摘要
砂泥岩组合方式在不同埋深条件下影响了砂泥岩界面附近储层的物性。在浅—中等埋藏条件下(深度 <2 5 0 0 m )砂泥岩界面附近的砂岩物性好于内部 ;在深埋藏条件下 ,砂泥岩组合方式、与砂岩接触的泥岩厚度以及砂泥岩的相对厚度比例对砂泥岩界面附近的砂岩物性影响很大。在泥岩夹砂岩的情况下 ,当砂岩厚度极薄、比例极低时砂岩物性很差 ;当砂岩厚度增大到中—厚层时 ,则从砂岩内部某一点开始向砂泥岩界面 ,物性逐渐降低 ,顶底界面都存在一个约为砂层厚度 1/ 5～ 1/ 4的物性过渡带 ;在上泥下砂或下泥上砂的情况下 ,仅在与厚层泥岩接触一侧的砂岩界面处出现物性过渡带。在砂泥岩近于等厚互层的情况下砂岩界面附近物性仍比内部差 ,且随着砂岩单层厚度减薄、厚度比例降低 ,泥岩比例增高 ,砂岩的物性越来越差。在砂岩夹泥岩的情况下 ,砂泥岩界面附近与砂岩内部物性趋于一致 ,物性过渡带消失。这一现象与泥岩的成岩演化密切相关 ,浅—中等埋藏条件下泥岩排出的为低矿化度、富含有机酸的流体 ,在砂泥岩界面附近溶蚀作用强于内部 ;在深埋条件下 ,从泥岩内排出的 K+ 、Na+ 、Ca2 +、Mg2 +、Fe3+与 Si4 +等物质以沉淀为主 ,砂泥岩界面附近胶结强于内部 ,泥岩的厚度越大 。
Porosity and permeability of sandstone near the sandstone-mudstone boundary is affected by the stacking pattern of sandstone and mudstone. At shallow buried depths (<2500 m), the reservoir quality near the boundary is superior to the inner part of the reservoir. At deep buried depths, the stacking pattern, mudstone thickness, and the ratio of sandstone in the strata heavily affect the physical properties of the reservoir near the boundary. When mudstone is interbedded with sandstone and the sandstone is very thin with a low ratio, the sandstone has very poor physical properties, while its thickness increases to some extent (becoming medium thick). The physical properties are getting poorer from the interior of the sandstone to the sandstone-mudstone boundary. There exists a physical property transition zone whose thickness is 1/4~1/5 that of the sandstone. When mudstone at the top while sandstone at the bottom, or sandstone at the top while mudstone at the bottom, there is a physical transition zone only on the side of the contact with the mudstone. When sandstone and mudstone are alternated with almost the same thickness, the reservoir quality near the boundary is still inferior to the inner part of the reservoir, and with the decrease of the thickness and ratio of sandstone, quality of the sandstones is getting poorer. When the sandstone is interbedded with thin mudstone, physical properties of the reservoir around the boundary tend to be the same as that of the inner part of the reservoir, so the physical transition zone disappears. This phenomenon is closely connected with the diagenesis of mudstone. Fluids discharging from mudstone at shallow or medium depths are low in salinity and rich in organic acids. The dissolution near the boundary is more active than that in the inner part of the reservoir at shallow buried depths, whereas at deep buried depths, K+, Na+, Ca 2+, Mg 2+, Fe 3+, Si 4+ and so on discharging from the mudstone are precipitated in most cases, so the cementation near the boundary is stronger than that in the interior, especially when the mudstone has greater thickness.
出处
《地质学报》
EI
CAS
CSCD
北大核心
2004年第6期863-871,共9页
Acta Geologica Sinica
基金
国家"十五"重点科技攻关项目 (编号 2 0 0 1BA60 5 A0 9-1-5 )资助的成果
关键词
泥岩
砂岩储层
埋藏条件
物性
岩组
过渡带
埋深
砂岩厚度
成岩演化
胶结
buried depth
stacking pattern of sandstone and mudstone
sandstone-mudstone boundary
physical properties of reservoirs
variation characteristics of physical properties
mechanism
