X射线元素录井在文23储气库膏盐岩盖层中完卡层的现场应用

Application of X-ray element logging in horizon determination of halfway completion of gypsum salt caprocks in Wen 23 gas storage facility

膏盐岩盖层厚度是影响储气库盖层封闭性的首要因素,同时膏盐岩层段顶底的确定也决定着固井质量是否合格。文23储气库作为超大型储气库,精准卡取盖层顶底和厚度对该储气库建设至关重要。利用X射线元素分析能更直观地反映出地层元素变化,文23储气库膏盐岩盖层段特征元素Sr、Zr和Ca元素具有线性相关性,进入膏盐岩层Sr、Zr元素值急剧升高,膏盐岩层底Sr、Zr含量出现异常高值,曲线呈台阶状;Fe、K元素值变小,膏盐岩层底具有异常低峰值,S元素在膏盐岩层底有异常高峰值。Sr/Ba比值、Fe/Mn比值在膏盐岩层底表现为异常高值和异常低值,据此判断进入膏盐岩层底;Mg/Al比值为该区膏盐岩顶底特征比值元素,进入膏盐岩层Mg/Al比值会大幅度升高,Mg/Al比值在膏盐岩层顶和膏盐岩层底均存在一个尖峰,据此可以判断到达膏盐岩盖层顶底。

The thickness of gypsum salt caprocks is the primary factor affecting the sealing property of caprocks of gas storage facilities.At the same time,the determination of the top and bottom of gypsum salt rock section determines whether cementing quality is qualified or not.Therefore,Wen 23 gas storage facility as the first ultra-large gas storage facility with 10 billion storage capacity in Sinopec,accurately determining the top,bottom and thickness of caprocks is very important for the construction of gas storage facility.Using X-ray element analysis can more intuitively reflect the changes of formation elements.The characteristic elements Sr,Zr and Ca in gypsum salt caprocks of Wen 23 gas storage facility have linear correlation.Sr and Zr values increase sharply when entering gypsum salt rock layer.The content of Sr and Zr at the bottom of gypsum salt rock is abnormally high,and the curve is stepped.Fe and K values become smaller,and the bottom of gypsum salt rock has an abnormal platykurtic value.S element has an abnormal peak value at the bottom of gypsum salt rock.The ratios of Sr to Ba and Fe to Mn show abnormal high value and abnormal low value at the bottom of gypsum salt rock.The bottom of gypsum salt rock is judged accordingly.The ratio of Mg to Al is the characteristic ratio of the top and bottom of gypsum salt rocks in this region.The ratio of Mg to Al in gypsum salt rock layers will increase greatly.There is a peakedness of the ratio of Mg to Al at the top and bottom of gypsum salt rock section,which can be used to judge the top and bottom of the caprocks.