晋南地穹列煤层气赋存区构造应力分析

根据晋南地穹列构造型相分析，恢复了4期应力场：①地洼初动期（印支期）近S－N水平挤压；②地洼激烈期（燕山期）NWW－SEE水平挤压；③地洼余动期（喜山早期）NNE－SSW水平挤压；④地洼余动期（喜山中期）NW－SE、NWW－SEE近水平伸展。其现代构造应力场以NW－SE向伸展应力场为主，但在沁水地穹则表现为NEE－SWW向近水平挤压应力场。有限元模拟分析证实：此局部挤压应力场的动力来源于挽近地质时期太行山和霍山的隆起与抬升，临汾地洼和太原地洼中的伸展应力场则与地洼壳体下部慢源物质逸散所导致的侧向拉伸有关。区内应力降的分布特点与晋南地穹列断裂构造发育程度具有良好的对应相关性，在高应力降区，单位体积煤层气含量显著高于其它地区。模拟主应力差等值线图中两个高主应力差值区恰好与东部沁水地穹中两个高含气量区相对应，充分说明地洼余动期构造应力场中高压应力区是煤层气富集的有利地区。

ANALYSIS OF STRUCTURAL STRESS IN THE COALBED GAS STORAGE AREA IN SOUTH SHANXI GEODOME SERIES

The four structural stress fields - the N-S, NWW-SEE, NNE-SSW trend horizontalcompress and NW-SE or NWW-SEE trend horizontal extension developed during the diwainitial-mobility period (Indosinian), the diwa maximum-mobility period (Yanshanian), thediwa residual-mobility period (Early Himalayanian) and the residual-mobility period (Middie-Late Himalayanian) - are reconstructed by the analysis of the structural style in theSouth Shanxi geodome series. In the geodome series, the current stress field shows principally NW-SE trend extension. However, in the Qinshui geodome, it shows NEE-SWWtrend horizontal compress. The result of the finite element simulation verifies that the dynamics of the compression stress field results from the uplifting of Taihangshang Mountainand Huoshan Mountain and that the extension stress field in Linfen diwa and Taiyuan diwarelates to the lateral extension resulted from the escaping of mantle material.The stress drop distributed over South Shanxi geodome series relates correspondingly tothe developing degree of the faults. In the area of high stress drop, the coalbed gas contentper unit volume is obviously higher than other areas. The two areas of the high differenceprincipal stress of finite element simulation are consistent with the two areas of the high content of coalbed gas in Qinshui geodome. This implies that during diwa residual-mobility period, the high compress stress area is the favorable area of coalbed gas accumulation.