Characteristics and genesis of the (Sinian) Dengying Formation reservoir in Central Sichuan, China

Abstract The Dengying Formation is an important stratum of exploration in the Gaoshiti-Moxi structure belt in the Sichuan Basin. Therefore, this study combines core, thin section, mud logging data and geochemical analysis (C, O and Sr isotopes) with seismic section data to investigate the basic characteristics and genesis of the Dengying Formation reservoir. Observations indicate that the reservoir rocks mainly consist of sand crumb dolomites, algae laminated dolomite and breccia. The reservoir space is dominated by porous dissolved holes, dissolved pores (or holes) along the direction of algal laminae, intra-grit holes and residual “grape lace” holes. The reservoir has the characteristics of low porosity and medium-permeability. There are three types of reservoir: porous reservoir, fractured porous reservoir and cave reservoir. The reservoir was formed by the common action of deposition, diagenesis and tectogenesis. Sedimentation is the basis and presupposition for reservoir development, but the effective reservoir is mainly controlled by the algal flat microfacies; Furthermore, compaction, cementation and filling are the main causes of reservoir density; Recrystallization is the basis for the formation of porous reservoir; Supergene dissolution is the key to reservoir formation; Buried dissolution also promotes the formation of a high quality reservoir. The fractures formed by tectogenesis significantly improve the permeability of the reservoir and contribute very little to porosity. The reservoir gradually evolved and formed under the control of various geological and diagenetic activities. This study provides important information and references for oil and gas exploitation and development in central Sichuan.

[1]  Shao-nan Zhang,et al.  Reservoir characteristics and main controlling factors of oil sand in Houba area, northwestern Sichuan Basin, China , 2014, Arabian Journal of Geosciences.

[2]  Xiuju Jin,et al.  Characteristics and genesis of the Feixianguan Formation oolitic shoal reservoir, Puguang gas field, Sichuan Basin, China , 2015, Frontiers of Earth Science.

[3]  Y. Qian,et al.  Sedimentary Facies and Distribution of Reservoir Rocks from the Feixianguan Formation in the Daxian‐Xuanhan Region, NE Sichuan , 2006 .

[4]  Ping Yang,et al.  Fluid activity and hydrocarbon accumulation period of Sinian Dengying Formation in northern Guizhou, South China , 2014 .

[5]  B. Glumac,et al.  Stable isotopes of carbon as an invaluable stratigraphic tool: An example from the Cambrian of the northern Appalachians, USA , 2002 .

[6]  Z. Zhen Reservoir Features and Physical Influences of the Sinian Dengying Formation(Sinian)in Central Sichuan,China , 2014 .

[7]  N. Clauer,et al.  Strontium isotopes as indicators of diagenetic recrystallization scales within carbonate rocks , 1989 .

[8]  D. Summers,et al.  Diagenesis and preservation of porosity in Norphlet Formation (Upper Jurassic), southern Alabama , 1989 .

[9]  W. Yong Reservoir features and controlling factors of Dengying Formation in Southeast Sichuan,China , 2010 .

[10]  J. E. Brasher,et al.  Influence of Lithofacies and Diagenesis on Norwegian North Sea Chalk Reservoirs , 1996 .

[11]  Weihua Lu,et al.  Paleo-geomorphology formed during Tongwan tectonization in Sichuan Basin and its significance for hydrocarbon accumulation , 2014 .

[12]  J. Gale,et al.  Late opening-mode fractures in karst-brecciated dolostones of the Lower Ordovician Ellenburger Group, west Texas: Recognition, characterization, and implications for fluid flow , 2007 .

[13]  R. Ehrlich,et al.  Petrographic image analysis and petrophysics: Analysis of crystalline carbonates from the Permian basin, west Texas , 1993, Carbonates and Evaporites.