渤海海域蓬莱9-1花岗岩潜山大型油气田储层发育特征与主控因素

Characteristics and controlling factors of reservoirs in Penglai 9-1 large-scale oilfield in buried granite hills,Bohai Sea

蓬莱9-1油田是近年来中国近海首次发现的一个以中生代花岗岩潜山风化壳为储层的大型油气田。在花岗岩潜山这个新的勘探领域,储层特征及储层形成机理条件是制约高效勘探的关键。通过镜下薄片鉴定、扫描电镜分析、矿物X-衍射分析、岩心与岩屑录井、测井曲线等资料综合分析,认为由表及里随着风化淋滤作用的逐渐减弱,蓬莱9-1花岗岩潜山可以划分为土壤带、砂-砾质风化带、裂缝带和基岩带,储集空间由孔隙型—裂缝-孔隙型—孔隙-裂缝型—裂缝型呈现有规律的变化。花岗岩潜山储层发育主要受表生岩溶作用、有机酸溶蚀作用、构造变形作用及微古地貌作用共同控制。这个认识对中国燕山期侵入的花岗岩潜山风化壳油气勘探开发具有借鉴意义。

Penglai 9-1 oilfield has been the first large-scale field found in weathering crust reservoirs of the Mesozoic bu-ried granite hills in coast waters of China in recent years .In this brand new area of exploration ,reservoir characterization and its forming mechanism are considered essential for efficient and successful exploration .Thin section,SEM,and clay mineral X-diffraction analyses were combined with logging data to provide insight into uncertainties of the area .The re-sults show that the buried granite hills can be divided into soil zone ,sand-conglomerate weathering zone ,fracture zone and base rock zone,and reservoiring space in them changes in a regular pattern from pore to fracture-pore,pore-fracture and fracture,from the surface to the center as weathering and leaching gradually weaken .Horizontally,granite reservoirs are continuously and widely distributed and paralleled to the top of the buried hills .Thicker reservoirs are mainly developed near large-scale faults with intensive activities and paleogeomorphic slope areas .The paper proposes that the reservoirs were controlled mainly by epigenic karstification ,organic acid dissolution ,structural deformation and micro-palaeogeomor-phology .The significance of the understanding may be felt in the future exploration and development of oil and gas in weathering curst reservoirs of buried granite hills intruded during Yanshan period .