Petroleum Reservoir Management

Considerations and Practices

Ashok Pathak

• Publisher: CRC Press
• Year: 2021
• eBook ISBN: 9781000429329
• Edition: 1
• Topic: Physical Sciences
• Subtopic: Chemical & Biochemical Engineering

Petroleum reservoir management considerations and practices are deeply rooted in the optimization of development objectives, requisite investments, operational costs, and philosophy in addition to the dynamics of timely decision-making. Petroleum Reservoir Management: Considerations and Practices highlights the key reservoir management topics and issues that engage the attention of exploration and production companies over the life cycle of an oilfield.

This is the only book to exclusively address petroleum reservoir management based on actual field development experience. It emphasizes the role of good project management, the value of a quantitative assessment of reservoir health, the importance of using good practices, and the need for true collaboration among various team players to maximize the benefits. The book expands the scope of reservoir management from field operations to boardroom discussions about capital financing to product pricing criteria, mechanisms, and strategies.

FEATURES

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• Reviews subsurface and surface management issues

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• Discusses project and price management factors critical to the oil industry

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• Describes macromanagement issues covering the reservoir life cycle from production to pricing

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• Includes the role and significance of teamwork, open communication, and synergy in reservoir management

This book is aimed at professionals and graduate students in petroleum and reservoir engineering, oil and gas companies, and environmental engineering.

1

Petroleum Reservoir Lifecycle

1.1 Introduction

Metaphorically, oilfields are comparable to humans. They are born when discovered and die when abandoned due to depletion or economic reasons. They may have the same physiology, yet they are so much different from each other in their physics and chemistry! Analogies work only to a limited extent.

Petroleum is a Latin word for “rock oil” formed from the remains of plants, animals, and ancient marine organisms. It is a fossil fuel like coal that can naturally occur in colorless to very dark brown/black color in gaseous, liquid, and semi-solid phases such as natural gas, condensate, crude oil, and tar. Primarily composed of an organic compound of two elements, hydrogen, and carbon, petroleum is also known as a hydrocarbon.

It is important to highlight the difference between a “Reservoir” and a “Field” before making extensive use of these terms in our discussion. A petroleum reservoir is an individual, separate, dynamically pressure-connected formation system characterized by three essential properties: porosity, permeability, and caprock. Porosity allows the rock formation to hold the oil and natural gas accumulation, and permeability allows its movement through the rock when pressure equilibrium is disturbed. The caprock is a tight or impermeable rock that constitutes the sealing mechanism to prevent the escape of hydrocarbons from the top under normal, natural conditions. In simple words, a field may have single or multiple reservoirs overlying each other, which may or not be in communication with each other.

1.2 Life Cycle

Like all living beings, an oil reservoir goes through the life cycle of exploration (embryonic), discovery (birth), delineation (childhood), growth (youth), decline (aging), and abandonment (termination). This progressive life cycle, as seen in Figure 1.1, will apply to each reservoir that an oilfield might contain. Depending on the size, potential, commercial viability, and business interest, an operating company must devise a strategy to manage the entire reservoir lifecycle to maximize the desired benefits. Good reservoir management strategy is fundamental for higher productivity, economic gains, and extension of the field life.

Figure 1.1
Symbolic Equivalence between Human and Oilfield Lifecycle.

Each of the oilfield phases, that is, exploration, appraisal, development, production, and abandonment, has its own set of unique challenges and characteristics. Most of the discussions presented in this book will cover the reservoir management aspects of the development and production phases, which form a large part of the reservoir lifecycle and generate most of the cash flow to keep operating companies interested in the business.

An oilfield over its lifecycle may be operated by a National Oil Company (NOC), International Oil Company (IOC), a Private Oil Company (POC), or a combination. The oilfield ownership and operating arrangements may change from time to time, calling for changes in the reservoir management strategy affecting the investment and the cash flow profiles based on the projected production rates and recoveries.

1.2.1 Exploration Phase

The first goal of the exploration phase is to examine the prospectivity of a petroleum province and rank geological plays and prospects to decide their priority. The most fundamental question for a company to pursue exploration work on a geological prospect is to ascertain the possibility of hydrocarbons. Exploration is a risky and costly business. E&P companies usually work for several years before spudding their first exploratory well. Their work involves applying geological and geophysical methods to establish the most favorable location for oil entrapment. Today, with the help of advanced computing systems, geophysicists can interpret the vast and complex 3-D volumes of seismic data relatively quickly and generate an image of the subsurface for locating the possible hydrocarbon accumulation. The integration and evaluation of geological and geophysical information by the subject matter experts prepare the ground for high-grading a prospect for drilling the first exploratory well.

An exploratory well is drilled to confirm the presence of oil/gas on a structure. This process proves or disproves the geological hypothesis that is used to drill exploratory wells. Coring, well logging, and well testing methods permit collecting additional information about the hydrocarbon-bearing formation. Coring is a direct method to obtain a sample of rock from the wellbore. Several plugs can be extracted from this rock to perform Routine Core Analysis (RCA) and Special Core Analysis (SCAL). Well-logs provide quantitative estimates of pay thickness and fluid saturations for the geological formations. A well-test is conducted to measure the production rate of oil, gas, and water. Multiple choke test is an excellent method to determine the production potential of a well and optimize its flow rates. The success of the exploratory oil/gas well kicks off the field lifecycle as hypothetical resources are upgraded to proven estimates of hydrocarbons-in-place and reserves.

The exploration phase is usually characterized by high geological uncertainties and capital investments in seismic surveys and exploratory drilling. Exploratory areas have high uncertainty about the discovery and expose investments to many risks, including the risk of dry holes or uncommercial ventures. Drilling operations in some exploratory areas may be unsuccessful due to unexpected drilling conditions such as abnormal pressure and temperature, causing equipment failures and blowouts. The exploration risks cannot be eliminated but can be reduced significantly by adopting appropriate workflows and technological innovations.

1.2.2 Delineation Phase

The next most important questions for an E&P company, having discovered oil or gas, are about the discovery size and its commercial viability. Seismic data is undoubtedly beneficial to map the size of the subsurface structure. Still, the only way to prove whether this structure or what part contains oil is to drill delineation appraisal wells.

The delineation/appraisal phase aims to address these questions by drilling wells that help define the reservoir limit and understand the variation in well-productivity across the reservoir. Extensive analysis of data gathered from drilling, logging, coring, sampling, and testing reduces uncertainty in the size of the oil or gas reservoir, its properties, and production rates.

The drilling and completion program of delineation wells is carefully planned to minimize operational risks and maximize gains. Continuous improvement and optimization of this program aids in building a learning curve that is useful ...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Dedication
• Contents
• Forewords
• Petroleum Kalpa Vriksha
• Preface
• Acknowledgments
• Author
• 1 Petroleum Reservoir Lifecycle
• 2 Operating Arrangements and Reservoir Development Objectives
• 3 Reservoir Management Requirements
• 4 Significance of Reservoir Health and Its Impact on Reservoir Performance
• 5 Reservoir Management Policy Framework
• 6 Oilfield Water Management
• 7 General Reservoir Management Practices, Aberrations, and Consequences
• 8 Reservoir Development and Management: Important Lessons Learned
• 9 Proactive Reservoir Management
• 10 Pricing of Crude Oil
• Acronyms and Abbreviations
• Index