Hydraulic Fracturing in Unconventional Reservoirs

Theories, Operations, and Economic Analysis

Hoss Belyadi, Ebrahim Fathi, Fatemeh Belyadi

• Publisher: Gulf Professional Publishing
• Year: 2019
• ISBN:
  9780128176665
• Edition: 2
• Topic: Technology & Engineering
• Subtopic: Fossil Fuels
• Index: Technology & Engineering

Hydraulic Fracturing in Unconventional Reservoirs: Theories, Operations, and Economic Analysis, Second Edition, presents the latest operations and applications in all facets of fracturing. Enhanced to include today's newest technologies, such as machine learning and the monitoring of field performance using pressure and rate transient analysis, this reference gives engineers the full spectrum of information needed to run unconventional field developments. Covering key aspects, including fracture clean-up, expanded material on refracturing, and a discussion on economic analysis in unconventional reservoirs, this book keeps today's petroleum engineers updated on the critical aspects of unconventional activity.

• Helps readers understand drilling and production technology and operations in shale gas through real-field examples
• Covers various topics on fractured wells and the exploitation of unconventional hydrocarbons in one complete reference
• Presents the latest operations and applications in all facets of fracturing

Chapter One

Introduction to unconventional reservoirs

Abstract

This chapter introduces unconventional resources and their importance in improving the quality of life. Basic concepts and terms used in the oil and gas industry are introduced and defined, and then expanded to different gas types, natural gas transportation, and usage. Next, the chapter explains the major differences between conventional and unconventional hydrocarbon resources and various characteristics of different unconventional resources, such as coalbed methane, tight sands, shale gas, and gas hydrates reservoirs. At the end of the chapter, detailed discussions on shale gas reservoirs, their pore structure, mineralogy, and rock characteristics are presented.

Keywords

Natural gas; Natural gas transport; Shale gas; Coalbed methane; Gas hydrates; Total organic content; Vitrinite reflectance

Introduction

Oil and natural gas are extremely important. Our society is dependent on fossil fuels. They alone afford many of our greatest everyday comforts and conveniences. From the packaging used for our foods to the way we heat our homes, to all of our various transportation needs, without fossil fuels our way of life would come to a screeching halt. In light of current technological advancements, oil and natural gas will be the major player in the energy industry for years to come. Other sources of energy, such as wind, solar, electricity, biofuel, and so forth will eventually contribute along with fossil fuels to meet the growing global energy demand. When compared to different fossil fuels, natural gas is the cleanest because it emits much smaller quantities of CO₂ when burnt. Natural gas is a hydrocarbon mixture that primarily consists of methane (CH₄). It also includes varying amounts of heavier hydrocarbons and some nonhydrocarbons (as presented in Table 1.1). General usages of natural gas components are also presented in Table 1.2.

Table 1.1

Typical natural gas components

Natural gas components	Chemical formula	Short formula
Methane	CH4	C1	Light ends
Ethane	C2H6	C2
Propane	C3H8	C3	Heavier hydrocarbons
i-Butane	C4H10	i-C4
n-Butane	C4H10	n-C4
i-Pentane	C5H12	i-C5
n-Pentane	C5H12	n-C5
Hexane^+	C6H14	C6^+
Nitrogen	N2	N2	Inert/no heat content
Carbon dioxide	CO2	CO2
Oxygen	O2	O2

Table 1.2

General uses for natural gas components

General uses for natural gas components
Methane	Cooking, heating, fuel, hydrogen gas production for oil refining, and ammonia production
Ethane	Ethylene for plastics, petrochemical feedstock
Propane	Residential and commercial heating, cooking fuel, petrochemical feedstock
i-Butane	Refinery feedstock, blend in gasoline, petrochemical feedstock
n-Butane	Petrochemical feedstock, gasoline blend stock
i-Pentane	“Natural gasoline” blended into gasoline, jet fuel, naphtha cracking
n-Pentane	“Natural gasoline” blended into gasoline, jet fuel, naphtha cracking
Hexane^+	“Natural gasoline” blended into gasoline, jet fuel, naphtha cracking
Nitrogen	Air is 78% N2
Carbon dioxide	Air is 0.04% CO2
Oxygen	Air is 21% O2

Natural gas can be found in pockets as structural or stratigraphic gas reservoirs or in oil deposits as a gas cap. Gas hydrates and coalbed methane are considered as a major source of natural gas. Natural gas is measured by MSCF, which is 1000 standard cubic feet (SCF) of gas. Combustion of 1 ft³ of natural gas produces an equal amount of 1000 British thermal units (BTUs), the traditional unit for energy. One BTU by definition is the amount of energy needed to cool or heat one pound of water by 1°F. Each hydrocarbon has a different BTU and the heavier the hydrocarbon the higher the BTU becomes. Table 1.3 shows the BTU/SCF and BTU factor for each natural gas component. As can be seen below, methane has a BTU of 1012. If the price of gas is assumed to be $4/MMBTU, 1 MSCF of pure methane would be valued at $4.048/MSCF. To measure the actual BTU of natural gas, a gas sample is taken from a producing well. This sample is then taken to the lab, and by using a device called a gas chromatograph the natural gas composition (mol%) can be measured by component. After measuring the gas composition of the natural gas sample, the approximate weighted average BTU of the gas can be calculated. It is important to note that natural gas is sold by volume and heat content. Therefore, the heat content (weighted average BTU) of natural gas must be measured and calculated for sales purposes. Fig. 1.1 shows the gas chromatograph instrument.

Table 1.3

BTU of each natural gas component

Natural gas components	BTU/SCF	MMBTU per MSCF (BTU factor)
Methane	1012	1....