微生物采油技术在中国胜利油田罗801区块试验A英文译文2

1、 . . 10/10MEOR Field test at Block Luo801of Shengli Oil Field in ChinaAbstractA Microbial Enhanced Oil Recovery (MEOR) field test has been implemented for 10 consecutive years at the 75-80 Block Luo801 in Shengli Oil Field in China, where microbial formulation and nutrient, producing biosurfactant,

2、were injected into oil wells. After the implementation of MEOR, theproduced fluid samples from the oil wells were analyzed and found an increase of bacteria and archaea in waterphase stabilizing at 103-4cell/ml and a soar of acetate in concentration from 70mg/Lto 523.0 mg/L without finding the type

3、of injected microbial types, suggesting the nutrient injected has activated the indigenous bacteria in the reservoir, whose activities wereenhanced toprevent the water cutfrom rising up in the block so as to increase the oil output. Up to December 2010, the cumulative increasedproduction of oil has

4、been 9.75 104t with the total output surpassing that of Water Flooding Oil Recovery (WFOR)by 3.35%. Considering the cost of injected microbial fluid and nutrient, oil increased per tonne costs about RMB339.56. Keywords: Microbial Enhanced Oil Recovery (MEOR),Field Test,Water Flooding 1. Introduction

5、Fault block oil reservoirs occupy an important proportion in Shengli Oil Field of China, whosedevelopedgeological reserves have reached 9.22 108tbut with thecomprehensive water cut 91.5%.Thus how tostop the production declineand enhance the crude oil recovery becomesa major challenge to develop faul

6、t block oil reservoirswith high water cut. Due to the smaller area bearing oil and the incompleteproductionwell grid, it is not suitable to carryout chemical enhanced oil recovery technology for fault block oil reservoirs and alternative oil recovery technology is expected to be developed for them.

7、Microbial Enhanced Oil Recovery (MEOR)technologyis considered promisingfor fault block oil reservoirs,whose related research was not launched until 1990s in Shengli Oil Field by a specialized team engaged in research and test in MEOR.Once their purpose was to select the bacteria type, suitable for t

8、he reservoir environment and capable to enhance the oil displacement efficiently, which was first ground cultured then injected into the reservoirs. At the beginning of this century, research revealed indigenous bacteria in reservoirsare very active, so the research focus shifted to indigenous bacte

9、ria enhanced oil recovery. Currently, oil reservoirs have been considered as an ecosystem into which material such as specific microbial formulation,inorganic or organic nutrient and air have been injected to regulate them: the microbial community structure and function inside might change, increasi

10、ng the bacteria density, producingbiosurfactant and improving the oil-wash efficiency throughin situbreeding. Based on research in the laboratory, a MEOR field test has been carried out inBlock Luo801 in Shengli Oil Field since 1999. The test method hasbeen adjusted twicein the 10 year period in the

11、 hope of exploring the potential of MEOR technology to improve oil recovery in fault block oil reservoirs. 2.Test Area Reservoir Geology Block Luo801 is a small block in Shengli Oil Field, a lithologic - structural reservoir with a temperature ranging from 75 to 80 . It is open in the north and the

12、southern part is closed by an east-west arc fault, where the test area is located on the hanging wall. The areabearing oil is1.95 km2 with the crude oil reserves 291 104 t. The reservoir depth is from 1680 mto 1800 m and the original formation pressure is 17.5 MPa. The oil pool of the test area is l

13、ocated on the West Wing of the nose-like structure, whose strataare high in the south and low in the north with an angle ranging from 5 to 6. It passes through Permian strata including Shahejie Fm., Dongying Fm., Guantao Fm. and Pingyuan Fm. as a lake phase mesoporous and meso-permeable reservoir, w

14、hose oil bearing units are S1, S3, S4of sand section.with an average porosity 23.5%, an average permeability 211.610-3m2, and the ground oil viscosity 221.7mPa.s, formation water typeNaHCO3 and TDS 7795 mg/L. Test area reservoir parameters are shown in Table 1 and the wells positionis shown in Figur

15、e 1. Table 1 MEOR test area reservoir parameters of Luo801ItemDataItemDataOil bearing area（km2）1.25Formation water TDS mg/L9794Reserves（104t）291Formation water typeNaHCO3Reservoir typelithologic-structuralOriginal oil and gas ratio30Reservoir depth (m)1680-1800Original formation pressure (MPa)17.5Po

16、rosity（%）23.4Saturation pressure (MPa)9.24Air permeability（10-3um2）218Formation saturation pressure difference(MPa)8.26Oil saturation（%）60Current formation pressure10Ground crude oil viscosity（MPa.S）353Formation pressure 75-80Figure 1 Tectonic position of MEOR test area in Luo8013. Test Area Develop

17、ment Process Lou801has been formally developed since May 1994,in June 1998 flooding oil recovery began here, in July 1999 the first MEOR field test launched and in 2003air aided MEOR began to develop. According to the test area production curve, the development can be divided into four stages, namel

18、y capacity building stage, natural energy development stage, flooding development stage andMEOR teststage. 3.1 Capacity Building Stage, 1994 Wells Luo801 and 805 have been finished drilling in Block Luo801inApril and May 1994 respectively. Sinceindustrial oil flow obtained in S3 and S4, the block wa

19、s under rolling development as in the same year, an oil bearing area of 1.25km2 went into operation involving oil reserves 291 104t witha new production capability 6 104t. In December 1994, 16wells were opened and produced 446t of fluid and417t of oil per day withthe water cut6.5%, oil production ra

20、te 5.23%, recoverypercentage 3.16%, outputting 9.2097 104t of oilannually. 3.2 Natural Energy Development Stage, 1995 May 1998This stage features relying on natural energy when the reservoir was developed at a high speed. With the formation pressure dropping rapidly, the production declined fast whe

21、n it fell from 17.34MPa to 6.47MPa with a pressure dropup to 10.87MPa, less than 30% of the saturation pressure9.24MPa.The elastic yield is 3.81104t/MPa. The annual output of oil decreased from the highest 11.9 104t to 6.3 104t, with the annual declining 12%. Late in this stage, 16 wells were open,

22、producing 328.3t of liquid and 195.3t of oil per day with the water cut 40.5%, whose working fluid level was 958m. In this stage,the oil output reached 30.3114 104t atthe recovery percentage 10.4%. Cumulative oil production was 39.5211 104t covering 13.58% of the reserves. 3.3 Flooding Development S

23、tage, June 1998-June 1999Block Luo801 was developed by floodingin June 1998, first with Wells L801-7, L801-15, L801-17. At the end of this stage, 13wellswere open, producing 259.6t of liquid and 96.7t of oil per day withthe water cut 62.8%. Theworking fluid level was 1399m. At this stage, 2.3612 104

24、t of oil, 0.81% of the reserves, was obtained. The cumulative oil production reached 41.8823 104t, 14.39% of the reserves. 3.4 MEOR TestStage, July 1999-December 2010MEORwas launched in Luo801 in July 1999. In the initial phase, micro-organisms was injected intothree injection wells (L801-7, L801-15

25、, L801-17), in September 2002 the recovery pattern was adjusted to have the middle two injection wells ( L801-3, L801-18) injected with the aid of air compressorsinjecting air.As of December 2010, 14 oil wells in Luo801 were put into operation, 12 were opened and producing 448.2t of liquid and 60.3t

26、 of oil per day. The cumulative oil recovery was 85.6572 104t with the water cut 86.5%, covering 28.17% of the reserves. The oil producing rate was0.77 %. A total of five injection wells were opened, injecting 316.2m3 per day with a cumulative injection110.023 104m3. The monthly injection-production

27、 ratio was 0.71 and the cumulative injection-production ratio was 0.40. Two MEOR test wells were injected with 145m3 of water per day. 4. Overview of MEOR Field Test Implementation The implementation of MEOR field test of Block Luo801 can be divided into two phases. July 1999 to September 2002 is th

28、e routine MEOR phase, when microbial liquid and nutrient were injected from the threeside injection wells. The liquid contains 4 types of bacteria, producing similar substance as biosurfactant; main ingredients of the nutrient solution were sugarand a small amount of inorganic salt. 11wells were aff

29、ected in the test. By periodic injection technique, the bacterial liquid and nutrient solution were injected into the formation once every 20 dayswith water. September 2002 to December 2010 is the air aidedMEOR phase. Air injection equipment was adopted. Microbial liquid and nutrient solution were i

30、njected into two middle wells (L801-3, L801-18) of the block, affecting 14 wells. In addition to water injection normally, air was injected 12 hours a day. As to December 2010, 3235tof bacteria liquid, 3475t of solid nutrient and 36.41 104Nm3 of air were injected. 5. Analysis of Test Results After t

31、he implementation of MEOR, the overall comprehensive water cut increasing is inhibited in the test area, the natural decline ofproduction is slowed down andthe daily oil production rises steadily. Especially after the implementation of air-aidedMEOR, the production is better than MEOR stage and appa

32、rently better than the production status before the test. 5.1 Affect of MEORon Comprehensive Water Cut of Oil Wells in Test AreaAfter changing into the water injection recovery, the water cut increasing reached as high as up to 8.43%. During the implementation of MEOR, the water cut increasing signi

33、ficantly slowed down. The water cut increasing rate has been less than 1% for 7 years continuously, showing that the water cut increasing has been effectively suppressed. The water cut curvein the test area shows two trends with different characteristics 5-6 months after the implementation of MEOR a

34、nd air aided MEOR. Compared with the water cut curve of water flooding development, the curve of MEOR has a “funnel” shape with wider opening and shallower bottom, lasting a longer time with a slower pick up. Furthermore, with the recovery percentage, the water cut increasing rises slower. This indi

35、cates that MEOR technique,milder and effective in longer time, has better improving effect on reservoirs than chemical flooding recovery, (Figure 2). Figure 2 Relationship between water cut and recovery percentage 5.2 Effect of MEOR on Oil ProductionDuring the period of MEOR test inBlock Luo801, no

36、measures of significantly changing production were adopted, such as drilling newholes, drilling new wells and increasing injection,besidesroutinemaintenance like oil well pump inspection, operation and parameter adjustment. Therefore, the result can be compared before and after the MEOR test. Based

37、on reservoir engineering methods, the production decline of the test area consists with thehyperbolic diminishing law. As of December 2010, cumulativelyan additional 9.75 104t of oil were produced, and the total product is 3.35% more than that of flooding oil recovery, showing MEOR development is ob

38、viously better than flooding recoveryin the same type of reservoirs (Figure 3). Figure 3 Actual production and decline forecast curves of Luo 801 5.3 Development Effect Improvement1)Slow the natural declineAfter the implementation of MEOR, the production decline has slowed down significantly in Luo8

39、01 with the highest natural decline rate from 32% to -2.3% in 2005. Though production has an overall downward trend, the average decline rate is far lower than that before flooding recovery ( Figure 4). Figure 4 Production decline curve of the test area 2) Enhance oil recoveryAfter the implementatio

40、n of flooding and MEOR, the situation has been improvedin Luo801. The recovery rate rises obviously, which was 38.02% based on Flooding Dynamic Calibration, increasing by 9.42% over the one calculated with the empirical formula of Shengli Oilfield, 28.6%. If the MEOR operation goes on under the curr

41、ent conditions, theultimate oil recovery rate is expected to increase by 10.17%to achieve extra recoverable reserves 29.6 104 t. 5.4 ExtendOil Pump Inspection Cycle Statistics of the oil pump inspection cycle before and after MEOR show that the inspectioncycle is prolonged tremendously, 9.7 monthsvs

42、 21.5 months, 11.8 months outreached. Analysis reveals that micro-organisms and their metabolic production migrated to oil wells to lower the speed of waxingand to maintain the shaft.5.5 Better than Flooding Recovery of Same TypeFault Block Oil Reservoir Blocks Luo9 and Luo801 of Luojia Oilfield are

43、of the same typedevelopment units with similarreservoir conditions. Luo9 is situated to the south of Luo801, its main oil-bearing stratum is S1 of sand section. It was put into operation in 1989, and switched to flooding recovery in 1990 (Table 2). The parameters of the two blocks are listed in the

44、following table. Table 2 Reservoir data sheet of Blocks Luo9 and Luo801ItemBlockItemBlockLuo801 Luo9 Luo801 Luo9Reservoir typeLithologic- structuralLithologic- structuralReservoir temperature ()75-8095Oil bearing area (km2)1.253.7Oil volume factor1.12791.26Reserves(104t)291231Ground oil viscosity(mP

45、as)221.716.8Commissioning date1994.51988.12Original oil and gas ratio3289Injection date1998.61990.11Relative density0.9460.91Reservoir depth(m)1680-19202020-2040Porosity (%)2123Net thickness(m)15.55.5Oil saturation (%)6066Air permeability (10-3um2)211.6174Formation water TDS (mg/L)5000-1100011000Oil

46、 freezing point（）11-2029Formation water typeNaHCO3NaHCO3By comparison, it is clear that the nature of oil from Luo9 is better with the ground oil viscosity 16.8MPa.s, formationoil viscosity 6.5mPa.s, sulfur 0.8%, wax 17.1%, freezing point 29and its water and oil ratio is lower than that of Luo801. I

47、t was water injected during the initial stage so as to compensate the formation energy in time, ensuring the flooding development effect. Its benchmark flooding recovery is 34.1%. The reservoir temperature of Block Luo801 is ranging from 75 to 80, the viscosity of crude oil is relatively high with t

48、he ground oil viscosity 221.7mPa.s, formationcrude oilviscosity 12.8mPa.s and wax 3.7%. It has been degassedby dissolved gas during the stage of natural energy development. At the pre-MEOR stage, its ground viscosity of crude oil reached 221.7mPa.s, the viscosity difference between water and oil was

49、 relatively large. The water cut and recovery percentage curves of the two blocks show when recovery percentage is greater than 20%, Luo801 curveextends downward to form a “funnel”. The development data of Luo801after adopting MEOR can establish the recovery of Luo801 as 38.0%, better than flood dev

50、elopment recovery in Luo9. This shows that MEOReffect is better than that of water flooding (Figure 5). Figure 5 Relationship between water cut and recovery percentage curves5.6 Characteristics of Microbial Activity in ReservoirsDuring the test, microorganisms and their metabolic productionof the pr

51、oduced fluid have been sampled and analyzed regularly.The analysis result shows that after implementing MEOR, the bacterial density increases significantly in theproduced fluid, gradually stabilizing ata magnitude103-4 / ml, while density of the samplebefore the test is only below 10 / ml. Analysis

52、on concentration of acetate in the produced fluid discloses thataverage acetate concentration from the test area is 70mg/L before the test, which changes to 420.0mg/L- 682.0mg/L, averaging 523.0 mg/L, after the implementation of MEOR(Figure 6). During the test, the composition of produced gas was an

53、alyzed and the relative concentration of methane gas was found to increase (Figure 7). The researchers believe that as the anaerobic anaerobicbacteria in the reservoir is activated, part of the acetate is utilized by anaerobic microorganisms to have the acetate concentration decrease. Monitoring onthe methanobacterium content in theproduced fluid reveals that the number of total bacteria and methanogenic bacteria levels continue to rise, which might be