四川盆地川西气田雷口坡组气藏储层特征及其主控因素

近年来,中国石油化工股份有限公司在四川盆地西部中三叠统雷口坡组天然气勘探中取得了重要的进展,川西气田已成为其"十三五"天然气勘探开发增储上产的重点区块。为了进一步认识川西气田雷口坡组储层的特征及控制因素,基于对岩石薄片、岩心等的观察,利用岩心物性和压汞曲线分析资料,结合测井解释成果,研究了该区石羊场—金马—鸭子河地区的储层特征及储层发育控制因素。研究结果表明:①该区雷口坡组发育潮坪相白云岩储层,可划分为上、下两个储层段和一个隔层段;②上储层段储层岩性、储集空间类型和孔喉组合相对简单,以微(粉)晶云岩为主,局部发育相对优质的中孔隙度—低渗透率的微晶云岩储层,主要为孔隙型储层;③下储层段储层岩性、储集空间类型和孔隙结构复杂多样,非均质性强,以(特)低孔隙度—(特)低渗透率储层为主,主要为裂缝—孔隙型储层;④储层纵向上非均质性较强,各类储层呈薄互层交替出现,有效储层厚度介于30.0～56.6 m,但下储层段的累计厚度和整体物性优于上储层段;⑤云坪、藻云坪微相和白云石化作用控制了白云岩的分布,为储层发育奠定了岩性基础;⑥潮间带高频旋回控制的多期准同生溶蚀作用是优质储层发育的关键因素;⑦埋藏期的油气充注抑制了规模胶结物的形成,使得早期形成的孔隙得以较好的保存。

Reservoir characteristics and main controlling factors of the Leikoupo gas pools in the western Sichuan Basin

Significant progress in natural gas exploration in the Middle Triassic Leikoupo Fm of the western Sichuan Basin have been achieved by Sinopec in recent years, and the western Sichuan gas field has become the key block for the increase of reserves and output of Sinopec in natural gas exploration and production in the 13th Five-Year Plan. For further understanding of the reservoir characteristics and the controlling factors of the Middle Triassic Leikoupo Fm reservoir in western Sichuan gas field, reservoir characteristics and the controlling factors of reservoir development in Shiyangchang–Jinma–Yazihe area were investigated based on detailed observation of rock slices and cores, utilizing porosity, permeability and intrusive mercury analysis in combination with well logging interpretation results. The research results show that: (1) the dolomite reservoirs of tidal flat facies were developed in the Leikoupo Fm of this area, which can be divided into an upper reservoir section, a lower reservoir section and an interlayer section; (2) the upper reservoir section is relatively simple in reservoir lithology, reservoir space type and pore–throat assemblage, and the main lithology is microcrystalline (crystal powder) dolomite with mainly pore-type reservoirs, and relatively high-quality microcrystalline dolomite reservoirs with medium porosity and low permeability are locally developed; (3) the lithology, reservoir space type and pore structure of the lower reservoir section are complex and strongly anisotropic, and the reservoirs are mainly of fracture–pore type with (extremely) low porosity and permeability; (4) the reservoirs are vertically anisotropic, and different types of thin reservoirs are interbedded. The thickness of effective reservoirs is between 30 m and 56.6 m. The total thickness and overall physical properties of the the lower reservoir section is superior to the upper section; (5) the distribution of dolomite is controlled by the flat and algae flat microfacies as well as dolomitization, which lay a lithological foundation for reservoir development; (6) multi-stage quasi-syngenetic dissolution controlled by high-frequency intertidal cycles is the key factor for the development of high-quality reservoirs; (7) hydrocarbon filling during the burial stage inhibits the formation of scale cements, and makes the early-formed pores better preserved.