鄂尔多斯盆地陆相页岩气特殊性及面临的挑战

Characteristics and Challenges of Continental Shale Gas in Ordos Basin

国内外海相页岩气产量的突破得益于工程技术的成功研发,其基础是对页岩气地质特征研究的长期攻关。陆相页岩与之相比存在较多特殊性,笔者以鄂尔多斯盆地三叠系延长组陆相页岩气为典型实例,在地质特征、资源背景及勘探开发技术等方面进行研究分析,与国内外海相页岩气进行对比后认为:延长探区长7、长9页岩形成于陆相湖泊沉积背景,分布范围广,含气页岩层单层厚度大,有机质干酪根类型总体以II1型为主,有机质丰度大,各项指标相近或优于国外页岩气盆地,生气条件有利;但是,长7、长9陆相页岩气为偏腐泥型干酪根初次裂解形成的低成熟度油型气,页岩吸附能力大,以吸附气为主。黏土矿物含量高,地层压力低,地质条件复杂,钻井压裂施工困难。目前我国陆相页岩气仍处于勘探开发初期,成本高,初期产量低,在页岩生成机理、"甜点"识别、储层精细刻画、资源落实方面的认识尚不成熟,还需通过开展页岩气勘探开发先导性试验,实现科技突破,形成资源接替,促进陆相页岩气产业取得经济效益。

The foundation of the success of exploration and development of North America marine shale gas is a rich understanding of reservoir characteristics from decades of experience, and the production breakthrough is mainly attributed to engineering technology research and development. Learn from North America successful experience, we studied the Triassic continental shale gas horizon of Yanchang formation by analyzing the sedimentary-tectonic setting, geological characteristics and exploration technology comprehensively, and come to a conclusion when comparing to the marine shale gas formation. In Yanchang exploration area, Chang7 and Chang9 strata are mainly deep lacustrine, shallow lacustrine and delta front deposits. The dark shale strata are widespread and the single shale gas bearing layer is thick with generally large amount of Type Ⅲ kerogen. The geochemical and geophysical parameters are similar or even better compared to other overseas shale gas hearing basins which are quite favorable for gas generation and accumulation. The shale gas from Chang7 and Chang9 strata is oil type gas with low maturity from pri- mary pyrolysis, because the kerogen is sapropelic. Therefore the shale have large absorption capacity which is favorable for different phases of shale gas to accumulate. However, the drilling and fracturing work is difficult because of complicated formation mechanical properties. Comparing to marine shale, continental shale has its own characteristic, and high development cost and low production is mainly because of the utilizing of shale gas is still in a early stage. We need to launch pilot projects aiming to promote the shale gas economical to finally realize the energy resources replacement.