渝西地区龙马溪组页岩低阻主控因素及有利区预测

Main controlling factors of the low resistivity Longmaxi Formation shale and prediction of favorable area in Yuxi Area

根据岩心、测井、地震及分析化验资料,分析渝西地区龙马溪组页岩含气量与测井电阻率、测井电阻率与黄铁矿、总有机碳质量分数、热演化程度、含水饱和度、裂缝发育程度,以及含气量与低阻主控因素的关系,明确低阻页岩的电阻率界限与分布特征,研究页岩低阻的主控因素及其对含气性的控制作用并优选低阻页岩气有利区。结果表明:研究区低阻页岩的电阻率小于15Ω·m,分布于云锦向斜南部、临江向斜南部;云锦向斜南部远离断裂区域的页岩低阻主控因素为黄铁矿、过成熟的大量有机质,云锦向斜南部靠近断裂区域的页岩低阻主控因素为含水饱和度、过成熟的大量有机质及黄铁矿,临江向斜南部页岩低阻主控因素为含水饱和度、过成熟的大量有机质,当导电物质在页岩中达到一定量时,页岩内部形成高导电通道,从而形成低阻;低阻页岩发育区内有3个低阻页岩气有利区,面积由大到小为213.6、29.8、8.6 km^(2)。该结果为降低低阻页岩气勘探风险提供地质基础。

Based on core,well logging,seismic and analytical data,the resistivity boundary and distribution characteristics of low resistivity shales in Longmaxi Formation of Yuxi Area are clarified,the main controlling factors of low resistivity shale are identified,the control effect of main controlling factors of low resistivity shale on gas content is revealed,and the favorable area of low resistivity shale gas is optimized by analyzing the relationship between gas content and well logging resistivity,the relationship between good logging resistivity and pyrite,organic matter,thermal evolution degree,water saturation and fracture development degree,and the relationship between gas content and main control factors of low resistivity shale.The results show that the resistivity in low resistivity shale is less than 15Ω·m and distributes in the south of the Yunjin Syncline and Linjiang Syncline.The main controlling factors of low resistivity in the shale of the southern part of the Yunjin Syncline away from the fracture area are pyrite,over-mature large amounts of organic matter,the main controlling factors of low resistivity in the shale of the southern part of the Yunjin Syncline near the fracture area are water saturation,over-mature large amounts of organic matter and pyrite,and the main controlling factors of low resistivity in the shale of the southern part of the Linjiang Syncline are water saturation,over-mature large amount of organic matter,when these conductive materials reach a certain amount in the shale,high conductive channels are formed inside the shale,thus forming low resistivity.There are three favorable areas of low resistivity shale gas in the low resistivity shale development zone,and the areas are 213.6,29.8 and 8.6 km^(2)respectively.The research results provide a solid geological foundation for reducing the risk of low-resistivity shale gas exploration.