塔里木和四川盆地白云岩规模优质储层形成与发育控制因素

Controls on formation and development of large-sized high-quality dolomite reservoirs in the Tarim and Sichuan Basins

通过对塔里木和四川盆地典型实例的对比,基于白云石化作用与孔隙形成机制和期次的分析,梳理了白云岩规模优质储层发育控制因素,提出了准同生期白云石化作用是储层规模化发育的关键;溶蚀作用是提升白云岩储层质量的必要条件;规模优质储层发育的前提在于白云石化作用和溶蚀作用发生的耦合关系。提出3种有利于规模优质白云岩储层发育的地质过程:(准)同生云化伴生溶蚀型、埋藏云化继承型和后生溶蚀改造型。云化伴生溶蚀型指白云岩储层主要形成于准同生白云石化作用伴生溶蚀作用改造,主要发育于海平面下降背景下的高能礁/丘滩相和潮坪相。埋藏云化继承型为先期储层经浅埋藏期白云石化作用改造而成,储层质量和规模性受控于相带和云化前溶蚀改造的强度。后生溶蚀改造型为白云岩储层经热液或表生岩溶改造而成,兼具相控性、断控性和面控性,储层质量和规模性受先期储层发育状况的显著控制。以上认识对深层白云岩规模优质储层的预测具有重要指导意义。

Following a comparative analysis of the main mechanisms and periods of dolomitization and dissolution in typical dolomite reservoirs in Tarim and Sichuan Basins,we identified the factors controlling the development of largesized high-quality dolomite reservoirs:penecontemporaneous dolomitization is crucial to the scale of the reservoirs and dissolution modification is necessary for the quality of the reservoirs,thus the coupling of dolomitization with dissolution is the prerequisite for the development of large and high-quality dolomite reservoirs.Three geological processes that facilitate the development of the reservoirs were also brought forward:the(pene-)contemporaneous dolomitization associated with dissolution that mainly formed high-energy mound/reef-shoal and tidal-flat reservoirs against the backdrop of sea level fall;the adoptive burial dolomitization that mostly created reservoirs through shallow dolomitization of preexisting reservoirs,with quality and scale conditioned by the facies and dissolution intensity of preexisting reservoirs;and the epigenetic modification by dissolution that formed reservoirs after a hydrothermal or meteoric karstification of preexisting dolomite reservoirs,with quality and size controlled by facies,faults and unconformities as well as the development of the preexisting dolomite reservoirs.The above understandings may shed light on the prediction of large-sized deep high-quality dolomite reservoirs.