川西南下三叠统嘉陵江组四—五段孔隙型储层特征及勘探前景

四川盆地下三叠统嘉陵江组主体为一套克拉通台地相沉积,其西南部地区具有埋深浅、储层薄、含气性较好的特点,早期发现了麻柳场、磨溪、赤水为代表的中小型气藏,近年来中国石化在川西南探区井研JS1井嘉四段测试获气2.32×10⁴m³/d、威远JH1井嘉五段测试获气5.58×10⁴m³/d。为了进一步明确川西南嘉陵江组孔隙型储层分布及下步勘探的有利目标区,通过区域地质特征、钻井岩心岩屑、铸体薄片及实验地质分析等研究,对嘉陵江组四段—五段孔隙型储层进行了地质评价。嘉四—五段孔隙型储层主要分布于嘉四¹、嘉五¹层段,灰岩和白云岩储层均有发育,纵向上表现为(灰)云坪与颗粒滩多期叠置的发育模式;储层主要岩石类型为晶粒白云岩、颗粒白云岩和颗粒灰岩,优质储层孔隙结构表现为大孔中喉、大孔细喉及中孔细喉的特征。有利沉积微相云坪和颗粒滩控制了储层的分布,准同生期溶蚀是形成优质孔隙型储层的关键,印支—燕山中晚期流体充注抵御了后期成岩压实和胶结作用对孔隙的破坏;位于泸州古隆起西缘的川西南井研...

Characteristics and exploration potential of porous reservoirs in 4th to 5th members of Lower Triassic Jialingjiang Formation in southwestern Sichuan Basin

The main body of Lower Triassic Jialingjiang Formation in the Sichuan Basin is a set of cratonic platform facies deposits. It is characterized by shallow burial depth, thin reservoir thickness and good gas-bearing property in the southwest. Some small- and medium-scale gas reservoirs such as Maliuchang, Moxi and Chishui were discovered in the early stage. In the southwestern Sichuan exploration zone of SINOPEC, a gas production of 2.32×104 m3/d has been discovered in the 4th member of Jialingjiang Formation in well JS 1 in Jingyan area, and a gas production of 5.58×104 m3/d has been discovered in the 5th member of Jialingjiang Formation in well JH 1 in Weiyuan area in recent years. In order to further clarify the distribution of pore-type reservoirs in the Jialingjiang Formation in the southwestern Sichuan Basin and favorable target areas for further exploration, the pore-type reservoirs of the 4th and 5th members of Jialingjiang Formation were evaluated in this study based on the analyses of regional geological characteristics, drilling core cuttings, casting thin sections and experiments. The pore-type reservoirs are found to be mainly distributed in the 1st section of the 4th/5th member of Jialingjiang Formation. Both limestones and dolomites were developed. Vertically, (grey) dolomitic flat and granular beach superimposed in multiple periods. The main rock types of the reservoirs are crystalline dolomite, granular dolomite and granular limestone. The pore structure of high-quality reservoirs is characterized by large pores with medium throat, large pores with fine throat, and medium pores with fine throat. Favorable sedimentary microfacies such as dolomitic flat and granular beach controlled the distribution of reservoirs. Quasi-contemporaneous dissolution was the key to the formation of high-quality pore-type reservoirs. Fluid charging in the Indosinian and mid-late Yanshanian resisted the destruction of pores caused by later diagenetic compaction and cementation. The areas of Jingyan, Rongxian-Yibin and Weiyuan on the western margin of Luzhou paleo-uplift are favorable targets for future exploration.