岩石物理相在砂砾岩储层分类评价中的应用——以M1井区上乌尔禾组为例

Application of Petrophysical Facies for Sandy-conglomerate Reservoir Evaluation:A Case Upper Wuerhe Reservoir in the M1 Well Block,Junggar Basin

玛湖凹陷M1井区上乌尔禾组砂砾岩储层非均质性强,孔隙结构和试油产能差异大,主控因素不明。利用岩心、薄片、测录井及试油等资料,对M1井区上乌尔禾组的沉积相、成岩相、裂缝相以及储层综合分类展开研究。结果表明,扇三角洲砂砾岩储层主要为重力流及牵引流2种成因类型,对应扇面河道、水下分支河道、泥石流3种沉积微相。可识别出弱成岩作用相、溶蚀相、压实致密相、方解石胶结相4种成岩相。沉积相与成岩相是影响该区储层的主控因素,依此将储层分为水下分流河道-弱成岩作用相、水下分流河道-溶蚀相、扇面河道-弱成岩作用相、扇面河道-溶蚀相、泥石流-压实致密相、砂砾岩方解石胶结成岩相6种岩石物理相。依据沉积相和成岩相对于储层的影响,将6种岩石物理相归纳为3种类型储层,其中Ⅰ类和Ⅱ类储层最好,Ⅲ类储层最差,胶结致密。该区岩石物理相与试油结果匹配好,可有效预测有利储层分布区。

The sandy-conglomerate reservoir of upper Wuerhe formation in the M1 well block of Mahu Sag shows strong heterogeneity in pore structure and oil testing productivity.The sedimentary facies,diagenetic facies,fracture facies,and reservoir comprehensive classification of upper Urho formation in M1 well block were studied by using core,thin section,logging,and oil testing data.Results show that there are mainly two types of sedimentation of fan delta glutenite reservoir:gravity flow and traction flow;three types of sedimentary microfacies:fan channel,underwater distributary channel,and debris flows;and four types of diagenetic facies:weak diagenesis facies,dissolution facies,compacted compact facies,and calcite cementation facies.The sedimentary facies and diagenetic facies are the main factors affecting reservoir formation.In the study area,reservoirs can be divided into 6 combinations in petrophysical facies and further be grouped into three types.Type 1 includes underwater distributary channel-weak diagenesis facies,featuring the most favorable conditions of little compaction,certain dissolution,and good porosity,being a good type of reservoir.Type 2 includes underwater distributary channel-dissolution facies,fan channel-weak diagenesis facies,and fan channel dissolution facies,which is also favorable for reservoir formation despite poor pore structure,being also a good type of reservoir.Type 3 includes gravity flow compaction tight facies and glutenite calcite cemented diagenetic facies,having experienced cementation in the later stage,being a worse reservoir type.The petrophysical facies match well with the oil test results,which can effectively predict the favorable reservoir distribution area.