AMT法在黔东北岑巩地区的页岩气勘探试验

A shale gas exploration test with AMT method in Cengong area,Northeast Guizhou

页岩气常见于泥岩、高碳泥岩、页岩及粉砂质岩类夹层中,而储气地层相对于围岩电阻率普遍较低,页岩气的富集指标取决于储气地层有机碳含量、成熟度、干酪根类型、生烃率、埋深和裂缝等,故以先寻找低阻层再进行页岩气富集指标测试的找气思路具有一定可行性。本次试验选择在黔东北岑巩地区开展音频大地电磁(AMT)勘探,确定了两套可能储气的低阻目标层,结合前人在该区的地化分析结果统计出牛蹄塘组页岩地层的技术指标参数,确定了变马冲组下部及牛蹄塘组为主要生气储气地层,前者富集规模较小,后者富集规模较大。W-2井的钻探结果验证了大地电磁法勘探加岩石样品地化分析的组合手段可以以较高的分辨率确定页岩气富集地层的埋深及厚度。

Shale gas is normally in the mudstone,high carbon mudstone,shale and silty rocks.The enrichment indicator of shale gas depend on many factors such as organic carbon content,maturity,kerogen type,hydrocarbon rate,and stratum depth and crack.Because the resistivity of these kinds of strata is always lower than that of the country rocks,we usually look for low resistance layer first and then test the enrichment indicator.To test audio magnetotelluric(AMT)method in the shale gas exploration,we have conducted an AMT survey in Cengong area,Northeast Guizhou,and we have identified two low resistivity targets based on indicator parameters of Niutitang Formation by preview geochemical studies,lower part of Bianmachong Formation and Niutitang Formation.Latter drilling results show that AMT method combined with geochemical tests can effectively determine shale gas formation depth and thickness.