陕北三叠纪煤田蟠龙至高家屯勘查区煤层气赋存规律研究

Study on CBM Hosting Pattern in Panlong-Gaojiatun Exploration Area,Northern Shaanxi Triassic Coalfield

煤层气的富集规律受多种地质因素的影响。在分析蟠龙至高家屯勘查区煤层气地质特征的基础上,从埋深,顶板岩性,水文地质三个方面探讨了研究区煤层气富集规律。研究表明,研究区瓦窑堡组含有效煤层三层,分别为5号煤、3号煤和3^(-1)号煤,煤层以薄煤层为主,埋藏较浅,R_(o,max)平均0.78%,生烃能力较强。研究区煤层气平均含气量为0.470m^3/t,含气量较低。三叠世晚期印支运动和早白垩世燕山运动使煤系抬升造成煤层气逸散是影响研究区煤层气含气量低的关键因素。蟠龙至高家屯勘查区煤层气富集主要受埋深和水文地质条件影响。研究区煤层气含气饱和度低,致使煤层顶板岩性对煤层气富集影响不明显。

The CBM enrichment pattern has impacted by multiple geological factors. On the basis of the Panlong -Gaojiatun exploration area CBM geological features analysis has discussed CBM enrichment pattern from buried depth, roof lithology and hydrogeology three aspects. The result has shown that the Wayaobu Formation in the study area has three pay grade coal seams namely Nos. 5, 3 and 3 - 1. They are mainly thin coal seams with shallower buried depth, average Ro,max 0.78%, stronger hydrocarbon generation capacity. Study area CBM average content is 0. 470m^3/t, slightly lower. The late Triassic Indosinian movement and early Cretaceous Yanshanian movement have made strata uplift and caused CBM dissipation, thus the key factor to bring about low CBM content. Exploration area CBM enrichment is mainly impacted by buried depth and hydrogeological condition. The lower CBM gas saturation has made impact on CBM enrichment from roof lithology inconspicuous.