UNI - CIPR CENTRE FOR INTEGRATED PETROLEUM RESEARCH

Transcription

1 Oil related microbiology Terje Torsvik UNI - CIPR CENTRE FOR INTEGRATED PETROLEUM RESEARCH

2 Important microbial processes in oil production: Reservoir souring Microbial Influenced Corrosion (MIC) Produced water reinjection (PWRI) Microbial Enhanced Oil Recovery VFA VFB

3 Reservoir souring in offshore oil production Sea water is injected into the reservoir as pressure support Oxygen is removed to reduce corrosion Sea water contains 28 mm sulphate Sea water injection promotes growth of SRB in the water injection system and in the reservoir SRB use sulphate for respiration: SO 2-4 H 2 S H2S cause problems because it is toxic and corrosive Traditionally biocides have been used to inhibit SRB An alternative method based on nitrate injection have been developed in collaboration with Statoil and Hydro

4 Microbial production of H2S in the oil reservoir H2S production increases dramatically over the lifetime of a production well. High H2S levels may result in shut down of the well and reduced oil and gas production. H2S is toxic and corrosive Strong restrictions on H2S concentration in export gas Ref. : Sunde et al. (1993). Field related mathematical model to predict and reduce reservoir souring. SPE (1993)

5 Laboratory experiments: Effect of nitrate injection on H2S production Sulphide production and nitrate injectin in column. mm H2S 1,4 mm NO3 1,2 mm H2S, NO3-1,0 0,8 0,6 0,4 0,2 0, Time (days) Ref.: Myhr et al. (2002). Inhibition of microbial H2S production in an oil reservoir model column. Appl. Microbiol Biotechnol 58:

6 Gullfaks Water injection system Monitoring SRB in the field: Biofilm sampling Sampling point Sampling point Biocoupons collected from pipiline Placed in box for anaerobic transportation Filled up with anaerobic injection sea water

7 Metal coupons incubated in pipeline Measuring microbial activity in the water injection system The biofilm is analyzed for microbial activity GAB SRB NRB

8 Water injection system at Gullfaks. Bacteria in biofilm before and after nitrate treatment 1,0E+10 1,0E ,0E+08 1,0E+07 Log cells/cm m2 10E 1,0E ,0E+05 1,0E+04 1,0E+03 1,0E+02 1,0E+01 1,0E+00 feb.89 jun.90 dec.91 mar.93 apr.94 nov.94 jul.95 jun.96 feb.97 mar.98 may.99 feb.00 aug.00 may.01 mar.02 feb.03 Time (months) Biocide (glutaraldehyde) Nitrate (start oct. 99) SRB-FA SRB-MPN NRB Total bacteria Detection limit FA method: 1e+05 cells/cm2 Detection limit MPN method: 6 cells/cm2

9 Sulphate respiration rate (µg H2S/cm 2 /day) 1,2 1,0 0,8 0,6 0,4 0,2 SRB activity and corrosion rate at GFB Nitrate added Corrosion rate (mm/year) apr.94 sep.94 nov.94 mar.95 jul.95 oct.95 mar.96 jun.96 sep.96 dec.96 feb.97 mar.97 may.97 aug.97 nov.97 jan.98 feb.98 mar.98 may.98 sep.98 des.98 may.99 aug.99 nov.99 feb.00 jun.00 aug.00 nov.00 des.00 feb.01 may.01 aug.01 nov.01 mar.02 jul.02 oct.02 feb.03 jun.03 0,0 Corrosion rate SRBactivity Time (month) 0

10 m g H 2S /litre water H2S in produced water on Gullfaks C Start of nitrate injection measured mg H2S in water Theoretical H2S development nov-97 sep-98 jul-99 mai-00 feb-01 des-01 okt-02 aug-03 Date Sunde, Egil; Lillebø, Bente-Lise Polden; Bødtker, Gunhild; Torsvik, Terje; Thorstenson, Tore. H2S inhibition by nitrate injection on the Gullfaks field. NACE Corrosion 2004, Paper No 04760; 2004

11 Produced Water Reinjection (PWRI) Produced Water Reinjection (PWRI) has been used on platforms, mainly due to requirements from the Norwegian Pollution Agency regulating release of hydrocarbons to the sea. In the event of permission to produce oil in the Barents Sea, there must be zero release of hydrocarbons to the environment. Challenges: High temperature stimulate growth of thermophilic SRB Increased supply of VFA in the injected water stimulate reservoir souring

12 PWRI at Statfjord Microboal analysis of back flooded injection water Injection water: Cold sea water (StA) Hot produced water (StC) Ocean floor Injection water St A and B: Sea water Injection well Production well St C: Produced water Oil reservoir

13 Samples Back-flooded injection water from wells 3000 meters below sea floor. From each injector: 9 samples taken at different times (0 96 hours) of back-flooding. Sample Statfjord A Statfjord B Statfjord C Injected with Sea water Sea water Produced water Temperature 30 C 30 C 60 C Treatment Deoxygenated, biocide treatment Deoxygenated, nitrate treatment Deoxygenated, 75 % produced water 25 % seawater Souring potential H 2 S mg/liter (calculated by Statoil) 30 <

14 Principal component analysis of native populations at St A and C 1.0 epsilon Thermoc Archaeog Actinob Deferrib StC Statfjord A (StA) Statfjord C (StC) Produced water (PW) delta Backflow StA beta Firmic -1.0 PW alpha K. Lysnes, G. Bødtker, T. Torsvik, E. Ø. Bjørnestad & Egil Sunde: Appl Microbiol Biotechnol (2009) 83:

15 MEOR Principles reservoir effects BACTERIA + OIL + N + P + O2 REDUCED INTERFACIAL TENSION REDUCE CED WAT ATER PERMEABILITY MOBILISED RESIDUAL OIL ENHANCED SWEEP EFFICIENCY

16 Microbial biofilm on oil crude oil Bacterial colony surrounded by water

17 IFT laser-light light scattering Best suited for low values (< 30 mn/m) Measurement range is mn/m Method has been successfully applied down to 10-4 mn/m

18 Bacterum: Dietsia maris Dodekan, aerobic synthetic ti sea water IFT (mn/m) ,1 OW IFT OWB IFT 4.0 ml/h 0.9 ml/h 1.8 ml/h 2.7 ml/h 5.4 ml/h 0,01 0, Run time (days) Kowalewski, E., Rueslåtten, I., Gilje, E., Sunde, E., Bødtker, G., Lillebø, B.L.P., Torsvik, T., Stensen, J.Å., Bjørkvik, B. and Strand, K.A., 2005, "Interpretation of Microbial Oil Recovery from Laboratory Experiments", Paper presented at the 13th European Symposium on Improved Oil Recovery, Budapest, Hungary, Apr 25-27

19 Hopeman sandstone core Laboratory experiments 45 cm long, 5 cm diameter Statfjord model oil Flow rate: 0,1 ml/min = 1 PV/d Sor 0,38 Anoxic synthetic seawater Microbes, O2, N, P 0,36 0,34 0, Time (days)

20 MEOR at Norne Injection of aerobic seawater from start in 1997 MEOR implemented in January 2001 by adding N and P to the injection water to stimulate bacterial growth in the reservoir Nitrate is also added in order to inhibit reservoir souring

21 MEOR at Norne 2002: Increased oil production from MEOR at Norne m 3 1 % of producible oil At an oil price 20 $ per barrel and 1$= 5 NOK this amounts to approximately NOK. (Reported from Norne to OD in 2002)