Micro- and Nanoscale Flow Mechanisms in Shale Oil: A Fluid–Solid Coupling Model Integrating Adsorption, Slip, and Stress Sensitivity

TL;DR

This paper introduces a new model to understand how oil flows in shale reservoirs by combining fluid and rock interactions.

Contribution

The novel fluid–solid coupling model integrates adsorption, slip effects, and stress sensitivity for shale oil transport.

Findings

Larger pore diameters and higher porosity improve stress dissipation and permeability preservation.

Tortuosity controls stress distribution, with low tortuosity causing stress concentration and permeability loss.

High fracture conductivity leads to heterogeneous stress fields and early mechanical failure near the wellbore.

Abstract

Shale oil reservoirs are complex multi-scale nanoporous media where fluid transport is governed by coupled micro-mechanisms, demanding a robust modeling framework. This study presents a novel fluid–solid coupling (FSC) numerical model that rigorously integrates the three primary scale-dependent transport phenomena: adsorption in organic nanopores, slip effects in inorganic micropores, and stress-sensitive conductivity in fractures. The model provides essential quantitative insights into the dynamic interaction between fluid withdrawal and reservoir deformation. Simulation results reveal that microstructural properties dictate the reservoir’s mechanical stability. Specifically, larger pore diameters and higher porosity enhance stress dissipation, promoting long-term stress relaxation and mitigating permeability decay. Crucially, tortuosity governs the mechanical response by controlling pressure transmission pathways: low tortuosity causes localized stress concentration, leading to rapid micro-channel closure, while high tortuosity ensures stress homogenization, preserving long-term permeability. Furthermore, high fracture conductivity induces a severe, heterogeneous stress field near the wellbore, which dictates early-stage mechanical failure. This work provides a powerful, mechanism-based tool for optimizing micro-structure and production strategies in unconventional resources.

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