沁水盆地与鄂尔多斯盆地上古生界致密气成藏条件类比及勘探潜力

Comparative study on accumulation conditions of the tight gas in the upper paleozoic of the Qinshui Basin and Ordos Basin and its exploration potential

为了探讨沁水盆地上古生界致密气的勘探潜力,采用类比分析的方法,系统分析了沁水盆地与鄂尔多斯盆地的构造-沉积演化、源储条件及成藏规律的差异性。研究表明：（1）沁水盆地与鄂尔多斯盆地共同经历了构造稳定期、构造分异期和构造定型期,二者在石炭—二叠纪具有相似的沉积演化过程,主要以海陆过渡相和陆相沉积为主。（2）沁水盆地上古生界煤层总厚度介于3～17 m,与鄂尔多斯盆地相当,镜质体反射率介于2.0%～4.5%,热演化程度高于鄂尔多斯盆地,生烃强度更大。（3）鄂尔多斯盆地致密气主要目的层为太原组、山西组和下石盒子组,次为上石盒子组和石千峰组;沁水盆地103口井测井解释结果显示,太原组和上石盒子组可疑致密气层较多,共计72层,占总数的64.9%,次为山西组和下石盒子组。（4）沁水盆地上古生界致密气具有初次运移和二次运移成藏两种模式,保存条件是成藏的关键因素,盆地中南部的向斜核部、断裂不发育的翼部是勘探的有利区。

To discuss the exploration potential of tight gas in the Upper Paleozoic of Qinshui Basin,a systematic analogy analysis on difference about tectonic-sedimentary evolution,source-storage conditions,and accumulation regulation in Ordos and Qinshui basin was made.Some conclusions are as follows：（ 1） Qinshui Basin and Ordos Basin have experienced tectonic stability,differentiation and finalization phase with similar sedimentary evolution mainly composed of transitional and continental sediments in carboniferous-Permian.（ 2） The total coal seam thickness in the Upper Palaeozoic of Qinshui Basin is about 3-17 m,as same as in the Ordos Basin; and its vitrinite reflectance is about 2. 0%-4. 5% with higher thermal evolution and stronger hydrocarbon-generating intensity than that of Ordos Basin.（ 3）Taiyuan,Shanxi and Xiashihezi Formations are the main targets,and the next are Shangshihezi and Shiqianfeng Formations in the Ordos Basin.103 well logs were reinterpreted in the Qinshui Basin,which indicates that there are 72 questionable tight gas bearing layers accounting for 64.9% of the totals in the Taiyuan and Shangshihezi Formations,fol-lowed by Shanxi and Xiashihezi Formations.（ 4） Based on the comprehensive analysis,two gas accumulation models of primary migration and secondary migration are presented in the Upper Paleozoic of the Qinshui Basin,preservation condition is the key factor in the tight gas accumulation,and the syncline core and wing with little fault in the southcentral basin are favorable exploration areas.