Study on Flow in Fractured Porous Media Using Pore-Fracture Network Modeling

Abstract

Microscopic flow in fractured porous media is a typical problem for the exploitation of tight reservoirs. The rapid-flow in the fractured porous-media is of great significance to efficient and continuous oil/gas exploitation. The fractures are expected to enhance flow conductivity and mass transfer between matrix and fractures, and to improve oil displacement during water flooding. However, the fractures may also lead to water channeling under some conditions. The understanding on the mechanism of the microscopic flow in the fractured porous media has been insufficient until now. In this paper, a two-dimensional pore-fracture network model is presented to study the role of fractures in the flow. The effects of two main dimensionless parameters, fracture length to network length l f /l and fracture density N f /N, on the absolute permeability and the oil displacement efficiency are investigated. The results show that the flow in the matrix plays a controlling role at a low fracture density. Once the fracture density exceeds a certain value, the flow is controlled by fractures. With the increase of the fracture density, the oil displacement efficiency develops into three typical stages: when N f /N < 0.1, the oil displacement efficiency increases rapidly; when 0.1 < N f /N < 0.5, the oil displacement efficiency changes slowly; and when N f /N > 0.5, the oil displacement efficiency decreases rapidly. In the case l f /l > 0.8, the water mainly flows through a concentrated path connected by some fractures, resulting in it bypassing most oil regions, and thus the oil displacement efficiency decreases rapidly, similar to the water channeling.

A Triple Pore Network Model (T-PNM) for Gas Flow Simulation in Fractured, Micro-porous and Meso-porous Media

“…Despite PNM simplifications, it is still interesting due to the low computational cost, especially with the Fig. 1 Network structure of the previous single PNMs and D-PNMs compared to the presented T-PNM, a single PNM (Blunt 2001;Fatt 1956), b D-PNM with meso-pores coupled to a lattice micro-pores (Bekri et al 2005), c dual with meso-pores and parallel micro-pores and throats (Bauer et al 2012), d a fully twoscale PNM with micro-and meso-pores (Jiang et al 2013), e dual with extra micro-throats to connect the meso-pores (Bultreys et al 2015), f dual with meso-pores and fractures with variable aperture (Hughes and Blunt 2001), g dual with meso-pores and fractures with fixed aperture (Erzeybek and Akin 2008), h D-PNM with extra bypassing fracture links (Liu et al 2017), i dual with unstructured network and variable geometry of fracture (Jiang et al 2017), j the presented T-PNM which includes meso-and micro-pores, meso-and micro-throats, fracture nodes, and fracture links have been accomplished by researchers to enhance the capability and reliability of PNMs (Baychev et al 2019) to realistically simulate and predict the properties of porous materials (Garboczi 1990;Joekar-Niasar and Hassanizadeh 2012;Xiong et al 2016), from hydraulic permeability (Dong and Blunt 2009) and mass diffusivity (Burganos and Sotirchos 1987;Erfani et al 2019) to electrical (Friedman and Seaton 1998) and thermal conductivities (Plourde and Prat 2003).…”

Dynamic Variation Characteristics of Seawater Intrusion in Underground Water-Sealed Oil Storage Cavern under Island Tidal Environment

“…However, in practice, the rock mass of the research area contains complex fracture networks. The groundwater seepage and seawater intrusion also mainly develop along the penetrating fissures [46,47]. In the following research, the fracture should be added into the model for more accurate simulation.…”

Effects of Cracks and Geometric Parameters on the Flow in Shale

“…The dwindling of conventional reservoirs means that the current developments in oil and gas production have to spread to unconventional reservoirs, such as tight gas, tight oil, shale gas, and shale oil reserves, in order to meet the growing demand. 1 Fluid flow in unconventional reservoirs is affected by many factors, such as pore structure characteristics, matrix wettability, organic matter, and so forth. 2 , 3 The most noteworthy feature of unconventional reservoirs is the low to ultralow permeability due to the very small pore-throat system, which severely influences the fluid flow, adsorption/desorption, and so forth.…”