中国重点地区二叠系海陆过渡相页岩气勘探前景

我国海陆过渡相页岩气勘探至今仍未取得较大的突破。通过对重点地区二叠系海陆过渡相页岩的分布特征、有机地球化学特征和储集特征等方面的研究，并与海相和陆相页岩进行对比，分析预测了我国海陆过渡相页岩气的勘探前景。中国海陆过渡相页岩分布面积大，但具有单层厚度薄、岩性变化快的特点；干酪根类型以Ⅲ型为主，除碳质泥岩外，页岩总有机碳含量整体偏低，生烃潜力最小；孔隙类型以无机质孔和微裂缝为主，有机孔不发育，孔体积和比表面积低于海相页岩，储集空间相对不足，气体吸附能力较差；泥页岩黏土矿物含量极高、脆性矿物较少，低孔低渗，储层物性差，不利于后期开发。研究表明，海相页岩仍是页岩气最有利的勘探区域，海陆过渡相页岩气勘探前景在某些方面不如演化程度高的陆相页岩气。

Exploration prospect of shale gas with Permian transitional facies of some key areas in China

The shale gas exploration of marine-continental transitional facies in China has not yet gained a significant success. To analyze and predict the exploration prospect of transitional shale gas, the distribution, organic geochemical and reservoir characteristics of transitional shale in some key areas of China were compared. The transitional shale is widely distributed in China and is characterized by the thin thickness of single layer and the rapid variation of lithology. The kerogens of transitional shale are mainly of type Ⅲ. Except for carbonaceous mudstone, the total organic content is generally low, and the hydrocarbon generation potential is the lowest. The dominant pore types of transitional shale are inorganic pores and micro-fractures, while the organic pores on the other hand were not developed. The pore volume and pore specific surface area of transitional shale are lower than those of marine shale, the reservoir space is relatively insufficient, and the gas adsorption capacity is poor. Transitional shale has a remarkable high content of clay minerals, less brittle minerals, low porosity and permeability, and poor reservoir physical properties indicating unconducive for the late-stage development. Results show that marine shale is still the most favorable area for shale gas exploration, and the exploration prospect of shale gas in transitional facies may not be regarded as good as that of continental shale gas which has a higher thermal mature degree in some aspects.