鄂尔多斯盆地三叠系延长组7段高伽马砂岩测井识别及其展布特征

Logging identification and distribution characteristics of high-gamma sandstones in the 7th member of Triassic Yanchang Formation, Ordos Basin

游富粮 柳广弟 孙明亮 李超正 刘祥柏 安成 王子昕 李亿殊

YOU Fuliang LIU Guangdi SUN Mingliang LI Chaozheng LIU Xiangbai AN Cheng WANG Zixin LI Yishu

中国石油大学(北京) 地球科学学院，北京 102249 油气资源与探测国家重点实验室，北京 102249 中国石油勘探开发研究院，北京 100083

College of Geosciences, China University of Petroleum Beijing (Beijing), Beijing 102249, China State Key Laboratory of Petroleum Resource and Prospecting, China University of Petroleum (Beijing), Beijing 102249, China Research Institute of Petroleum Exploration & Development, PetroChina, Beijing 100083, China

鄂尔多斯盆地三叠系延长组长7段泥页岩层系内发育大量的砂岩夹层，这些砂岩夹层常伴有自然伽马值异常高的现象，部分砂岩的自然伽马值可高达330.5 API，在测井剖面上极易与泥页岩混淆。为识别高伽马砂岩，按照粒度和结构特征将该区延长组长7段碎屑岩划分为细砂岩、粉砂岩、泥质粉砂岩、粉砂质泥岩、泥岩和页岩，并应用常规测井数据运算组合成2个新参数——参数A和参数B，参数A和参数B组成的交汇图版以及自然伽马测井曲线，可有效区分识别出长7段中的正常砂岩和高伽马砂岩。长7段高伽马砂岩的累计厚度平面展布图表明，高伽马砂岩主要位于研究区的西南部；高伽马砂岩由湖盆边缘向湖盆中心呈指状发散展布的特征指示，其形成可能与长7段沉积期间的火山喷发有关。

A large number of sandstone interlayers were developed in the shale strata of the 7th member of the Triassic Yanchang Formation (Chang 7 member) in the Ordos Basin. These sandstone interlayers are frequently accompanied by abnormally high natural gamma values as high as 330.5 API. As a result, they are undistingui shable from shale on well profile. To characterize the high-gamma sandstones, the clastic rocks of the Chang 7 member were classified into fine sandstone, siltstone, argillaceous siltstone, silty mudstone, mudstone and shale according to grain size and structural characteristics. Conventional logging data were recalculated and combined into two new parameters—A and B. The new intersection chart composed of parameters A and B and natural gamma logging data can effectively distinguish and identify normal sandstone and high-gamma sandstone in the Chang 7 member. The plane distribution of cumulative thickness of high-gamma sandstone in the Chang 7 member shows that the high-gamma sandstone is mainly located in the southwest of the study area. The finger-like distribution of high-gamma sandstone from the edge to the center of the lake basin indicates that its formation may be related to the volcanic eruption during sedimentary period.

中国石油天然气集团有限公司—中国石油大学(北京)战略合作科技专项 ZLZX2020-02

https://doi.org/10.11781/sysydz202301099