摘要
塔里木盆地下奥陶统蓬莱坝组白云岩经历了复杂的成岩演化过程,具有多期次、多成因的特征,为了系统研究蓬莱坝组白云岩的岩石学特征、白云石化机理及储集层主控因素,基于露头、岩心、薄片及地球化学测试开展分析。研究表明,蓬莱坝组主要发育粉晶白云岩、细—中晶白云岩、粗晶白云岩及斑状白云岩,其形成受控于准同生—浅埋藏及埋藏环境下的白云石化作用;细—中晶白云岩晶间孔发育,自形程度高,粗晶白云岩保留部分晶间孔,抗压实能力强;白云岩普遍为埋藏条件下的交代或重结晶成因,白云石化流体主要为早奥陶世海水,部分受深部热液及蒸发岩层间热卤水影响;颗粒滩相为储集层发育最有利的沉积相类型,其早期粒间孔系统为白云石化流体提供了良好的运移通道和储集空间,促进了白云石化作用的进行;海平面变化通过改变水动力条件、流体运移特征以及影响岩溶作用发生,影响了白云石化的物理、化学条件;古地貌高点区域白云石化程度高,顺层溶蚀孔洞发育为优质储集层提供了有利条件。研究成果为塔里木盆地奥陶系深层白云岩勘探提供了重要依据,揭示了白云石化机理及储集层主控因素,对进一步勘探开发具有重要的指导意义。
The dolomites in the Lower Ordovician Penglaiba formation in the Tarim Basin have undergone a complex diagenetic evolution characterized by multi-stage and multi-genesis.To systematically study their petrological features,dolomitization mechanisms,and main factors governing reservoir quality,investigations were conducted using outcrops,core samples,thin sections,and geochemical tests.The re-sults show the presence of four major dolomite types in the Penglaiba formation,including micritic dolomite,fine-to medium-grained dolo-mite,coarse-grained dolomite,and porphyritic dolomite,all of which are genetically controlled by penecontemporaneous-shallow burial and burial dolomitizations.Fine-to medium-grained dolomites display abundant intercrystalline pores with high euhedral degree,whereas coarse crystalline dolomites retain some intercrystalline pores and have strong compaction resistance.The dolomites generally formed through replacement or recrystallization under burial conditions,with Early Ordovician seawater serving as the primary dolomitizing fluid,variably modified by deep hydrothermal fluids and evaporite-derived brines.Grain-shoal deposits provide the most favorable sedimentary microfacies for reservoir development because the early intergranular pores not only act as pathways for fluid migration but also serve as ini-tial storage space,thereby accelerating dolomitization.Sea-level fluctuations modulated the physical and chemical conditions of dolomitiza-tion by altering hydrodynamic regimes,fluid-migration patterns,and the karstification processes.Palaeogeomorphic highs experienced more intense dolomitization,and well-developed stratiform dissolution pores and vugs provide favorable conditions for high-quality reser-voirs.These insights provide a sound basis for deep dolomite exploration in the Ordovician strata of the Tarim Basin,clarify dolomitization mechanisms and main reservoir-controlling factors,and offer practical guidance for future exploration and development.
作者
闫博
罗富文
曹阳
程林峰
YAN Bo;LUO Fuwen;CAO Yang;CHENG Linfeng(PetroChina Daqing Oilfield Company Ltd.,Research Institute of Exploration and Development,Daqing,Heilongjiang 163712,China;PetroChina Daqing Oilfield Company Ltd.,Chengdu Research Institute of Exploration and Development,Chengdu,Sichuan 610000,China)
出处
《新疆石油地质》
北大核心
2025年第4期419-428,共10页
Xinjiang Petroleum Geology
基金
中国石油科技重大专项(1016E-0204)。
关键词
塔里木盆地
蓬莱坝组
白云岩
白云石化
碳氧同位素
锶同位素
主控因素
Tarim Basin
Penglaiba formation
dolomite
dolomitization
carbon and oxygen isotopes
strontium isotope
controlling factor
