普光气田台地建造过程及其礁滩储层高精度层序地层学研究

doi:10.11743/ogg20080502

摘要/Abstract

摘要：

普光气田及近年来川东北地区一系列重大发现,实现了按海相深层构造-岩性复合气藏和岩性气藏勘探思路寻找大型礁滩气藏的目标。应用沉积学、层序地层学和地震沉积学的理论和方法,系统研究普光气田上二叠统长兴组至下三叠统飞仙关组典型的镶边型碳酸盐岩台地建造过程及巨厚礁滩和鲕滩复合体的发育和分布规律发现:普光气田长兴期台缘礁及开阔台地生屑滩和飞一、飞二段台缘和开阔台地鲕滩的垂向加积过程构筑了四川盆地和国内厚度最大的镶边型碳酸盐岩台地。普光气田长兴礁起源于二级层序海泛期的陆棚环境,它建造成台地镶边,在地震剖面上表现为丘状空白反射;普光气田飞仙关组台缘及台内鲕滩形成于二级层序高位期早期,在地震剖面上表现为丘状杂乱-不连续强反射。长兴礁及礁后沉积为后继飞仙关组鲕滩的形成提供了浅水高能背景。从碳酸盐岩层序地层学角度,普光气田长兴组和飞仙关组由5个三级层序组成,而每个三级层序又由2～3个四级层序组成。碳酸盐岩沉积学和层序地层学的结合揭示了普光碳酸盐台地的演化过程。随着探井的钻探,碳酸盐岩高精度层序地层序揭示出普光气田礁、滩白云岩储层对称的高频旋回特征。在每一旋回内,孔隙度随自然伽马和电阻率的减小、白云石晶体的变粗而增大。普光气田台地建造过程及高频层序内储层孔隙度分布特征,不仅为拓展今后礁滩勘探提供了理论依据,还对后继气藏开发具指导意义,是实现碳酸盐岩气藏勘探、开发一体化的重要研究内容。

关键词: 海相深层, 碳酸盐岩台地, 高精度层序地层学, 优质储层, 普光气田, 四川盆地

Abstract:

Puguang gas field and other major discoveries in northeastern Sichuan Basin obtained in recent years prove the correctness of the strategy searching for large gas pools in reservoirs of reef and oolitic shoal facies according to the exploration idea of structural-lithologic combination gas pools and lithologic gas pools occurring in deep marine sequences.Theories and methodologies of sedimentology,sequence stratigraphy and seismic sedimentology are applied to systematically study the building-up process of carbonate platforms and the formation and distribution of super-thick complexes of reef and oolitic shoal facies in sequences from the Upper Permian Changxing Formation to the Lower Triassic Feixianguan Formation.It is discovered that the vertical superimposition of platform-margin reef and open platform bioclastic shoal of the Changxing Formation and the platform-margin and open platform oolitic shoal in the first and second members of Feixianguan Formation resulted in the largest and thickest carbonate platform in Sichuan Basin and China.The Changxing Formation reef was formed on continental shelf during marine transgression of second-order sequence and is represented by moundy blank reflections on seismic profile.The Feixianguan Formation platform-margin and intra-platform oolitic shoal was formed at the early HST of second-order sequence and is represented by moundy chaotic-discrete strong reflections.The Changxing Formation reef and post-reef deposits provided a high energy shallow water environment for the formation of the successive Feixianguan Formation oolitic shoal.Carbonate sequence stratigraphic research shows that the Changxing Formation and the Feixianguan Formation can be divided into 5 third-order sequences, each of which can be subdivided into 2 to 3 fourth-order sequences.Integrated study of carbonate sedimentology and sequence stratigraphy reveals the evolution of Puguang carbonate platform.High-resolution sequence stratigraphic research of the carbonates based on drilling data reveals the symmetrical high-frequency cyclic features of the dolomite reservoirs of reef and shoal facies.Reservoir porosity increases along with the decreasing of gamma ray and resistivity and the coarsening of dolomite crystalline in each cycle.The building-up process of the platform and the characteristics of reservoir porosity distribution in the high-frequency sequences provide not only the necessary theoretical bases for further exploration of carbonate sequences of reef and shoal facies,but also a guide to gas development.They constitute an important part of the integrated research of exploration and development of carbonate oil/gas pools.

Key words: deep marine sequence, carbonate platform, high-resolution sequence stratigraphy, high-quality reservoir, Puguang gas field, Sichuan Basin

中图分类号:

TE121.3

马永生,储昭宏. 普光气田台地建造过程及其礁滩储层高精度层序地层学研究[J]. 石油与天然气地质, 2008, 29(5): 548-556. doi: 10.11743/ogg20080502 Ma Yongsheng,Chu Zhaohong. Building-up process of carbonate platform and high-resolution sequence stratigraphy of reservoirs of reef and oolitic shoal facies in Puguang gas field[J]. Oil & Gas Geology, 2008, 29(5): 548-556. doi: 10.11743/ogg20080502

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