煤层气向斜控气论

THEORY OF SYNCLINE-CONTROLLED COALBED METHANE

煤层气富集规律的研究贯穿着煤层气勘探开发的始终,融合了煤田地质学、天然气地质学、流体力学 等学科。文章从向斜部位煤层气富集的实例研究出发,深入分析了向斜部位煤层水对煤层气的作用机理以及应力 性质在褶皱部位的表现特征对煤层气赋存的影响,向斜部位的煤层水具有向心流动机制,流速缓慢,溶解气不因水 的流动而大量散失;另一方面,向斜部位煤层水矿化度高,减小了煤层气在水中的溶解度,从而对煤层气起到一定 的封堵作用;向斜构造的两翼与轴部中和面以上表现为压应力,顶板与煤层断裂或裂隙不发育,阻止了煤层气向上 逸散,有利于煤层气在此部位的富集。最后从煤田生产资料实践证实了向斜部位煤层气富集这一理论,对煤层气 勘探具有一定的指导意义。

The research on coalbed methane enrichment law permeates through the whole process of coalbed methane exploration and development, and is merged with these disciplines as coalfield geology, natural gas geology and fluid mechanics. Proceeding from the cases of syncline-enriched coalbed methane, the authors analyze thoroughly the mechanism of the effect of coalbed water at syncline portion upon coalbed methane and investigate the influence of the stress property at fold portion on coalbed methane occurence. Because of the centripetal flowing mechanism and low flow velocity of the coalbed water at cyncline portion, the dissolved methane couldn’t be largely dissipated owing to water flow; and on the other hand, because of high salinity of the water, the solubility of coalbed methane in the water decreased, thus playing the role of sealing coalbed methane. The compressive stresses existed in the two flanks and axis above neutral plane of synclinal fold, and the faults and fractures are undeveloped in coal bed and its roof, thus preventing the coalbed methane from being upward dissipated, which is favorable to coalbed methane’s being enriched at the cyncline portion. Therefore, the theory of cyncline-controlled coalbed methane is of a certain guids significance for coalbed methane exploration, having been proved by the production practice.