摘要
Shale needs to contain a sufficient amount of gas to make it viable for exploitation. The continental heterogeneous shale formation in the Yan-chang （YC） area is investigated by firstly measuring the shale gas content in a laboratory and then investigating use of a theoretical prediction model. Key factors controlling the shale gas content are determined, and a prediction model for free gas content is established according to the equation of gas state and a new petrophysical volume model. Application of the Langmuir volume constant and pressure constant obtained from results of adsorption isotherms is found to be limited because these constants are greatly affected by experimental temperature and pressures. Therefore, using measurements of adsorption isotherms and thermodynamic theory, the influence of temperature, total organic carbon （TOC）, and mineralogy on Langmuir volume constants and pressure constants are investigated in detail. A prediction model for the Langmuir pressure constant with a correction of temperatures is then established, and a prediction model for the Langmuir volume constant with correction of temperature, TOC, and quartz contents is also proposed. Using these corrected Langmuir constants, application of the Langmuir model determined using experimental adsorption isotherms is extrapolated to reservoir temperature, pressure, and lithological conditions, and a method for the prediction of shale gas content using well logs is established. Finally, this method is successfully applied to predict the shale gas content of the continental shale formation in the YC area, and practical application is shown to deliver good results with high precision.
页岩气藏实现经济开采的关键条件之一是其具备充足的含气量。本文针对延长地区(以下简称YC)陆相非均质泥页岩,开展了泥页岩含气性实验测试及理论分析,确定了影响泥页岩含气量的关键因素,根据泥页岩体积模型及气体状态方程,确定了泥页岩游离气预测模型。由等温吸附实验确定的Langmuir体积常数和压力常数受到实验温度和压力条件及样品性质的限制,难以应用于实际泥页岩的吸附气量预测。为此,根据实验结果与热动力学原理,本文研究了地层温度、总有机碳含量(TOC)以及矿物组分对Langmuir体积常数和压力常数的作用,分别建立了Langmuir压力常数温度校正方程和Langmuir体积常数的温度、TOC及石英含量校正方程,将等温吸附试验建立的Langmuir方程的应用范围外推至任意储层温度、压力及岩性条件;建立了利用测井资料预测泥页岩含气量的计算方法,并将该方法应用于延长陆相泥页岩地层含气量预测分析中,预测结果经实验数据标定,表明本文所述方法具有较高精度。
基金
sponsored by National Natural Science Foundation(Project number:41274136)
