A Simple Effective Method for Three-Dimensional Modelling of Cementation, Fracturing and Dissolution of Carbonate Rocks: Illustrated through Oolitic Limestone

James Buckman,Sean Higgins

doi:10.3390/geosciences9060246

Abstract

Sandstones and many carbonates (e.g., oolitic limestone and other grainstones), comprise solid particulates (grains) and pores, which have a given pore network architecture relationship, and associated porosity—permeability values. Over time, through the process of diagenesis, the pore network architecture may be extensively altered. Changes can include compaction, particle deformation, cementation, dissolution and fracturing, with the pathway followed after deposition depending on factors such as the energy level, rate of burial, degree of biological activity, local heat flow, sediment composition, Eh, pH and the presence or absence of organic materials. Any method that provides a means of modelling changes is therefore highly desirable, in particular, allowing a prediction of changes in porosity and permeability with time. The current work illustrates a simple method that uses freely available open source image analysis software to model the development of cement phases within an oolitic limestone in three-dimensions. As well as cementation, it demonstrates the modelling of fracture development and dissolution processes, and records how porosity and permeability change during such processes.

Highlights

Oolitic limestones are geologically common, within the Jurassic of Europe [1,2,3,4,5], and common within the Carboniferous [5,6,7], Permo-Triassic [8] and with recent to modern oolitic sands forming within the Bahaman Banks area [9,10]
The technique does not directly replicate the increase of 9.47%, which in the case of the cartoon model is greater than original porosity left after the formation of the phase 1 rimming cement
Its importance lies in the fact that it can be performed on standard desktop or laptop in the X and Y directions indicates a degree of computers, and that the majority of modelling is carried out using open source software (FIJI).inIn connectivity between pores introduced through the vertical fractures

Summary

Introduction

Oolitic limestones are geologically common, within the Jurassic of Europe [1,2,3,4,5], and common within the Carboniferous [5,6,7], Permo-Triassic [8] and with recent to modern oolitic sands forming within the Bahaman Banks area [9,10] Such limestones are highly variable in both porosity and permeability [7,8], but are commonly well cemented [11]. Numerous publications have dealt with the 3D modelling of geological porous media, such as sandstones and carbonates, producing stochastically constructed binary models of solid and pore distribution [13,14,15,16,17,18] Such models typically use specialised software, require substantial computational

Methods

Results

Conclusion