页岩气储层“四孔隙”模型建立及测井定量表征方法

‘Four-pore'modeling and its quantitative logging description of shale gas reservoir

页岩气储层微观孔隙组分复杂,分为有机孔隙、碎屑孔隙、粘土孔隙和微裂缝。在岩心和测井响应特征分析基础上,提出利用测井资料定量评价页岩储层总孔隙及其微观孔隙组分的方法:①基于体积模型,利用密度测井资料或声波测井资料确定页岩储层总孔隙度;②综合利用常规测井资料和自然伽马能谱测井资料确定有机质体积含量,依据扫描电镜(SEM)技术确定刻度系数,得到有机孔隙度计算方法;③粘土孔隙是束缚水主要赋存空间,利用测井资料逐点确定粘土含量,并与邻近泥岩相关联,得到粘土孔隙度计算方法;④基于微裂缝的双侧向测井响应特征,通过正反演数值模拟计算,得到微裂缝计算方法;⑤总孔隙度与有机孔隙、粘土孔隙和微裂缝之差即为碎屑孔隙度。岩心结果表明,采用上述方法计算各微观孔隙组分与岩心测试结果吻合,表明方法的正确性。

The micropores of the shale gas reservoir consist of organic pore ,clastic pore ,clay pore and micro-fracture .After a comprehensive analysis of core properties and the logging response characteristics ,several new methods are proposed to evaluate total porosity and porosity of each micropore type of shale gas reservoir quantitatively .1） Based on the volume model,the DEN or DT is used to determine the total porosity of shale gas reservoir .2）Conventional logs and SGR （Natural Gamma Ray Spectroscopy ） logs are utilized to determine the volume-percent of organic matter content of shale gas reservoir , a scale parameter is determined by SEM technique ,and finally a method for calculating the organic porosity is set up .3） Considering the clay pore is the main storage space for bound water ,clay content is obtained from logs and correlated with the adjoining shale to get the evaluation method of clay porosity .4） Based on the response characteristics of dual laterolog for micro-fracture,an evaluation method of micro-fracture porosity is proposed by forward and inverse numerical simulation computations.5）The clastic porosity can be determined by subtracting organic porosity ,clay porosity and micro-fracture po-rosity from the total porosity .A good agreement is found between the core analysis and the micropore porosity computed by using the above methods ,which indicates the validity of the methods proposed in this paper .