四川盆地中西部上三叠统天然气有利勘探区带

BENEFICIAL ZONES OF EXPLORING FOR NATURAL GAS IN UPPER TRIASSIC IN THE WEST-CENTRAL PART OF SICHUAN BASIN

四川盆地中西部上三叠统属煤系地层 ,沉积厚度大 ,烃源丰富 ,储层发育 ,圈闭多 ,保存条件良好 ,具备形成大中型气田的成藏条件 ,是四川盆地内重要的天然气勘探接替领域。天然气成藏主要控制因素为 :一是储渗条件较好的储层 ;二是规模较大、形成较早的古隆起背景上的古圈闭 ;三是运移通道的发育。根据天然气的成藏机理、成藏特征和构造位置等因素综合分析 ,建立了上三叠统天然气成藏模式 ,将其分为三种类型 ,即山前型、凹陷型和隆起型。天然气勘探有利区带为 :龙门山推覆体前缘断褶构造带、米仓山前缘断褶构造带、梓潼凹陷、川西—川中斜坡带、川中北部构造带和川中南部构造带。

The Upper Triassic in the west-central part of Sichuan Basin is composed of coal measure strata with a large thickness,abundance hydrocarbon source,developed reservoir beds,many traps and good preservation conditions.It will be the important succeeding domain of exploring for natural gas in Sichuan Basin,being of the reservoiring conditions of forming large-and medium-sized gas fields.The main control factors of forming gas reservoir are:①the reservoir with fair store-permeability conditions;②the large-sized paleotrap on the background of early formed ancient uplift;and ③the developed migration passages.The reservoiring modes of the natural gas in the Upper Triassic in this region were set up on the basis of comprehensively analyzing these factors as reservoiring mechanisms,reservoiring characteristics and structural locations,etc.There are three types there,i.e.mountain front type,sag type and uplift type.The beneficial zones of exploring for natural gas include:the fault-fold structural belt of Longmenshan mountain nappe front,the fault-fold structural belt of Micangshan mountain front,the Zitong Sag,the West Sichuan-Central Sichuan slope zone,the structural belt in the north part of Central Sichuan and the structural belt in the south part of Central Sichuan.