In response to the difficulty of further tapping the remaining oil and improving the oil recovery rate after heavy oil thermal recovery,taking the Ng5-6 oil reservoir in the Gudao southern area of Shengli Oilfield as an example,an indoor experimental study and field application of endogenous microbial cold production huff and puff after heavy oil thermal recovery were conducted.Experimental studies have shown that the microbial community in the reservoir formation after heavy oil thermal recovery is mainly composed of Bacillus and Pseudomonas;Using orthogonal experimental method to optimize the activator formula,the proportions of carbon source,nitrogen source,and phosphorus source were determined to be 1.0%soluble starch,0.2%potassium nitrate,and 0.05%potassium dihydrogen phosphate.After activation,the bacterial concentration remained above 5×108 cells/mL;The activated metabolites can effectively reduce the viscosity of crude oil,with a viscosity reduction rate of over 90%.It can effectively reduce the interfacial tension between oil and water,and the interfacial tension can be reduced to 0.027 mN/m.After application in the field,the daily production increased from 1.75 t/d before the measures to 6.7 t/d.The water cut decreased from 96.8%before the measures to 78.5%.The effective period of the measures is 640 days,with an accumulated oil production of 1,936 tons and a staged increase in oil production of 1,012 tons.According to the oil price of 2,350 yuan/t,the input-output ratio is as high as 1∶21.6.
heavy oil thermal recoveryendogenous microorganismscold production huff and puffimprove oil recoveryfield application
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