鄂尔多斯塔巴庙地区上古生界天然气成藏机理分析

以鄂尔多斯塔巴庙地区上古生界气藏的天然气组分特征、气藏产层现今压力特征和区域性裂缝特征研究为基础,对气藏的成藏过程进行了分析。据二次运移特征把成藏分为两个阶段:一是天然气首先主要富集于盒1段及其以下层段中,形成高温高压的太原组、山西组和盒1段等早期气藏;二是区域抬升剥蚀后,下伏天然气沿后期产生的大量高角度裂缝再运移进入浅部的盒2~3段中形成压力系数高和轻烃含量高的晚期气藏。具有物性封闭和超压封闭双重作用的上石盒子组泥质岩区域盖层和天然气运聚动平衡,使大量天然气得以保存至今。

Analysis on Hydrocarbon Accumulation Mechanism of Upper Paleozoic Gas in Tabamiao Area of Ordos Basin

By studying the characteristics of natural gas composition, the process of gas accumulation is analyzed in Tabamiao area of Ordos Basin. The process of gas accumulation can be divided into two stages according to the secondary migration: the natural gas is concentrated in P_1X_1 and under-layers, high temperature and pressure for early stage gas accumulation in C_3t, P1s and P_1X_1 is formed; the natural gas produced in formation migrates upwards to the P_1X_2, P_1X_3 after the regional uplift and erosion along quantities of high angle fracture are developed at the late stage, high pressure coefficient and light hydrocarbon content of gas accumulation are formed. The argillite regional caprock is physical seal and overpressure seal in upper Shihezi Formation, dynamic balance with natural gas migration and accumulation is caused, thus quantities of natural gas are conserved to nowadays.