Safety through Process Management Lessons Learned at Sour Gas Production Facilities

Transcription

1 Paper ID : Safety through Process Management Lessons Learned at Sour Gas Production Facilities Shafiullah Rana Chief Engineer (Electrical), Electrical Section, KDMIPE, ONGC, Dehradun India Sanyal_sarah@yahoo.co.in Abstract This paper discusses the lessons learned from Safety & Environment Audits conducted at Sour Gas Production Facilities A of offshore field in Mumbai, India. Production and processing systems have undergone significant changes since the inception of platform operations. Safety & Environment Audits have been a prudent tool and hence conducted during to identify and correct conditions that could threaten the Production Facilities, personnel and the environment. The production facilities were over 16 years old and typically employ older control and safety systems with limited capability compared to more current technology. Employing a more comprehensive audit/ inspection program was seen as an essential protection initiative that could significantly decrease the likelihood of damages of of MMT. The reservoir is producing under volumetric depletion drive with finite aquifer support. The XYZ Sour gas field comprises of two production platform complexes A and B and five well head platforms. Well fluid from well platforms flow to A & B process complexes where the sour gas and condensate are processed before its dispatch to the shore terminal. The gas produced is sour in nature with H 2 S in the range of PPM. The reservoir pressure and temperature were about 140 KSC & C respectively at that time. Surface pressure & temperature of the gas produced were KSC & C respectively. The sour gas produced is saturated with condensate & water. CO 2 in the gas is of the order of 5-6% that along with H 2 S makes the produced gas highly corrosive in nature. The field has been developed in phases. Accordingly, the field has witnessed addition of new wells, pipelines and wellhead platform. Process complex A which was originally designed to process 10 MMSCMD gas has been subsequently upgraded in two phases and further up-graded of processing facilities with installation and commissioning of Production Facilities and Environment. These audits took a comprehensive look at conformance with all applicable laws and regulations and accepted industry standards. Process, Safety, Electrical and Mechanical engineers conducted comprehensive evaluations of the process operation using a whole system approach to assess age and conditions of the equipment, pipelines, design of the facility, human organizational factors, mechanical and electrical maintenance and programs. The program has completed Audits at main process complex and unmanned production wellhead facilities with over 4560 action items identified and over Rs million spent on needed up gradation works. After Safety & Environment Audit, the Quarterly inspection results have shown significant improvement. Common items found result from age of the facility, changes in standards and regulations and revisions in the API/OISD Recommended Practices. These efforts have translated into reduced risk to the Production facilities, personnel and the environment. 1. Introduction The XYZ Sour gas field of Mumbai offshore, India was put on commercial gas production with initial gas rate of 2 MMSCMD. The North-South anticline structure of the field has an aerial extent of about 250 squires Kilometers. The hydrocarbon accumulation is confined with in Middle Eocene to Lower Oligocene. The producing reservoir is limestone and has been discovered into two distinct hydrocarbon producing zone. The first zone comprises of free gas while the second zone has bulk oil and gas. This has been further categorized into gas, oil and water layers based on the respective saturation values. The in place reserves of gas has been estimated in the range of Billion cubic meter and that of oil in the range Booster process complex at both the complexes. At the time of 1

2 Audit it was producing 16.3 MMSMD of sour gas, 2300 M 3 /Day of condensate and 240 M 3 /Day of produced water. The processing facilities at A Complex can be divided into three main groups i.e. gas system, condensate system and produced water system. Each process is described below: 1.1. Gas System The Process flow of the gas system is as under: Inlet Well Fluid Production Headers Well Stream Coolers High Pressure Separators (HP), Test Separator and Compressed gas from Intermediate Separator (IP) Suction Knock-out Drum Booster Compressors Discharge Knock-out Drum Gas Scrubber cum Glycol Contactor Glycol Recovery Vessel Gas Metering Trunk lines to Shore The controlled flow of well fluid at very high pressure and temperature collects in a production header and is routed to two gas-processing trains. The well fluid is cooled in shell & tube type well stream coolers where condensable water vapor & hydrocarbons condense and enters the high-pressure separator. In high pressure production separator, phase separation takes place. Gas, condensate and produced water separate out of well stream. The separated gas is dehydrated i.e. moisture or water vapor in gas is removed which is in the range of 3.5 to 4.0 Lbs/MMSCF as against maximum allowable limit to gas trunk-line transportation requirements i.e. 5 Lbs/MMSCF. The dehydration of gas is performed in glycol contactor where counter flowing tri-ethylene glycol (TEG) absorbs moisture from the up moving gas. The dehydrated gas after metering is dispatched to shore terminal via sub-sea trunk line. TEG rich with moisture is regenerated for re-circulation Condensate System The Process flow of the condensate system is as under: HP & Test Separators IP Separator Condensate Pumps Condensate Coalescers Condensate Meters Trunk lines to Shore The liquid from HP Separators and condensate from Test separator joins together and routed to the three phases IP (Intermediate Pressure) Separator. The liquids separated in Gas scrubber and Knock-out Drums (KOD s) also joins the inlet stream of IP Separator. The IP Separator pressure is maintained at 23 KSC for separation of gas, condensate and water. While the gas is routed to the (High Pressure) HP Compressor and separated water to the Produced water Flash drum, the condensate is pumped to Condensate Coalescers with the help of condensate pumps. During the total process the water content in the condensate is reduced to less than 15 PPM which is well with in the allowable parameters of 20 PPM. The condensate is then metered before dispatching to the gas trunk line Produced water System The Process flow of the produced water system is as under: IP Separator/Test Separator/Condensate Coalescers/KOD of HP & Booster Compressors/Fuel gas Scrubber Produced water Flash Vessel Produced Water conditioner Sump Caisson Before safe disposal to sea through sump caisson, produced water from IP Separator/Test Separator/Condensate Coalescers/KOD s of HP & Booster Compressors/Fuel gas Scrubber is treated in produced water conditioner. Hence there is practically no condensate accumulation in treated produced water. 2. Areas of Concerns in Operations A complex was originally designed to process 10 MMSCMD gas but has been subsequently upgraded. The up gradation in production and processing of sour gas, however, was not smooth. With 2

3 increase in production and gas processing, a number of operational problems and limitations surfaced. Some of them were as follows: 2.1. Process Observed reduced efficiency of Well stream coolers. Well stream coolers had problem of air locking. Cooling water flow across coolers has been reduced considerably. Observed abnormal high pressure differentials across heat exchangers resulting in drastic reduction in heat transfer efficiency in Plate heat exchangers. Heat exchangers are used for cooling of gas cooling water outlet of well stream cooler. The gas processing temperature exceeded the normal operating temperature (43 0 C). There was difficulty to contain the temperature within the operating parameters. The moisture content of export gas indicated a rising trend exceeding the pipeline transportation maximum allowable limit of moisture temperature. Observed increase in carry over of tri-ethylene glycols (TEG) from glycol contactor beyond the normal value. Observed increase in Glycol vapor loss in glycol regeneration system beyond the normal value. Observed High liquid load on Glycol contactors, packing failures in glycol re-boiler, frequent choking of charcoal filters, and over-pressurization of the system in glycol regeneration system Mechanical Observed frequent failures of pipe & pipe fittings of condensate and gas cooling system. Observed high vibration in Decks of Turbo generators for Power generation. Observed high vibrations and increased frequency of replacement of plunger packing of condensate pumps. Observed increased frequency of replacement of plunger packing of glycol pumps. Observed high vibrations in HP gas Compressors Electrical and Instrumentation Observed complete Power shutdown in case of tripping of one out of three Power turbine generators due to fault in load sequence logic control mechanism of Power Turbine generators. Observed high failure of closure of unmanned platform s wells in stipulated time, resulting in deployment and transportation of manpower to unmanned platforms through offshore vessel in odd hours for opening of the wells Safety & Environment Observed reduced Efficiency of the Tilted Plate Interceptors (TPI) and Dissolved Gas Floatation units of Produced water conditioner; threatening the Marine Environment. Observed minor leakage from flanged hub gasket of header valves of two unmanned platforms; depositing excess salt sticks due to oozing water with little leaking gas, which is rare phenomenon. Though the salinity of Produced water was well with in limit (7.5 mg/litre) compared to the sea water salinity of about 34mg/Litre. Observed Pressurized Pig receiver due to leakage in the isolation valve making the operations very risky during pig receiving. Observed continuous leakage of Lube Oil from the plunger driven condensate pumps and also from Power Turbine Generators making unsafe conditions in the deck areas and Turbine room. Observed leakage in the open deck drain, LLP (Low low pressure) gas flare line and Sewage piping making unsafe conditions. Out of seven number Life boats only four Life Boats were fully operational. The other three boats can be used for evacuation but cannot hoisted back to their positions electrically. 3

4 Both the Breathing Air Compressors were non-functional due to various electrical, mechanical and Quality control problems. As a result refilling of Breathing Air Apparatus was done at nearby process complex B, which was not a safe working condition. The working principle of Both Sewage Treatment Plants was based on Electrolysis and quality of Hypochlorite generation. Due to aging the environmental parameters like BOD, COD etc. were beyond the upper limit. Quality and frequency of Calibrations of F&G Detectors were not met as in many cases the self life spare sensors acceded the time limitations. The doors/enclosures of many rooms like Power Turbine generators, Control room, and Battery banks were not properly closing, making Halon System ineffective. In the light of above observations in the operations, the Safety & Environment Audits Program began with an initial Audit at Process complex A in the year Over 4560 action items were identified demonstrating a clear need for comprehensive auditing. The quantity and significance of the identified audit items prompted Asset Management to re-evaluate the facility inspection and environmental aspect prevention program. There was concern as there were gaps in the monthly safety & environment inspection programs, because the inspection specifics were prescribed by regulation as contained in organizations own safety & environment policy and programme based on API/OISD. It was observed and deliberated that the inspection program could not alone ensure safe operation of these facilities. The production facilities were over 16 years old and typically employ older control and safety systems with limited capability compared to more current technology. Production and processing systems have undergone significant changes since the inception of this platform operation. Employing a more comprehensive audit/inspection program was seen as an essential safety and environmental protection initiative that could significantly decrease the likelihood of operational and environmental damage. The deployed audit programme used Process, Safety, Electrical and Mechanical engineers to conduct comprehensive evaluations of the operation. These experts would assess age and conditions of the equipment, pipelines, design of the facility, human organizational factors, mechanical and electrical maintenance and programs using a whole system approach. The audits took a comprehensive look at conformance with all applicable laws and regulations and accepted industry standards such as with the API Recommended Practice RP-750 & SEMP-RP-75 on Management of Process Hazards, OSHA regulation 29 CFR on Process Safety Management of highly hazardous chemicals and EPA-40CFR-435/OISD on Environment management control. These regulations contain specific requirements for operations, plans and equipment on oil & gas production operations and environment control. 3. Audit Approach Each Audit is an in depth verification that an oil and gas facility complies with all applicable API/OSHA/EPA/OISD laws and regulations, follows industry standards, and continually re-evaluates and incorporates best achievable technology to safeguard the public and the environment. Each audit has five main areas or groups: Management Technical design Equipment Functionality-Integrity & Mechanical Electrical & Instrumentation Human Resource and Safety Management The groups identify action items with priorities and recommendations that are based on the information and requirement provided in a matrix (Annexure-I) as well as a written report in various Management manuals that highlights significant problems or design issues. 4. Results Process, Safety, Electrical and Mechanical engineers conducted Audit and comprehensive evaluations of the process operation using a whole system approach to assess age and conditions of the equipment, pipelines, design of the facility, human organizational factors, mechanical and 4

5 electrical and instrumentation maintenance and programs. The program has completed Audits at main process complex and unmanned production wellhead facilities with over 4560 action items identified. Over Rs million spent on needed up gradation works to comply for liquidations of these action items. All but only few long term action items from this audit have been resolved. The following table shows the Priority levels that action items may be assigned. The distribution of action items by Priority level and identification of action items respectively are shown in the table-i & II: Table-I S.No. Priority Action Items Percentage of total Action Items % % % Grand Total 4560 Table-II S.No. Group Action Items Percentage of total Action Items 1. Management 91 2% 2. Technical design 228 5% 3. Equipment Functionality-Integrity & % Mechanical 4. Electrical & Instrumentation % 5. Human Resource and Safety Management % Grand Total 4560 The table shows that: The majority of items are identified by the Equipment Functionality-Integrity & Mechanical group, followed by Human Resource and Safety Management group. These items include the review of required plans and drawings to verify they are up to date, as well as condition or maintenance problems found. These items tend to show up as a Priority 1 or 2 action item. The number of Equipment Functionality-Integrity & Mechanical group items also appears large because of the potential risks involved with these conditions, design, or rating problems. The Electrical & Instrumentation group action items include maintenance and any electrical system design problems identified as well. Where as the overall facility design, piping, and processing equipment design problems are located in the separate Technical design group s action items. These items tend to show up as a Priority 1 or 2 action item. Technical design group action items may be the most critical for correcting to prevent accidents or catastrophes because they deal with the facility design and required safety features. These items tend to show up as a Priority 1 or 2 action item. Management group where common problems found in operations manuals are among the least. Management group action items also tend to be Priority 3 items because of their low likelihood to initiate a catastrophe and the prerequisite chain of events that must occur. 5. Lessons Learned The lessons learned from audits are many. The result can be a better audit performance with fewer action items and ultimately less risk. This can also be used to augment internal audits and inspections to avert potential accidents and Environment damage. A number of the Equipment Functionality and Integrity action items occurred for improvement. In some cases, this seemed to occur because of limited facility and maintenance engineering support. A planned schedule for all tank and pressure vessel internal inspections and ultrasonic thickness measurement should be available. Further, piping and pipeline maintenance assessment and scheduling of maintenance and repair can also avert environment damage. 5

6 Many of the electrical & Instrumentation action items are the result of years of service in the harsh marine environment. Many junction boxes, conduit, and enclosures were found damaged or corroded to where they could not function as designed. Cable tray systems heavily corroded or in disrepair; produced a significant number of action items. Bonding and grounding of equipment and tanks also proved to be a very common action items. Piping and Instrumentation Drawing errors also accounted for significant numbers of lower Priority action items. Commonly identified Technical issues included balk at applicability of Process Safety Management (PSM) regulations. Process Hazards Analyses (PHA s) or Hazards Operability Studies (HAZOP s) are tools within PSM that are effective in identifying and managing risks at sour gas processing facilities. Process complex A had previous PHA or HAZOP studies on file; however, it had not implemented corrections, or proceeded with new projects without evaluating the available information. Sour gas processing system design may require review in intermediate stages of development due to corrosive nature of gas flow in operating equipment. 6. Conclusion In today s environment, the Safety and Environmental practices impact the entire industry. The Audit Program is an example of such activity to supplement existing inspection programs. The programs is proving to ensure in cooperation with users that each facility is designed, constructed, maintained, monitored and operated in full compliance with applicable industry codes, regulations and accepted practices and ensure that organization has adequate safety and environmental programs in place. Adopting these guidelines Process complex A sorted out all those operational, maintenance and safety & environment related issues. Process complex A got with full fledged accreditations of integrated quality, health, safety and environment management (ISO 9001, ISO & OHSAS 18001) and international safety rating level 5 (ISRS-5) certification for their efforts in the end part of the year References 1. Operations & Maintenance Manuals of Process complex A 2. Analysis, Design, Installation and Testing of Basic Surface Safety Systems for Offshore Production Platforms. American Petroleum Institute Recommended Practice API RP-14C 3. Recommended Practices for Development of a Safety and Environmental Management Program, American Petroleum Institute Recommended Practice API RP Process Safety Management of Highly Hazardous Chemicals, Title 29, Code of Federal Regulations (CFR) Part Guidelines on Safety Management System in Petroleum Industry, OISD-GDN Environment Management in E&P Sector, OISD-RP-201 6

7 MATRIX FOR AUDIT Annexure-I S. Group Responsibilities No. 1. Management 1. Review the various manuals, plans, policies, procedures and practices, emergency response plans, training programs and safe work practices for compliance with laws, regulations and industry standards. 2. Evaluate the use and application of this information by personnel at the facility. 3. Address Process HSE Management issues from a documentation or Management stand point much like the internal audits required by the various ISO Standards. 2. Technical design 1. Conduct a review of the Design of the facilities for compliance with API/EPA/OISD regulations for oil and gas production facilities as well as other requirements and standards. 2. Verify Process Hazards Analysis (PHA) being conducted by Process complex to identify appropriate safeguards and operations. 3. Review Existing PHA s for quality, adequacy of supporting process, safety information, appropriate analysis technique, all hazards addressed, proper documentation and meeting all requirements. 4. Check the sizing of pressure safety relief valves and the relief system as well as the coordination of a review of the various Detection systems and Fire protection systems. 5. Verify other design requirements involves verification of adequate 3. Equipment Functionality- Integrity & Mechanical 4. Electrical & Instrumentation 5. Human Resource and Safety Management containment volumes as identified in the Environment protection plan. 1. Examine the physical condition of the facility including operational and maintenance practices and the proper functioning of safety and environment protection system, prevention and response systems and equipment. 2. Review preventive maintenance procedures and schedule and compliance, equipment specification information for maintenance and design selection of equipment. 3. Verify the important tank, pressure vessel and safety relief valve inspections code or recommended industry practices and complete tables of information that summarize this information. 4. Verify that Cathodic and other corrosion protection system inspections, piping assessment and pipeline integrity inspections including smart pigging or hydrostatic tests are occurring on schedule. 1. Examine the physical condition of the Electrical & Instrumentation systems including operational and maintenance practices as well as proper design and installation to meet applicable code requirements. 2. Verify the accuracy of Process and Instrumentation Diagrams (P&ID s), Emergency and EM Response, Equipment diagram, Process Flow Diagrams and observe required periodic testing of this critical equipment. 3. Verify line diagrams and hazardous location area classification diagrams. Also specific requirements for backup, auxiliary, or emergency power as well as electrical & instrumentation controls, communications and other related equipment. 1. Conduct Safety Assessment of Management Systems (SAMS) that is based on interviews of company personnel and contractors at all levels of the organization. 2. Provide a separate and confidential report intended for impartial third party feedback and observations regarding apparent root causes and related management conditions as mentioned in the Lessons Learned. 7