Pore size distribution, their geometry and connectivity in deeply buried Paleogene Es1 sandstone reservoir, Nanpu Sag, East China

Abstract

The study of pore characteristics is of great importance in reservoir evaluation, especially in deeply buried sandstone. It controls the storage mechanism and reservoir fluid properties of the permeable horizons. The first member of Eocene Shahejie Formation (Es1) sandstone is classified as feldspathic litharenite and lithic arkose. The present research investigates the pore characteristics and reservoir features of the deeply buried sandstone reservoir of Es1 member of Shahejie Formation. The techniques including thin-section petrography, mercury injection capillary pressure (MICP), scanning electron microscopy and laser scanning confocal microscope images were used to demarcate the pores including primary intergranular pores and secondary intergranular, intragranular, dissolution and fracture pores. Mercury injection test and routine core analysis were led to demarcate the pore network characteristics of the studied reservoir. Pore size and pore throat size distribution are acquired from mercury injection test. Porosity values range from 0.5% to 30%, and permeability ranges 0.006-7000 mD. Pore radii of coarse-grained sandstone and fine-grained sandstone range from 0.2 to > 4 µm and 1 nm to 1.60 µm, respectively, by MICP analysis. The mineral composition also plays an important role in protecting the pores with pressure from failure. Fractured sandstone and coarse-grained sandstone consist of large and interconnected pores that enhance the reservoir porosity and permeability, whereas fine-grained sandstone and siltstone consist of numerous pores but not well interconnected, and so they consist of high porosity with low permeability.

Static reservoir modeling using stochastic method: a case study of the cretaceous sequence of Gamtoos Basin, Offshore, South Africa

“…However, in the southern part of the study area, the porosity distribution indicates poor to fair porosity values ranging from 8 to 10% within the Ha-B2, Ha-K1, and Ha-A1 wells. Reservoir properties, which include the porosity of tight sandstones, have an intimate relationship with depositional facies, features, and clay minerals (Calderon and Castagna 2007;Kashif et al 2019). Consequently, we infer that facies, diagenetic effects, and clay mineral present may be due to the variation in the porosity distribution in the study area.…”

Stress sensitivity of porosity and permeability under varying hydrostatic stress conditions for different carbonate rock types of the geothermal Malm reservoir in Southern Germany

“…Based on the distribution of the pore throat sizes, a porous rock can be categorized according to specific pore types: sub-capillary pore throats when d < 0.4 µm (micro-throats), capillary pore throats when 0.4 < d < 8.4 µm (meso-throats) and 8.4 < d < 60 µm (macro-throats), and supra-capillary pore throats when d > 60 µm (mega-throats) (Kashif et al 2019;Nabawy et al 2009). Permeability Darcy (1856) defined that the water flow through a column is directly proportional to the hydraulic head and inversely proportional to the column length.…”

“…The classification of porosity and pore types in thin sections is based on the fundamentals of Choquette and Pray (1970). The geometry of the pores and the pore throat sizes were classified using the the capillary curves of the MIP tests using the work of Luo and Machel (1995) and Kashif et al (2019) as a guideline.…”

Geometric and Fractal Characterization of Pore Systems in the Upper Triassic Dolomites Based on Image Processing Techniques (Example from Žumberak Mts, NW Croatia)

“…There are a variety of different methods for pore-structure characterization: fluid invasion methods (mercury and helium porosimetry (MICP)) [25][26][27][28][29][30][31], low-temperature adsorption isotherms by adsorption of N 2 or CO 2 [18,20,25,27,[30][31][32][33][34][35][36], nuclear magnetic resonance [37], and X-ray methods (SANS/USANS) [12,18,27,33,38] although these methods can estimate porosity values but do not give information about pore morphology. CT scans [12,30,39,40], scanning electron microscopy [16,19,25,26,29,30,33,[41][42][43][44][45], and thinsection analysis [29,37,46] are methods that can quantify geometrical parameters of the rock pore structure. These methods in themselves cannot define heterogeneity and pore shape complexity of analyzed rocks [26,[47]…”