考虑地层温度和压力的页岩吸附气含量计算新模型

A New Model for Shale Adsorptive Gas Amount under a Certain Geological Conditions of Temperature and Pressure

页岩气在页岩储层中的赋存方式主要以吸附和游离为主,页岩吸附气含量是页岩气资源评价和目标区优选的关键性参数,也是评价页岩是否具有开采价值的一个重要标准。通过室内不同温度下的等温吸附实验,获得页岩等温吸附特征曲线及Langmuir体积和Langmuir压力值,分析温度对页岩吸附气含量的影响程度,利用Langmuir模型计算地层压力条件下的吸附气含量。根据温度、压力、TOC值、RO值与吸附气含量之间的关系,建立考虑地层温度、压力、有机碳含量和成熟度4个因素的页岩吸附气含量计算新模型。新模型可计算任意埋藏深度下的页岩吸附气含量,埋藏深度越大,页岩吸附气含量越小。最后应用某一页岩气藏基础资料进行实例分析,建立得到的温度、压力、TOC值、RO值与页岩吸附气含量的复相关系数可达0.9以上。通过新模型计算未知页岩吸附气含量的页岩,计算结果准确可靠,能正确评价页岩气资源量,可以作为一种计算页岩吸附气含量的新方法。同时采用新的页岩吸附气含量计算模型,弥补了目前普遍采用没有考虑地层温度的等温吸附实验方法所获取吸附气含量的不足,具有重要的现实意义。

Shale gas mainly occurs as the state of absorption and free in shale reservoirs. The amount oi shale adsorbed gas is not only a key parameter of shale gas resource evaluation and target area selection, but also an important standard to evaluate the mining value of shale. We do the isothermal adsorption experiment to obtain the curve of shale adsorption and the parameters of Langmuir volume and Langmuir pressure. We discuss the influence of temperature on shale adsorbed gas and use the Langmuir model to cal culate the amount of shale adsorbed gas under formation pressure conditions. According to correlation between temperature,pressure,organic carbon,maturity and gas adsorbed amount, we establish a new model to calculate the amount of shale adsorbed gas as considering formation temperature,pressure, organic car bon,thermal maturity. The new model can calculate the amount of shale adsorbed gas at any burial depth; with the burial depth increases,the amount of shale adsorbed gas decreases. We use the data from one shale gas reservoir to establish the correlation between temperature, pressure, TOC,Ro, and gas adsorbed amount,the multiple correlation coefficient is more than 0.95. So,the new model has a potential ability to calculate the amount of the unknown shale adsorbed gas;the calculation result is accurate and reliable and can be used to correctly evaluate the resources yield of shale gas. The new model for calculating the amount of shale adsorbed gas will repair the current method which is generally used without considering the amount of shale adsorbed gas under the isothermal adsorption condition.