酒泉盆地营尔凹陷深层下沟组砂岩方解石胶结物特征  

Characteristics of calcite cements in deep Xiagou Formation sandstones of Ying'er Depression,Jiuquan Basin

作　　者：唐海忠 魏军 周在华 肖文华 俞海东 魏浩元 Tang Hai-zhong;Wei Jun;Zhou Zai-hua;Xiao Wen-hua;Yu Hai-Dong;Wei Hao-yuan(Research Institute of Exploration and Development of PetroChina YumenOilfield Company,CNPC,Jiuquan 735000,China)

机构地区：[1]中国石油玉门油田分公司勘探开发研究院,甘肃酒泉735000

出　　处：《天然气地球科学》2019年第5期652-661,共10页Natural Gas Geoscience

基　　金：中国石油天然气股份有限公司科技重大专项"成熟探区精细勘探关键技术--酒泉盆地精细地质研究及勘探目标优选"(编号:2018D-0704)资助

摘　　要：酒泉盆地营尔凹陷深层下沟组砂岩异常高孔带中方解石是体积最大的胶结物。通过铸体薄片、扫描电镜、电子探针等技术观察和测试方解石胶结物的赋存状态与化学组成,研究了其成因机制及与异常高孔带的关系。结果表明:方解石胶结物以浸染状、团块状和斑点状赋存于砂岩中;浸染状方解石的胶结作用使砂岩致密,其形成于早成岩阶段A期,物质来源于泥岩压释水;团块状和斑点状方解石胶结物是浸染状方解石胶结物经5期多源化和多样化的溶蚀流体改造形成,伴随着铁方解石向无铁方解石转化,致密砂岩向异常高孔带砂岩转化;5期方解石胶结物溶解作用的叠加区是油气勘探开发的首选目标区。针对陆相深层富含方解石胶结物的砂岩异常高孔带,强调和推广岩石学证据作为研究方解石胶结物成因机制和厘定异常高孔带类型的第一手资料,其他资料的应用解释都应服从于岩石学证据。Authigenetic calcites are the biggest volume cement in the anomalously high porosity zones of the deep Xiagou Formation sandstones in Ying’er Depression,Jiuquan Basin.By casting slice,scanning electron microscope and electron microprobe analyses,the occurrences of these calcite cements were observed in detail and their geochemical compositions were probed,in order to investigate their genetic mechanisms and their relationship with the anomalously high porosity zones.The result shows that the calcite cements have three occurrences including disseminated,blocked and starlike structutes in the deep sandstones.The disseminated calcite cement is deposited from the compressed released water that is from the nearby muddy sediments during the early diagenetic stage A.The blocked and starlike calcite cements are the product of the dissolution-precipitation reactions of the disseminated calcite cement by 5-stage acid fluids with the multiple resources and diversified ways,which makes the ferrocalcite transmuted into the calcite and the tight sandstones with the disseminated calcite cement turned into the anomalously high porosity zones with the blocked and starlike calcite cements.The superimposition areas of 5-stage dissolutions of these calcite cements are the preferred targets of the hydrocarbon exploration and development.In view of this,aimed at the anomalously high porosity zones in the deep calcite-rich continental sandstones,the petrological characteristics should be the foundation for the study of the genetic mechanisms of the calcite cements and the confirmation of the anomalously high porosity zones,and the other information must obey this foundation.

关 键 词：方解石胶结物 赋存状态 异常高孔带 深层下沟组砂岩 营尔凹陷 酒泉盆地 

分 类 号：TE122.2[石油与天然气工程—油气勘探]