四川盆地东部上石炭统黄龙组规模储层形成主控因素与发育模式

Formation controlling factors and development patterns of large-scale reservoirs in Carboniferous Huanglong Formation of eastern Sichuan Basin

石炭系黄龙组是四川盆地东部地区(以下简称川东地区)重要的天然气产层之一,石炭系储层是控制气藏发育的关键因素。为了深入评价川东地区黄龙组储层,拓展勘探新领域,寻找接替区,在前人研究的基础上,应用大量钻井、岩心、露头和分析化验等资料,系统研究了黄龙组储层发育的主控因素和发育模式,并预测规模储层的展布。研究结果表明:(1)黄龙组储集岩主要为颗粒白云岩、角砾白云岩和晶粒白云岩,储集空间主要为晶间孔/晶间溶孔、粒间溶孔/粒内溶孔、溶洞和裂缝,颗粒滩为有利储集体,裂缝-溶蚀孔洞型储层质量好;(2)储层发育主要受乐山—龙女寺古隆起和开江古隆起、沉积作用及成岩作用的共同控制,古隆起控制颗粒滩分布和准同生期成岩作用,是规模成储的基础,准同生期白云石化作用、层间岩溶和风化壳岩溶作用的叠加是形成规模储层的关键,喜马拉雅构造运动产生大量构造裂缝,提高了储层的渗滤性和规模性;(3)一定厚度和较大面积的Ⅰ—Ⅲ类储层可形成规模储层区,对5个规模储层发育区进行了评价,已发现气藏主要分布在这5个区域的背斜构造部位。结论认为,川东地区石炭系仍有较大的天然气勘探开发潜力,向斜区发育大面积的规模储层,是下一步天然气增储上产的重要方向。

The Carboniferous Huanglong Formation in the eastern Sichuan Basin is one of the important natural gas producing layers in the Sichuan Basin.The Carboniferous reservoirs are the key factor controlling the development of gas reservoirs.In order to further evaluate the Carboniferous reservoirs in the eastern Sichuan Basin,expand new exploration fields and search for replacement areas,this paper systematically studies the main factors controlling the development of the Huanglong Formation reservoirs,summarizes the development models,and predicts the distribution of large-scale reservoirs,based on the previous studies,combined with the data of drilling,core,outcrop and assay.And the following research results are obtained.First,the Huanglong Formation reservoirs are mainly composed of granular dolomite,brecciate dolomite and crystalline dolomite.The reservoir space is dominated by intercrystalline pores/intercrystalline dissolved pores,intergranular pores/intergranular dissolved pores,karst caves and fractures.The grain shoal is the favorable reservoir,and the fractured-dissolution porous reservoir is of high quality.Second,reservoir development is mainly under the joint control of sedimentation and diagenesis of Leshan-Longnüsi Paleo-uplift and Kaijiang Paleo-uplift.The two paleo-uplifts control the distribution of grain shoals and the penecontemporaneous diagenesis,which is the basis of large-scale reservoir formation.The superposition of penecontemporaneous dolomitization,interlayer karstification and weathering crust karstification is the key to the formation of large-scale reservoirs.The Himalayan movement has generated a large number of structural fractures,improving the permeability and scale of reservoirs.Third,Type I-III reservoirs with a certain thickness and a large area can develop into large-scale reservoirs.Five development areas of large-scale reservoir are evaluated.It indicates that the discovered gas reservoirs are mostly distributed in the anticlinal structures of the five large-scale reservoir areas.In conclusion,the Carboniferous in the eastern Sichuan Basin still has greater potential in natural gas exploration and development,and the large-scale reservoirs which are developed extensively in synclinal areas are the important direction for increasing natural gas reserves and production in the following step.