致密砂岩气储层岩性测井综合评价技术

Integrated logging evaluation technology for tight sandstone gas reservoir lithology

鄂尔多斯盆地大宁区块石炭系和二叠系致密砂岩气储层发育,具有横向分布广泛、纵向分布稳定的特点。岩心及试油等资料显示,大宁地区致密砂岩气储层岩石类型多样,且岩石类型不同,储层物性及含气性也存在明显差别,利用常规测井方法开展致密砂岩气储层岩石类型评价困难。通过综合分析地质、岩心资料,确定了目标区块致密砂岩气储层4种主要岩石类型,分别为石英砂岩、岩屑石英砂岩、长石岩屑砂岩、岩屑砂岩。在明确这4种主要岩石类型测井资料响应特征的基础上,优选补偿密度、补偿声波、补偿中子、自然伽马测井曲线,采用“三步剥离法”开展岩石类型精细评价,有效提高了致密砂岩气储层岩性识别准确率,并实现了岩石类型分类连续自动判别。该方法有效解决了致密砂岩气储层岩石类型测井评价难题,提高了利用常规测井资料进行岩性评价的精度。

Carboniferous and Permian tight sandstone gas reservoirs are developed in Daning area of Ordos Basin,with the characteristics of wide horizontal distribution and stable vertical distribution.According to core,well test and other data,the tight sandstone gas reservoirs in Daning area have various rock types and different rock types,and there are obvious differences in reservoir physical properties and gas bearing properties.It is difficult to evaluate the tight sandstone gas reservoir rock types by conventional logging methods.Through integrated analysis of geologic and core data,four main rock types of tight sandstone gas reservoirs in the target block are determined,namely quartzose sandstone,lithic quartzose sandstone,feldspar lithic sandstone and lithic sandstone.On the basis of clarifying the response characteristics of the logging data of the four main rock types,the compensated density,compensated acoustic wave,compensated neutron and gamma ray logs are optimized,and the"three-step stripping method"is used to carry out the fine evaluation of rock types,which effectively improves the lithology identification accuracy of tight sandstone gas reservoirs and realizes the continuous and automatic discrimination of rock type classification.This method effectively solves the problem of rock type logging evaluation of tight sandstone gas reservoirs and improves the precision of lithology evaluation using conventional logging data.