微生物采油技术在中国胜利油田罗801区块的试验A-英文译文2

1、MEOR Field test at Block Luo801of Shengli Oil Field inChinaAbstractA Microbial Enhanced Oil Recovery (MEOR) field test has been implemented for 10 consecutive years at the 75°C -80°C Block Luo801 in Shengli Oil Field in China, where microbial formulati on and nu trie nt, produc ing biosurf

2、acta nt, were injected in to oil wells. After the impleme ntatio n of MEOR, the produced fluid samples from the oil wells were an alyzed and found an in crease of bacteria and archaea in waterphase stabilizi ng at 1&4cell/ml and a soar of acetate in concen trati on from 70mg/L to 523.0 mg/L with

3、out finding the type of injected microbial types, suggesti ng the nu trie nt in jected has activated thein dige nous bacteria in the reservoir, whose activities were enhan ced to preve nt the water cut from rising up in the block so as to in crease the oil output. Up to December 2022, the cumulative

4、 in creased product ion of oil has bee n 9.75104t witHthe total output surpass ing that of WaterFloodi ng Oil Recovery (WFOR) by 3.35%. Con sideri ng the cost of injected microbial fluid and nu trie nt, oil in creased per tonne costs about RMB339.56.Keywords: Microbial En ha need Oil Recovery (MEOR)

5、, Field Test, Water Floodi ng1. In troduct ionFault block oil reservoirs occupy an importa nt proporti on in She ngli Oil Field of8China, whose developed geological reserves have reached 9.22 x 10 t but with the comprehe nsive water cut 91.5%. Thus how to stop the product ion decli ne and enhance th

6、e crude oil recovery becomes a major challe nge to develop fault block oil reservoirs with high water cut. Due to the smaller area beari ng oil and the in complete product ion well grid, it is not suitable to carry out chemical enhan cedoil recovery tech no logy for fault block oil reservoirs and al

7、ter native oil recovery tech no logy is expected to be developed for them. Microbial Enhanced Oil Recovery (MEOR) tech no logy is con sidered promisi ng for fault block oil reservoirs, whose related research was not launched until 1990s in Shengli Oil Field by a specialized team en gaged in research

8、 and test in MEOR. Once their purpose was to select the bacteria type, suitable for the reservoir environment and capable to enhance the oil displaceme nt efficie ntly, which was first ground cultured the n injected in to the reservoirs. At the begi nning of this cen tury, researchrevealed in dige n

9、ous bacteria in reservoirs are very active, so the research focus shifted to indigenous bacteria enhan ced oil recovery. Curre ntly, oil reservoirs have bee n con sidered as an ecosystem into which material such as specific microbial formulation, inorganic or organic nu trie nt and air have bee n in

10、jected to regulate them: the microbial com mun itystructure and function in side might cha nge, in creas ing the bacteria den sity, produc ing biosurfacta nt and impro ving the oil-wash efficie ncy through "in situ breedi ng". Based on research in the laboratory, a MEOR field test has been

11、 carried out in Block Luo801 in Shengli Oil Field since 1999. The test method has been adjusted twice in the 10 year period in the hope of explori ng the pote ntial of MEOR tech no logy to improve oil recovery in fault block oil reservoirs.2. Test Area Reservoir GeologyBlock Luo801 is a small block

12、in Shengli Oil Field, a lithologic - structural reservoir with a temperature ranging from 75 °C to 80 °C . It is open in the north and the southern part is closed by an east-west arc fault, where the test area is located on the hanging wall. The area bearing oil is 1.95 km with the crude o

13、il reserves 291 104 t. The reservoir depth is from 1680 m to 1800 m and the original formation pressure is 17.5 MPa.The oil pool of the test area is located on the West Wing of the nose-like structure, whose strata are high in the south and low in the north with an angle ranging from 5o to 6o It pas

14、ses through Permian strata including Shahejie Fm., Dongying Fm., Guan tao Fm. and Pin gyua n Fm. as a lake phase mesoporous and meso-permeable reservoir, whose oil beari ng un its are S1, S3, S4 sand sect ion. with an average porosity 23.5%, an 10-3 m2, and the ground oil viscosity 221.7mPa.s, forma

15、tion water type NaHCO3 and TDS 7795 mg/L. Test area reservoir parameters are shown in Table 1 and the wel' positiois shown in Figure 1.Table 1 MEOR test area reservoir parameters of Luo801ItemDataItemDataOil bearing area km2Formation water TDS mg/L9794Reserves 104t291Formation water typeNaHCO3Re

16、servoir typelithologic-structuralOriginal oil and gas ratio30Reservoir depth (m)1680-1800Original formation pressure (MPa)Porosity %Saturation pressure (MPa)Air permeability 10-3um2218Formation saturation pressuredifference (MPa)Oil saturation 60Current formation pressure10Ground crude oil viscosity

17、 丨353Formation pressure C75-80Figure 1 Tecto nic position of MEOR test area in Luo8013. Test Area Developme nt ProcessLou801 has 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 2003 air aided MEOR began to

18、develop. According to the test area production curve, the developme nt can be divided into four stages, n amely capacity build ing stage, n atural en ergy developme nt stage, flood ing developme nt stage and MEOR test stage.3.1 Cap acity Buildi ng Stage, 1994Wells Luo801 and 805 have bee n fini shed

19、 drilli ng in Block Luo801 in April a nd May 1994 respectively. Since in dustrial oil flow obta ined in S3 and S4, the block was under rolling development as in the same year, an oil bearing area of 2 went into operation involving oil reserves 291 104t with a<new production capability 6104t.In De

20、cember 1994, 16 wells were ope ned and produced 446t of fluid and 417t of oil per day with the water cut 6.5%, oil production rate 5.23%, recovery percentage 3.16%, outputting 9.2097 104t ofoil annually.3.2 Natural Energy Development Stage, 1995 -May 1998This stage features relying on natural energy

21、 when the reservoir was developed at a high speed. With the formatio n pressure dropp ing rapidly, the product ion decli ned fast when it with a pressuredrop up to 10.87MPa, less than 30% of the saturation pressure . The elastic yield is 104t/MPa. The annual output of oil decreased from the highest

22、11.9 104tto 6.3104t, with the ann ual decli ning 12% . Late in this stage, 16wells were open, producing 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 x 104t at the recovery percentage 10.4%. Cumulative o

23、il production was 39.5211 X t coveri ng 13.58% of the reserves.3.3 Flooding Development Stage, June 1998-June 1999Block Luo801 was developed by flooding in June 1998, first with Wells L801-7, L801-15, L801-17. At the end of this stage, 13 wells were open, producing 259.6t of liquid and 96.7t of oil

24、per day with the water cut 62.8%. The working fluid level was 1399m. At this stage, 2.3612104t of<oil, 0.81% of the reserves, was obta in ed. Thecumulative oil production reached 41.8823 1 04t, 14.39% of the reserves.3.4 MEOR Test Stage, July 1999-December 2022MEOR was launched in Luo801 in July

25、1999. In the initial phase, micro-organisms was injected into three injection wells (L801-7, L801-15, 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 compressors injecting air.As of December 2022, 14

26、 oil wells in Luo801 were put into operation, 12 were opened and producing 448.2t of liquid and of oil per day. The cumulative oil recovery was 85.6572 x 104t with the water cut 86.5%, covering 28.17% of the reserves. The oil producing rate was 0.77 %. A total of five injection wells were opened, in

27、jecting3 per day with a cumulative injection 110.023104m3. Thexmonthlyinjection-production ratio was and the cumulative injection-production ratio was 0.40.3Two MEOR test wells were injected with 145m of water per day.4. Overview of MEOR Field Test ImplementationThe implementation of MEOR field test

28、 of Block Luo801 can be divided into two phases. July 1999 to September 2002 is the routine MEOR phase, when microbial liquid and nutrient were injected from the three side injection wells. The liquid contains 4 types of bacteria, producing similar substance as biosurfactant; main ingredients of the

29、 nutrient solution were sugar and a small amount of inorganic salt. 11 wells were affected in the test. By periodic injection technique, the bacterial liquid and nutrient solution were injected into the formation once every 20 days with water. September 2002 to December 2022 is the air aided MEOR ph

30、ase. Air injection equipment was adopted. Microbial liquid and nutrient solution were injected 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 2022, 3235t of bacteria liquid, 3475t of so

31、lid nutrient and 36.41 x104Nm3 of air were injected.5. Analysis of Test ResultsAfter the implementation of MEOR, the overall comprehensive water cut increasing is inhibited in the test area, the natural decline of production is slowed down and the daily oil production rises steadily. Especially afte

32、r the implementationof air-aided MEOR, the product ion is better tha n MEOR stage and appare ntly better than the product ion status before the test.5.1 Affect of MEOR on Comprehe nsive Water Cut of Oil Wells in Test AreaAfter cha nging in to the water injectio n recovery, the water cut in creas ing

33、 reached as high as up to 8.43%. During the implementation of MEOR, the water cut in creas ing sig nifica ntly slowed dow n. The water cut in creas ing rate has bee n less tha n 1% for 7 years continuously, showing that the water cut increasing has been effectively suppressed.The water cut curve in

34、the test area shows two trends with different characteristics 5-6 mon ths after the impleme ntati on of MEOR and 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 Ion ger time with

35、 a slower pick up. Furthermore, with the recovery perce ntage, the water cut in creas ing rises slower. This in dicates that MEOR tech niq ue, milder and effective in Ion ger time, has better impro ving effect on reservoirs tha n chemical floodi ng recovery, (Figure 2).Figure 2 Relati on ship betwee

36、 n water cut and recovery perce ntage5.2 Effect of MEOR on Oil Productio nDuring the period of MEOR test in Block Luo801, no measures of significantly cha nging product ion were adopted, such as drilli ng new holes, drilli ng new wells and increasing injection, besides routine maintenance like oil w

37、ell pump inspection, operati on and parameter adjustme nt. Therefore, the result can be compared before and after the MEOR test. Based on reservoir engin eeri ng methods, the product ion decli ne of the test area consists with the hyperbolic diminishing law. As of December 2022, cumulatively an addi

38、tional 9.75104t of oil were produced, and the total product is3.35% more than that of flooding oil recovery, showing MEOR development is obviously better tha n flood ing recovery in the same type of reservoirs (Figure 3).Figure 3 Actual producti on and decli ne forecast curves of Luo 8015.3 Developm

39、e nt Effect Improveme nt1) Slow the n atural decli neAfter the impleme ntati on of MEOR, the product ion decli ne has slowed dow n significantly in Luo801 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

40、 lower than that before flooding recovery ( Figure 4).2515%率5减递-5-15-2519951997199920012003200520072022时间(年)Figure 4 Product ion decli ne curve of the test area2) Enhance oil recoveryAfter the implementation of flooding and MEOR, the situation has been improved in Luo801. The recovery rate rises obv

41、iously, which was 38.02% based on Floodi ng Dyn amic Calibrati on, in creas ing by 9.42% over the one calculated with the empirical formula of Shengli Oilfield, 28.6%. If the MEOR operation goes on under the curre nt con diti ons, the ultimate oil recovery rate is expected to in crease by 10.17% to

42、achieve extra recoverable reserves 29.6104 t.5.4 Exte nd Oil Pump In specti on CycleStatistics of the oil pump inspection cycle before and after MEOR show that the in specti on cycle is prolon ged treme ndously, 9.7 mon thsvs 21.5 mon ths, 11.8 mon ths outreached. Analysis reveals that micro-organis

43、ms and their metabolic production migrated to oil wells to lower the speed of wax ing and to maintain the shaft.5.5 Better tha n Flood ing Recovery of Same Type Fault Block Oil ReservoirBlocks Luo9 and Luo801 of Luojia Oilfield are of the same type development units with similar reservoir conditions

44、. Luo9 is situated to the south of Luo801, its main oil-beari ng stratum is S1 of sand sect ion. It was put into operati on in 1989, and switched to floodi ng recovery in 1990 (Table 2). The parameters of the two blocks are listed in the following table.Table 2 Reservoir data sheet of Blocks Luo9 an

45、d Luo801ItemBlockItemBlockLuo801Luo9Luo801Luo9Reservoir typeLithologic- structuralLithologic- structuralReservoir temperature (C)75-8095Oil bearing area (km2)Oil volume factorReserves(1(ft)291231Groundoilviscosity(mPas)Commissioning dateOriginal oil and gas ratio3289Injection dateRelative densityRes

46、ervoir depth(m)1680-19202022-2040Porosity (%)2123Net thickness(m)Oil saturation (%)6066Airpermeability(10-3um2)174Formation water TDS(mg/L)5000-1100011000Oil freezing pointC11-2029Formation water typeNaHCO3NaHCO3By comparison, it is clear that the nature of oil from Luo9 is better with the ground oi

47、l viscosity 16.8MPa.s, formation oil viscosity 6.5mPa.s,sulfur 0.8%, wax 17.1%, freezing point 29 °C and its water and oil ratio is lower than that of Luo801. It was water injected during the initial stage so as to compensate the formation energy in time, ensuring the flooding development effec

48、t. Its benchmark flooding recovery is 34.1%. The reservoir temperature of Block Luo801 is ranging from 75C to 80C , the viscosity of crude oil is relatively high with the ground oil viscosity 221.7mPa.s, formation crude oil and wax 3.7%. It has been degassed by dissolved gas during the stage of n at

49、ural en ergy developme nt. At the pre-MEOR stage, its ground viscosity of crude oil reached 221.7mPa.s, the viscosity differenee between water and oil was relatively large. The water cut and recovery perce ntage curves of the two blocks show whe n recovery perce ntage is greater tha n 20%, Luo801 cu

50、rve exte nds dow nward to form a funnel . The development data of Luo801after adopting MEOR can establish the recovery of Luo801 as 38.0%, better than flood development recovery in Luo9. This shows that MEOR effect is better than that of water flooding (Figure 5).100Figure 5 Relati on ship betwee n

51、water cut and recovery perce ntage curves5.6 Characteristics of Microbial Activity in ReservoirsDuring the test, microorga ni sms and their metabolic producti on of the produced fluid have bee n sampled and an alyzed regularly. The an alysis result shows that after impleme nting MEOR, the bacterial

52、den sity in creases sig nifica ntly in the produced fluid, gradually stabilizing at a magnitude 103-4 / ml, while density of the sample before the test is only below 10 / ml. Analysis on concentration of acetate in the produced fluid discloses that average acetate concentration from the test area is

53、 70mg/L before the test, which changes to mg/L -mg/L, averaging 523.0 mg/L, after the implementation of MEOR(Figure 6). During the test, the composition of produced gas was an alyzed and the relative concen trati on of metha ne gas was found to in crease (Figure 7). The researchers believe that as t

54、he an aerobic an aerobicbacteriain the reservoir is activated, part of the acetate is utilized by an aerobic microorga nisms to have the acetate concen trati on decrease. Mon itori ng on the metha nobacterium content in the produced fluid reveals that the number of total bacteria and methanogenic bacteria levels continue to rise, which might be caused by acetate-like m