页岩气资源潜力评价的几个关键问题讨论

综合国内外的页岩气研究现状,认为页岩气是未来重要的补充能源,但其发展尚需要大量的工作;中国学者对页岩气的概念和资源评价方法的认识逐渐趋向于统一,关注的泥页岩评价指标主要是总有机碳、成熟度、连续厚度和泥页岩中脆性矿物含量.在对页岩气的定义进行限定的基础上,提出了含气泥页岩层段和泥页岩含气系统的概念,应用这种概念更有利于页岩气的资源评价和开发.除了常规的泥页岩评价指标外,应对泥页岩层段和系统中顶、底板的研究给予高度重视;提出了顶、底板主要特征,特别是不渗透岩层能封堵泥页岩中形成的天然气.在页岩气资源量计算中,应考虑到烃源岩纵横向上的非均质性,应用权重系数考虑不同厚度烃源岩的有机质丰度参数;同时,提出了一种新的泥页岩含气系统纵向单元精细划分方法.由于国内对页岩气中吸附气和游离气的测试方法尚不统一,对同一样品测试结果相差较大,缺乏相应的分析测试标准,因此提出了按照泥页岩总有机碳含量及氢指数确定含气量的方法;该方法尽管结果不一定很精确,但对于目前测试数据误差较大或缺乏的情况,能提供重要参考.页岩气资源评价总体上应兼顾评价方法的科学性、合理性、可靠性和可操作性;依据勘探程度选择评价方法,分类评价与分级评价相统一.最后,建议采用镜质体反射率与总有机碳的乘积和开采系数的关系图,来预测开采系数.

Discussion on the Key Issues of Resource Potential Evaluation for Shale Gas

According to the review on shale gas,it is believed that shale gas is important additional energy in future,but the development still needed a lot of work;the scholars’ outlook on concept of shale gas and resource evaluation method gradually reach unanimity in China,and the evaluating indicators of clay shale focused are mainly total organic carbon,maturity,continuous thickness and content of brittle mineral in clay shale.The concepts of gas-bearing clay shale section and clay shale gas-bearing system were suggested based on the limited definition of shale gas,and the application was more favorable to the resource evolution and development of shale gas.Besides the normal evolution indicator of clay shale,the study on the top and floor of slay shale section and system was very important;the main features of top and floor were introduced,especially the impermeable terrane could seal the gas from clay shale.For the calculation of resource amount of shale gas,the inhomogeneity of hydrocarbon source rock in vertical and horizontal directions should be considered,and the abundance of organic matter of hydrocarbon source rock with different thicknesses was considered with the application of weight coefficient;meantime,a new method to subtly divide the vertical unit of clay shale gas-bearing system was proposed.Because the test methods of adsorbed and free gases were not yet uniform in China,the test results for the same sample were different and the corresponding analysis test standard was shortage,so that a new method for calculating gas content was proposed according to the total organic carbon and hydrogen index of clay shale;the result calculated by the new method might not be very accurate,but it was important under the condition of measurement data with error significantly or shortage.Characteristics of resource evolution of shale gas could include scientificity,rationality,reliability and operability;evaluation method was selected according to the degree of exploration,and classification evaluation was integrated with grade evaluation.The relation diagram between recoverable coefficient and the product of vitrinite reflectance and total organic carbon was recommended to predict the recoverable coefficient.