Research Of Improving Water Injection Effect Of Lower Karamay Formation In Xia 18 Block

Lower karamay formation in X18 district is a complicated and massive conglomerate low permeability reservoir with gas cap.The porosity of reservoir is 12%and the permeability is 8.3×10^-3?m².The reservoir was development by linear well network since 1991.The distance between wells is 350 meters.Due to poor physical property,long time development and gas channeling,the development indicators gradually become worse from the early stage of development to the end of 2010.For example,the formation pressure has been decreased from 16MPa to 8.3MPa,the rate of insufficient water injection wells has increased to 45%and the composite decline rates of verified oil has increased to 15.2%.In order to slow down the decrement,according to the existing reservoir geological conditions and ground technology equipment,it is urgent to carry out the research on the comprehensive management countermeasures for improving water flooding effectiveness,so as to improve the effect of water injection.This article concern over the characteristic that fault block in this area is complex and varied,carried out studies of increase pressure of waterflood,improving water flooding regime,fine water injection and partition reasonable injection/production strategy.In addition,combined with fine research of formation,research of numerical simulation and reservoir engineering,research of residual oil distribution disciplinarian,Governance programmers and measures have been carried out.Four aspects of work have been carried out in recent years:Through the analysis of geological factors,we think that the reservoir has poor physical property and moderate-strong water sensitivity.After long time waterflood development,waterflood pressure is bound to rise.This is the primary cause of lack of injection of injection wells.Through the analysis of water injection system factors,we believe that the mismatch between the increasingly aging water injection system and the growing geological demand is the main factor of reservoir under injection.After carrying out the transformation of pumping stations in 2014 and the system was pumped up for 2.0MPa,insufficient water injection wells has reduced by 8 wells and amount of insufficient water injection decreased by 382 m^3/d.This is the foundation for the reservoir to"inject enough water".Combining the reservoir description,we realize that the remaining oil is enriched in S₇⁴⁺⁵and S₈ subzones.The adjustment of injection/production structure and fine injection of subzone is carried out pertinently.5 wells is converted,re-perforation is used in 5 wells and separate injection is used in 5wells.The rate of reservoir separate injection increased by22.5%.The cumulative thickness of the liquid section and the cumulative thickness of the water absorption section increased by 17.2%,and reached target of"inject good water and fine water injection".Based on the research of reasonable injection/production strategy which is“zoning,classification and separate wells”.We have determined some reasonable parameters like formation pressure?East area is 10.5MPa,West area is 11MPa?and injection production ratio?1.6?.Combined with well group"adjustment,expansion,extraction,control and citation",the three-dimensional regulation from reservoir to single well is carried out.The pressure maintenance degree is increased by 9.6%,so as to achieve“effective reservoir water injection”.Through fine structure research,we believe that the remaining oil enrichment area is located in some high point near the fault.Measures to increase production are carried out pertinently on 29 wells.In the first year,additional well production increased from 140 tons to455 tons.Through nearly four years of comprehensive management,reservoir production situation gets better and better every year.Water cut rising rate decreased from 8.2%to-14%,composite decline rates of verified oil decreased from 15.2%to 2.7%,single well measures average annual growth of more than 388 tons.Final waterflood recovery efficiency increased by 4.7%.Corresponding waterflood recoverable reserves increased 440 thousand tons.