合川地区须二段储层沉积特征研究及有利勘探区预测

Research on Sedimentary Characteristics and Prediction of Favorable Exploration Zone in Second Member of Xujiahe Formation in Hechuan Area

须二段是合川地区油气勘探的潜力目标层系,沉积微相控制了有利储层的展布特征。通过岩石颜色、岩石结构、古生物标志、测井相标志等相标志,明确了合川地区须二段沉积环境为三角洲前缘沉积亚相,主要发育水下分流河道沉积微相、河口坝沉积微相,砂体连片发育,储层厚度大。通过物性分析,须二段主要为低孔低渗储层,工区内裂缝不发育,其中沉积相对储层的岩性、物性有一定的影响,水下分流河道沉积微相和河口坝沉积微相储层物性较好,孔隙度较高,有利于油气运移。根据单井沉积相,结合研究区地质背景,提出了合川地区沉积模式,在沉积模式的指导下,结合储层物性特征,划分了三类有利储层,其中有利区主要为Ⅰ类和Ⅱ类储层,孔隙度大于8%的储层厚度较大,有利于油气成藏,为下一步勘探目标提供了方向。

The second member of Xujiahe Formation is a potential target layer for oil and gas exploration in Hechuan area.Sedimentary microfacies control the distribution characteristics of favorable reservoirs.Based on the rock color,rock structure,paleontology and logging facies,the sedimentary environment of the second member of Xujiahe Formation in Hechuan area is defined as delta front sedimentary subfacies,mainly developed underwater distributary channel sedimentary microfacies and estuary bar sedimentary microfacies,with contiguous sand bodies and large reservoir thickness.According to the analysis of physical properties,the second member of the Xujiahe Formation is mainly low porosity and low permeability reservoirs,and no fractures are developed in the area.Sediment facies have a certain influence on the lithology and physical properties of the reservoirs.The reservoirs of distributary channel sedimentary microfacies and estuary bar sedimentary microfa-cies have better physical properties and higher porosity,which is conducive to oil and gas migration.According to the sedimentary facies of single well and the geology background of study area,the sedimentation models of Hechuan area are proposed,and three kinds of favorable reservoirs are classified under the guidance of the sedimentary models and according to the features of reservoir property,among them,the favorable areas are Class Ⅰ and Class Ⅱ reservoirs mainly,and the reservoirs with more than 8% of the porosity are thicker and beneficial to hydrocarbon accumulation,which provides a direction for the next exploration target.