元坝地区须二段低电阻率气层成因与测井评价方法

针对元坝地区须二段储层气层判识难度大、传统测井评价方法解释符合率较低的问题，开展了低电阻率气层成因分析及测井评价方法研究。在深入分析须二下亚段沉积微相、储层特征和测录井、测试及试验分析资料的基础上，认为储层矿物组分、孔隙结构、岩石粒径和胶结类型等是影响气层电阻率高低的主要因素，石英含量与测井电阻率呈正相关关系；建立了储层内岩性细分及识别有效储层的测井模式，综合岩性、电阻率和含水饱和度等参数，形成了不同岩性气层的评价标准和低电阻率气层的测井评价方法。该评价方法在元坝地区多口探井陆相致密砂岩气层评价中进行了应用，提升了致密砂岩气层的测井评价成功率，使元坝地区陆相致密砂岩气藏勘探取得了突破性进展。研究与应用表明，利用建立的低电阻率气层测井评价方法可以解决低电阻率气层的漏层和错判的问题，提高解释的成功率。 

The Origin of Tx_2 Low Resistivity Gas Reservoirs in the Yuanba Area and Their Logging Evaluation Method

Due to the fact that gas reservoir identification is difficult in the Tx2 formation in the Yuanba Area,and the interpretation coincidence rate is lower by conventional logging evaluation methods,the origin of low-resistivity gas reservoirs and its logging evaluation methods have been studied.On the basis of analysis of sedimentary microfacies,reservoir characteristics,the data of well logging,mud logging,testing and experiment in Tx2x gas reservoirs,a conclusion was drawn that the main factors influencing the resistivity value in gas reservoirs are reservoir mineral composition,pore structure,grain size and cementation type,and quartz content had a positive correlation with logging resistivity. The logging mode for lithology subdivision and identification in reservoir was established,and determined the comprehensive lithology, resistivity and water saturation,etc.,so it was possible to form the evaluation criteria for gas reservoir with different lithology and logging evaluation method for gas reservoir with low resistivity. This method has been applied in multiple exploration wells in Yuanba Area to evaluate continental tight sandstone gas reservoirs,and as a result,the success rate of logging evaluation was improved significantly,and a breakthrough was made in the exploration of continental tight sandstone gas reservoir in the Yuanba Area. Research and application showed that the success rate of logging evaluation on tight sandstone gas reservoirs could be increased by establishing the logging evaluation method for low resistivity gas reservoirs,which thus could solve the problems of overlooking low resistivity gas reservoirs and accompanying errors in judgment.