Accessible to Total Nanopore Structure and Complexity in Cambay Shales, India: An Implication on Storage and Transport of Hydrocarbon

Abstract

Accessible to inaccessible nanopore structure, distribution and complexity controls the storage, transport, and recovery of gas-shale. Fluid- (low-pressure N2 and CO2 adsorption) and radiation-based (small-angle scattering) methods used to characterize the connected and isolated nanopores in the early Tertiary sequence (1043-2573 m) of Cambay basin, India. The obtained continuous pore size distribution was deconvoluted into12 pore families. The mean width (w) of the micropore and mesopore families are w~0.50, 0.61, 0.77, 1.11 nm, and ~4.85, 8.0, 10.5, 14.5, 17.0, 30.0 nm, respectively. The multivariate partial least square regression model estimated the dependency of various dependent pore parameters (e.g., deconvoluted pore families, micro-, meso-, total pore volume, specific surface area – SSA, etc.) on intrinsic, independent variables (e.g., quartz, Fe-bearing minerals, clay and total organic carbon -TOC) of the shale samples. Our result suggests, TOC strongly enhances the storage capacity by increasing SSA and pore volumes (micro-, meso-, total pore volume), which eventually enables higher sorption and free gas storage capacity. Increased clay content increases the inaccessible pores, whereas TOC increases the accessible pore volumes. Families from micropore region (w~0.50, 0.61, 0.77, 1.11 nm) show positive dependency with the TOC, while the Families with w~ 10.5.14.5,17.0 nm show negative dependency with TOC.

Laboratory Observation of Fluid Flow in Depleted Shale Gas Reservoir: Coupling Effect of Sorbing and Non-sorbing Gas on Stress, Slippage, Flow Regime in Anisotropic and Fractured Shales

“…As a result, understanding the flow dynamics in shale gas reservoirs is fundamental for predicting gas production rates, optimizing extraction processes, and ensuring efficient and environmentally friendly operations. However, the extraction of shale gas is complicated due to complex nanopore structures and distributions, intricate pore-throats and matrix compressibility, the extremely low and nonuniform permeability, and the spatial variability of flow behavior within the shale gas reservoir. − Furthermore, the presence of gas in different forms, such as adsorbed, dissolved, and free, − leads to diverse flow behaviors governed by complex interactions among gas molecules within nanopores . Therefore, accurately describing fluid flow dynamics in such complex formations presents a considerable challenge and remains an active area of research.…”