Chemical Nanofluids in Enhanced Oil Recovery

Fundamentals and Applications

Rahul Saha, Pankaj Tiwari, Ramgopal V.S. Uppaluri

• Publisher: CRC Press
• Year: 2021
• Print ISBN: 9780367425241
• eBook ISBN: 9781000433616
• Edition: 1
• Topic: Technology & Engineering
• Subtopic: Industrial & Technical Chemistry
• Index: Technology & Engineering

Sustainable world economy requires a steady supply of crude oil without any production constraints. Thus, the ever-increasing energy demand of the entire world can be mostly met through the enhanced production from crude oil from existing reservoirs. With the fact that newer reservoirs with large quantities of crude oil could not be explored at a faster pace, it will be inevitable to produce the crude oil from matured reservoirs at an affordable cost. Among alternate technologies, the chemical enhanced oil recovery (EOR) technique has promising potential to recover residual oil from matured reservoirs being subjected to primary and secondary water flooding operations. Due to pertinent complex phenomena that often have a combinatorial role and influence, the implementation of chemical EOR schemes such as alkali/surfactant/polymer flooding and their combinations necessitates upon a fundamental understanding of the potential mechanisms and their influences upon one another and desired response variables. Addressing these issues, the book attempts to provide useful screening criteria, guidelines, and rules of thumb for the identification of process parametric sets (including reservoir characteristics) and response characteristics (such as IFT, adsorption etc., ) that favor alternate chemical EOR systems. Finally, the book highlights the relevance of nanofluid/nanoparticle for conventional and unconventional reservoirs and serves as a needful resource to understand the emerging oil recovery technology. Overall, the volume will be of greater relevance for practicing engineers and consultants that wish to accelerate on field applications of chemical and nano-fluid EOR systems. Further, to those budding engineers that wish to improvise upon their technical know-how, the book will serve as a much-needed repository.

1

Introduction to Chemical and Nanofluids-Induced Oil Recovery

1.1 Importance of Crude Oil

The world economy after globalization has witnessed a massive transformation in terms of industrialization, transportation and urbanization. Invariably, a greater proportion of such advancement involves the overwhelming consumption of fossil fuels such as crude oil which are the gifts provided to mankind by mother earth. Constituting a mixture of hydrocarbons, crude oil is a naturally occurring thick dark brown flammable liquid. Crude oil is hypothesized to have formed due to the decomposition of dried plants and animals under the prevalent high temperature and pressure conditions beneath the earth’s surface that existed millions of years ago.

Ancient civilizations did not have the know-how of crude oil, and they very much depended upon tar in the Stone Age to make brick and mortar to enable their residences to be waterproof. Additionally, tar-based coatings were used during these civilizations for the leak-proof requirements of their boats. Contrary to this, today, a large portion of the growing world energy demands is being fairly met with the adequate production and supply of crude oil. Moreover, current modern society is the major consumer of a wide variety of crude oil-based by-products. The huge crude oil reserves of the Middle Eastern countries transformed them into flourishing rich economies undergoing rapid urbanization. Hence, crude oil is regarded as black gold and extensively catalyses the economic growth of many countries. Worldwide market demand and supply dictate the fluctuations and stabilities of crude oil prices and are coordinated by the Organization of the Petroleum Exporting Countries (OPEC).

1.2 Crude Oil – Demand and Supply

The existing energy consumption profiles in the world indicate the near impossibility of replacing crude oil completely with renewable energy. As a major contributor to meet the world’s energy demands, crude oil contributes enormously to the world economy. Figure 1.1a depicts an increase in oil production and consumption profiles on a worldwide basis. As depicted in the figure, during the initial time period 2000–2009, the net crude oil production and consumption in the world increased from 77 million to 85 million barrels per day. However, in the past 10 years, i.e., from 2009 to 2019, the net world crude oil production and consumption rate rose sharply from 85 million to 98 million barrels per day. This is significantly higher in comparison to the previous 10 years’ time period and thus indicates higher demand for crude oil.

For India, the profiles are distinct as shown in Figure 1.1b. Being one of the largest importers of crude oil, India’s net import is bound to increase in the near future, given that the trend grew from 73% in 2000 to 77% in 2016. Despite the improved oil production rate from 0.75 (2009) to 1 million barrels (2016), the crude oil import rate has increased in recent years at a greater rate in comparison to that prevalent in the country prior to 2010. In summary, both figures are in good agreement with one another to infer upon the fact that the worldwide crude oil demand and crude oil import rate for India are increasing significantly after 2009.

FIGURE 1.1
Petroleum liquid production and consumption in (a) worldwide and (b) India scenario [1].

The ongoing demands for crude oil are mainly due to continuous increase in energy consumption and the use of hydrocarbon-based products by modern society. Thus, a greater emphasis is placed on the cost-effective production of larger quantities of crude oil either from newly discovered reservoirs or from mature reservoirs that are already operating past their peak production levels. This is because the industry does not guarantee the discovery of new oil reserves, and if they are discovered, it is likely they will be located deep offshore or in other areas difficult to access. Also, the crude oil production from unconventional sources will be very expensive from mature oil fields [2]. Hence, considering the available data for Indian crude oil reservoirs, mature oil reservoirs have been targeted for enhanced oil production. Figure 1.2 represents the distribution of crude oil reserves in India. The chart illustrates that the majority of oil reserves exist in the eastern offshore (52.29%) and Assam regions (23.48%) of India. Hence, it is apparent that to increase crude oil production in such regions of India and to meet the growing energy demands of the country, enhanced oil recovery methods are to be deployed. Thereby, net import costs associated with the crude oil system can be minimized along with an emphasis on the self-sustainability of the country’s demanding energy needs.

FIGURE 1.2
Region-wise reserves of crude oil in India [3].

1.3 Enhanced and Improved Oil Recovery

The recovery of crude oil from reservoirs is accomplished due to the natural pressure difference that exists within the bottom well hole and the oil field. Oil recovery by such natural pressure differences is known as the primary method. However, with continued oil production, the pressure inside the reservoir system decreases. Therefore, to overcome this feature, the pressure inside the reservoir system is increased through the injection of water during secondary flooding operations. It is well known that the oil production from primary and secondary (water) flooding operations accounts for only 30%–40% of the original oil in place (OOIP) [4,5]. Thus, even after secondary recovery, about two-thirds of the OOIP is not recovered and remains trapped in the porous structure of the reservoir rock [5,6]. The viscous fingering effect of water flooding is primarily responsible for trapping crude oil in such a system. Therefore, more complex procedures and methodologies need to be adopted to recover the trapped oil economically. The enhanced oil recovery (EOR) process is a tertiary oil recovery process that deploys advanced methods for oil extraction. Depending on the working principle fundamentally explored, the EOR schemes are often classified into various categories such as thermal, gas, chemical and other recovery processes (Figure 1.3). On the other hand, the improved oil recovery (IOR) method involves a wider production range of recovery technologies. Thus, EOR processes are regarded as sub-classes of the IOR methodology [2]. A brief of various EOR methods is presented as follows.

1.3.1 Thermal-Enhanced Oil Recovery

This method involves heating of the crude oil. The thermal EOR targets the application of either heat or thermal energy to the reservoir system, which reduces the viscosity of crude oil and enhances oil recovery [7–9]. The well-known thermal EOR methods include hot water or steam injection, stimulation using cyclic steam, combustion (in-situ) and gravity drainage assisted with steam. The steam-based methods involve the injection of steam into the reservoir through injection wells. Therefore, crude oil viscosity is effectively reduced and aids in the oil’s flow to the surface of the reservoir production wells. The in-situ combustion involves generation of heat through burning a portion of crude oil in the reservoir itself. This is achieved through the injection of air or oxygen-enriched air. Eventually, oil recovery is enhanced through the generated heat and gases from combustion. Thermal recovery methods are applicable for low-depth reservoirs with highly viscous oil and lower API [10]. Thermal recovery methods constitute the risk of safety issues during larger production schemes and can severely damage the underground oil well structure. This is regarded to be a very serious limitation of the thermal EOR technique in oil reservoirs [11].

FIGURE 1.3
Schematic of various enhanced oil recovery methods.

1.3.2 Gas-Enhanced Oil Recovery

The gas injection method involves injection of miscible and immiscible gases into the reservoir and is known to be one of the oldest EOR techniques. The injected gas dissolves into the oil phase and eventually reduces crude oil viscosity and interfacial/surface tension of the oil–water interface. Thereby, sweep efficiency can be improved considerably to enhance the production of crude oil. Among alternate gas injection schemes, nitrogen and flue-gas injection, hydrocarbon injection, CO₂ flooding and so on are popular for their precise screening criteria in flooding applications [10]. For nitrogen and flue-gas flooding, these correspond to a depth of >6000 ft and an API gravity of 35°–48°. For hydrocarbon injection, the screening criteria refer to a depth of >4000 ft and an API gravity of 23°–41°. For the CO₂ flooding method, the suggested depth is more than 2500 ft and the recommended API gravity is about 22°–36°. The CO₂ flooding method is also applicable at higher depths and higher API gravities. Additionally, during gas flooding specific reservoir conditions are required which can expand the injected gas and drive the crude oil for recovery [11].

1.3.3 Chemical-Enhanced Oil Recovery

The chemical EOR process involves the recovery of residual oil through the injection of chemicals into the reservoir system. The injected chemicals interact with the crude oil and enable the alternation of pertinent mechanisms to enhance oil recovery. The chemical EOR system performance is very much dependent upon the characteristics of the reservoir system such as crude category, rock properties, temperature and salinity.

Apart from chemical EOR, other EOR categories such as microbial, solvent, acoustic and electromagnetic technologies do exist. However, a detailed account of the working principle and relevant screening...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Dedication
• Table of Contents
• Preface
• Acknowledgements
• Authors
• Abbreviations
• Introduction
• 1 Introduction to Chemical and Nanofluids-Induced Oil Recovery
• 2 Alkali Flooding – Mechanisms Investigation
• 3 Alkali and Surfactant Flooding
• 4 Surfactant Adsorption Characteristics on Reservoir Rock
• 5 Nanofluid Flooding for Oil Recovery
• 6 Problems and Challenges in Chemical EOR
• 7 Application of Nanotechnology in Unconventional Reservoirs
• Index