南襄盆地南阳凹陷核桃园组储层中碳酸盐胶结物富集规律

Enrichment pattern of carbonate cements in reservoirs of the Hetaoyuan Formation in Nanyang sag,Nanxiang basin

通过铸体薄片和分析化验资料,分析了张店油田核桃园组二段储层中碳酸盐胶结物的产状及其含量随深度变化的规律。储层中碳酸盐含量总体上随深度增加而不断加大,但在不同成岩阶段具有不同特点。在有机质成熟期尤其是半成熟-低成熟阶段(晚成岩早期),碳酸盐含量下降明显,是次生孔隙主要发育期。在晚成岩B亚期(晚成岩晚期)以后即有机质生烃高峰期以后,储层中尤其是高孔隙储层中碳酸盐胶结物含量增加明显。碳酸盐在储层中的不断富集与泥岩压实作用和有机质成熟期的酸性孔隙水溶解作用有关。不同微相中碳酸盐富集部位不同。对于三角洲前缘分支水道微相,它主要富集于砂体底部;而对于河口砂坝,则主要富集于砂体顶部。碳酸盐在储层中的富集是造成储层孔隙度下降的主要因素之一,它对2 450 m深度以下储层影响尤为严重。

Based on cast thin section and test data, a study is carried out on the occurrence of the carbonate cements in the reservoirs of the second member in Hetaoyuan Formation of Zhandian oilfield and the change of their contents with burial depth. The carbonate but presents different characteristics in different content increases on the whole with its increasing burial depth diagenetic stages. In the mature stage of organic material especially the semi-or low-maturity stage（ the early of late diagenetic stage）, the content of carbonate drops sharply and the secondary pores are well developed. After the late diagenetic substage B （the late of late diagenetic stage） when the hydrocarbon generation peak is past, the content of carbonate cements reservoirs especially those of high porosity obviously increases. The continuous enrichment of carbonate in reservoirs is related with shale compaction and dissolution of acid pore water during the mature stage of organic materials. The locations where carbonate enriches vary in different microfacies. It mainly enriches at the bottom of sandbodies in delta front distributary channels, and at the top of sandbodies in mouth bar. The enrichment of carbonate in reservoirs is one of the key factors that cause the reduction of reservoir porosities, especially the reservoirs with a burial depth larger than 2 450 m.