Mechanics of Hydraulic Fracturing

Ching H. Yew, Xiaowei Weng

• Publisher: Gulf Professional Publishing
• Year: 2014
• Print ISBN: 9780124200036
• eBook ISBN: 9780124200111
• Edition: 2
• Topic: Technology & Engineering
• Subtopic: Fossil Fuels
• Index: Technology & Engineering

Revised to include current components considered for today's unconventional and multi-fracture grids, Mechanics of Hydraulic Fracturing, Second Edition explains one of the most important features for fracture design — the ability to predict the geometry and characteristics of the hydraulically induced fracture. With two-thirds of the world's oil and natural gas reserves committed to unconventional resources, hydraulic fracturing is the best proven well stimulation method to extract these resources from their more remote and complex reservoirs. However, few hydraulic fracture models can properly simulate more complex fractures. Engineers and well designers must understand the underlying mechanics of how fractures are modeled in order to correctly predict and forecast a more advanced fracture network.Updated to accommodate today's fracturing jobs, Mechanics of Hydraulic Fracturing, Second Edition enables the engineer to: - Understand complex fracture networks to maximize completion strategies- Recognize and compute stress shadow, which can drastically affect fracture network patterns- Optimize completions by properly modeling and more accurately predicting for today's hydraulic fracturing completions- Discusses the underlying mechanics of creating a fracture from the wellbore- Enhanced to include newer modeling components such as stress shadow and interaction of hydraulic fracture with a natural fracture, which aids in more complex fracture networks- Updated experimental studies that apply to today's unconventional fracturing cases

Chapter 1

Fracturing of a wellbore and 2D fracture models

Abstract

The early fracture models are reviewed. And, the effects of dry zone and filter-cake on the behavior of a hydraulically induced fracture are discussed in this chapter.

Keywords

Constant height fracture

Breakdown pressure

KGD model

PKN model

Circular fracture

Energy method

Dry zone

Filter-cake

Poroelasticity

Introduction

The hydraulic fracturing process has been employed to enhance the production of oil and gas from underground reservoirs for many decades. In the process, the frac-fluid is pumped at a high pressure into a selected section of wellbore. This fluid pressure creates one or more fractures extending into the rock medium that contains oil or gas. Since the fracturing operation is conducted at a great depth, the minimum compressive in situ stress is typically in horizontal direction, the hydraulically induced fracture is a vertical fracture.

The dimension and propagation characteristics of a hydraulic fracture are important information in design of fracturing operations. Knowing the properties of reservoir rock, frac-fluid, and the magnitude and direction of in situ stresses, one seeks an accurate prediction of the dimension (opening width, length, and height) of the hydraulically induced fracture for a given pumping rate and time. Many fracture models have been developed for this purpose. The initiation of a hydraulic fracture from a vertical wellbore and two-dimensional fracture models are discussed in the following sections.

Fracturing of a wellbore

Consider an uncased vertical wellbore (or an open hole) under the action of horizontal in situ stresses σ_min and σ_max as shown in Fig. 1-1.

Figure 1-1 Horizontal section of a vertical wellbore under the action of in situ stresses and borehole pressure.

Assume that the rock is an elastic medium and has a tensile failure stress σ_T. The breakdown pressure p_b for introducing a fracture at the surface of borehole can be calculated by applying elasticity theory [1] to give

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Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Preface to the First Edition
• Preface to the Second Edition
• Chapter 1: Fracturing of a wellbore and 2D fracture models
• Chapter 2: Three-dimensional fracture modeling
• Chapter 3: Proppant transport in a 3D fracture
• Chapter 4: Deviated wellbores
• Chapter 5: Link-up of mini-fractures from perforated holes
• Chapter 6: Turning of fracture from a deviated wellbore
• Chapter 7: Fracture propagation in a naturally fractured formation
• Chapter 8: Stress shadow
• Chapter 9: Experimental studies
• Notations
• Author Index
• Subject Index