大庆头台油田微生物驱油先导性矿场试验室内评价研究

Preparatory Laboratory Researches to Pilot Trial Project on MEOR at Toutai, Daqing

选定进行微生物先导性矿场试验的大庆头台油田,有效孔隙度11.5%,平均渗透率0.125μm2,油层温度60～65℃,原油含蜡25%,凝固点31.5℃,地下粘度4.0mPap·s,地面密度0.8624t/m3,地层水矿化度627mg/L,pH值7～8。对筛选出的多株采油菌进行了室内评价,结果表明:6个菌种(P24,SHB,X2,RB,A白,AQ)在65℃下与头台原油共同发酵后,原油中轻组分增加,按参数∑C21/∑C22计算的增加率为41.0%～97.0%,以X2(97.0%)和SHB(94.0%)为最高;原油粘度(48.9mPa·s)下降17.7%～44.2%,以A白(44.2%)和SHB(41.5%)下降最多;发酵液pH值由7.0降至5.0～6.0,发酵液与原油间的界面张力(35.6mN/m)下降56.8%～66.3%;5个菌种(SHB,X2,P24,U1 6,A白)在45～65℃下都能生长,菌数达108～1010个/mL以上;7种菌(以上5种及AU1,5号)尺寸最大为1.2～2.4μm,与头台油藏的渗透率相适应;在渗透率0.559,0.581,0.590μm2的2个均质、1个非均质人造岩心上,水驱之后(水驱采收率33.1%,36.5%,53.6%)注入菌数为107～108个/mL的菌液0.3PV,继续水驱,流出液菌数为108～109个/mL,采收率提高6.08%,5.81%,4.60%,平均为5.81%。图2表6参5。

The reservoirs of Toutai, Daqing, where a pilot trial project on MEOR is to be performed, are characterized by effective porosity 11.5%, average permeability 0.15 μm2, and temperature 60—65℃, the crude oil—by wax content 25%, pour point 31.5℃, viscosity inplace 4.0 mPa·s, and density at surface 0.862 4 t/m3 and the formation water—by TSD=627 mg/L and pH value 7—8. A lot of bacterial strains selected for this project is evaluated in laboratory and following results are obtained. Fermentation of the crude oil with 6 bacterial species (denoted as P24, SHB, X2, RB, Awhite, and AQ) at 65℃ leads to enrichment of light fractions by 41.0—97.0% according to variation of parameter ∑C21/∑C22 with the highest increment 97.0% for X2 and 94.0% for SHB, to reduction in crude oil viscosity from 48.9 mPa·s by 17.7—44.2% with the most decrease 44.2% for AWhite and 41.5% for SHB, to lowering pH value of bacterial cultures from 7.0 to 5.0—6.0, to reduction in IFTs between the crude and the cultures from 35.6 mN/m by 56.6—66.3%. 5 bacterial species (SHB,X2,P24,U16, and AWhite) grow well at 45—65℃ and the population of bacteria reaches 108—1010 cell/mL. 7 bacterial species (the 5 above mentioned plus Au1 and #5) have the largest size of 1.2—2.4 μm, which fits to the reservoir permeability. Into 2 heterogeneous and 1 homogeneous artificial cores of permeability 0.559,0.581,and 0.590 μm2 after having water flooded to 33.1%, 36.5%, and 53.6% of oil recovered 0.3 PV of bacterial culture with bacteria population 107—108 cell/mL is injected at 65℃ and is followed by water flooding, the bacteria population in effluent increases to 108—109 cell/mL and the enhancement in oil recovery of 6.08%, 5.81%, and 4.60%, respectively, and 5.81% in average are observed.