页岩气有机质纳米孔气体传输微尺度效应  

Micro-scale effects of gas transport in organic nanopores of shale gas reservoirs

作　　者：吴克柳[1,2] 李相方[2] 陈掌星[1,2] 

机构地区：[1]Department of Chemical and Petroleum Engineering, University of Calgary [2]中国石油大学石油工程教育部重点实验室

出　　处：《天然气工业》2016年第11期51-64,共14页Natural Gas Industry

基　　金：国家自然科学基金项目"页岩油气多尺度渗流特征与开采理论"(编号:51490654);国家自然科学基金项目"各向异性裂缝页岩气藏渗流机理与理论研究"(编号:51374222);国家重大科技专项"西非深水油田注采参数优化及单井产能预测研究"(编号:2011ZX05030-005-04)

摘　　要：页岩气有机质孔隙多为纳米尺度且气体赋存方式多样,因此页岩气有机质纳米孔中的气体存在多种传输机理,而如何建立能描述高压条件下所有传输机理的纳米孔体相气体传输模型、如何描述页岩有机质纳米孔表面扩散,以及确定表面扩散对气体传输贡献究竟有多大等则是目前亟待解决的难题。为此,综合考虑体相气体传输、表面扩散、真实气体、吸附层和应力敏感等微尺度效应的影响,建立了页岩气有机质纳米孔气体传输模型。研究结果表明:①通过滑脱流动和努森扩散加权叠加建立的体相气体传输模型能合理描述体相气体传输;②表面扩散是重要的传输机理,尤其在尺度小的纳米孔中,主宰了气体传输;③页岩气应力敏感效应不同于常规油气藏,其不仅与有机质力学属性、有效应力等有关,而且还与气体传输机理有关。结论认为,所建模型能够从室内低压条件直接推广到页岩储集层高压条件,能为页岩气生产动态分析、产能预测和生产制度制订提供指导。The organic pores in shale gas reservoirs are mostly of nanometer scale and the shale gas exists in multiple patterns, so multiple gas transport mechanisms coexist in organic nanopores of shale gas reservoirs. At present, it is in urgent need to figure out the way to establish a nanopore bulk phase gas transport model which can be used to describe all transport mechanisms under high pressure, to describe the surface diffusion in organic nanopores of shale gas reservoirs and to determine the contribution of the surface diffusion to gas transport. In this paper, a model for gas transport in organic nanopores of shale gas reservoirs was built by analyzing comprehensively the micro-scale effects of bulk phase gas transport, surface diffusion, real gas, and adsorption layer and stress sensitivity. Results show that the bulk phase gas transport model which was established based on the weighted superposition of slip flow and Knudsen diffusion can reasonably describe the bulk phase gas transport process; surface diffusion is an important transfer mechanism, and especially in nanopores, and it dominates the gas transport; and the stress sensitivity effect of shale gas reservoirs is different from that of conventional oil and gas reservoirs, and it is related to the organic mechanical properties and the effective stress, as well as the gas transport mechanisms. The model can be extended directly from indoor low-pressure conditions to high-pressure shale reservoirs. It provides a guidance for shale gas production performance analysis, productivity prediction and production system preparation.

关 键 词：页岩气 有机质孔隙 纳米级孔隙 微尺度 滑脱流动 努森扩散 表面扩散 应力敏感 

分 类 号：TE31[石油与天然气工程—油气田开发工程] TE37