页岩储层不同赋存状态气体含气量定量预测——以四川盆地焦石坝页岩气田为例

摘要

国内外学者已总结出多个页岩气含量及其相关参数的计算模型,但都存在着一定的缺陷.为了提高计算结果的准确度,基于四川盆地东南缘焦石坝页岩气田上奥陶统五峰组至下志留统龙马溪组一段页岩储层4口取心井的岩心描述及室内分析成果,结合连续的地球物理动态数据,充分考虑页岩储层在纵、横向上的非均质性,在兰格缪尔(Langmuir)模型中加入硅质矿物和黏土矿物组分,在体积模型中加入有机质影响因子,动态修正了以兰格缪尔模型和体积模型为基础的吸附气量和游离气量外推预测模型.计算结果表明:①修正后的模型对涪陵国家级页岩气示范区焦石坝页岩气田单井天然气赋存状态关键参数的预测结果与岩心分析结果相关性好,其计算所得的游离气量、吸附气量和总含气量均与储层的实际含气特性相吻合;②该预测方法更适用于陆相或构造改造作用较强的海相页岩储层含气量的计算.结论认为,修正后的模型对焦石坝气田页岩储层吸附气、游离气含气量的预测是合理可行的.%Many scholars around the world have developed multiple models for calculating shale gas contents and relevant parameters,but none of these models is completely satisfactory by present.The extrapolation forecasting model of adsorbed gas content and free gas content based on the Langmuir and volume models was dynamically corrected by adding silicoide and clay minerals into the Langmuir model and introducing organic influence factor into the volume models so that the accuracy of calculation results can be increased.The corrected model was established based on the description and laboratory tests on the cores taken from four coring wells in the shale reservoirs of the Upper Ordovician Wufeng Fm and the first member of Lower Silurian Longmaxi Fm in Jiaoshiba at the southeastern margin of the Sichuan Basin,together with the continuous geophysical performance data,and with consideration to the vertical and lateral heterogeneity of shale reservoirs.It is shown from the calculation results that the key parameters of natural gas occurrence states in each well of the Jiaoshiba shale gasfield in the Fuling shale gas demonstration area,which are predicted using the corrected model,are well correlated with the core analysis results.The calculated contents of adsorbed gas,free gas and total gas are consistent with the actual gas-bearing properties of the reservoirs.Besides,this model is more suitable for calculating the gas contents of continental or marine shale reservoirs needed to be significantly stimulated.It is concluded that the corrected model can provide rational and feasible prediction of adsorbed gas and free gas contents of Jiaoshiba shale reservoirs.