Reservoir characteristics and pore evolution of the Lower Shihezi Formation in Duguijiahan zone, Hangjinqi area, Ordos Basin

Abstract

The Duguijiahan zone in Hangjinqi area is an important target for natural gas exploration and development in the northern Ordos Basin.The Upper Paleozoic sandstone reservoirs in the zone have strong heterogeneity and large differences in gas saturation.This has great influence on the development characteristics and development of tight reservoirs.The study of pore evolution history is not systematic and thorough.Based on drilling cores, rock thin slices and related testing data, on the basis of statistical and comparative analysis of the petrological and physical characteristics of Upper Paleozoic sandstone reservoirs in Duguijiahan area, through the analysis of diagenesis, the main factors that control the development of reservoir pores are determined factors to reconstruct the pore evolution history of the main reservoir section.Studies have shown that the Upper Paleozoic sandstones in Duguijiahan area are mostly ultra-low permeability reservoirs, with high permeability sections with developed fractures locally; compaction and cementation are destructive to the evolution of the reservoir pores in the study area. The porosity reduction rate is 84.8% and 7.1%, respectively, and the dissolution is a constructive diagenesis, and the porosity increase rate is 9.5%; the present porosity of the He 1st member reservoir basically inherits the characteristics of the end of the Early Cretaceous, and the pore evolution has gone through early diagenesis. In stage A, compaction and cementation are rapidly reduced, and in stage B, continuous compaction is reduced.In the middle diagenesis, the dissolution and pore-enhancing effects of phase A coexist with compaction and cementation and the process of weak change in phase B.

Keywords

• reservoir characteristic
• porosity evolution
• diagenesis
• hanjinqi area
• ordos basin