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四川盆地长宁区块是中国最早进行页岩气勘探开发的地区,但以往地震工作量投入相对较少,尚未精细刻画出页岩气商业开采的“甜点区”。为此,基于测井及三维地震解释成果等资料,通过地震岩石物理分析和建模,确定页岩气储层甜点地球物理响应特征,并以此为依据,应用全道集叠前反演技术预测了总有机碳含量(TOC)、优质储层厚度、地层脆性及地层压力等关键评价参数的平面分布情况;应用模糊优化综合评价方法确定了甜点的空间展布。研究结果表明:(1)该区页岩气储层甜点具有明显的低密度、低纵波速度、低泊松比、低纵横波速度比特征,且TOC越高,上述特征越明显;(2)优质页岩储层(Ⅰ、Ⅱ类区)在纵向上主要分布于下志留统龙马溪组底界上部约30 m范围内,平面上主要分布于三维地震区块的中部,建议优先开发;(3)Ⅲ类储层区各项关键评价指标均较低,建议选择性开发。
The Changning block in the Sichuan Basin is the earliest area for shale gas exploration and development in China. However, the workload on earthquakes in the past was relatively small, and the “sweet spot” for commercial exploitation of shale gas has not been elaborated. Therefore, based on the data of well logging and 3D seismic interpretation, the geophysical response characteristics of shale gas reservoir are determined by seismic petrophysical analysis and modeling. Based on this, the whole channel prestack inversion technique The planar distribution of key evaluation parameters such as total organic carbon (TOC), thickness of good reservoir, formation brittleness and formation pressure was predicted. The spatial distribution of dessert was determined by the method of fuzzy optimization. The results show that: (1) The shale gas reservoirs in this area have obvious features of low density, low P wave velocity, low Poisson’s ratio and low P wave velocity ratio, and the higher the TOC, the more obvious the above characteristics are. (2) The high-quality shale reservoirs (Class I and II) are mainly distributed in the longitudinal direction about 30 m above the bottom of the Lower Silurian Longmaxi Formation, and are mainly distributed in the middle of the 3D seismic block in the plane. (3) The key evaluation indexes of Class Ⅲ reservoir area are all low, and it is suggested to develop selectively.