Abstract

Suitable chemical treatment of North Sea oil and gas production plays a small but vital role in determining the production plays a small but vital role in determining the success of the project. During the initial period of production from a new oilfield, the chemical treatment requirements are generally minimal. This situation changes dramatically as the field life progresses and water production commences. At that time a variety of chemicals will probably be required including demulsifiers, corrosion inhibitors. effluent treatment compounds and scale inhibitors. Whilst for many of these products there are well defined test methods and selection techniques available, this is a particular problem with scale inhibitors. In the majority of particular problem with scale inhibitors. In the majority of cases it is very difficult to simulate the scaling situation present in the field by laboratory methods. present in the field by laboratory methods. The paper reviews some scale inhibitor selection techniques used in the past and describes a novel simulation test to monitor inhibition and flow pattern influence around an injection or production well bore. This method has been used to rank the efficiency of commercially available scale inhibitors for both the Forties injection and production systems and will be discussed in terms of the practical problems involved. problems involved

Introduction

Problems arising from the production of scale are commonplace in oilfields. The precipitation mechanism is often complex and may be due to a variety of effects including changes in system conditions (e.g. pH, pressure. temperature etc.), reservoir conditions or incompatibility between injected water and formation water. The present paper discusses carbonate and sulphate scale formation in the Forties Field and some of the laboratory inhibitor selection techniques used in the selection of suitable scale inhibitors for field use both in the Forties injection and production systems. In particular a novel test method is described which is being used in the laboratory to monitor inhibitor and flow pattern influence on formation scaling.

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