页岩气藏数值模拟及井底压力动态分析

为研究页岩气藏生产过程中井底压力动态及影响因素,基于质量守恒定律,考虑解吸和压力敏感系数,建立页岩气藏双孔双渗数学模型,对数学模型差分离散得到数值模型并求解;分析解吸、兰氏体积、兰氏压力、吸附时间、压力敏感系数等对井底压力双对数曲线的影响.结果表明:吸附气解吸使压降速率变缓且较晚触到边界;兰氏体积或兰氏压力越大,井底压力双对数曲线的下凹部分越明显;吸附时间常数越短,扩散效果越好,越容易达到整体径向流段;压力敏感系数越大,双对数曲线上翘越明显.该研究结果对页岩气藏开发具有指导意义.

Simulation of shale-gas reservoirs and dynamic analysis of bottom hole pressure

In order to deal with the dynamic of bottom hole pressure and its influencing factors in the production process of shale gas reservoir,a mathematical model of shale gas reservoir with dual-porosity and dual-permeability was established.This model is based on the law of conservation of mass,considering the desorption and the pressure sensitivity.Numerical model then can be obtained by means of finite differeace approach.Through the analysis of influences on the bottom hole pressure double logarithm curve which can be attributed to desorption,Langmuir volume,Langmuir pressure,adsorption time,pressure sensitive,it finally comes to the conclusions that the more absorbed gas in the well,the slower pressure drops,the later boundary to be touched.The increase of Langmuir volume or Langmuir pressure makes the concave part of the double logarithm curve of the bottom hole pressure more obvious.The smaller the time constant of adsorption is,the better the diffusion effects,and the easier to achieve the section of integral radial flow.The greater the pressure sensitivity coefficient,the more obvious double logarithm curve up.The results of the study for shale gas reservoir development has a guiding significance.