INTRODUCTION

I do not claim an expertise in manufacture, but I want to make three points briefly in this chapter and then to enlarge on the last of them.

Market information is usually inaccessible, and there may be a case for research centers to work together to provide a better source of data for industry. It is clear that there is not always an entirely satisfactory information flow, even within companies, between the marketing department and the technical and manufacturing operations.

My first point is, therefore, to suggest the need for better market information both within and outside companies.

My second point is to indicate the need for the flow metering industry, on the one hand, and the science base as it relates to instrumentation, on the other hand, to create an effective means for technology transfer, which in the process will raise the profile of the sector and ensure that government is aware of its importance. Past experience of encouraging collaboration suggests that industry and the science base do not always appreciate the value of working together. Collaboration between industry and the science base should be mutually beneficial in providing an antenna for new information on developing technologies.

The third point is that the production of instrumentation is a special case in which the effect of the production process on the final accuracy of the instrument may, in some cases, be predicted and used to specify the production requirements.

INITIAL CONSIDERATIONS

Some years ago at Cranfield, where we had set up a flow rig for testing the effect of upstream pipe fittings on certain flowmeters, a group of senior Frenchmen were being shown around and visited this rig. The leader of the French party recalled a similar occasion in France when visiting such a rig. The story goes something like this.

A bucket at the end of a pipe seemed particularly out of keeping with the remaining high tech rig. When someone questioned the bucket's function, it was explained that the bucket was used to measure the flow rate. Not to give the wrong impression in the future, the bucket was exchanged for a shiny new high tech flowmeter. In due course, another party visited the rig and observed the flowmeter with approval. “And how do you calibrate the flowmeter?” one visitor asked. The engineer responsible for the rig then produced the old bucket!

This book sets out to guide those who need to make decisions about whether to use a shiny flowmeter, an old bucket, nothing at all, or a combination of these! It also provides information for those whose business is the design, manufacture, or marketing of flowmeters. I hope it will, therefore, be of value to a wide variety of people, both in industry and in the science base, who range across the whole spectrum from research and development through manufacturing and marketing.

Introduction

In a petroleum industry context, emulsions comprise a mixture of oil and water in which one of the phases, the dispersed phase, occurs as droplets dispersed within the other, the continuous phase. The droplet diameters are typically of the order of 0.1 to 100 μm, but may be as small as a few nanometres or as large as many hundreds of micrometres. Two types of emulsion are readily distinguished, oil-dispersed-in-water (O/W) and water-dispersed-in-oil (W/O). However, emulsion characterization is not always so simple and it is not unusual to encounter multiple emulsions, O/W/O, W/O/W, and even more complex types. Figure 1 shows an example of a crude oil W/O/W/O emulsion.

Petroleum industry foams comprise a mixture of gas with either oil or water, where the gas phase occurs in the form of bubbles dispersed within the liquid. The bubble diameters are typically on the order of 10 to 1000 μm, but may be as large as several centimetres. Although both aqueous and oleic foams may be encountered, the former are by far the most common.

Introduction

Acidizing treatments are used to remove wellbore damage, enhance matrix permeability or both. The acid reacts with the rock matrix and, as a result, the permeability of the formation will increase. Reagents commonly used to stimulate carbonate reservoirs are hydrochloric (15 or 28 wt%), formic (9 wt%), and acetic (10 wt%) acids. Recently, Fredd and Fogler introduced ethylenediamine tetraacetic acid (EDTA) as an alternative fluid to acidize carbonate formations.

Acids commonly used in sandstone formations include hydrofluoricbased acids. Full strength mud acid (12 wt% HCl + 3 wt% HF) has been used to stimulate sandstone reservoirs for several decades. Because of the fast reaction of hydrofluoric acid with clay minerals, various retarded mud acids were introduced.

Introduction

Environmental risks associated specifically with the use of surfactants in the petroleum industry generally have not been an issue. This is because surfactants are perceived as being less environmentally hazardous compared to certain other chemicals used in the petroleum industry. Also, surfactants should not reach sensitive receptors unless there is an unexpected release, such as a spill or inappropriate discharge of process waters containing the surfactants. Consequently, there are few published studies on the fate and effects of surfactants in the petroleum industry. However, the times are changing. Environmental data are required on all chemicals listed as part of the pre-manufacturing notification (PMN) compliance with the Toxic Substances Control Act (TSCA), and even Material Safety Data Sheets (MSDS) currently have a section on environmental safety. There is a need to understand the environmental properties of large volume chemicals, and chemical manufacturers are responding by collecting more data. Likewise the users of these chemicals must understand the environmental risks associated with their use which in the case of the petroleum industry can be unique.

Role of Wettability Alteration

Wettability alteration of porous reservoir rock with surfactants is one means to improve the flow and distribution of fluids in a reservoir. However, much remains to be learned regarding how surfactants interact with the rock minerals and organics found both within the pores and on the pore surfaces of reservoir rock. It is the objective of this chapter to provide an initial understanding and review of the following:

1. Theoretical aspects of wettability

2. Methods for measuring wettability

3. Surfactant induced wettability alteration

4. Laboratory and field studies

Background. Surfactants have been introduced into oil reservoirs to increase oil recovery, minimize adverse mobility ratios, clean plugged wellbores and improve drilling.

Introduction

Several excellent reviews of demulsifier chemistry and properties can be found in the literature. For this chapter, the important factors in demulsifier selection and characterization will be discussed, accompanied with specific examples.

Chemical demulsification is commonly used to separate water from heavy oils in order to produce a fluid suitable for pipelining (typically less than 0.5% solids and water). A wide range of chemical demulsifiers are available in order to effect this separation. In order to develop the fundamental understanding necessary to optimize demulsifier selection for a particular emulsion, it should be sufficient, in principle, to obtain a complete chemical and physical characterization of both the emulsion to be separated and the demulsifier to be used.

Introduction

Surfactants have a variety of applications in the petroleum industry, and surfactant adsorption is a consideration in any application where surfactants come in contact with a solid surface. In enhanced or improved oil recovery (EOR or IOR) surfactants can be used in classic micellar/polymer (surfactant) flooding, alkaline/surfactant/polymer (ASP) flooding or in foams for mobility control or blocking and diverting. Surfactants can act in several ways to enhance oil production: by reducing the interfacial tension between oil trapped in small capillary pores and the water surrounding those pores, thus allowing the oil to be mobilized; by solubilizing oil (some micellar systems); by forming emulsions of oil and water (alkaline methods); by changing the wettability of the oil reservoir (alkaline methods) or by simply enhancing the mobility of the oil. In selecting a suitable surfactant for any EOR application, one of the criteria for economic success is minimizing surfactant loss to adsorption.

Introduction

The contamination of groundwater by nonaqueous phase liquids (NAPLs) is a cause for concern throughout the world. NAPLs can be classified by their density as those lighter than water (LNAPLs) and denser than water (DNAPLs). NAPLs migrate into aquifers because of gravity and capillary forces and may be trapped in the form of immobile blobs or ganglia or when present in sufficient volume DNAPLs may form pools above aquitards.

This book provides an introduction to the nature, occurrence, physical properties, propagation, and uses of surfactants in the petroleum industry. The primary focus is on applications of the principles of colloid and interface science to surfactant applications in the petroleum industry, and includes attention to practical processes and problems. Books available up to now are either principally theoretical (such as the colloid chemistry texts), much more general (like Rosen's Surfactants and Interfacial Phenomena, Myers' Surfactant Science and Technology, or Mittal's Solution Chemistry of Surfactants), or else much narrower in scope (like Smith's Surfactant Based Mobility Control). The applications of surfactants in the petroleum industry area are quite diverse and have a great practical importance. The area contains a number of problems of more fundamental interest as well. Surfactants may be applied to advantage in many parts of the petroleum production process: in reservoirs, in oilwells, in surface processing operations, and in environmental, health, and safety applications. In each case appropriate knowledge and practices determine both the economic and technical successes of the industrial process concerned.

In this volume, a wide range of authors' expertise and experiences are brought together to yield the first surfactant book that focuses on the applications of surfactants in the petroleum industry. Taking advantage of a broad range of authors' expertise allows for a variety of surfactant technology application areas to be highlighted in an authoritative manner.