Energy Issues and Options for Developing Countries

United Nations

• Publisher: Routledge
• Year: 2019
• ISBN:
  9780429560651
• Edition: 1
• Topic: Betriebswirtschaft
• Subtopic: Energiebranche

Originally published in 1989. This book presents the situation regarding energy provision and policy in developing countries. It looks at Enhanced Oil Recovery, Hydropower and small energy packages suitable for rural areas including renewable energies and the various needs and systems affected such as water pumping and telecommunications. Each section is broken down into salient issues and information is provided on environmental issues, socioeconomic issues, costs and limitatioons and what is considered the state-of-the-art in each area. The final section offers a view of the application of computing technology in energy planning.

Part I
Enhanced Oil Recovery

1

Introduction

Large volumes of oil remain in reservoirs after applying primary and secondary production methods. In the more mature oil-producing areas of the world such as the United States and some countries of western Europe, a great deal of effort has gone into improving the recovery efficiency of primary and secondary operations. Even so, these methods of operation still leave more than half of the oil present in the reservoirs at the time of discovery. In the developing countries of the world, the primary and secondary methods of operation are sometimes not too sophisticated. Consequently, recovery efficiencies are not as high as in the United States and other more developed countries. The oil remaining in the reservoirs of these countries after primary and secondary operations may be significantly more than half of the in-place oil at the time of discovery. Also, some of the reservoirs of the developing countries have been exploited through recovery by “skimming.” Here, only the most easily recovered oil is produced from the reservoir and a significant fraction of the original oil in place remains in the reservoir.

Oil remaining in reservoirs after primary and secondary operations is the target for enhanced oil recovery (EOR) operations. Vast quantities of this kind of target oil are available in reservoirs of the developing countries. This oil is located in known reservoirs and represents a national resource base for each of the developing countries. No additional funds are required to find the oil. In some cases, existing wells and surface equipment can be used to reduce the costs of EOR operations. Of course, existing equipment becomes less valuable with time as normal wear by corrosion and other factors takes its toll.

Another and perhaps the most important cost factor relates to the oil saturation existing in the reservoir at the start of EOR. Generally, the higher the reservoir oil saturation at the start of EOR operation, the lower the per barrel cost for recovery. Here, the developing countries should be in a good position because their reservoirs normally would have higher oil saturation at the completion of the conventional recovery operations.

In the developing countries, EOR should be looked upon as a method of recovering an otherwise unrecoverable national resource. Also, EOR should be considered an alternate liquid hydrocarbon source when considering the development of other liquid hydrocarbons sources such as oil shale, tar sands, and coal. In most cases, the EOR source will prove to be less expensive when compared on a cost basis with these other sources. However, the cost of EOR oil generally will be more than the oil recovered by more conventional methods. It should be kept in mind that: (1) conventional methods generally “skim the cream,” (2) “skimming the cream” is the least expensive method of recovery, and (3) oil recovered by EOR can be obtained by no other method. The oil remaining in the reservoir is either recovered by EOR or may be lost forever once the reservoir is plugged and abandoned. In very few, if any, cases will reservoirs by redeveloped for EOR once the wells have been plugged and abandoned. In most cases, the additional costs will be prohibitive. Loss of potential resource through plugging and abandonment should bring a sense of urgency to EOR development throughout the world, especially in the developing countries.

This section starts with an overview of the different types of EOR processes including comments on screening criteria and injectant availiability. Next, application of EOR techniques is considered in terms of reservoir screening, reservoir evaluation, performance prediction and selected field histories. Then, EOR state-of-the-art is discussed on the basis of the status of EOR techniques in the United States and worldwide, as well as technical factors, economic considerations, and factors influencing EOR development. Finally, information is presented on EOR training along the lines of technology transfer and available training programs. Conclusions are given at the end of the section.

2

Overview

This section considers only the EOR processes categorized as chemical, miscible, and thermal. Immiscible is treated as a subset of miscible. Other types of EOR methods are being studied in the laboratory, such as electrical heating and injection of microorganisms. Commerical use of these methods appears to be far in the future, and it is not considered here.

Following an overview of the different types of chemical, miscible, and thermal EOR processes, the concept of screening criteria is introduced in terms of the need for the use of these criteria. Then, injectant availability is considered as affecting the selection and development of a particular EOR process.

TYPES OF EOR PROCESSES

Reduced interfacial tension and mobility control are the two factors that are used in EOR to improve oil recovery. Cleaning solvent will remove a spot of oil from cloth, whereas water will not. The solvent reduces or eliminates the interfacial tension, whereas water does not mix with the oil. Molasses pushes water from a tube effectively with its favorable mobility ratio, whereas water is not efficient in displacing molasses from the same tube.

Chemical methods use chemicals to lower the interfacial tension and polymer for mobility control. Miscible methods eliminate or reduce interfacial tension by developing a fluid mixture that is miscible with the in-place oil and injected gas. Thermal methods use heat to reduce the oil viscosity, thereby providing improved mobility control conditions in the reservoirs.

EOR processes are categorized as chemical, miscible, or thermal. The chemical category includes the polymer, surfactant, and alkaline flooding processes. Figures 2.1-2.3 show schematic diagrams of these three processes (1). In the miscible category are included processes in which a gas is injected into the reservoir under conditions where miscibility is obtained between the gas and reservoir oil. Gases of choice include carbon dioxide, hydrocarbons such as methane, ethane, propane, and others, and mixtures of these gases, and nitrogen. Figure 2.4 shows a schematic diagram for a miscible process where carbon dioxide is being injected. (1). The diagram would be similar for other injected gases. Steam and in-situ combustion processes are used in the thermal category. Cyclic and continuous steam injection are used in the steam process. Figures 2.5 and 2.6 illustrate the two techniques for steam injection (1). With the in situ combustion process, air is injected into the reservoir to provide oxygen to burn a portion of the oil. Water is sometimes simultaneously injected with air for mobility control. Figure 2.7 is a schematic of the wet in-situ combustion process (1).

Figure 2.1 Polymer flooding. (Source: Adapted from original drawings by Joe R. Lindley, U.S. Department of Energy, Bartlesville Energy Technology Center)

Figure 2.2 Surfactant flooding. (Source: Adapted from original drawings by Joe R. Lindley, U.S. Department of Energy, Bartlesville Energy Technology Center)

Different types and amounts of chemicals are used in the three chemical processes. Both synthetic and biologically produced polymers have been used in polymer flooding, which differs from the other two chemical methods in that no reduction in interfacial tension takes place. Increased recovery by polymer flooding occurs because of improvement in vertical and areal conformance. As seen in Figure 2.2, a polymer solution also is used for mobility control behind the alkaline solution. Sometimes for mobility control polymer is mixed into the surfactant and alkaline solutions. At other times cost prohibits the use of polymer in either the surfactant of alkaline systems. In most of the surfactant systems, all chemicals are mixed at the surface before injection. A wide variety of surfactants have been used, including petroleum sulfonates, synthetic sulfonates and sulfates, and ethoxylated alcohols and sulfonates. The alkaline process differs from the surfactant process in that the surfactant is generated in-situ. Here alkaline reacts with organic acids in the crude oil to form surfactant. Sodium hydroxide and various orthosilicates have been used as alkaline agents. Some experts feel that sodium carbonate has merit; others do not.

Figure 2.3 Alkaline flooding. (Source: Adapted from original drawings by Joe R. Lindley, U.S. Department of Energy, Bartlesville Energy Technology Center)

Figure 2.4 Miscible flooding. (Source: Adapted from original drawings by Joe R. Lindley, U.S. Department of Energy, Bartlesville Energy Technology Center)

Figure 2.5 Cyclic steam stimulation. (Source: Adapted from original drawings by Joe R. Lindley, U.S. Department of Energy, Bartlesville Energy Technology Center)

Figure 2.6 Steam flooding. (Source: Adapted from original drawings by Joe R. Lindley, U.S. Department of Energy, Bartlesville Energy Technology (Center)

Figure 2.7 Wet in-situ combustion. (Source: Adapted from original drawings by Joe R. Lindley, U.S. Department of Energy, Bartlesville Energy Technology Center)

The gases used in the miscible methods generally do not experience first contact miscibility with the crude oil in the reservoir. Miscibility takes place in the reservoir after repeated contacts of a given volume of gas with fresh crude...