浅水粗粒辫状河三角洲沉积微相特征与油气产能的关系——以焉耆盆地宝浪油田为例

Relationships between hydrocarbon productivity and characteristics of shallow-water and coarse grain braided river delta deposit microfacies——Taking Yanqi Basin Baolang oilfield as an example

焉耆盆地宝浪油田含油气层段位于中生界下侏罗统三工河组(J1s),为典型的浅水缓坡型粗粒辫状河三角洲—湖泊沉积体系。储层成分成熟度和结构成熟度低,粒度概率曲线以牵引和悬浮二段式为主,C M图以PQ段和QR段为主,宝浪油田侏罗系三工河组划分出12种有成因意义的岩石相,采用Coleman的方案将浅水辫状河三角洲划分为:上三角洲平原(洪水线之上)、下三角洲平原(枯水线-洪水线之间)和水下三角洲平原(枯水线之下)3个亚相带。研究区主要发育了(水下)分流河道微相、水下分流河道间微相、决口水道(扇)微相、溢流沉积微相、滨湖沼泽沉积微相,河口坝微相不发育。(水下)分流河道微相占研究区储层的90%以上,根据砂体的岩石相组合、冲刷程度、水流能量大小的变化规律,其又可分为:充填河道、废弃河道、进积河道3种基本类型。储层物性以废弃河道为最好,单井油气产能亦最高,充填河道次之,进积河道和决口水道(扇)则相对较差。

Relatively to common delta and fan-delta, these studies mainly concentrate on the braided river with high slope drop and less study is given to braided channel delta and the braided river with low slope drop. Hydrocarbon-bearing intervals in Baolang Oilfield in Yanqi Basin are typical shallow-water, gentle slope type coarse grain braided river delta-lacustrine deposit systems. Reservoir component maturity and structural maturity are low; granularity probability curve is characterized with drag and suspension, and is divided into twelve kinds of lithofacies with genesis significance.These shallow-water delta types may be divided into three subfacies tracts by using Coleman Programs:the upper delta plain (above the flood line),the lower delta plain (between depleted water line and flood water line) and submerged delta plain (below the depleted water line). Distributary channel microfacies (submerged), distributary interbasin microfacies (submerged), crevasse channel (fan) microfacies, overflow deposit microfacies, lakeshore paludal deposit microfacies have been mainly developed in research area. The microfacies in debouch bar is not developed. Distributary channel microfacies (submerged) are 90% of reservoirs in research area and may be further divided into 3 basic types:filling channel, abandoned channel and progradational channel according to the varying laws of petrographical assemblage of sand bodies, scorn degree and water flow rate. In one single well, reservoir physical properties in abandoned channel are the best and hydrocarbon productivity is the highest, the second is in filling channel, and the relatively poor are in progradational channel and overflow channel.