四川盆地二叠、三叠系环海槽礁、滩富气带勘探

四川盆地北部广元-旺苍海槽及开江-梁平海槽的形成、发展和消亡过程对该区上二叠统-下三叠统飞仙关组沉积相的演化及其生物礁、鲕粒滩分布有着明显的控制作用,因而决定了礁、滩气藏的类型、规模及其分布：二叠纪长兴期的海绵-水螅边缘礁集中发育在环海槽的台地边缘相带,是天然气富集的有利储集相带;三叠纪飞仙关期环海槽的碳酸盐台地区鲕粒滩发育,是大中型气藏孔隙性鲕粒云岩、鲕粒灰岩储层发育有利相区。在“环海槽的碳酸盐台地边缘富气带是边缘礁、滩巨厚优质储层发育有利区” 重要勘探思路的指导下,自渡口河飞仙关组鲕滩气藏发现后,在环海槽的台地边缘相区又相继发现了罗家寨、铁山坡、滚子坪、普光等大中型气藏,近期在仪陇、苍溪地区礁、滩气藏的勘探也先后获得突破性进展,一个绵延600 km,范围近1×10⁴km²的环海槽礁、滩气藏富气带已清楚地显现出来。目前沿该带已发现了8个长兴组边缘礁气藏和13个飞仙关组鲕粒滩气藏,获天然气储量近1×10¹²m³,其中最大的气藏目前探明储量达到3560×10⁸m³。随着勘探的不断深入,环海槽礁、滩富气带的勘探将会有更大的发现。

EXPLORATION OF REEF-BANK GAS RESERVOIRS SURROUNDING PERMIAN AND TRIASSIC TROUGHS IN SICHUAN BASIN

Formation, development and consumption of Kaijiang Liangping trough in the northern Sichuan Basin have obviously controlled the evolution of the sedimentary facies and the distribution of organic reef and oolitic bank in the Permian and Triassic Feixianguan Formation, thus have determined the types, sizes and distributions of the reef bank gas reservoirs. The Spongia and Hydrozoa reefs in the Permian Changxing age are concentrated in the marginal facies belt of platform surrounding the trough, which is favorable for enrichment of gas. Oolitic banks are well developed in the carbonate platform surrounding the trough in the Triassic Feixianguan age, which is favorable for the development of large to medium porous oolitic dolomite and oolitic limestone gas reservoirs. Under the guidance of the exploration idea "gas enrichment zone on the carbonate platform margin surrounding the trough is favorable for development of the very thick marginal reef bank reservoirs of high quality", several large to medium gas reservoirs, such as Luojiazhai, Tieshanpo, Gunziping and Puguang, have been discovered successively in the marginal facies belt of platform surrounding the trough, and some breakthroughs have been made in exploration of reef bank gas reservoirs in Yilong and Cangxi areas since the discovery of the oolitic bank gas reservoir in the Feixianguan Formation in Dukouhe area. A 600 km long reef bank gas reservoir belt with an area of near 10 thousand km2 surrounding the trough has been clearly recognized, where 8 marginal reef gas reservoirs in the Changxing Formation and 13 oolitic bank gas reservoirs in the Feixianguan Formation have been discovered and their gas reserves are near 1 tcm, with the largest gas reserves of a single gas reservoir being up to 356 bcm. More significant discoveries will be achieved in this belt by further exploration.