Water Treatment for Flooding with Lower Salinity than Formation Water

Transcription

1 Copyright: Shell Brands International AG 2008 Water Treatment for Flooding with Lower Salinity than Formation Water Paul Verbeek & Andreas Matzakos Shell International Tekna Produced Water Conference, Stavanger, January 2009

2 Content 1. Effect of Lower Salinity Injection Water for flooding 2. Engineering the option Water sourcing/composition Water pre-treatment, desalination Equipment line-ups 3. Facilities Design Space/weight/power/Cost Case studies w/ synergies Upsides & Downsides 4. Conclusions & Recommendations 2

3 Effect of Low Salinity Waterflooding Adsorbed hydrocarbons Factors (neg) Ca 2+ Clay (neg) Fresh water sensitive clay mineralsother minerals, contaminations 0 Pore wall 1 Crude oil Fraction of pore wall Take Ca-ion out to de-absorbe the oil Remove cations by flooding with low-salinity brine to destabilize double layer & de-absorb crude oil from pore wall feasible if: Originally highly saline formation water, rich in divalent ions, present. Low-swelling clays present in reservoir rock Injection of low salinity brine changes rock wettability from oil-wet to more water-wet. The effectiveness depends upon: Multi component ion exchange Clay content of formation Electric charge of sandstone formation Composition of formation water Oil composition Initial water saturation ph of water TDS range ppm 3

4 What does that mean for water treatment? PWRI oil/solids Gravity, Filtration, Extraction, Adsorption LowSal oil/solids /salt Nanofiltration Reverse Osmosis EOR + ASP chem + emulsion treatment + Scale control + Oil spec + Water Disposal Injection Water quality - complexity due to demand for high water quality: IOR: formation plugging, fracturing, wettability change due to salinity, souring, scaling Chemical EOR: tighter requirements compared to traditional waterflood: emulsions, oil spec., scale Challenges: how clean is clean? Hardness, Salinity, OiW, TSS, increasing quantities, treatment of back-produced fluids Enabling technologies: membranes and chemicals? 4

5 Treatment technologies - How to achieve Water Quality? Erosion Lift/injection Pumps Frac growth Injectivity Fouling RO membrane Desalination Clay swelling Souring, Scale LowSal flooding Solids Oil/solids Oil/solids Salinity TSS < 100pm TSS < 10ppm OiW<100ppm TSS < 1ppm OiW<1ppm TDS~2-5,000ppm Hardness Ca<40, Mg<100ppm SO 4 <20ppm SW PW Base technology Base technology Base technology Key technology Key technology Lab/Piloted Lab/Piloted Emerging 5

6 Water treatment - options Step 1: Water Source Produced Water Sea Water Aquifer Water Process Waste Water Ground/River Water Step 2:Water characteristics for injection / disposal Salinity: up to 500 ppm 500-2,000 ppm over 15,000 ppm Divalent cations (SO 4, Mg, Ca) Solids and fines Hydrocarbons: dispersed/dissolved Biological/bacterial activity Oxygen (corrosion scaling) Organics, other like metals (Fe). Step 3: Select Water Treatment Removal hardness, sulphate and salinity by membranes, resins, thermal etc. Solids/fines removal by settling/ filtration/membrane Hydrocarbons removal by settling /cyclonic/centrifuge/flotation/ chemical/absorbent/extraction De-aeration by vacuum, scavengers Ion exchange UV, ECA (sterilisation) Chemicals Water chemistry Bio-treater, Reed beds, etc. 6

7 Desalination techniques - options Desalination method Feasible Reason Limitations RO YES Modular and compact Skid mounted systems Small space requirement Less CAPEX Not proven for Produced water Skilled manpower required to maintain the system MSF YES Proven and used industry wide Requires less pre-treatment compared to RO waste heat make it cheap High reliability Large footprint, not easily mobile High scaling potential due to high temperatures Contribute to thermal pollution Proven and used industry wide MED YES Requires less pre-treatment compared to RO waste heat make it cheap High reliability Compact compared to MSF, still large footprint weight Power requirement highest among desalination methods Less footprint compared to MSF Ion exchange NO up to 2000 ppm TDS Generates chemical wastes Uses more chemicals Electro deionization Membrane Distillation NO upto 40 ppm TDS in feed water Used in high purity applications NO Not proven in industry Low level Waste heat MVC NO Large foot print High power requirement Heavy weight for on-shore. Power consumption 8-11 kwh per m 3 of distillate. 7

8 Pre-treatment technologies screened removal of oil & suspended solids Oil removal Oil in Water [ppm] Conventional dispersed oil < 100 < 10 < 1 Plate interceptors, skimmer Induced gas flotation (WEMCO) Hydrocyclones + degasser Performance enhancing concepts Coalescing devices (physical) Condensate addition (Ctour) Enhanced flotation (EPCON, Enhanced dispersed oil removal Centrifuges Filters / filter coalescers Membranes (ceramic) Dissolved oil removal Condensate addition(ctour) Adsorption (Torr, CrudeSorb, PS65) Solvent extraction (MPPE) Polishing Dissolved gas flotation Biological treatment Reed beds Solids removal Centrifuge Microfibre Filter Dual media Filter Microfiltration Ultrafiltration Coagulation/Flocculation Deepbed nutshell filters Pre Coat Filtration Dissolved Air Filtration Induced gas flotation Solids in Water [ppm] < 100 < 10 < 1 Pre-treatment for desalination of PW (RO limits: TSS < 1ppm; OiW<1ppm) Limited choice of treatment technologies Hybrid/novel solutions 8

9 Concept engineering and field candidate screening - Case studies Equipment line-up depends on: Salinity of source water Salinity of injection water Location Scale (small large) Energy cost Onshore Source water TDS [ppm] Arabian gulf 45,000 North Sea 32,000 Caspian Sea 9,660 River water 1,000 GoM 38,000 Courtesy GE Offshore Courtesy WaterStandard 9

10 Equipment line-up - Low Salinity waterflooding 1. Pre-treatment for Seawater Sea water Dual Media filter Microfiltration RO Inlet Removes particles upto 2 microns Removes TSS upto 1 ppm 2. Pre-treatment for Produced Water Produced water Hydro cyclone Ctour/ UF RO CFU Inlet Removes dispersed oil upto <4 ppm OiW Removes the dissolved organics upto 95% Removes TSS upto 1 ppm 3. Desalination with Hardness matching 10

11 Case study - Equipment line-ups Electro chlorinator Package Coarse Filter Package Fine Filter Package Vacuum Pumps De-aerator Towers Proposed (BfD) 45,000 m 3 /day To Champion Seawaterflood case Base equipment: source/injection pumps, filters Seawater Lift Pumps Reject ~21% 12,000 m 3 /day 57,000 m 3 /day Electro chlorinator Package Coarse Filter Package Seawater Lift Pumps Fine Filter Package Reject ~21% 26,700 m 3 /day RO Reject ~55% 55,000 m 3 /day Vacuum Pumps New Platform De-aerator 45,000 m 3 /day Towers To Champion SE LowSal case (retrofit) Seawater lift pumps for 55% extra water extra pumps power for lift & membranes Concentrated brine discharge system 126,700 m 3 /day RO: Reverse Osmosis De-aerator downstream RO 11

12 Facilities for Low Salinity Waterflood Case description Retro-fit to Seawater 3 /d Incremental facilities comprising: seawater lift, pre-treatment and RO (seawater TDS ~34,000ppm injection TDS ~ 2800ppm). SWRO most attractive desalination method for offshore application due to its weight, footprint and power consumption. Space, Weight, Power (Vendor reports) Item No. Equipments Dry Weight Wet Weight Footprint Power Tonnes Tonnes m 2 kwh/m 3 Vendor A UF NF - SWRO Vendor B MMF - SWRO Dry weight is lower due to lower weight of UF compared with MMF. Due to higher load of water in UF compared to MMF, wet weights are similar. Difference of footprint is due to the NF train (two passes). Power consumption ~ 2MW (lower due to ERD and lower pressure in NF). 12

13 Downside effect of produced water salinity on capacity of separating equipment CONTINUOUS DEHYDRATION TANK FROM WELLS CRUDE TOFINAL SETTLING AND EXPORT TANKS CORRUGATED PLATE INTERCEPTOR BLANKET GAS LP FLARE SKIMMED OIL TO EXPORT TANKS GAS FLOTATION VESSEL TO PWRI SKIMMED OIL TO EXPORT TANKS HOLDING BASIN Typical Onshore Facility lineup for produced water treatment. CLEAN WATER DISPOSAL Facility de-rated capacity for different formation water salinity and formation water dilution percentages. Low salinity water flooding is not expected to affect the produced water handling facilities significantly; e.g for salinities <50,000 ppm for upto 50% dilution of formation water salinity the de-rated capacity is <10%. Risk to form oil/water emulsions increases when reducing salinity 13

14 Seawater desalination cost factors (ref. vendor quotes & in-house data) 11% 10% 4% 21% 17% Depreciation Electricity Seawater Lifting Chemicals Operations & Maintenance 58% Breakdown of Lifecycle Cost for RO Desalination at large scale using seawater Onshore ~ $ 0.8/m 3 water injected Offshore > $ 2.2/m 3 water injected incl. installation cost factors, excl. cost of floating structure & pre-treatment Brackish water is half cost of seawater 14

15 Treatment for Low Salinity Waterflooding - Conclusions RO is preferred desalination technology, in particular for situations where space and weight are constraints (offshore/seawater). To make projects viable there is a need for: fit-for-purpose & low-cost & compact desalination technology. desalination technologies capable to supply injection water with optimal TDS at high energy efficiency offshore concepts for mobile seawater desalination vessel systems to meet offshore field requirements. pre-treatment methods to allow use of produced water. Plea to vendors to innovate their technologies to oil industry needs Operators need to develop Facility engineering tools for concept studies and field candidate screening. 15

16 Thanks? 16