川东北地区长兴组-飞仙关组油气成藏组合特征及有利勘探区带

随着油气勘探的逐渐深入，近年在川东北地区相继发现了铁山坡、渡口河、普光、龙岗以及元坝等大中型气田后，长兴组-飞仙关组礁滩储层逐渐被重视，成为目前川东北地区主要的勘探层系。因此，本文以长兴组-飞仙关组储层为核心开展川东北地区油气成藏组合特征的研究，并最终预测有利勘探区带。针对以上研究目的，本文从川东北地区长兴期-飞仙关期沉积相入手，结合川东北地区含油气系统以及成藏事件，并通过对典型油气藏特征的剖析，研究川东北地区成藏组合特征。受开江-梁平海槽演化的控制，研究区长兴期-飞仙关期主要发育开阔台地-蒸发台地以及陆棚。长兴组-飞仙关组主要发育有生物礁相孔缝型灰岩储层、台缘（内）滩相孔缝型白云岩储层以及台内滩相孔隙型白云岩储层。以下志留统、中-上二叠统烃源岩为研究核心，研究区主要发育S₁-P₃ch 含油气系统以及P₂.P₃-P₃ch.T₁f 含油气系统。通过对川东北地区典型气藏剖析，将长兴组-飞仙关组油气藏划分为S₁.P₂.P₃生-P₃ch 储短距离垂向运聚模式（元坝模式）以及S₁.P₂.P₃生-P₃ch.T₁f 储垂向运聚模式（龙岗-普光模式）。以长兴组-飞仙关组礁滩储层为核心建立3 类油气成藏组合，分别为生物礁相灰岩成藏组合、台内滩相白云岩成藏组合以及浅滩相白云岩成藏组合。综合对川东北地区油气成藏条件及其在时空上配置关系的研究，认为南大巴山前冲断带、川东冲断带的达州-开江-梁平一带以及阆中-平昌斜坡带的龙岗地区为长兴组-飞仙关组礁滩储层有利勘探区带；通南巴背斜西南部、九龙山背斜中南部以及中部断褶带为较有利勘探区带。

Characteristics of oil and gas reservoir formation and favorable exploration zone of Changxing-Feixianguan Formations,in the northeast of Sichuan Basin

In recent years, with the deepening of oil and gas exploration, the reservoirs of Changxing-Feixianguan Formations reef shoal are gradually valued and become the main exploration layer after the medium-large gas fields such as Tieshanpo, Dukouhe, Puguang, Longgang and Yuanba were found in the northeast of Sichuan Basin. Therefore, this paper studies the characteristics of reservoir-forming assemblages of Changxing-Feixianguan Formations as the core, and finally predicts the favorable exploration plays in the northeast of Sichuan Basin. In view of the research purposes, this paper starts from sedimentary facies in the Changxing-Feixianguan period and combines with petroleum systems and accumulation events, and analyzes the characteristics of typical oil and gas reservoirs, and finally studies characteristics of oil-gas reservoir-forming assemblages in the northeast of Sichuan Basin. Controlled by the evolution of Kaijiang-Liangping trough, study area is mainly open platform-evaporation platform and shelf environment in Changxing-Feixianguan period. The Changxing-Feixianguan Formations develops reef pore-cracks limestone reservoirs, dolomite reservoirs, platform edge（inner）shoal pore-cracks dolomite reservoirs, intraplatform shoal pore dolomite reservoirs. Based on the Lower Silurian source rocks and the Middle-Upper Permian source rocks, the study area is mainly develops S₁-P₃ch petroleum system and P₂.P₃-P₃ch.T₁f petroleum system. Through the analysis of the typical gas reservoirs in the northeast of Sichuan Basin, the Changxing-Feixianguan Formations oil and gas reservoirs are divided into S₁.P₂.P₃ sources-P₃ch reservoir short distance vertical migration model（Yuanba model）and S₁.P₂.P₃ sources-P₃ch.T₁f reservoirs vertical migration model（Longgang-Puguang model）. Based on the reservoirs of Changxing-Feixianguan Formations, three types of reservoir-forming assemblages were established, they are reef limestone reservoir-forming assemblage, intraplatform shoal dolomite reservoir-forming assemblage and the shallows dolomite reservoir-forming assemblage. Based on the study of hydrocarbon accumulation conditions and its relationship in time and space, the South Daba Mountain front thrust belt, the Dazhou-Kaijiang-Liangping area in the thrust belt of eastern Sichuan Basin and the Longgang area in Langzhong-Pingchang slope are favorable exploration plays for Changxing-Feixianguan Formations reef?shoal reservoirs. The southwest of Tongnanba anticline, the middle south of Jiulongshan anticline and the middle broken fold belt are less favorable exploration plays.