Study On The Under-injection Regularity Of The Chang 8 Interval In The Z Blocks Of Ultra-low Permeability Reservoirs

Z Blocks,as one of the important areas of increase reserve and production in Ji'Yuan Oilfield,its main production reservoir,Chang 8 reservoir,is a typical ultra-low permeability reservoir.In recent years,the insufficient injection of water injection wells has been particularly serious.In order to solve the problem of difficult water injection with high pressure of water injection wells in the Chang 8 reservoir in the study area,comprehensive geological research,core analysis experiments,reservoir engineering analysis,and fuzzy comprehensive evaluation were used to analyze the reservoir characteristics and reservoirs of the Chang 8 reservoir in the study area.Analysis on factors such as sensitivity,water quality and water type compatibility,carry out research on the status,distribution law,undercharacteristics,and influencing mechanism of underinjection wells in the study area,and systematically analyze the causes of underinjection.Involving many factors and complicated interactions among factors,mathematical methods such as principal component analysis and principle of maximum membership are used to carry out auxiliary analysis to form a method for determining the main control factors of under-injection wells,one by one for the 52under-injection wells in the study area The main control factors for injection are analyzed.The analysis result is that the main control factors for the under-injection in Chang 8 reservoir in the study area are mainly the poor reservoir properties of the reservoir,followed by incompatible water types and poor water quality of the injected water.At the same time,water injection wells caused by reservoir physical properties and water type compatibility are mostly long-term under-injection wells,and water injection wells caused by sensitivity and injection water quality are mostly late-injection wells."One major influencing factor three minor influencing factors" characteristics: " One major influencing factor " refers to poor physical properties of the reservoir and is widely distributed throughout the study area;" three minor influencing factors " refers to incompatible water types,poor injection water quality,strong reservoir sensitivity,and local impact Larger.It also puts forward the under-injection treatment ideas for various types of under-injection wells,and provides the theoretical basis for the subsequent targeted development of comprehensive reservoir treatment plans.