川中低孔渗砂岩成岩相定量评价与快速预测——以遂宁—蓬溪须二段为例

Quantitative evaluation and prediction of diagenesis facies with low porosity and permeability sandstone in central Sichuan:A case study of 2nd member of Xujiahe Formation in Suining-Pengxi area

四川盆地中部上三叠统须家河须组须二段砂岩储层是中国低渗致密砂岩的突出代表,成岩作用对于砂岩致密化具有重要影响。借助铸体薄片、阴极发光、电子探针、扫描电镜等实验分析手段,分析不同成岩作用类型及特征,以控制孔隙演化的主要或特征的成岩作用划分出6种成岩相;引入视压实率、视胶结率、视微孔率、成岩系数结合孔渗参数,定量评价不同成岩作用强度,区分不同成岩相类型;探索地应用稳健回归方法建立孔渗-成岩系数解释模型;利用成岩系数解释模型解释未取心井参数,绘制成岩系数等值线平面图,预测有利成岩相区域分布。绘制储层(孔隙度>6%)成岩系数等值线平面图,预测有利成岩相-有利储层发育区,实现了成岩作用、成岩相定量评价,成岩相的快速预测,并为有利储层发育区的筛选提供了依据,对于致密砂岩气藏勘探开发具有指导性意义。

The sandstone reservoir in 2nd member of the Upper Triassic Xujiahe Formation in central Sichuan Basin is the prominent representative of China＇s low permeability tight sandstone.Diagenesis has an important influence on sandstone＇s compaction.Based on the cast-slice,cathodoluminescence,electron microprobe analysis,SEM and other means of experimental analysis,the authors analyzed different types of diagenesis and features and divided diagenetic facies into six kinds according to the dominant or characteristic diagenesis that controls the porosity evolution.Quantitative evaluation of the intensities of different diagenetic activities was made,and different diagenetic facies types were distinguished by introducing such indexes as the compaction rate,the cementation rate,the microporosity and diagenetic coefficient.The porosity and permeability-diagenetic coefficient interpretation model was tentatively established with the exploratory application of robust regression method.Un-coring well＇s parameters were explained by the diagenetic coefficient interpretation model,the diagenetic coefficient contour map was drawn,and the regional distribution of favorable diagenetic facies was predicated.The reservoir （＞ 6％ porosity） diagenetic coefficient contour map was drawn,and the favorable diagenetic facies-favorable reservoir development area was delineated.All these results obtained by the authors provide a possibility for realizing quantitative evaluation of diagenesis and diagenetic facies,and the rapid prediction of diagenetic facies provides a basis for the screening of favorable reservoir development areas.These achievements have guiding significance for the exploration and development of tight sandstone gas reservoirs.