低渗透油田生物酶降压增注技术

Technique of Pressure Decreasing and Injection Increasing by Biological Enzyme in the Low Permeability Oilfield

生物酶能将岩石表面的润湿性转变为亲水性,使原油从岩石颗粒表面脱落,降低残余油饱和度,可有效改善低渗透油田注水压力高、油井受效差的问题,提高驱油效率。通过洗油能力评价、界面张力测定、表面吸附性评价、腐蚀性检测、生物酶降压能力等室内模拟实验对生物酶性能进行评价,结果表明:生物酶浓度在2.0%时,界面张力较低,注入压力平均降幅为51.4%,并且对N80钢质不具腐蚀性,综合考虑多方面因素,最终决定注入生物酶体积倍数选为0.006PV。现场试验选取了A油田试验区块的6口水井极其连通的24口油井作为试验井组,累计注入生物酶原液270t,酶溶液总注入量为11422m3。试验一年以后,水井注水压力下降,视吸水指数上升,层间吸水状况得到改善;连通油井产量略有回升,综合含水保持稳定,地层压力恢复速度明显提高,并且增加了新的采出油位,累计增油3519t,阶段采收率提高了0.38%,为解决外围三类储层注水开发无法建立有效驱替体系的问题进行了有益的探索。

Biological enzyme can make residual oil saturation drop for turning wettability of rock surface to water wet and making crude oil fall off from rock particles surface.It also can solve the problems of high injection pressure and poor response of the oil well in the low permeability oilfield and then enhance displacement efficiency.The properties of the biological enzyme were evaluated through the laboratory experiments on displacement efficiency,interfacial tension,and characteristic of surface adsorption,corrosion behavior and depressurization of the biological enzyme.The results show that when the concentration of the biological enzyme is 2.0%,the interfacial tension is low and injection pressure drops by 51.4% averagely ,and it has no corrosiveness for N80 steel.So 0.006PV of the biological enzyme should be injected according to the comprehensive factors.In the field,six injection wells and their connected 24 oil wells make up of the test well group in the tested block of A oilfield.Cumulative injected original enzyme is 270t and total injected enzyme solution is 11422m3.After one year,injection pressure dropped and apparent water injectivity index rose,and interbedded injectivity behavior was improved in the injection wells.In the connected oil wells ,oil production rose a little and composite water cut has no change and rate of formation pressure recovery increased obviously.And more oil was produced with 3519t of cumulative incremental oil production and interval rate of production enhanced by 0.38%.It may help to establish an efficient displacement system in water flooding in peripheral three-type reservoirs.