XX地区长8中高电阻率储层出水原因分析

鄂尔多斯盆地某地区长8储层为水下分流河道砂体,岩性以细-中粒岩屑长石砂岩为主,录井显示以油斑为主,测井电性显示为中高电阻率(30～150Ω·m),电性与油层相当,甚至好于油层,常规测井解释多为油层或油水层。但经过压裂改造后试油出水,测井解释符合率极低。利用地质、测井、分析化验和试油等资料,从储层岩心、物性、地层水、原油性质和润湿性等5方面开展了该区长8中高电阻率储层出水原因分析。形成了基于常规测井及核磁共振测井高电阻率储层流体性质判识技术,提高了长8储层测井解释符合率,在实际生产中应用效果显著。

Water-production Causation Analysis for Medium-high Resistivity Reservoir of Changba Formation in XX Area

Chang 8 Formation developed underwater distributary channel sand body in an area of Ordos Basin.The lithology of the reservoir was mainly composed of fine-medium grained lithic argillaceous sandstone,the display of mud logging was dominated by oil spots,and the electricity characteristics of reservoirs was medium-high resistivity(30~150Ω·m).This electrical characteristic was the same as the electrical characteristic of oil layer,even better than the oil layer,so the conventional log interpretation result of this kind of reservoirs were mostly the oil layer or oil-water layers.However,after fracturing and testing,the results shown that most of these reservoirs were water layers,and the log interpretation coincidence rate was very low.Based on the data of geology,logging,analysis test and oil test,this paper analyzes the causes of water production in high resistivity reservoirs in the Chang 8 Formation from 5 aspects,such as reservoir core,physical properties,formation water,crude oil properties and wetting property.According to the results of the analysis,the fluid identification technology of high resistivity reservoir based on conventional logging and NMR logging was formed in this paper.The technology improved the log interpretation coincidence rate of the Chang 8 reservoir greatly and has achieved remarkable application results in the actual production.