塔里木盆地深层碳酸盐岩建造-改造作用与多类型储层有序性分布

Formation and modification of deep-burial carbonate rocks and orderly distribution of multi-type reservoirs in the Tarim Basin

我国深层海相碳酸盐具有埋藏深度大、地质时代老、地质演化过程复杂等特点,其储层形成和分布受到众多因素制约,是海相油气勘探面临的关键问题之一。本文总结了团队在塔里木盆地长期研究成果,从深层碳酸盐岩建造和改造作用出发,揭示塔里木盆地多类型碳酸盐岩储层的主要发育条件和有序性分布。(1)塔里木盆地台地格局、地层发育演化及后期的埋藏与改造,均是盆缘构造事件在盆内的构造-沉积作用响应。早古生代盆地经历了地貌张裂分化与小型裂陷群形成、地貌挤压分化与层间不整合发育、古隆起与大型不整合作用、多期不整合叠加与古隆起埋藏改造等演化过程。(2)碳酸盐岩台地沉积过程中存在着不同尺度、不同类型的分异演化作用,可分为雏形期、建造期、鼎盛期和分解-消亡期,相应的台地边缘演化经历了缓斜坡、进积镶边、加积镶边和退积陡坡等建造过程,控制着台缘礁滩、台内滩、早期白云岩化潮坪等有利于规模化储集岩发育的沉积相带分布。(3)多级次不整合和断裂-流体改造是优质储层形成的重要机制。多期区域构造活动和周期性海平面变化控制了不同级别的不整合面发育,海平面下降主导的层序界面导致碳酸盐岩周期性暴露,形成了不同规模的层间岩溶和同沉积岩溶,区域构造运动所对应的大型不整合控制了大规模表生岩溶储层发育,不同规模的断裂和裂缝既是储层发育带,也是流体活动和改造的主要区带。(4)塔北-顺北地区不整合发育强度和断裂活动强度由北向南有序变化,控制了碳酸盐岩储层类型与分布的有序性变化,自北向南依次发育雅克拉断凸潜山型白云岩储层、塔河主体区古风化壳型岩溶储层、塔河斜坡区层控型岩溶储层、塔河覆盖区断溶型储层和顺北断控型储层,反映出由剥蚀区至覆盖区不整合控储作用逐渐变弱,而断裂控储作用增强。

The deep-burial carbonate rocks in China are characterized by great burial depth,old numerical age,and complex geological evolution process.The formation and distribution of carbonate reservoirs,constrained by many factors,are one of the key scientific issues in marine oil and gas exploration.This paper summarizes the results of the team’s long-term research and reveals the main development conditions and orderly distribution of multi-type carbonate reservoirs relevant to the formation and modification of deep-burial carbonate rocks in the Tarim Basin.(1)The platform pattern,stratigraphic development and evolution,and late-stage burial and modification of the basin are all the tectono-sedimentary responses of the basin margin tectonic events.The early Paleozoic basin experienced the evolution process of geomorphic extensional differentiation and formation of small rift groups,geomorphic compression differentiation and interlayer unconformity development,paleo-uplift and large-scale unconformity,multi-stage unconformity superposition and buried modification of paleo-uplift.(2)Complex sedimentary differentiation and evolution(in terms of type and scale)during carbonate platform sedimentation can be divided into embryonic stage,construction stage,heyday stage and decomposition-extinction stage.The corresponding platform margins have undergone the construction process of gentle slope,progradation rimmed,aggradation rimmed and retrogradation steep slope.They control the distribution of sedimentary facies zones favorable for large-scale reservoir development,such as platform margin reef shoals,intraplatform shoals and early dolomitization tidal flats.(3)Multi-level unconformity and fault-fluid modification are important mechanisms for the formation of high-quality reservoirs,where multi-stage regional tectonic activities and periodic sea-level changes control the development of unconformities at different levels,while sequence boundaries dominated by sea-level fall leads to periodic outcropping of carbonate rocks to form interlayer karst and synsedimentary karst of different scales;meanwhile large-scale unconformities formed by regional tectonic movements control the large-scale carbonate outcropping and development of large-scale epigenetic karst reservoirs,as faults and fractures of different scales are not only the reservoir development zones but also the main zones of fluid activity and modification.(4)The size of unconformity and the intensity of fault activity in the Tabei-Shunbei area change gradually from north to south controlling the orderly change of reservoir type and distribution,which result in the sequential developments of,from north to south,buried hill dolomite reservoirs in the Yakla fault convex,paleo-weathered crust karst reservoirs in the main area of Tahe area,stratabound karst reservoirs in the slope area of Tahe,fault karst reservoirs in the covering area of Tahe area,and fault-controlled karst reservoirs in the Shunbei area,reflecting the gradual weakening of unconformity control on reservoirs and strengthening of fault control on reservoirs from denudation area to covering area.