Jingsheng Ma

Bio: Jingsheng Ma is an academic researcher from Heriot-Watt University. The author has contributed to research in topics: Oil shale & Permeability (earth sciences). The author has an hindex of 24, co-authored 80 publications receiving 1721 citations.

3D stochastic modelling of heterogeneous porous media - applications to reservoir rocks

Abstract: The creation of a 3D pore-scale model of a porous medium is often an essential step in quantitatively characterising the medium and predicting its transport properties. Here we describe a new stochastic pore space reconstruction approach that uses thin section images as its main input. The approach involves using a third-order Markov mesh where we introduce a new algorithm that creates the reconstruction in a single scan, thus overcoming the computational issues normally associated with Markov chain methods. The technique is capable of generating realistic pore architecture models (PAMs), and examples are presented for a range of fairly homogenous rock samples as well as for one heterogeneous soil sample. We then apply a Lattice–Boltzmann (LB) scheme to calculate the permeabilities of the PAMs, which in all cases closely match the measured values of the original samples. We also develop a set of software methods – referred to as pore analysis tools (PATs) – to quantitatively analyse the reconstructed pore systems. These tools reveal the pore connectivity and pore size distribution, from which we can simulate the mercury injection process, which in turn reproduces the measured curves very closely. Analysis of the topological descriptors reveals that a connectivity function based on the specific Euler number may serve as a simple predictor of the threshold pressure for geo-materials.

Efficient extraction of networks from three-dimensional porous media

Abstract: [1] Fluid flow through porous media, and the thermal, electrical, and acoustic properties of these materials, is largely controlled by the geometry and topology (GT) of the pore system, which can be considered as a network. Network extraction techniques have been applied in many research fields, including shape representation, pattern recognition, and artificial intelligence. However, the set of algorithms presented here significantly improves the efficiency of common thinning algorithms by introducing a sufficiency condition based on the idea of a simple set. This paper describes an efficient and accurate algorithm for extracting the geometrical/topological network that represents the pore structure of a porous medium, referred to as the GT network. The accurate medial axis and the specific GT description of the network are achieved by applying symmetrical and interval strategies during the erosion step in the image processing. The GT network extraction algorithm presented here involves a number of steps, including (1) calculation of the three-dimensional Euclidean distance map; (2) clustering of voxels; (3) extraction of the network of the pore space; (4) partitioning of the pore space; and (5) computation of shape factors. The focus of this paper is mainly on the thinning method that underpins points 1–3. The paper is primarily a method description, but we illustrate the functionality of the technique by extracting a pore scale GT network from micro–computer tomography images of three sandstones.

A comprehensive review of pore scale modeling methodologies for multiphase flow in porous media

Abstract: Multiphase flow in porous media is relevant to amount of engineering processes, such as hydrocarbon extraction from reservoir rock, water contamination, CO2 geological storage and sequestration. Pore scale modeling, as an alternative approach to lab measurement, firstly serves as an effective bridge to link the pore scale properties (pore geometry and wettability) and displacement mechanisms to continuous scale multiphase flow in porous media; and secondly allows us to determine essential flow functions, such as capillary pressure and relative permeability curves, which are required for continuous scale modeling. In the literature, three methodologies, Bundle of Capillary Tube Modeling (BCTM), Direct Pore Scale Modeling (DPSM) and Pore Network Modeling (PNM), have appeared to be mostly widely adopted in the investigation of the pore-scale mechanics of fluid-fluid and fluid-solid interactions in porous media by numerical simulation. In this review article, a comprehensive review is provided to show their strengths and weaknesses and to highlight challenges that are faced in modelling of multiphase flow, key challenges include: are contact angle characterization, validation and upscale pore scale findings to core, or even field scale.

GeoDa: An Introduction to Spatial Data Analysis

Abstract: The development of specialized software for spatial data analysis has seen rapid growth since the lack of such tools was lamented in the late 1980s by Haining (1989) and cited as a major impediment to the adoption and use of spatial statistics by GIS researchers. Initially, attention tended to focus on conceptual issues, such as how to integrate spatial statistical methods and a GIS environment (loosely vs. tightly coupled, embedded vs. modular, etc.), and which techniques would be most fruitfully included in such a framework. Familiar reviews of these issues are represented in, among others, Anselin and Getis (1992), Goodchild et al. (1992), Fischer and Nijkamp (1993), Fotheringham and Rogerson (1993, 1994), Fischer et al. (1996), and Fischer and Getis (1997). Today, the situation is quite different, and a fairly substantial collection of spatial data analysis software is readily available, ranging from niche programs, customized scripts and extensions for commercial statistical and GIS packages, to a burgeoning open source effort using software environments such as R, Java and Python. This is exemplified by the growing contents of the software tools clearing house maintained by the U.S.- based Center for Spatially Integrated Social Science [CSISS] (see http://www.csiss.org/clearinghouse/).

VALIDITY OF CUBIC LAW FOR FLUID FLOW IN A DEFORMABLE ROCK FRACTURE - eScholarship

Abstract: The validity of the cubic law for laminar flow of fluids through open fractures consisting of parallel planar plates has been established by others over a wide range of conditions with apertures ranging down to a minimum of 0.2 µm. The law may be given in simplified form by Q/Δh = C(2b)3, where Q is the flow rate, Δh is the difference in hydraulic head, C is a constant that depends on the flow geometry and fluid properties, and 2b is the fracture aperture. The validity of this law for flow in a closed fracture where the surfaces are in contact and the aperture is being decreased under stress has been investigated at room temperature by using homogeneous samples of granite, basalt, and marble. Tension fractures were artificially induced, and the laboratory setup used radial as well as straight flow geometries. Apertures ranged from 250 down to 4µm, which was the minimum size that could be attained under a normal stress of 20 MPa. The cubic law was found to be valid whether the fracture surfaces were held open or were being closed under stress, and the results are not dependent on rock type. Permeability was uniquely defined by fracture aperture and was independent of the stress history used in these investigations. The effects of deviations from the ideal parallel plate concept only cause an apparent reduction in flow and may be incorporated into the cubic law by replacing C by C/ƒ. The factor ƒ varied from 1.04 to 1.65 in these investigations. The model of a fracture that is being closed under normal stress is visualized as being controlled by the strength of the asperities that are in contact. These contact areas are able to withstand significant stresses while maintaining space for fluids to continue to flow as the fracture aperture decreases. The controlling factor is the magnitude of the aperture, and since flow depends on (2b)3, a slight change in aperture evidently can easily dominate any other change in the geometry of the flow field. Thus one does not see any noticeable shift in the correlations of our experimental results in passing from a condition where the fracture surfaces were held open to one where the surfaces were being closed under stress.