The technical and commercial feasibility of connecting the fields at Escravos, Nigeria with an offshore pipeline was conducted by a consortium of private oil companies. The construction of WAGP began in January 2005 and the first free flow natural gas supply through the pipeline arrived in Ghana in December In 2009, Volta River Authority (Ghana) started generating power using natural gas from WAGP (WAGPA 2011). Figure 1 shows the WAGP pipeline. The total length of the WAGP is 678 km. The pipeline consists of 56 km onshore segment from Ikoti to Lagos (both in Nigeria) and 569 km offshore segment from Lagos (Nigeria) to Takoradi (Ghana). The pipeline also consists of lateral lines for delivering gas at Contonou (Togo), Lome (Togo) and Tema (Ghana). 1

9 Figure 1 : WAGP pipeline (WAPCo 2012) The total length of the WAGP is 678 km. The Escravos-Lagos pipeline system in Nigeria has a capacity of 800 MMscfd. Initially the WAGP carries a capacity of 170 MMscfd but it is designed to carry up to 474 MMscfd. The West African gas pipeline specifications can be summarized as shown in Table 1. Total Length 678 km Details: 56 km onshore pipeline of 30 pipeline from Ikoti to Lagos beach 569 km offshore pipeline of 20 pipeline offshore from Lagos to Takoradi Delivery points Contonou (Benin) - 8 lateral line Lome (Togo) 10 lateral line Tema & Takoradi (Ghana) - 18 lateral line Depth of pipeline From 30 m up to 70 m water depth Approximately 15 km to 30 km offshore Pipeline capacity 474 MMscfd Operating pressure barg under free flow Barg when fully operational with full compression Pipeline cost $1.2 billion Table 1: WAGP data (WAGPA 2011) 2

10 85% of the total gas delivered through WAGP to Togo, Benin and Ghana will be utilized by the power plants while the remaining 15% will be sent to other industries for heating purposes (Leonce 2007). The WAGP gas will not be used for domestic purposes since it cannot be bottled easily like Liquefied Petroleum Gas (WAPCo 2012). The ownership of the WAGP is as shown in Table 2. Company Ownership (%) Chevron West African Gas Pipeline Ltd 36.7 Nigerian National Petroleum Corporation 25.0 Shell Overseas Holdings Ltd 18.0 Takoradi Power Company Ltd 16.3 Bengaz SA 2.0 Societe Togolaise de Gaz SA 2.0 Table 2 : WAGP Ownership (WAPCo 2007) 1.2. Energy Situation in Nigeria Nigeria is rich in natural resources including oil and gas. Nigeria is estimated to have trillion cubic feet (tcf) of natural gas reserves (BP 2012). Nigeria produced 820 billion cubic feet (bcf) of marketed natural gas in It however consumed only 255 bcf. 60% of the consumed natural gas was used for electricity generation (IEA 2011). The consumption patterns are shown in Figure 2. Lack of infrastructure for producing and marketing associated gas has resulted in significant gas flaring in Nigeria. In 2010, the total natural gas flared in Nigeria was 536 bcf of natural gas. This was approximately 33% of the total gas produced. Estimates by Nigerian National petroleum Corporation (NNP) indicate that the country lost US$ 2.5 billion/year in revenue due to flaring. Figure 3 illustrates the production and flaring trends in Nigeria. 3

11 Figure 2: Nigeria s dry natural gas production and consumption (IEA 2011) Figure 3: Annual natural gas production in Nigeria (IEA 2011) 4

12 1.3. Objectives of the WAGP project New markets for Nigerian gas. This will also lead to a reduction in the gas flaring in Nigeria. Conservation of Environment and Energy security- Access to cleaner fuel for power generation and industries in Ghana, Benin and Togo thereby reducing dependence on crude oil. Regional Economic Integration 1.4. Benefits of WAGP According to World Bank estimates, in the first next 20 years after WAGP commercialization, the countries Ghana, Benin and Togo are expected to save over US$ 500 million on fuels cost for electricity generation. By using gas to run the power plants, Ghana is expected to save 15,000-20,000 barrels per day of crude oil. Chevron estimates that WAGP will help in creation of up to 20,000 primary sector jobs in the region. The industrial growth due to WAGP has the potential for creating another 30,000 60,000 jobs in the region (Knowland and Kannan 2002). Before the WAGP project, Nigeria contributed to 12.5% of the total worldwide gas flaring. The associated gas was flared while the non-associated gas was being used for LNG production. With the development of WAGP, it is estimated that the emission of greenhouse gases (GHG) to the environment would reduce by 100 million tons in the first 20 years (Ayodele 2010). As per the estimates of WAGPA, the emission of GHG will be reduced by 52%. The gas producers in Nigeria are expected to earn additional revenues by selling the associated gas to WAPCO. Other benefits of WAGP include (Yeboah 2009) Economic growth for the countries Ghana, Benin, Togo and Nigeria Long term supply of clean and cheaper fuel (Natural Gas) by Nigeria to Ghana, Benin and Togo The co-operation and the economic integration due to the project could result in an increased regional stability under ECOWAS The pipeline as an energy infrastructure is expected to catalyze direct foreign investment in the project states. 5

13 West African Power Protocol (WAPP) was set up to develop integrated electric power infrastructure throughout the region. Electricity will be made more reliable and will help in migration to cleaner hydropower and gas fired power plant. The electricity generation cost is also expected to be reduced by 50%. A single fiscal regime is adopted between the four countries for the WAGP activity. The income tax rate is fixed at 35%. There are no transit royalties for the pipeline. There is a 5 year tax holiday period. Once the tax free period is completed, WAPCo has to start paying the income tax. The income tax which each country receives is calculated using the formula (Barandao 2007) ( ) (( ) ( )) Where, APs = Apportionment percentage for a state LS = Length in state LT = Total length of pipeline RCS = Reserved Capacity by State RCT = Total Reserved Capacity Over the lifetime of the project, Ghana is projected to earn US$466 million to US$588 million income tax from West African Pipeline Company(WAPCo 2004(a)) Source of natural gas for WAGP and the gas specifications The natural gas required for the WAGP is supplied by Chevron Nigeria Limited (CNL) NNPC and Shell Petroleum Development Company (SPDC) NNPC operating joint ventures. The gas supply for WAGP is primarily from the various associated gas from Oil fields and nonassociated gas from the gas fields in Niger Delta. The composition of flared associated gas in Niger Delta basin is shown in Table 3. 6

14 % composition Component (by volume) CH 4 47 C 2 H 6 18 C 3 H 8 20 C 4 H 10 5 C 5 H 12 9 Others 1 Table 3: Composition of flared associated gas in Niger Delta basin (Abdulkareem 2005) In order to supply gas to WAGP, SPDC modified its non-associated gas (NAG) plant in the Utorogu fields in the western Niger Delta. To meet the stringent gas specifications, the plant modification included addition of process modules to improve the liquid recovery from the gas well stream (Okere 2011). As per the WAGP treaty, these two entities have exclusive rights to transport natural gas up to a volume of 200 MMscfd or 10 years (depending on whichever occurs first). The natural gas quality specifications for WAGP for the various constituents on volume basis are shown in Table 4. Parameter Limitation (maximum) H 2 S 4 ppm by volume Total Sulfur 28 ppm CO 2 4 vol % N 2 3 vol % O 2 10 ppm by volume Total Inert (CO 2 + N 2 ) 5 vol % Solid, Dust, Gums, Other Solids Free by normal commercial standards Water content 7 lb/mmscfd Table 4: WAGP Gas Pipeline Receipt Gas Quality Specification (WAPCo 2004(b)) 7

15 The composition of natural gas for the WAGP on mole fraction basis can be seen in Table 5. Components Mole fraction (%) CH C 2 H C 3 H i-c 4 H n-c 4 H i-c 5 H n-c 5 H C 6 H C 7 H CO N Table 5: Typical natural gas composition for WAGP (WAPCo 2007) 1.6. Scope of Project Report The objective of this project is to cover the technical construction of the West African Gas Pipeline and to assess the impact on the major players in the project, Nigeria and Ghana. The scope of this report includes but not limited to: (i) Overview of WAGP (ii) Source of gas supply for WAGP including the gas compositions and specifications. (iii) WAGP system and technical assessment including implementation and construction. (iv) Simple pressure drop calculation across the pipeline system and comparison with other regions in the world like the North Sea (v) Power generation in Ghana and how the WAGP ties into the energy scenario in that country (vi) Oil and Gas developments in Ghana and its impact the WAGP project (vii) Socio-Economic and Environmental benefits and challenges that WAGP will have on all the four participating countries: Nigeria, Benin, Togo and Ghana 8

16 2. Technical Parameters of Pipeline and Simple Pressure Drop calculation The 678 km West African Gas Pipeline links into the existing Escravos-Lagos pipeline and proceeds from Lagos beach (Nigeria) to Takoradi (Ghana) via offshore pipeline. The pipeline is buried at a water depth of 35 m (WAGP) but along the route, the depths vary only slightly. The Lagos beach station currently consists of two compressors (2 x HP). Only one of the compressors is currently used while the other is on standby(barandao 2007). By employing a series of assumptions, such as assuming a steady state operation with a fixed flow rate, and also assuming a straight pipeline, a detailed calculation of the simple pressure drop across the entire length of the pipeline is shown in Appendix-B. From the compressor station at Lagos Beach, gas at a temperature of 16 C, and 153 bar is put into 20 inches main pipelines. If the temperature is assumed constant over the pipeline, and using both the reduced temperature and pressure variables, T r, P r, respectively, the compressibility factor z of the natural gas is read from the Hall-Yarborough method and the Standing-Katz diagram, a value of z = is obtained. At an operating capacity of M Sm 3 /d, gas with mass flow rate at 43 kg/s the gas travels a distance of 678 km to Takoradi in Ghana. Also a friction factor f = , was evaluated based on the Haaland equation with known Reynolds number Re = x 10 5 and the relative roughness calculated by using the roughness factor k = 45 microns for commercial steel. In addition to computed gas molecular weight of M gas = kg/kmol, we used the iteration method specified for calculating the pressure drop in a horizontal gas pipeline. Approximate calculations was carried out for gas pipelines using the Darcy-Weisbach equation p f f 2 L u d 2 where average gas properties are used (Gudmundsson 2012). 9

17 In the Pressure drop calculation clearly shown in Appendix-B, we arrived at the following conclusion; from Lagos to Takoradi there is a pressure drop of 22 bars and a pressure gradient of approximately bar/100 km. The pressure drop and gradient compares favorably with the average of roughly 20 bar in the North Sea pipelines as per computed by Sletfjerding (Sletfjering 1999). The reader is referred to Appendix-B where we have shown a detailed step by step approach to the pressure drop as well as a number of simplifying assumptions we made along the way. It should be also noted that we assumed a straight route for the gas pipelines and ignored the smaller laterals connecting various cities along the route. So a straight 678km long pipeline was used in the calculation. 10

18 3. Energy demand in Ghana 3.1. History of Electrical Power in Ghana Ghana relies heavily on hydroelectricity. The river Volta was identified as a source of hydro power way back in 1915 itself. However, the need for cheap electricity for aluminum production from the locally mined Bauxite resulted in establishing the Volta River Authority (VRA) in 1961 and the first hydroelectric station at Akosombo was commissioned in The initial capacity of the station was 912 MW. Currently the hydropower station has a capacity of 1020 MW. Kpong was the next hydropower plant commissioned in 1982 with a capacity of 160 MW. Ghana experienced a drought in 1983/84 and the water levels in dams decreased significantly. This resulted in severe load shedding and made the government realize the country s overdependence on hydroelectricity. This prompted the Ghana Government to look at thermal power as a way of decreasing the over reliability on rainfall. The first thermal power plant was constructed in 1997 at Takoradi. The plant operates on combined cycle and had a capacity of 330 MW. Light Oil was the fuel used to fire the plant. The minimum operating level at Akosomo dam is 240 feet. However, Ghana again experienced low rainfall in 1998 and the water level in the dam fell to feet resulting in frequent power cuts. The simple cycle 220 MW plant Takoradi -2 came into operation in the year The increased electricity demand due to economic growth and the reduced hydro power generation resulted in another power crisis in 2006 and 2007 (Malgas 2008). The perennial power crisis forced VALCO to partially shut down its operations from March 2007 and the plant was shut down completely in early The plant resumed its operations in January 2011 after a 2 year shutdown. The grid electricity generation capacity available for the year 2012 is given in Table 6. 11

19 Generation Plant Fuel Type Capacity (MW) Installed Dependable Hydropower plants Akosombo Kpong Hydro Hydro Thermal Power Plants T1 Takoradi Power Company (TAPCO) T2 Takoradi International Company (TICO) Sunon-Asogli Power (SAPP) Tema Thermal Plant 1 (TT1P) Tema Thermal Plant 2 (T2PP) Mines Reserve Plant (MRP) LCO/NG/diesel LCO/NG/diesel NG LCO/NG/diesel NG/diesel NG/diesel Total Table 6: Grid power generation capacity available for 2012 (EC 2012) Combined Cycle Power Plant at Takoradi T1 The takoradi T1 plant is a combined cycle has an installed capacity of 330 MW. It consists of two combustion turbines (2 X 110MW), two heat recovery steam generators and one 110MW steam turbine. Sea water is fed to a cooling tower system which is then used for cooling the steam turbine condenser (Jacobs 2010). A simple sketch of a combined cycle gas plant is as shown in Figure 4 In a combined cycle power plant, one or more gas turbines are operated in cascade followed by a steam turbine. A gas turbine consists of compressor, combustor and a turbine. The air fed into the compressor has to be free of contaminants. The compressor draws air, compresses it and feeds into the combustor. The compressed air and fuel (natural gas) are mixed and ignited which leads to production of a high temperature high pressure gas steam. The combustion gas expands through the turbine and spins the turbines blades which are attached to a shaft and a generator thereby generating electricity. The heat from the exhaust gas of the turbine is used to generate steam by passing it through a Heat Recovery Steam Generator (HRSG). The Steam obtained from the HRSG is at a temperature of C. The steam then rotates the steam turbine and 12

20 the coupled generator to produce electricity. The exhaust gases leave the HRSG at a temperature around 140 C (Ramireddy 2012) (U.S.DOE 2011). Figure 4: Combined Cycle Power Plant ( Simple Cycle Thermal Power plant at Takoradi T2 The existing Takoradi T2 plant is a simple cycle thermal plant of capacity 220 MW. It uses two gas turbines (2 X 110 MW) for generating electricity. The T2 expansion project was approved by the Ghanian Parliament in June The company Mitsubishi and Co will be adding a steam turbine (120 MW) and two heat recovery heat exchangers. A sea water direct cooling system will also be added to the existing gas turbines. The plant will thereby be converted to a combined cycle power plant of 340 MW capacity. A simple power plant does not have a heat recovery section. The thermal efficiency of the plant is far lower than a combined cycle power plant. Figure 5 is a simple sketch of cycle thermal power plant. 13

21 Figure 5: Simple Cycle thermal plant( The current ongoing projects in Ghana for power generation are illustrated in Table 7. Project Type Installation Expected Year of Capacity commissioning MW Fuel type Takoradi-3 Thermal CC 132 Nov 2012 LCO/Gas/Diesel Kpone Thermal Power Plant (KTPP) Thermal SC Gas/Diesel Bui Hydro Power Project Hydro Water type Table 7: Ongoing Power plant projects in Ghana (VRA 2012) 3.2. Fuel supply to thermal plants and Challenges In 2011, Ghana consumed 2 million barrels of Oil for power generation. The mean natural gas flow rate through the WAGP was MSm 3 /day. Out of this amount, 1.42 MSm 3 /day of the gas from WAGP is utilized by the thermal plants in Tema while 1.13 MSm 3 /day of gas is utilized by the thermal plants in Takoradi. Due to the poor quality of gas supplied by Nigeria, WAGP had to temporarily shut down in February, Even after restarting, the supply of gas from Nigeria to Ghana has been very erratic. Political developments in Nigeria have fuelled conspiracy theories that the gas may not 14

22 flow at all in In case the gas supply through WAGP stops, the Sunon Asogi plant will be completely shut down since it runs entirely on natural gas. This would mean that 200 MW of electricity generation will not be available (EC 2012). The Nigerian Commercial Group had agreed to provide a minimum of 147 MMBtu/day of gas to Ghana. However, other than in the month of January 2012, the gas flow has reduced and the company has not honoured the commitment. Therefore the Energy Commission in Ghana expects that only MMBtu/day of gas is expected to be delivered for the rest of the year For the year 2012, the total electricity requirement is expected to be in the range GWh and the peak demand is expected to be in the range MW. Currently Nigeria has an installed power capacity of 6000 MW. However, the actual generation is only MW. There is a huge difference between the demand and supply of electricity. At present, Nigeria is unable to meet its domestic supply and export plans. The total demand is 5 bcfd (this includes domestic needs, LNG and WAGP commitments). The government policy is to meet local domestic demand first before exporting. Nigeria has also set a target of increasing its capacity to MW by the year 2020 (EC 2012). The pricing of the gas would be guided by the principle of taking into account the price of development of field and infrastructure and also at the other end of the spectrum; it should be low enough to be competitive with other fuels. For example the total delivered gas price as shown in Table 8 below, $6.68/MMBtu $8.814 MMBtu compares favorably with global prices such as the US Henry Hub and European Contract gas price with a range of $ 5/MMBtu - $10 MMBtu for the year 2011 (Nysæter and Wottrich 2012). The tariffs for WAGP gas to Ghana in 2011 was priced as shown in Table 8. Price (USD/MMBtu) Average price for WAGP gas WAGP transportation tariff Total delivered gas price Table 8: Tariff for gas delivered through WAGP (EC 2012) 15

23 3.3. Electricity demand forecast in Ghana The electricity consumption in Ghana is expected to increase to GWh by the year This represents a 26% increase from the electricity consumption in Ghana plans to increase its installed electrical capacity to 3600 MW by the end of 2013 (Market-Publishers 2011). The Ministry of Energy in Ghana has set a target of increasing the installed capacity to 5000 MW by the year The government is also planning to achieve gas based power generation in at least 50% of the thermal plants and also to become an exporter of electricity (Frost 2012). The natural gas demand forecast for internal consumption in Ghana is expected to gradually increase as shown in Table 9. Year Minimum (MMscfd) Maximum (MMscfd) Table 9: Natural gas demand forecast for Ghana (EC 2012) The gas transported in WAGP is expected to increase from 170 MMscfd in 2017 to 474 MMscfd in the year 2026 (Adeniji 2012). At when the WAGP is operating in full capacity, the share of gas received by each terminal will be as shown in the following Table 10. Station Name Ultimate Initial Capacity Capacity (MMscfd) (MMscfd) Cotonou Lome Tema Takoradi Table 10: Station capacity (WAPCo 2007) The figures indicate that Ghana also has to look to other areas for meeting its gas demand. It is also more expensive to generate electricity from gas. The cost of electricity generated from 16

24 hydropower is US$ 0.05 per KWh while that from thermal sources is greater than US$ 0.2 KWh. (REEEP 2012) Energy Utilization in Ghana In the year 2011, the demand for electricity in various sectors is shown in Table 11. Demand Sector GWh % Share Industrial Non- Residential Residential Total Table 11: Breakup of Electricity demand in Ghana(EC 2012) Among the Industrial sector, Voltas Aluminum Company (VALCO) is the largest consumer of energy when under full operation. The installed smelter of 200,000 tons/year of aluminum production at company consumes 2900 GWh. VALCO however pays not more than US$ 0.07 per KWh for electricity. The other major industry consuming energy is mining. 17

25 4. State of Oil and Gas Industry in Ghana 4.1. Oil and Gas Resources Energy is a basic input that is required to meet many basic human needs such as heating, motive power (e.g., water pumps, transport sector), as well as industrial, and other public services like healthcare just to name a few. In Ghana, a great majority of people lack access to sufficient energy services. This in turn stunts economic growth and improvement in human development and welfare. The challenge for Ghana is that the world energy council (WEC) forecasts that the primary energy demand for developing countries will triple from its present state and constitute two thirds of global consumption by 2050 (RCEER 2006). With this backdrop, it came as a welcome and pleasant surprise that Ghana struck oil in late December Despite exploration activities since 1896, which resulted in drilling over 66 wells (RCEER 2006) it was not until 2007, when oil in commercial quantity was discovered in deep-water offshore in western Ghana and the oil field was named Jubilee Field with a recoverable reserves in the range of 3 billion barrels (480,000,000 m 3 ) to 5 billion barrels (790,000,000 m 3 ). A map of the location of relevant oil and gas field is shown in Figure 6. It is located 60km offshore between the Deepwater Tano and West Cape Three Points blocks in Ghana and 130 km south west of the port city of Takoradi, where incidentally the WAGP and the Thermal Power Plant is located. The oil found in the waters of Ghana can be described a worldclass sweet oilfield, in that it has API gravity of 37.6 degrees and 0.25 wt% sulphur (TullowOil 2010). In addition associated natural gas, that is gas found in nature with oil discoveries, has contributed immensely to changing the energy patterns in Ghana. Prior to the present scenario,there were discoveries of oil and gas in the Saltpond Field (1970), Cape Three Points (1974) and North and South Tano Fields (between 1978 and 1981). 18

26 Figure 6: Oil fields in Ghana (Kosmos-Energy 2012) Discoveries such as the Tweneboa-Enyenra, Dzata, Sankofa Oil and gas discoveries all in offshore Ghanaian waters, have been reported to hold Natural Gas probable reserves in the range of 4,845 bcf (GIP 2011). For example, seismic data and analytical techniques conducted on the Jubilee field established that the oil contains high volumes of associated gas with gas to oil ratio (GOR) of between scf/stb. This will translate into a possible output capacity of 140 MMscfd. Presently (in 2012) natural gas has to be flared or re-injected into the wells in the Field. But because of safety of the oil wells and platforms and environmental reasons these practices cannot be sustained. In march 2011 oil production in the Jubilee Field came on stream, and from a modest average production of 60,000 bbls per day, the capacity has been increased to as high as 90,000 bbls per day (MOE 2012) in just under a year from the initial production date. Production of oil takes place in different blocks offshore in the southwest of western region. The targeted production capacity is pegged at 120,000bbls per day but due to technical reasons amongst others, this figure is yet to be attained. To date a little over 36 million barrels of crude oil has been produced (MOE 2012). This is quite significant for a country of Ghana s size and considering the energy consumption deficit scenario the country faces. 19

27 Drilling blocks include the deep-water Tano basin, with water depths of 3000m, the Tullow and Kosmos basin in region of 1000m 2000m extending from shallow to deep waters. The associated gas is currently flared, used as fuel gas for powering the Floating Production Storage Offloading (FPSO) named Kwame Nkrumah which is shown in the picture in Figure 7 below. Figure 7 : FPSO (TullowOil 2010) A considerable amount is re-injected into the wells to maintain production levels. As late as May 2011, a daily average of 78 MMscfd of gas was produced at the Jubilee field, of which 10MMscf was used to power the FPSO while the remaining gas was simple flared (GIP 2011). The FPSO has on it installed: a water treatment plant, turret and a 120-room accommodation module, A crude separation plant, gas processing unit and a power generation plant (Offshore- Technologies). Production of oil and gas is started once sizes of the oil field and production wells are established and then drilling starts. The oil and gas located in several reservoirs subsea are drilled by means of complex subsea infrastructure consisting of flowlines and umbilicals which is used to get the hydrocarbons from the reservoir to the processing units located on the FPSO. To maintain reservoir pressures and ensure flow of hydrocarbons techniques such as injecting gas, water or steam into the reservoir is routinely done in order to maintain pressures and optimize production rates. Other methods of improving production rates include hydraulic fracturing and acid treatment. On the floating storage and production platform, the separation processing takes place. This includes the three-phase separation of oil, gas and water. The produced water is 20

28 often treated and disposed off. The separated oil and gas in different streams is let down in pressures, oil is treated with processes such as propane de-asphalting, removal of sludges and other solid contaminants. The gas on the other hand is treated with dehydration methods, glycol additives added to remove free water and avoid formation of hydrates. Auxillary gas separation processes such as desulfurization, de-ethanenization, gas sweetening to make the produced gas comply with transportation and sales specification can be done on the FPSO. Once the specification is met in terms of pressure, temperature, composition, it is compressed and put into sales gas pipelines. A schematic process from subsea to the platform is shown in Figure 8 Figure 8: Typical crude oil processing (adapted from etechinternational.org) As the chart in appendix-a shows, production levels in the Jubileee Field have gone high and so has the amount of gas re-injected back into the wells. So from a technical point view and socio- 21

29 economic justification has led to better utilization of the associated gas as explained in the next paragraph. The oil as previously stated has with it associated natural gas. Prior to mid-2011, there were no plans to utilize this huge gas reserves but upon further reflection the government of Ghana (GOG) issued a whitepaper named Gas Infrastructure Project Document that called for monetization of the gas reserves. The Gas Infrastructure project (GIP), which is in initial phase, was borne out of the necessity to better utilize this highly priced regional and international commodity. Consequently the Ghana Government produced a master plan, that is the Gas Infrastructure Project Document, under the auspices of the Ministry of Energy, to utilize the associated gas. A company, Ghana National Gas Company (GNGC), was then set up to implement series of projects for the utilization of the associated gas. The initiation of the GIP has called for a technical assessment of the planned pipeline (onshore and offshore) as well as a Gas Processing Plant to produce lean gas to be fed initially to the Aboadze Thermal Plant for power generation. It is noteworthy that the offshore pipeline construction in deep and shallow water has been completed and onshore construction is on-going when this report was written. One of the authors of this report took part in a summer-internship program with the GNGC and Sinopec, the client and contractor respectively of the GIP Technology used for exploration As previously stated, the main production block for the oil and gas is located in the Jubilee field, situated 60 km offshore between the Deepwater Tano and West Cape Three Points blocks in Ghana at a water depth of 1,100 m (Offshore-Technologies) The oil and gas field was developed in phases, with phase I consisting of 17 wells which can be broken down into nine production wells which will be used to bring the oil and gas from the underground reservoir to the surface, and six water and two gas injection wells (TullowOil 2010) for oil enhancement and pressure maintenance. 22

30 Because of the water depths, the sub-sea technology employed can be summarized as follows (TullowOil 2010), detailed explanation can be found in the literature. It is of interest to note the Norwegian content in providing Oil and gas technological solutions to the oil and gas development in Ghana. Aker Solutions was part of the sub-sea development. Subsea fabrication includes 46 km of subsea flowlines supplied by Technip connect the wells to the FPS0 28 km of umbilicals supplied by Aker control the wells 19 Subsea trees, 8 manifolds and 2 riser bases supplied by FMC 14 vessels directly involved in installation operated from the Takoradi Sekondi Port Deep Figure 9: Subsea flow lines (TullowOil 2010) 23

31 5. Challenges WAGP Global focus is gradually turning away from crude oil as a major source of energy to natural gas due to its abundant availability, environmental friendliness and cost effectiveness. This has effectively increased the trans-boundary pipeline networks (Obanijesu and Macaulay 2009) and with this comes unintended consequences and challenges. International energy investment projects have tended to evolve into multi-dimensional development program involving formal and informal partnership arrangements (Knowland and Kannan 2002). This in turn tends to pose challenges in cases of cross-boundary projects like the WAGP involving 4 different countries: Nigeria, Benin, Togo and Ghana. These countries have different political system of governance, different economic models and a varying degree of political stability which is conducive for realizing the objectives of huge investment ($400 million for the pipeline construction and over $600 million to renovate existing power stations and build new ones to better utilize the gas (Knowland and Kannan 2002) project like the West Africa Gas Pipeline. The success of the WAGP is critical in the integration and optimization of the ECOWAS region s energy sector, thus challenges posed by the project should be thoroughly assessed. The various challenges can be classified under different sub-sections ranging from the technical issues to environmental concerns. We elaborate on these issues in the following sub-sections Technical integrity of the pipeline Nigeria has a history of an alarming frequency at which hydrocarbon pipeline failure (Obanijesu and Macaulay 2009) which poses challenges across board, such as loss of revenue, environmental and human consequences. In addition it was discovered that any failure along the offshore segment of the pipe length poses high risk of hydrate formation and dissolution of some constituents which could result to problems ranging from behavioral nature (e.g. fish excitement, increased activities and scattering in the water body) to chronic poisoning, fire outbreak, loss of human lives and livestock and climate change (Obanijesu and Macaulay 2009). 24

32 Pipeline failure is the failure of the pipe body due to metallurgical or processing abnormalities. Apart from pipeline vandalism, WAGP project is susceptible to failure through corrosion, defect welding, incorrect operation, defective pipe and malfunction of equipment amongst others (Obanijesu and Macaulay 2009). After a failure along any part of the offshore portion of the project, the conveyed fluid escapes into the immediate environment (which is water-body) to cause hazardous impacts on the ecosystems. At the points of discharge either in Togo, Benin or more especially so in Ghana, due to high pressure of discharge, failure of discharge systems could cause catastrophic incidents. Examples such as Lake Nyos (Cameroon) incident in August 1986 where an enormous volume of carbon dioxide (CO 2 ) was released from an underwater pipeline, killing about 1,700 people (Clarke 2001) and livestock up to 25 km away; and Lake Monoun incident of 1984 where a smaller release of CO 2 killed 37 people (Steven 2000). But such worst case scenario can avoided in the WAGP (Obanijesu and Macaulay 2009). This challenge called for the development of pragmatic management scheme, robust leak detection model and predictive model on natural gas flow pattern in water-body (Obanijesu and Macaulay 2009) Gas composition and conditioning challenges The risk of hydrate formation in the pipeline is one of the main challenges of the WAGP. This is because formation of the solid hydrates presents operational difficulties in the oil and gas industry. It is a known fact that a combination of low temperatures, free water content, the presence of small gas molecules such as N 2, CO 2 and high pressures all lead to the formation of hydrates. Hence conditioning of the natural gas in the WAGP is one of the challenges faced by the operators. Measures such as processing of the gas as well as addition of inhibitors like glycol (mono ethylene glycol) are routinely done. Temperature and pressure profile monitoring is also critical to prevent the formation of hydrates, which can cause pipelines to burst and leak the hydrates into the marine ecosystem, thereby causing adverse effects. 25

33 5.3. Regulatory framework The WAGP as previously stated involves four different countries with diverse culture and working laws. The harmonization of the framework that will ultimately enhance the achievement of the project objectives is one of the key challenges that had to be overcome and that is also being assessed on a regular basis. So Ghana, like the other states, passed a legislative act in 2005 which acted as framework to guide the smooth implementation of the WAGP. The purpose of that act of parliament titled West Africa Gas Pipeline Regulation, 2005 was among other things to provide a consistent and enforceable code governing the design, construction, operation and maintenance of the Pipeline System which will harmonize the regulation of those matters in each of the States (WAGPA 2005). Nigeria, Togo and Benin passed similar regulatory policies and the ECOWAS secretariat helped with negotiation and harmonization of these frameworks. It should be noted that the regulatory framework covered different aspect of the project, with much technical details, which for reasons of space and more is beyond the scope of our project. Details can be found in the literature (WAGPA 2005). The model for harmonizing regulations and tariffs among member states in the WAGP is a dynamic model, which is constantly being fine-tuned in order to the main objective of regional integration, in terms of economic development and political unification in the West African Region Environmental Challenges An in-depth look at what challenges the WAGP poses to the various environment is covered in the Environmental Impact section of this report. The reader is referred to it in the subsequent chapters Project Cost and Delays The implementation of the WAGP master plan was delayed by a number of factors that included the ever-present danger of political instability in the volatile Niger- Delta region (the gas is taken from this area), where indigenes have agitated for years about working conditions and endemic poverty among the locals. The project was intended to be in operation in 2007 but that was beset 26

34 with problems such as compensation to local communities, safety, fishing and livelihood impacts, and the project s supposed contribution to a reduction in gas flaring. Corruption issues prompted World Bank, one of the major sponsors of the project to address concerns. These and other issues pushed the original cost of the project estimated to be around $600m, to a high of $1billion (Abankroh). Also initially the WAGP was intended to extend to countries to the West of Ghana, such as Ivory Coast, and Senegal but owing to various conflicts and political instabilities in countries such as Ivory Coast, Liberia and Sierra Leone, these plans were shelved Current Challenges Besides increased frequent pipeline pilfering and sabotage in the Niger-Delta region, the other challenges include; 1. The gas supplied from Nigeria to Ghana in 2011 was 50% lower than that agreed upon. Nigeria is not able to meet its domestic as well as export demands. If the Ghana government proceeds with its plan to increase the installation capacity, there is going to be more strain on Nigeria. The current Nigerian policy is to first meet the local demands before exporting. 2. The encroachment on the WAGP Right of Way (RoW) and the sand mining at Paako beach, Ajirdo are a threat to the pipeline. In order for eliminating the problem, it is necessary that the mining in the area has to be declared illegal (Nwachuku 2011). 3. Pipeline vandalism is a common problem in the West African Countries. In August 2012, there was a pressure drop observed at the Lome, Togo due to pipeline vandalism. The pipeline had to be shut down since it was badly damaged. As a result WAPCo will be unable to meet the target set for the year and has lost $591 million in the first 47 days of shutdown. The Company is losing $500,000 to $600,000 every day of shutdown (AfricanGlobe 2012). In conclusion there has not been a verifiable mechanism to measure the benefits the WAGP Project intended to provide to the various countries, and this has given rise to a critical assessment that needs to be done by all parties involved to know how far down the road this project can go and lessons need to be taken from it. In Nigeria, the WAGP was sold as a 27

35 panacea to all the ills of the society such as chronic lack of energy and power supply, end to flaring and hence the subsequent reduction in the emission of millions of tonnes of CO 2 gas into the air. Tight development schedules also precluded the effective mobilization and training of local hire labor, thus compromising the employment generation, projected at 60,000 jobs (EIB 2008) and this lack of transparency could be the root of agitation in the region where the gas is produced. These same problems currently persist in Nigeria and has not be adequately addressed. Similarly in Ghana, the lack of constant supply of gas from the WAGP owing to various reasons such as sabotage to pipelines in other countries, low pressure drop problems and a myriad of problems has put a dent in the Ghanaian power crisis. The WAGP was supposed to diversify the sources of power generation put on the national grid and this would in turn support the growth of Industries and boost economic growth. Again verifiable indicators are thus lacking and further studies in assessing the challenges encountered in the WAGP are needed. 28

36 6. Environmental Impact of WAGP The switch from conventional fuels such as coal and oil to Natural gas has seen a shift in attitudes towards the environment. Natural gas is known to burn cleaner that both oil and coal. However this does not mean processing or transporting of Natural gas is without its own environmental risks and impacts. The inherent risks of oil leakage in pipelines especially in Nigeria are well documented but for this project we look at how the construction of the West Africa Gas Pipeline has affected the environment and communities along the route in the four countries. A World Bank report on the WAGP project stated that The major positive environmental impact of WAGP will be the development and use of gas currently flared in Nigeria. (Goodland 2005). This cessation of flaring on-pre-wagp levels in the Niger Delta has contributed to the reduction in the global greenhouse gas emissions and hence positive impacts on the issue of global climate change. According to some estimates about 100 million tons of CO 2 emissions reduction will be recorded with the WAGP in a twenty year period, of which 78 percent will be achieved by reducing gas flaring in Nigeria (FOE 2006) but these figures are disputed by some environmental groups. The impact of using gas which hitherto would have been flared also makes much economic and environmental sense, because Gas flaring costs Nigeria about US$2.5 billion annually, while about 66% of its population live on less than US$1 a day. Capturing gas that is currently being flared in Nigeria alone could produce about 50 per cent of the current power consumption of the African continent. While Nigeria has approximately 30 percent of African gas reserves, it flares 75 percent of the gas it produces. This accounts for 19 per cent of the total amount of gas flared globally (FOE 2006). Another issue is that the first part of the WAGP route from Escravos to Lagos beach pipeline was built many years ago but crucially without an environmental impact assessment done on it. This exposes the indigenes along that route to potentially catastrophic accidents, in brief; it is sitting on a time-bomb. The social and environmental challenges encountered in the Niger Delta do not seem to abate and the WAGP project did the situation no good. Social unrest in the Niger Delta has and is on-going; the locals feel aggrieved and complain of destroyed means of livelihood. Currently there is a court case in The Hague, Netherlands, where 4 farmers are suing 29

37 Shell, because Shell has been accused of destroying fishing waters in that region. Perhaps resolving such challenges are best done in the political arena and not in a semester project like this work. In Ghana, a major beneficiary of the WAGP, some concerns have been raised about how the pipeline is going to meet to energy demands of the Ghanaian citizens. It is has been established that by switching to natural gas via WAGP and hence generating power by the Takoradi Thermal Power Plant, Ghana will benefit in the long run by saving between 15,000 20,000 barrels of crude oil per day (Knowland and Kannan 2002). This should mean cleaner and more efficient utilization of fossil fuel. With this said, still, some environmentalists fear that the thermal power generated will be diverted to the mining heartland of Ghana in the Western Region, where Gold, Manganese, Bauxite and other minerals are mined but where such mining companies carry out socially and environmentally destructive activities that do not benefit Ghanaian citizens. In conclusion, there has not been any reported major impact on the environment by way of leakage and disruption of marine ecosystems. Pipelines laid onshore which tend to disrupt communities by way of an established right of way (ROW) were largely avoided because most of the pipeline was laid offshore and a good distance from the shores of all four countries. Most of the challenges associated with this project is mainly located in Nigeria and in particular where the gas is taken from, the Niger Delta Region. It should be noted that problems such as pollution of water, destruction of farm lands and cash crops by oil companies like the global Oil and Gas company, Shell, existed even before the WAGP came on stream and trying to separate and identify unique environmental challenges of the WAGP will be a hard task. So any unforeseeable negative environmental effect during the lifetime of the West African Gas Pipeline is yet to be realized and reported. 30

38 7. Conclusion West African Gas Pipeline (WAGP) which is a 678 km pipeline, supplying Natural gas for various purposes in four different countries; Nigeria, Benin, Togo and Ghana has been in operation since the latter part of The pipeline has been designed to have maximum capacity of 474 MMscf/day of natural gas. In this report, we have evaluated the technical, socioeconomic and environmental aspect of the WAGP project. The main conclusions are summarized in the subsequent paragraphs. The pressure drop across the length of the 678 km pipeline was computed after a number of simplifying assumptions were made. We found out that from Lagos to Takoradi there is a pressure drop of 22 bars and a pressure gradient of approximately bar/100 km. These figures (pressure drop and gradient) compares favorably with the some of the pressure drops encountered in pipelines in the North Sea and Norwegian Continental shelf. The arrival of Natural gas supplied by the WAGP project has complemented the recent discoveries of oil and gas in the waters of Ghana. The discoveries and supply of gas prompted the Government of Ghana to initiate the Gas Infrastructure Project leading to the construction of pipeline (onshore and offshore), a gas processing plant which will produce lean gas for power generation in the Aboadze Thermal Plant. It is a known fact that natural gas is a clean burning fuel from the angle of greenhouse gas emissions. So in Ghana it has been estimated that, the country will save upwards of 15,000 barrels of crude oil which otherwise would have been used to generate power. This should mean cleaner and more efficient utilization of fossil fuel. So in the absence of unforeseeable negative environmental effect, the West African Gas Pipeline has been quite benign on the environment. It can be concluded that even though the West African Gas Project has been plagued with difficulties ranging from technical integrity of the pipeline, political nuisances and some environmental concerns, the project has delivered on most of the primary objectives it set out to achieve. 31

39 8. References Abankroh, E. "WAGP Tariff Setting Process." from Final%20Final%20Cotonou%20Workshop%20NARUC%20PResentation%20%20ea.pdf. Abdulkareem, A. S. (2005). "Evaluation of ground level concentration of pollutant due to gas flaring by computer simulation: A case study of Niger - Delta area of Nigeria." Leonardo Electronic Journal of Practices and Technologies(6): Adeniji, C. (2012). "WAGP to expand output in 24 years." from AfricanGlobe. (2012). "West African Gas Pipeline Misses Target Due To Vandalism." from Ayodele, A. O. (2010). The future of West African gas pipeline project on gas market : development in the West African sub region. Bergen, Norwegian School of Economics and Business Administration. Barandao, A. (2007). Developing transborder infrastructers: West African Gas Pipeline Project: A case study 11th African Oil and gas trade and Finance Conference & Exhibition, Nairobi, Kenya. BP (2012). British Petroleum Statistical Review of World Energy. Clarke, T. (2001). "Taming Africa's killer lake." Nature 409: Donkoh, E. K., S. K. Amponsah, et al. (2011). "Optimal Pipeline Connection for the West African Gas Pipeline Project." Journal of Applied Sciences, Engineering and Technology 3(2): EC (2012) Energy (Supply and Demand) Outlook for Ghana. E. C. (EC). Ghana. EIB. (2008). "West African Gas Pipeline." from EPA (2004). West African Gas Pipeline Act. E. P. Agency. FOE (2006). The Myths of the West African Gas Pipeline. Nigeria, Friends of the Earth. Frost. (2012). from GIP (2011). Gas Infrastructure Project Document, Ministry of Energy, Ghana. Goodland, R. (2005). Oil and Gas Pipeliness Social and Environmental Impact Assessment : State of the Art. USA. Gudmundsson, J. S. (2012). "Calculations and Data." from Gudmundsson, J. S. (2012). Calculations and Data in Natural Gas. Trondheim, NTNU. IEA (2011). International Energy Statistics, U.S. Energy Information Administration. Jacobs (2010). Project Asona T2, Conversion to Combined Cycle - Environmental Impact Statement Update for T2. 32

40 Knowland, W. and V. Kannan (2002). Raising the Common Denominator in Petroleum Development Partnerships - Looking for Light through West African Pipelines. SPE International Conference on Health, Safety and Environment in Oil and Gas Exploration and Production. Kuala Lumpur, Malaysia, Society of Petroleum Engineers. Kosmos-Energy. (2012). from Leonce, M. (2007). The West Africa Gas Pipeline WAGP. Regional Workshop on Natural Gas, Accra. Malgas, I. (2008). Energy Stalemate: Independent Power Projects and Power Sector Reform in Ghana. Cape Town, South Africa, University of Cape Town Graduate School of Business. Market-Publishers. (2011). "Ghana Power Sector Report 2011." from MOE (2012). Jubilee Field Production Data. Ghana, Ministry of Energy, Ghana. Nwachuku, C. A. (2011). "Nigeria: Mining Activities Threaten West African Gas Pipeline." from Nysæter, J. B. and V. Wottrich (2012). Gas Markets 101. Trondhiem, Statoil. Obanijesu, E. O. and S. R. A. Macaulay (2009). West African Gas Pipeline (WAGP) Project: Associated Problems and Possible Remedies. Appropriate Technologies for Environmental Protection in the Developing World. E. Yanful, Springer Netherlands: Offshore-Technologies. from Okere, R. (2011). Shell to begin gas supply to Taiwan, Benin and Togo. The Guardian. Nigeria. Ramireddy, V. (2012). "An Overview of Combined Cycle Power Plant." Electrical Engineering Portal, from RCEER (2006). Guide to Natural Gas in Ghana, Resource Center for Energy Economics and Regulation, University of Ghana. REEEP. (2012). from Sletfjering, E. (1999). Friction Factor in Smooth and Rough Gas Pipelines. Doctoral, NTNU. Steven, E. (2000). "Plan for Degassing Lakes Nyos and Monoun." TullowOil. (2010). "Jubilee Field development - the story so far." from U.S.DOE. (2011). "How Gas Turbine Power Plants Work." from VRA. (2012). "Ongoing Generation Projects." from WAGP. WAGPA (2005). West African Gas Pipeline Regulations. 33

41 WAGPA. (2011). "The West African Gas Pipeline Authority Data." from WAPCo (2004(a)). WAGP Environmental Impact Assessment - Ghana. WAPCo (2004(b)). Environmental Impact Assessment - Nigeria. WAPCo (2007). West African Gas Pipeline Company - Pipeline Project History and Technical Description. Workshop on Natural Gas, Abuja. WAPCo (2007). West African Gas Pipeline Project History and Technical Description Workshop on Natural Gas, Abuja. WAPCo. (2012). from Yeboah, K. (2009). The West African Gas Pipeline - An Overview. Alumni Workshop Africa Kumasi, Ghana. 34

42 Oil Produced (barrels) Associated gas (MMscf) 9. Appendices 9.1. Appendix-A: Daily Oil and Gas production in Jubilee Field, Ghana Daily Associated Gas Production (MMscf) Daily Gas Prodced Daily FPSO Gas Consumptiom Flared Gas Figure 10: Daily Associated Gas Production(MOE 2012) Daily oil production (barrels) Figure 11: Daily Oil Production (MOE 2012) 35

43 ` 04-Mar Mar Mar Mar Mar Mar Mar Mar Mar Mar Mar Mar Mar Mar Mar Mar Mar Mar Mar Mar Mar Mar Mar Mar Mar Mar Mar Mar-11 Natural Gas utilised (MMscf) ` 04-Mar Mar Mar Mar Mar Mar Mar Mar Mar Mar Mar Mar Mar Mar Mar Mar Mar Mar Mar Mar Mar Mar Mar Mar Mar Mar Mar Mar-11 Associated gas produced (MMscf) Associated Gas Produced Figure 12: Associated gas production (MOE 2012) Fuel for FPSO Figure 13 : Fuel for FPSO (MOE 2012) 36

44 ` 04-Mar- 05-Mar- 06-Mar- 07-Mar- 08-Mar- 09-Mar- 10-Mar- 11-Mar- 12-Mar- 13-Mar- 14-Mar- 15-Mar- 16-Mar- 17-Mar- 18-Mar- 19-Mar- 20-Mar- 21-Mar- 22-Mar- 23-Mar- 24-Mar- 25-Mar- 26-Mar- 27-Mar- 28-Mar- 29-Mar- 30-Mar- 31-Mar- Gas flared (MMscf) Flared gas Figure 14: Flared gas for the month (MOE 2012) One of the project members at the Ghana Infrastructure Project (Gas pipeline construction in summer 2012) 37

45 9.2. Appendix-B: Pressure Drop Calculations High pressure gas pipeline for the WAGP Main Assumptions Main pipeline diameters are being used, the lateral lines have been ignored, because it will be assumed the pressure drop is not significant. The flow is steady state and isothermal Flow is horizontal Heat transfer to and from the environment of the pipeline is ignored Calculations Pipeline diameter d ID = 20 = m A = cross-sectional area M = Molecular weight of Natural Gas = kg/kmole Gas Composition for the West African Gas Pipeline is shown in the next page. 38

46 Component Vol % Molecular weight (g/mole) Methane CH Ethane C 2 H Propane i-butane n-butane i-pentane n-pentane Hexanes Heptane CO N H 2 S Specific gravity@ 60 o F 0.64 Net Heat Value(BTU/scf) 960 Wobbe Index (Net) 45 Gross heat Value (BTU/scf) 1058 Wobbe Index (Gross) 49 Table 12: Typical Natural gas composition (WAPCo 2007) 39

47 Using the conversion factor 1sm 3 = scf ( ) Similarly ( ) ( ) ( ) ( ) and For a horizontal pipeline and using the simplified Darcy-Weisbach equation p f f 2 L u d 2 where the average gas properties are used. (Gudmundsson 2012) Specific gravity Using the definition of specific gravity, which is given by the ratio of the molecular weight of natural gas to that of common air (without water vapor) with the molecular weight, M taken from above. M gas gas air s. c. γ = M M gas air *28.97 [kg/kmol] 40

48 Reduced Pressure and Temperature Critical pressure and temperature can also be obtained from semi-empirical equations based on specific gravity, for example from Rojey & Jaffret (1997) p [MPa] pc T [K] pc From the above equations with specific gravity γ = Critical pressure = MPa Critical temperature = K Z factor From the Lagos compressor station at 153 bars pressure and gas temperature of 16 C The reduced pressure is p r and the reduced temperature T r From the Hall- Yarborough method and Standing- Katz diagram Z = Density of gas (ρ) = kg/m 3 R = 8314 ( J/kmol.k) Temperature = 16 C (EPA 2004) L = 678 kilometer = m P1 (inlet pressure) Lagos compression station = 153 bar R & M Stations in between (Lome, Cotonou, Tema, Takoradi) (Donkoh, Amponsah et al. 2011) 41

49 Friction Factor and Reynolds Number (Gudmundsson 2012) The friction factor in commercial pipes can be calculated from the Haaland equation 1 f log n Re n k 3.75d 1.11n where n = 3 for natural gas pipelines ( n = 1 for liquid flow). The Reynolds number is given by ud Re and the relative roughness by k/d. From the formula sheet provided, Re = For the roughness parameter k in k/d, for commercial steel k = 45 microns = 0.045mm Friction factor f = Conclusion From the above calculations and using the given Excel sheet for pressure drop Pressure drop across 678 km of WAGP = ( ) Pressure gradient / 100 km = ( ) bar/100km 42

50 9.3. Appendix-C: z-factor calculations Hall-Yarborough (1973) z-factor calculation Hall, K.R. & Yarborough, L. (1973): A New Euation of State for Z-factor Calculations, The Oil and Gas Journal, June 18, Molecular weight oxygen, MO g/mole Molecular weight sulfur, MS g/mole Molecular weight, carbon, MC g/mole Molecular weight, hydrogen, MH 1.01 g/mole Molecular weight air, MA g/mole Components Molecular weight Mole fraction Tci Tci Pci Pci g/mole yi or K psia Mpa Methan, CH Ethan, C2H Propan, C3H i-butane, C4H n-butane, C4H i-pentane C5H n-pentane C5H Hexane C6H Heptane C7H Hydogen, H Nitrogen, N Oxygen, O Carbon dioxid, CO Hydrogensulfid, H2S Dihydrogenoksid, H2O Σ Mole fraction Total molecular weight gas g/mole Spesific gravity 0.64 Temperature Pressure 1.530E+07 Pa Method used (1, 2 or 3) 1 o C K Compressibility factor, z

51 Method 1 (Properties from composition, Key's rule) Pseudo critical temperature TPc (oil field units) or TPc (SI units) K Pseudo critical pressure PPc (oil field units) psia PPc (SI units) 4.7E+6 Pa Method 2 (Sutton's correlations) Pseudo critical temperature TPc (oil field units) or TPc (SI units) K Pseudo critical pressure PPc (oil field units) psia PPc (SI units) 4.6E+6 Pa Method 3 (Standing's correlation) Pseudo critical temperature TPc (oil field units) or TPc (SI units) K Pseudo critical pressure PPc (oil field units) psia PPc (SI units) 4.6E+6 Pa If we have a "dry" gas, SG < 0,75 If we have a "wet" gas, SG 0,75 Pseudo reduced properties TPR PPR

52 Hall-Yarborough t a Reduced-density parameter, y Continue until f(y) < 1x10^(-5) Iteration 1 f(y) E-3 Derivated of f(y), df(y) Newton Rapson: Reduced- density parameter, y Compressebility factor, z Iteration 2 f(y) -27.8E-3 Derivated of f(y), df(y) Newton Rapson: Reduced-density parameter y Compressebility factor, z Iteration 3 fy 1.3E-3 Derivated of f(y), df(y) Newton Rapson: Reduced-desity parameter y

53 Compressebility factor, z Iteration 4 f(y) 5.8E-6 Derivated of f(y), df(y) Newton Rapson: Reduced-density parameter y Compressebility factor, z Iteration 5 f(y) 106.9E-12 Derivated of f(y), df(y) Newton Rapson: Reduced-density parameter y Compressebility factor, z

54 9.4. Appendix-D: Pressure Drop Calculation Gasstetthet og -viskositet p (bara) 153 T (C ) 16.0 M (kg/kmol) 18.5 z-faktor ρ (kg/m3) μ (mpa.s = cp) Sheet 2 Lee et al Reynolds-tall u (m/s) d (m) ρ (kg/m3) 164 µ (mpa.s=cp) Re Haalands friksjonfaktorligning (n=1 væske, n=3 gass) Eksponent (1 eller 3) 3 Reynolds-tall Diameter mm 508 Ruhet mm Friksjonsfaktor Hastighet m (kg/s) d (m) ρ (kg/m3) 164 u (m/s) Trykktap væske (friksjon) og for gass med snitt tetthet f (-) L (m) d (m) ρ (kg/m3) 164 u (m/s) Δp (bar) 22.0 Hydrostatisk trykk væske ρ (kg/m3) 1110 Δh (m) 570 Δp (bara) 62.1 Hydrostatisk trykk gass p_1 (bara) L (m) M (kg/kmol) 18.5 α (grader fra horisontal) z (-), snitt 0.8 T (K), snitt p_2 (bara)

55 Temperatur i rørledning T omgivelse C 5 T innløp C 51 U W/m2C 25 Rate kg/s 70 Cp J/kgC (ikke kj) 2600 d (m) L (m) 5000 T utløp C Kompressorarbeid (adiabatisk) m (kg/s) 50 M (kg/kmol) R (J/kmolK) T innløp C 40 k (Cp/Cv) p innløp bara 25 p utløp bara 125 P (MW) T utløp C 146 Produksjonsrate gassbrønn (PSS) p^2 metode k (md) 100 h (m) 50 p_r (bara) 170 p_wf (bara) 165 T (C ) 60 µ (mpa.s = cp) z (-) 0.77 r_w (m) 0.06 r_e (m) 564 s (-) 0 q_s.c. (Sm3/s) q_s.c. (ksm3/h) q_s.c. (MSm3/d) Finn diameter d (m) til gassrørledning ved prøv og feil M (kg/kmol) 18.5 f (-) snitt m (kg/s) 249 z (-) snitt R (J/kmol.K) 8314 T (K) snitt 319 p_2 (bara) 122 p_1 (bara) 128 Første ledd = X Andre ledd = Y L (m) er gitt