构造和古地理控制下的碳酸盐岩储集体旋回和集群性探讨:以四川盆地为例

Carbonate Reservoirs Cycles and Assemblages under the Tectonic and Palaeogeography Control: A Case Study from Sichuan Basin

四川盆地海相碳酸盐岩油气勘探突破不断,多个大气田群已初具雏形,并呈现出储集体集群分布的特点,而储集体集群结构及时空分布尚待探讨.在前人研究基础上,结合对四川盆地海相碳酸盐岩沉积储层等综合研究,系统探讨了四川盆地构造古地理演化控制下的碳酸盐岩旋回及集群类型、结构以及主控因素.以稳定碎屑岩层系和大型不整合面等为界,划分出8个垂向碳酸盐岩旋回,各旋回储集体构成具有差异性.总体而言,震旦系-下奥陶统、中二叠统-中三叠统的多个包含白云岩的储集体旋回更为有利;结合构造、古地理及储集体的时空配置,划分出板块边缘稳定的台缘礁滩储集体集群、持续迁移型古隆起及周缘岩溶和颗粒滩白云岩储集体集群、板块内部潮坪背景下的藻云岩和台内滩储集体集群、板块内部断裂相关的台缘和台洼礁滩相白云岩储集体集群、缓坡型灰岩致密型及岩溶型储层储集体集群等类型.稳定白云岩的存在对储集体集群起到了重要的控制作用,早期油气充注对白云岩储层保存影响明显;不同储集体集群受到了构造、海平面变化及岩相古地理的联合影响,表生岩溶、TSR、热流体活动成为特定地区储集体形成的影响因素.

The oil/gas exploration of marine carbonate rocks in Sichuan basin has achieved a lot of breakthroughs. Several large gas field clusters have been gradually presented,and have shown the clumped distribution characteristics of carbonate reservoirs,while the assemblage structure of the reservoirs and its spatial and temporal distribution remain to be further discussed. Based on previous studies,combined with the comprehensive research on marine carbonate reservoirs in Sichuan Basin,the types,texture,and major controlling factors of carbonate cycles and assemblages under the control of tectonic and paleogeography have been systematically studied. Limited by stable clastic rock strata and large unconformity surfaces,eight carbonate cycles are divided in this paper,and each cycle has different reservoir compositions.The cycles include dolomite favorable for reservoirs such as ones of Sinian to Lower Ordovician,andMiddle Permian to Middle Triassic.Combined with the tecotonic space-time distribution,and lithofacies paleography of reservoirs,carbonate rock assemblages are divided into several vertical cycles including：（ 1） stable platform edge reefs and shoals reservoirs on the edge of Upper Yangtze plate,（ 2） supergene karstification and grain beach dolomite around continuous migration paleo-uplift,（ 3） algal dolomite and intra-platform shoals under the background of tidal flat in the plate,（ 4） reef and beach dolomite reservoirs on the both sides of platform margin and intra-platform depression controlled by faults in the plate,and（ 5） dense limestone and karst reservoirs of carbonate ramp. It is suggested that carbonate reservoirs assemblages are controlled by dolomite which has been protected by early oil and gas charging. Carbonate reservoirs assemblages are influenced by tectonics,sea-level,and lithofacies paleography. And other factors such as karst,TSR,and hot fluids etc. influence carbonate reservoirs in local area.