华庆地区长6油层组方解石胶结物特征

华庆地区长6油层组是鄂尔多斯盆地中生界主要的油气储层和产层,方解石胶结物是导致储层致密的重要因素之一。薄片、扫描电镜、阴极发光、元素组分及碳、氧同位素分析表明,方解石胶结物除常见的粒状胶结物和嵌晶式胶结物外,还存在较少泥微晶结构方解石。泥微晶结构方解石是同沉积的湖相内杂基;沉积期后形成的粒状和嵌晶式方解石胶结物具多种成因机制,其中在早成岩阶段A期沉淀的方解石胶结物与铝硅酸盐矿物和变质岩、岩浆岩岩屑的水化作用有关;铁方解石胶结物充填于原生孔隙的同时,还充填于骨架颗粒溶蚀形成的次生孔隙中,其形成与有机酸对长石等铝硅酸盐矿物的溶蚀作用和黏土矿物的转化作用有关,为早成岩阶段B期沉淀作用的产物。大多数方解石、铁方解石的胶结作用对储层物性起负面影响。

Characteristics of calcite cements of Chang 6 oil reservoir set in Huaqing area

The Triassic Chang 6 oil reservoir set in Huaqing area is the main hydrocarbon reservoir and producing formation of Mesozoic in Ordao Basin.The cementation of calcite cements is a major factor for the tight reservoir.The analyses on thin section,cathodoluminescence,elemental composition and carbon isotope show that most of the calcites cemented in granular and poecilitic texture,and a few cemented in micrite texture which are the matrix of syndepositional lake facies.There are several different genetic mechanisms for the granular and poecilitic calcite cements formed during post sedimentary stages,and the calcite cements deposited during the early diagenetic A stage are in connection with the hydration of aluminum silicate minerals,metamorphic rocks and magmatic rocks.The ferrocalcite cements filled not only in the primary pore,but also in secondary pores.The formation of ferrocalcite cements are closely related to the aluminum silicate minerals and the transformation of clay mineral and occurred during the early diagenetic B stage.The most cementation of the calcites and ferrocalcite are disadvantageous for the reservoir properties.