Abstract

Effective scale control in production of hydrocarbon deposits is in many fields essential to the economic and safe production of hydrocarbon and associated fluids.Chemical inhibitors of inorganic scale (carbonate and sulphate) have long been applied to subsurface (continual injection or squeeze) to flow lines/process equipment along with the growing area of produced water reinjection.The following paper will outline a method of improved performance monitoring of such chemical treatments.The measurement of suspended solids is a common practice to determine injection water quality but the measurement of the type, amount, texture and composition of solids within produced fluids via environmental scanning electron microscopy (ESEM) combined with energy dispersive analysis (EDX) has not until now been used as a routine method to monitor the effective scale control programs applied downhole, topside and for produced water reinjection.The collection/filtration of small quantizes of produced water that are subsequently analyzed for the texture and composition of sulphate/carbonate solids has been used in a number of fields within the North Sea and Gulf of Mexico as a direct method of scale inhibitor performance.This novel method of measuring chemical performance that does not rely on chemical or brine analysis and allows drilling related solids to be differentiated from scale formed within produced brine.The paper will present results from 4 fields to illustrate the value this method of monitoring was able to bring the field operators to optimize scale squeeze treatments and topside treatment rates.

Introduction

The Water Life Cycle (Figure 1) can present many challenges in terms of controlling scale formation[1,2] associated with the changes in physical conditions of produced water (carbonate scale) or incompatibility observed when brines mix with incompatible ions (sulphate scales).In this paper an outline will be given of the value of the evaluation of suspended solids via environmental scanning electron microscopy (ESEM) to assess the degree of scale control across the water life cycle from source water wells, production wells from low to high water cut, across the topside process and for produced water reinjection.

Scale inhibitor performance monitoring.Historically the methods of monitoring the performance of a scale inhibitor program have relied on analysis of chemical residual and scaling ion concentration.More recently the development of real time monitoring[3,4,5] has taken the management of such programs to a new level.In previous publications the integration of these monitoring methods have been outlined.[6,7]Results are presented in the following sections that show that an understanding of the types of scale present, their textures within produced fluid via scanning electron microscopy and compositional analysis of these solids via energy dispersive X-ray (EDX) analysis adds an extra dimension to the understanding of scale management for downhole and topside applications.

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