东胜气田某井区山2段“幸存者偏差”影响下的测井气水识别

Logging Identification method of gas and water Affected by survivors’bias of the Shan 2 Member in A well block in Dongsheng gas field

近年来,东胜气田某井区山2段试气取得了较好的成果,但是部分层段试气成果显示,采用常规的声波时差-深感应(或深侧向)电阻率交会图版和常规的气水层测井解释标准选择的测试层段,其试气成果与预期并不对应。分析认为,在应用试气成果建立声波时差-深感应(或深侧向)电阻率交会图版和气水层测井解释标准时,对识别气水层有重要意义的关键信息,其实在选择测试层段的过程中已经被忽略,因而造成交会图版和解释标准识别可靠性较差,即幸存者偏差的影响导致了关键信息的被忽视;为克服幸存者偏差的影响,通过研究测试选层过程中未考虑到的影响因素,如深、中感应电阻率变化幅度差,进一步优化山2段气水识别交会图版和常规测井气水识别标准,较好的识别了气水层。

In recent years,good results have been achieved in the gas testing of Shan 2 member in A well block of Dongsheng gas field.However,some testing results show that the results of the test layers selected by using conventional acoustic time difference deep induction(or deep lateral)resistivity cross plot and conventional gas water layer logging interpretation standards do not correspond to the expectation.The analysis shows that the key information which is of great significance for identifying gas and water layers has been ignored in the process of selecting test intervals when the acoustic transit time deep induction(or deep lateral)resistivity cross plot and gas and water layer logging interpretation standard are established by using gas testing results,resulting in poor reliability of cross plot and interpretation standard identification.That is to say,the influence of survivor bias leads to the neglect of key information.In order to overcome the influence of the deviation,by studying the influence factors not taken into account in the process of testing layer selection,such as the difference in the variation amplitude of deep and medium induction resistivity,further optimizing the gas water identification crossplot of Shan 2 member and the gas water identification standard of conventional logging,the gas and water layers are well identified.