四川盆地威远地区下志留统龙马溪组页岩储层有利区评价

Evaluation on favorable shale reservoirs of Lower Silurian Longmaxi Formation,Weiyuan area,Sichuan Basin

中国石化西南油气分公司在四川盆地威远地区页岩气勘探中获得工业气流,实钻结果表明该区勘探开发潜力巨大。为了推动该区规模建产,促进西南地区页岩气增产创效,急需对该区有利区进行评价。为此,通过黏土矿物分析、扫描电镜、有机碳及镜质体反射率分析等实验分析手段和方法,应用石油地质、矿物学及油气成藏等理论,研究威远地区下志留统龙马溪组页岩储层特征及影响页岩气形成和富集的因素,建立评价威远地区龙马溪组页岩储层标准,形成评价龙马溪组页岩气有利区分类标准,并对威远地区龙马溪组页岩气储层有利区进行评价。研究结果表明:①威远地区龙马溪组页岩的储集空间主要为微孔隙和微裂隙,有机质微孔隙最为发育,其储集性好;②有机质丰度、适中热演化和好的保存条件的区域是威远地区页岩气有利区的发育区,也是该区勘探开发取得成功的有利区;③威远地区页岩储层为优质页岩气储层段,适合大规模开发,满足规模建产的地质条件;④本评价方法对威远地区龙马溪组页岩储层有利区的评价技术有效,为威远地区龙马溪组规模建产提供了技术支撑。

In recent exploration,Sinopec Southwest Oil&Gas Company has obtained industrial gas flows from shale-gas reservoirs in Weiyuan area,Sichuan Basin.And drilling practices also show a huge exploration and development potential.In order to promote the large-scale construction of production capacity and increase the production and effective development of shale gas in Southwest China,it is urgent to evaluate favorable shale-gas zones in this area.So,through experimental analysis on clay minerals,organic carbon,and vitrinite reflectance,and scanning electron microscope,and based on petroleum geology,mineralogy,and reservoir-forming theory,some characteristics of shale reservoirs of Lower Silurian Longmaxi Formation in Weiyuan area were analyzed.And some factors affecting the formation and accumulation of shale gas were investigated.Then several standards to evaluate and classify favorable shale reservoirs were established.Finally,these favorable reservoirs were evaluated.Results show that,(1)for Longmaxi shale reservoirs in Weiyuan area,the reservoir space is composed of micropores and microfractures,of which organic micropores are the most developed and their properties are good;(2)zones with high organic abundance,appropriate thermal evolution,and good preservation conditions are favorable for shale-gas accumulation,and have been explored and developed successfully;(3)the shale-gas reservoirs have been evaluated as good ones which meet geological needs of capacity construction,and can be developed on a large scale;and(4)the method to evaluate the favorable shale-gas zones may provide technical supports for large-scale capacity construction of Longmaxi Formation in Weiyuan area.