The Controls of Pore-Throat Structure on Fluid Performance in Tight Clastic Rock Reservoir: A Case from the Upper Triassic of Chang 7 Member, Ordos Basin, China

Abstract

The characteristics of porosity and permeability in tight clastic rock reservoir have significant difference from those in conventional reservoir. The increased exploitation of tight gas and oil requests further understanding of fluid performance in the nanoscale pore-throat network of the tight reservoir. Typical tight sandstone and siltstone samples from Ordos Basin were investigated, and rate-controlled mercury injection capillary pressure (RMICP) and nuclear magnetic resonance (NMR) were employed in this paper, combined with helium porosity and air permeability data, to analyze the impact of pore-throat structure on the storage and seepage capacity of these tight oil reservoirs, revealing the control factors of economic petroleum production. The researches indicate that, in the tight clastic rock reservoir, largest throat is the key control on the permeability and potentially dominates the movable water saturation in the reservoir. The storage capacity of the reservoir consists of effective throat and pore space. Although it has a relatively steady and significant proportion that resulted from the throats, its variation is still dominated by the effective pores. A combination parameter ( ) that was established to be as an integrated characteristic of pore-throat structure shows effectively prediction of physical capability for hydrocarbon resource of the tight clastic rock reservoir.

A Novel Modeling Approach to Stochastically Evaluate the Impact of Pore Network Geometry, Chemistry and Topology on Fluid Transport

“…Other experimental studies also confirm this assessment (Hu et al 2015). Zhang et al (2018) evaluated pore size distribution (PSD) and permeability of a tight reservoir, located in China, and reported that throat sizes are slightly positively correlated with permeability. On the other hand, Katsube and Issler (1998) found that the mode of the PSD significantly correlates with the permeability for various Canadian shale samples.…”

Effects of Microstructure and Rock Mineralogy on Movable Fluid Saturation in Tight Reservoirs

“…The permeability is less than 1 mD. So, the reservoir is the typical ultralow-permeability reservoir . This paper first studies the characteristics of movable fluid distribution.…”

“…According to the principle of pore radius calculation of NMR, the relaxation time, relaxation rate, and rock specific surface area are related. − , The relationship between the relaxation time and pore radius is as follows where ρ is the surface relaxivity, S is the cores surface area, and V is the cores volume. The relationship between the radius and surface area is established by the ratio of surface area to volume. where F s is the shape factor.…”

“…So, the reservoir is the typical ultralow-permeability reservoir. 21 This paper first studies the characteristics of movable fluid distribution. Then, this paper systematically studies the effect of porosity, permeability, mineral composition, and fractal geometry on the movable fluid saturation of the tight sandstone.…”

“…26−28 According to the principle of pore radius calculation of NMR, the relaxation time, relaxation rate, and rock specific surface area are related. [15][16][17][18][19][20][21]29 The relationship between the relaxation time and pore radius is as follows…”