Relationship Between Rock Velocity And Porosity

Electrical Electronics Engineering

The correlation between rock velocity and porosity is pivotal in geophysical exploration, particularly in fields such as seismic interpretation and reservoir characterization. Porosity, defined as the void space within a rock matrix, directly impacts the velocity of seismic waves passing through it. Rocks with higher porosity generally exhibit lower velocities due to the presence of air or fluid-filled pore spaces, which decrease the overall density and stiffness of the rock. Conversely, rocks with lower porosity tend to have higher velocities since their compacted structure allows seismic waves to propagate more efficiently. This relationship between rock velocity and porosity is fundamental in estimating subsurface properties like fluid content and lithology, making it crucial for reservoir assessment and hydrocarbon exploration. Understanding this intricate interplay aids in optimizing seismic data processing techniques and accurately interpreting subsurface geology for various engineering and resource extraction endeavors.

ABSTRACT

An empirical relationship between compressional wave velocity and porosity was developed for under-thrust sediments. The new transform includes a critical porosity transition. Corrections were calculated and applied to shipboard core measurements to account for unloading from in situ conditions. The results from the velocity-porosity transform indicate the sediments follow a normal consolidation curve. Although an accurate critical porosity transition was fit to these data, the critical porosity transition occurs over a range of porosity. However, the above methods are mainly used in the field of composite materials but are rarely applied in the fields of rock physics or geophysics. The main aim of this study is to analyze the internal relationships among seismic wave velocity and rock porosity.

TABLE OF CONTENTS

COVER PAGE

TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWELDGEMENT

ABSTRACT

CHAPTER ONE

INTRODUCTION

1.1 BACKGROUND OF THE STUDY

AIM AND OBJECTIVE OF THE PROJECT
SCOPE OF THE STUDY
LIMITED OF THE STUDY
METHODOLOGY
PROJECT ORGANISATION

CHAPTER TWO

LITERATURE REVIEW

OVERVIEW OF ROCK
TYPES OF ROCK
ROCK CYCLE
ROCK TEXTURE
ROCK POROSITY
POROSITY MEASUREMENT TECHNIQUES

CHAPTER THREE

METHODOLOGY

METHOD

CHAPTER FOUR

RESULT AND DISCUSSION
RESULT
DISCUSSION

CHAPTER FIVE

CONCLUSION
REFERENCES

CHAPTER ONE

1.0 INTRODUCTION

1.1 BACKGROUND OF THE STUDY

Rock mechanics parameters, seismic rock physics parameters, and rock porosity are very important rock properties in the field of geotechnical, mining and petroleum engineering. The bulk modulus (K), and shear modulus (μ), can be calculated from wave velocities [Birch F, 2017]. The rock specific results have been obtained through related geophysical research [Milkereit B, Eaton D, Wu J, et al, 2016]. There are many cracks distributed in natural rock because of forming conditions and changing environment. The properties of these cracked rocks are critically affected by the pressure (P) of the surrounding rocks. The constituent minerals and micro-cracks dictate the rock sample’s response to stress. This behavior is reflected in the compressional and shear velocities measured in the laboratory as a function of confining pressure. Therefore, laboratory velocities have been employed to solve important geologic problems. The nonlinear relationship of confining pressure (P) and seismic wave velocity (V) was first noticed by [Wepfer W W, Christensen N I, 2011].

Rock porosity (φ) also significantly impacts on the elastic properties and seismic velocities of a material [Wepfer W W, Christensen N I, 2011]. An in-depth analysis of void evolution and coalescence in simple shear was performed and revealed the complex relationship between the void. Mean Field method is used to explain the dynamic influences of both randomly oriented and aligned cracks. The Dislocation theory is developed to solve the deformations connected with a closer to the real crack geometry with tapered edges.

Numerous studies have been conducted to determine velocity-porosity transforms for a variety of sediment and rock types. In this paper, we present a velocity- porosity transform for the under thrust sediments based on the global empirical relationship.

1.2 AIM AND OBJECTIVES

In this paper, the main aim is to discuss the relationship between velocity and effective porosity of the rock. The objective is to determine the graphical and empirical relationship between rock velocity and porosity.

1.3 SCOPE OF THE STUDY

This work expresses the relation between the velocity and porosity for clean sandstone and another expresses the relation between the velocity and effective porosity of 100% clay minerals in the pore space. The effective porosity is moved between two lines. From the study we estimate the volume of bound water and show the effects of clay minerals for the relationship between velocity and effective porosity. The velocities of shale show the effects of velocity reduction due to clay minerals.

1.4 LIMITATION OF THE STUDY

As we all know that no human effort to achieve a set of goals goes without difficulties, certain constraints were encountered in the course of carrying out this project and they are as follows:-

Difficulty in information collection: I found it too difficult in laying hands of useful information regarding this work and this course me to visit different libraries and internet for solution.
Financial Constraint: Insufficient fund tends to impede the efficiency of the researcher in sourcing for the relevant materials, literature or information and in the process of data collection (internet, questionnaire and interview).

Time Constraint: The researcher will simultaneously engage in this study with other academic work. This consequently will cut down on the time devoted for the research work

1.5 PROJECT ORGANISATION

The work is organized as follows: chapter one discuses the introductory part of the work, chapter two presents the literature review of the study, chapter three describes the methods applied, chapter four discusses the results of the work, chapter five summarizes the research outcomes and the recommendations.