高邮凹陷古近系阜宁组一段沉积特征对储层成岩作用及物性的影响

The Impact of Sedimentary Characteristics on the Diagenesis and Reservoir Quality of the 1st Member of Paleogene Funing Formation in the Gaoyou Subbasin

本次通过对高邮凹陷阜宁组一段38口井的岩芯描述和400余块样品的普通薄片、铸体薄片和扫描电镜的镜下观察以及物性分析和含油性分析等,对储层的岩性、粒度、杂基含量、层理结构、生物扰动构造等因素与储层的成岩现象、物性特征和含油性的关系进行了详细研究,总结了沉积微相对成岩作用、储层物性的影响和与储层含油气性的关系。储层的岩石成分对储层的成岩作用及物性有重要影响,岩屑较软,易被压实和溶解,浅埋藏时,孔隙度和渗透率随着岩屑含量的增大而增大;当埋藏较深时,孔隙度和渗透率随岩屑含量增加而快速下降。储层的粒度对储层的成岩作用及物性也有重要影响,一般随着粒度的增大,孔隙度、渗透率都相应增大。储层的层理类型对成岩作用及物性也有重要影响,块状层理、交错层理或平行层理砂岩的分选性好,杂基含量较低,属于颗粒支撑结构,从而有利于原生孔隙的保存,为后期地下酸性流体对储层的溶蚀改造提供了渗流条件;波状交错层理等砂岩除不具备这一条件外,砂层内部弯曲的纹层给地下流体的流动增加了困难,不利于次生孔隙的发育和油气的进入。沉积微相对储层物性的控制,主要表现在其对原始物性的控制,分选好、原始物性好的储层在埋藏成岩演化过程中,由于对地层流体的流动的阻力小,其储集空间可以由于致密胶结作用完全消失,也可以得到溶蚀改善和保存;但泥质含量高的储层,其原始物性不好,对地层流体的流动阻力大,尤其是油气难于进入,储层主要遭受破坏,而难以得到改善和保存。

Through the core description of 38 Wells and the observation of ordinary thin section,cast thin section and scanning electron microscope of more than 400 samples,this study discusses in details the physical properties,oil bearing properties,and relation of various factors such as reservoir lithology,grain size,matrix contents,bedding structure,bioturbation structure,and the diagenetic phenomenon.The impact of sedimentary microfacies on diagenesis,reservoir properties and oil and gas is also summarized.Lithological compositions of the reservoir have an important impact on reservoir diagenesis and physical properties.Relatively-soft rock debris at shallow burial are easily compacted and dissolved,and porosity and permeability increases with increase of rock debris contents.When buried deeper,porosity and permeability decreases with the rapid increases of content of rock debris.Granularity of the reservoir also has important impact on the diagenesis and physical properties of the reservoir,and porosity and permeability increase wit increase of particle sizes.The bedding types of reservoir have vital effect on diagenesis and petrophysical properties.Sandstone with massive bedding,cross-bedding and parallel bedding has good sorting and low matrix contents,belonging to grain support structure.Such a structure is conducive to the preservation of primary porosity,which supplies good seepage conditions for the flow of underground acidic fluid and for the dissolution and alteration to reservoir at late stage.But wavy cross-bedding sandstone has no such features because curved lamina within sandstone make it difficult for underground fluid flow and such structure is not conducive to the development of secondary porosity and entrancement of oil and gas.The controls of sedimentary microfacies on the reservoir properties are mainly reflected by its control on original petrophysical properties.During the burial and diagenetic evolution process of good sorted reservoir with high original of petrophysical properties,the low resistance to the flow of formation fluids can result in the disappearance of reservoir space due to dense cementation,thus being preserved and improved due to the dissolution.Reservoirs with high mud content have bad original petrophysical properties,and have big resistance to the flow of formation fluids,especially difficult for oil and gas to enter the reservoir.Therefore,the reservoir space is mostly destroyed,and can not be improved and preserved.