High Density Clear Fluids for Completions and Workovers

Abstract

ABSTRACT In recent years, the practical operating range of clear brines as completion and workover fluids has been significantly extended by the introduction of formulations incorporating bromide, so that the advantages of clear brines can now be obtained with fluids having densities as high as 19.2 lb/gal (2.3 g/cm 3)at ambient temperatures, to give a series of fluids of provencost-effectiveness. The properties and formulation of a range of clear brines are described, including calcium chloride - calcium bromide calcium chloride - calcium bromide - zinc bromide calcium bromide - zinc bromide sodium chloride - sodium bromide Proper formulation of brines to achieve the best cost effectiveness is important and is emphasized in terms of the trade-off between costs and acceptable crystallization temperature. Handling, safety and environmental aspects of the various fluids are covered, as are practical operating aspects. The sodium salt brines are applicable in the special situation where calcium salts would be incompatible with connate water. Incorporation of various additives is discussed viscosifiers, fluid loss additives, corrosion inhibitors, as is the recovery and regeneration of fluids for re-use. The heavy clear fluids are used for completion and workover, as packer fluids, and as drilling fluids (both aqueous and oil-invert systems). Case histories from North Sea operations are presented. INTRODUCTION In recent years, the practical operating range of clear brines has been significantly extended by the introduction of formulations incorporating the bromide ion, so that the advantages of clear brines can now be obtained (Figure 1) with fluids having densities as high as 19.2 lb/gal (2.3 g/cm 3) at ambient temperatures and pressures [1,2,3].