冀中坳陷杨税务奥陶系深潜山储层特征及主控因素

储层非均质性强、主控因素不明是制约杨税务奥陶系内幕深潜山勘探的重要因素。以岩心、薄片及XRD观察为基础,综合扫描电镜、物性、成像测井、锶同位素资料,分析储层发育特征及主控因素。结果表明,奥陶系潜山从下而上发育3套似层状储层及1套局部分布的储层。Ⅰ号储层分布在亮甲山组—马家沟组一段,Ⅱ号储层分布在马家沟组二段上部—马家沟组三段,Ⅲ号储层分布在马家沟组四段上部—马家沟组五段。储层段沉积相为潮坪相,岩性以泥—粉晶云岩为主,储集空间为晶间孔、晶间溶孔及构造微裂缝、扩大溶蚀缝,孔隙度为0.7%~7.2%,平均为3.26%,渗透率为0.08~7.79 mD,平均为1.49 mD,为特低孔特低渗裂缝-孔隙型储层;3套似层状储层受到白云化作用、岩溶作用及构造作用的控制。白云化作用是储层形成的基础条件,岩溶作用是储层改善的重要因素,构造作用是形成含油气储层的关键因素。Ⅰ号储层受控于层间岩溶、埋藏白云化作用,Ⅱ号储层受控于回流渗透白云化和埋藏白云化作用,Ⅲ号储层受控于回流渗透白云化、表生岩溶和裂缝作用;Ⅰ号及Ⅲ号储层白云化作用程度深,白云岩厚度大,岩溶改造强,物性条件好,是本区的有利储层,其次为Ⅱ号储层。局部不连续型储层的发育与构造活动相关,受到断层、构造缝、热液白云化作用的影响。

Reservoir characteristics and main controlling factors of Ordovician Yangshuiwu deep buried hill in Jizhong Depression

Strong reservoir heterogeneity and their unclear controlling factors are essential factors which restrict the exploration of Ordovician Yangshuiwu deep-buried hill.Based on core and thin-section observations and bulk XRD analysis,combined with scanning electron microscopy(SEM),physical properties,FMI and Sr isotope,the reservoir characteristics and their main controlling factors in the study area were analyzed.The results show that there are three sets of stratiform continuous reservoir and one set of locally discontinuous reservoir in vertically from the bottom to the top of the Ordovician buried hill.The first set of reservoir is mainly distributed in Liangjiashan Formation and the first members of Majiagou Formation,the second set of reservoir is distributed on the third members of Majiagou Formation to the top of the second member of Majiagou Formation,and the third set of reservoir is distributed on the fifth member of Majiagou Formation to the top of the forth member of Majiagou Formation.The sedimentary facies of the reservoirs is dominated by tidal flat facies,the lithology is mainly mudsilty dolomite,and the reservoir space consists of intercrystalline pores,intercrystalline dissolved pores,structural micro-fractures and expanded dissolved fractures.The porosity varies from 0.7%to 7.2%with an average of 3.26%,and the permeability ranges from 0.08 mD to 7.79 mD with an average of 1.49 mD,which suggests the reservoirs are characterized by extremely low porosity and extremely low permeability.The three sets of stratiform reservoir are controlled by dolomitization,karstification and tectonism.Dolomitization is the basic condition for reservoir formation,karstification is an important factor for reservoir improvement,and tectonism is a key factor for the formation of oil-bearing reservoirs.The first set of the reservoir is mainly controlled by interlayer karst and buried dolomitization,the second set of reservoir is mainly controlled by seep-reflux dolomitization and buried dolomitization,and the third set of reservoir is mainly controlled by seep-reflux dolomitization,meteoric water leaching and fractures.The third set and the first set of reservoirs are the most favorable reservoirs with deep dolomitization,large dolomite thickness,strong karst transformation and good physical properties,followed by the second set.Locally discontinuous reservoirs are related to tectonic activities,and mainly affected by faults,tectonic fractures and hydrothermal dolomitization.