丘滩复合体是四川盆地震旦系灯影组天然气产出的最重要沉积相类型,而微生物丘是丘滩复合体建造的重要组成部分,关于其类型、规模、垂向演化的研究对灯影组储层预测具有重要作用.基于蓬莱气区灯四段11口钻井的岩心、薄片、测井等资料的综合分析,按空间形态划分了3类微生物丘,明确了其内部结构及演化规律.灯四段岩性以白云岩为主,按结构组分细分为微生物白云岩、颗粒白云岩、角砾白云岩、晶粒白云岩等岩石类型.微生物丘被划分为丘基、丘核、丘盖和丘翼等微相.灯四段发育3类微生物丘:垂向加积型微生物丘,形成于微生物丘营建速率与海平面上升速率接近的环境,呈"丘基→丘核→丘盖"的生长序列,在台地边缘发育的该类微生物丘单井累计厚度一般在64～93 m之间.侧向迁移型微生物丘,形成于微生物丘营建速率大于海平面上升速率的环境,呈"丘基→丘核→丘翼"、"丘核→丘翼"等生长序列,在台地边缘发育的该类微生物丘单井累计厚度一般在25～49 m之间.小型孤立型微生物丘分布于相对低洼的丘滩体之间,规模小,无法进一步识别生长序列.蓬莱气区灯四段微生物丘以垂向加积型和侧向迁移型为主,集中发育在灯四2-3亚段台地边缘,垂向累积厚度大,横向分布连续,是灯影组最有利的相带.

The mound-shoal complex is the most important sedimentary facies for natural gas in the Dengying Formation of the Sichuan Basin,and microbial mound is an important component of the mound-shoal complex.Based on a comprehensive analysis of the cores,thin sections,and logging of 11 wells in the fourth member of the Penglai gas field,three types of microbial mounds are classified according to spatial morphology,and the internal structure and evolution rule are clarified respectively.The rock types of microbial mounds are divided into microbial dolomite,residual granular dolomite,breccia dolomite and crystalline dolomite.The microfacies such as mound base,mound core,mound cover,and mound flank are identified.Three types of microbial mound developed as follows:Vertical accretion microbial mound was formed in an environment where the construction rate of microbial mounds was close to the rate of sea level rise,with a growth sequence of"mound base→mound core→mound cover".The cumulative thickness of this type developed at the platform margin is generally 64-93 m.Lateral migration of the microbial mound was formed in environments where the construction rate of microbial mounds was greater than the rate of sea level rise,with a growth sequences of"mound base→mound core → mound flank"and"mound core → mound flank".The cumulative thickness of this type developed at the platform margin is generally 25-49 m.Small isolated microbial mound was distributed between mounds,with a thickness of generally decimeters and a small scale.The microbial mounds of vertical accretion and lateral migration concentrated at the platform margin in the second to third sub-members of the fourth member,with large total thickness and continuous horizontal distribution,which are the most favorable facies for the Dengying Formation in the Penglai gas field.