营尔凹陷长沙岭构造带白垩系深部储层主控因素

Controlling factors of physical properties of Cretaceous deep reservoir in Changshaling tectocnic belt,Ying’er Sag

利用岩心、测井、分析化验及实测地层压力等资料对营尔凹陷长沙岭构造带白垩系下沟组一段储集层的岩石学特征、储集空间特征及物性特征进行了系统研究,分析物性主控因素,综合分析优势沉积微相、储集层厚度和构造因素,开展有利目标评价。结果表明:储集层岩石类型主要为长石岩屑砂岩和岩屑砂岩,填隙物主要为方解石,结构成熟度较低;储集空间以原生孔隙为主,次生孔隙改善了储集层物性,主要为原生粒间孔、晶间孔、粒缘溶孔、粒内溶孔及微裂缝;储集层孔隙度平均为8.75%,渗透率平均为4.18×10μm^(2),总体以特低孔-低孔、特低渗-低渗储集层为主,存在部分中孔、中-低渗储集层。明确了沉积相带、异常高压和溶蚀作用是影响储集层物性的主要因素,辫状河三角洲前缘水下分流河道、河口坝和湖底扇主水道、辫状水道为最有利的微相类型;异常高压可以减弱上覆地层的压实作用,使原生孔隙得以保存,同时促进有机酸对砂岩的溶蚀形成次生孔隙;长石、岩屑和方解石胶结物在酸性环境下溶蚀产生次生孔隙,为油气的运聚提供了有效的储集空间。研究结果可为长沙岭构造带白垩系深层油气勘探提供借鉴。

Based on the data of core,logging,analysis and testing,and measured formation pressure,the petrological characteristics,reservoir space characteristics and physical properties of the first member of the Cretaceous Xiagou Formation in the Changshaling tectonic belt of Ying’er sag are systematically studied,and the main controlling factors of physical properties are analyzed.And the dominant sedimentary microfacies,reservoir thickness and structural factors are comprehensively examined,and the favorable target evaluation is carried out.The results show that the reservoir rocks in the study area are mainly feldspathic lithic sandstone and lithic sandstone,the interstitial material is mainly calcite,and the structural maturity is low.The main reservoir space is primary pores,and the secondary pores improve the physical properties of the reservoir,mainly including primary intergranular pores,intergranular pores,intergranular dissolved pores,intragranular dissolved pores and microfractures.The average porosity of the reservoir is 8.75%,and the average permeability is 4.18×10μm^(2).The reservoir is mainly composed of ultra-low porosity and ultra-low permeability,and there are some medium porosity and medium low permeability reservoirs.It is clear that sedimentary facies belt,abnormal high pressure and dissolution are the main factors affecting reservoir physical properties.The most favorable microfacies are underwater distributary channel,mouth bar,main channel and braided channel of sublacustrine fan.On the one hand,abnormal high pressure can weaken the compaction of the overlying strata and preserve the primary pores;on the other hand,it can promote the dissolution of organic acids to form secondary pores.The dissolution of feldspar,cuttings and calcite cements in acidic environment produces secondary pores,which provides an effective storage space for oil and gas migration and accumulation.The research results can provide a reference for Cretaceous deep oil and gas exploration in Changshaling tectonic belt.