The Characteristics Of Sandstone Reservoir And Diagenesis In The Mid-devonian In The Northwest Of Sichuan

Erlangmiao area is located in Jiangyou city, the northern section of Longmenshan,and northwestern margin of Sichuan basin, the area is superposed with Kuangshanliang-Tianjingshan-Erlangmiao anticline thrust.In the course of more than 10 years of exploration,this district has been found sets of oil containing sandstone such as the Shaximiao Formation sand distributed in Jiangyou-Guangyuan area, the outcrop oil seepage is large and widely distributed. As early as in middle 20 th century the investigation and research of oil sand resources had begun in this area, one of the nine shallow well has 27 meter thickness of oil sand and show abundant reserves and good prospects for exploration. Recently the discovery of Devonian paleo-oil reservoir in the Tianjingshan tectonic zone, northern Longmen mountain, adds more significance on the exploration of oil sand resources in northern Longmen mountain.This article made comprehensive evaluation of reservoir of middle Devonian Haikou sandstone, Erlangmiao, Jiangyou area,Sichuan basin on the basis of measured stratigraphy sections and detailed core observation, section identification, scanning electron microscope, porosity and permeability analysis and the x-ray diffraction. The integrated evaluation was made up of mineral component research, grain size and diagenesis and it’s evolution mode impact on reservoir control, and the analysis of debris rock complex pores and it’s controlling factors. The understandings are listed as follows:(1). The study shows the Haikou formation in this area is principally a set of very pure middle-fine grained quartz sandstone whose micro-facies is foreshore and the compositional and structural maturity are notably high as well was washing bedding very well developed.(2). The pore types of this set reservoir are simple and include original intergranular, and intergranular. The original ones which is more developed is the main storage space. The dissolution of feldspar and lithic formed less amount of intergranular pores, and contribution to reservoir properties of intergranular and intragranular dissolved pores made by authigenic mineral filled in pore is far less than that of original intergranular pores.(3). The Haikou sandstone can be seen as a typical model of original intergranular pores reservoir. It’s pore connects very well, porosity and permeability relates, displacement pressure is very low, throats are generally large, and the structure is good, The quality of the reservoir is high.