The Influential Factors and Characteristics of Tight Sandstone Gas Reservoir: A Case Study in Ordos Basin in China

Dazhong Ren,Rongxi Li,Yuhong Li,Dengke Liu,Fu Yang,Qian Yin

doi:10.1155/2020/6690043

Abstract

To analyze the impact of the factors on physical properties and the mechanism of tightness as well as favorable accumulation space of tight sandstone reservoir, comprehensive analysis is conducted using various kinds of experiments. The results show that the predominant rock type is medium-coarse grained lithic quartzarenite, and the main accumulating space is the dissolved secondary pores. Reservoir pore-throat structures can be divided into four categories. Based on morphologies and parameters which derived from capillary pressure curves, the physical properties rank in the following descending sequence: Type I > Type II > Type III > Type IV . The reservoir quality is influenced by both sedimentation and diagenesis synthetically. The underwater distributary channel is the dominant space for favorable reservoir. Compaction and cementation play dominant roles in the reduction of permeability. The loss of primary pores caused by both those diagenesis are 20.52% and 16.91%, respectively. Secondary pores formed by dissolution improve the reservoir quality by increase the porosity (2.68%). This suggests that weak diagenesis greatly contributes to the improvement of reservoir quality.

Highlights

Tight sandstone is a heterogeneous porous media with tiny pore body and narrow pore throat [1,2,3,4,5,6]
It is of great significance to study the influential factors and characteristics of the tight sandstone reservoirs
The physical properties of tight sandstone are very complicated due to the heterogenously distributed grains and pore network, and the mechanism of tightness is dependent on those properties [15, 16]. Numerous studies on those properties and abundant methods have been applied, and the results show that large pores dominate the pore storage while tiny pores control the percolation ability [17,18,19]. When it comes to favorable accumulation space of tight sandstone reservoir, currently, various techniques including observations and quantitative determination are adopted [20, 21]

Summary

Introduction

Tight sandstone is a heterogeneous porous media with tiny pore body and narrow pore throat [1,2,3,4,5,6]. The physical properties of tight sandstone are very complicated due to the heterogenously distributed grains and pore network, and the mechanism of tightness is dependent on those properties [15, 16] Numerous studies on those properties and abundant methods have been applied, and the results show that large pores dominate the pore storage while tiny pores control the percolation ability [17,18,19]. When it comes to favorable accumulation space of tight sandstone reservoir, currently, various techniques including observations and quantitative determination are adopted [20, 21]. We analyzed the influential factors of physical properties, the mechanism of tightness, and favorable accumulation space of tight sandstone reservoir by various kinds of tests, such as casting thin slices (CTS), scanning electron microscope (SEM), cathodoluminescence (CL), X-ray diffraction (XRD), high-pressure mercury intrusion (HPMI), physical property testing, core testing, and well logging

Methodology

Result and Discussion

V: Feldsarenite VI: Lithic arkose VII: Feldspathic litharenite VIII

Findings

Conclusion