盆缘山地高陡地层冲断带页岩气地质特征浅析

Shale Gas Characters of Thrust Belt in High and Steep Strata of Marginal Forland

为了探讨城口区块盆缘冲断带页岩气特征,统计分析了下寒武统水井沱组页岩地球化学化验数据、钻井数据、岩心数据及解吸气数据。用各参数有利叠合分析了研究区块的页岩地质特征,并指出了有利勘探区带。研究表明,早寒武世深水陆棚相沉积环境为下寒武统水井沱组页岩发育提供了良好的条件;水井沱组页岩具有高有机碳含量、高成熟—过成熟的特征;页岩储层孔隙度和渗透率较差,但是脆性矿物含量较高,页岩中节理、裂缝及断裂发育有利于压裂改造;有机质为I型干酪根;钻井揭示页岩保存条件好;现场解吸实验初步显示,页岩整体含气效果良好,结合分析测试数据和探井数据预测了城口区页岩气勘探有利区在西南部。本研究为中国南方盆缘山地冲断带页岩气研究提供了一定的借鉴。

To probe into the shale gas characters of foreland thrust belt in Chengkou Block, we made statistical analysis on geochemical laboratory data, drilling data, core data and desorption data of shale in Shuijingtuo Formation of Lower Cambrian, which showed the geological characters of shale in the area, and pointed out favorable exploration zones. It was revealed that Early Cambrian shelf deposit provided good conditions for shale development in Shuijingtuo Formation, shale in Shuijingtuo Formation was characterized by high organic carbon content, high and superhigh maturity, shale reservoir had poor porosity and permeability but high content of brittle minerals, and development of joints, fractures and cracks was good for fracturing, and the organic matter was Type I kerogen. Drilling showed that shale was preserved well. Field desorption experiment prilimninarily indicated that shale owned good gas effect. It was predicted that favorable shale gas exploration area was located in southwestern Chengkou Block, on the basis of test data and exploratory well data. This could be reference for shale gas exploration in thrust belt of marginal forelands in South China.