靖边气田碳酸盐岩储层沉积-成岩演化模式

 靖边气田主产层次生溶蚀孔洞缝成层连片发育，孔洞缝分布受沉积相和成岩作用双重控制。本文结合98口井岩心观察、1000余块薄片鉴定及多种化验测试资料对储层沉积相、成岩作用进行了系统研究，探讨了储层沉积-成岩演化模式及其对孔洞缝储层发育的控制作用。结果表明，靖边气田储层为蒸发潮坪沉积，并可细分为潮上带泥云坪、膏岩洼地、含膏云坪；潮间带含藻云坪、泥云坪、颗粒滩、潮下带灰坪7种沉积微相；储层埋藏主要经历了白云化、溶解、充填、破裂、交代、压实-压溶、角砾化和重结晶8种成岩作用；储层沉积-成岩演化总体分为沉积同生期、近地表浅埋藏期、抬升风化期和后埋藏期4个阶段；马五1 1 ~马五13 、马五4 1a高孔渗段的形成主要受沉积同生期和抬升风化期溶解作用及含膏云坪、含藻云坪和颗粒滩微相控制，而马五3 2~马五3 3、马五4 1b~马五4 3b、马五5低孔渗段的形成主要受泥云坪、膏岩洼地和灰坪微相控制。

Sedimentary and Diagenetic Evolution Pattern of Reservoir Bed of Carbonate Rock in Jingbian Gasfield of Ordos Basin

Evaporation tidal flat facies are developed in the mid gas field of Ordos Basin. They can be subdivided into 7 microfacies, including mud-dolostone flat of the supralittoral zone, gypseous depression of the supralittoral zone, gypseous dolostone flat of the supralittoral zone, algae-dolostone flat of the intertidal zone, mud-dolostone flat of the intertidal zone, grain bank of the intertidal zone and limestone flat of the subtidal zone. Core observation and thin section analysis indicate that the diagenesis of reservoirs in the syngenesis diagenetic environment, freshwater diagenetic environment and buried diagenetic environment include dolomitization, dissolution, filling cohesion, fracture, replacement, compaction-pressure solution, recrystallization, breccia, etc. Based on the analyses of sedimentary facies and the effect of diagenesis on porosity and permeability characteristics of reservoirs, the sedimentary-diagenetic evolutions of carbonate reservoirs are divided into 4 periods, namely sediment-syngenesis diagenesis period, embedding diagenesis period, near floor, uplift-weathering period and late embedding diagenesis period. This unique evolution pattern constitutes vertical 5-layer reservoir architecture, including 2 high porous layers and 3 low porous layers, alternatively distributed. M51 1~M53 1 and M54 1a high porous layers are under the control of the paleokarst in sediment-syngenesis diagenesis period, uplift-weathering period and the microfacies of gypseous dolostone flat, M53 2~M53 3, M54 1b~M54 3b and M55 low porous layers are under the control of mud-dolostone flat, gypseous depression and limestone flat.