页岩气地质甜点评价方法——以四川盆地焦石坝页岩气田为例

An evaluation method of geological sweet spots of shale gas reservoir:a case study of the Jiaoshiba gas field,Sichuan Basin

"甜点"是页岩气评价的重要内容,以往对岩性、含气量、物性和应力分布等进行综合分析确定甜点的方法,没有对甜点类型和性质进行划分。通过对页岩气甜点参数的分析,将"甜点"划分为地质甜点和工程甜点。通过定性分析地质甜点参数对产气量的影响,利用相关系数法优选出页岩气的主要甜点参数,分别利用雷达面积模型和相关性权重模型定量地进行了页岩气地质甜点系数表征。通过研究焦石坝页岩气田的地质特征,提出总有机质含量、干酪根含量、含气饱和度、总孔隙度和孔隙压力梯度5个参数为主要地质甜点参数,运用两种模型评价其地质甜点系数在0.3～0.7,表明焦石坝页岩气田地质甜点较好、具有较高的产气能力。

"Sweet spot"is an important factor for shale gas evaluation.The previous sweet spot determination method based on a comprehensive analysis on lithology,gas content,physical properties and stress distribution is not capable of classifying the types and properties of sweet spot.Through analyzing the sweet spot parameters of shale gas,the sweet spot is divided into two types,i.e.,the geological and engineering sweet spot.Through qualitatively analyzing the influence of geological sweet spot parameters on gas production,the main sweet spot parameters of shale gas were selected using correlation coefficient method to choose.In addition,radar area model and correlation weight model were applied to quantitatively characterize the geological sweet spot parameters of shale gas.Through studying the geological characteristics of Jiaoshiba shale gas field,TOC,kerogen content,gas saturation,total porosity and pore pressure are five main geological sweet spot parameters.Using these two models,the geological sweet spot is evaluated between 0.3 and 0.7,indicating that Jiaoshiba shale gas field has better geological sweet spot and high gas production capacity.