Development of Oil Soluble Resin Mixture for Control of Fluid Loss in Water Base Workover and Completion Fluids

Abstract

American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. Abstract A new oil soluble additive has been developed to reduce fluid loss of workover and completion brines. This additive is composed of a mixture of finely divided friable and pliable oil soluble resins and is effective in all brine systems at temperatures up to 250 deg. F. Laboratory tests show good fluid loss control against permeabilities up to at least 900 md. An permeabilities up to at least 900 md. An additional oil soluble bridging agent is used with the additive in fractured or more permeable formations. permeable formations. Unlike the commonly used calcium carbonate type additives, which require acidizing following their use, this product forms a filter cake which is completely soluble in the produced oil. As a result, the danger of formation produced oil. As a result, the danger of formation damage is minimized. No supplemental water soluble gums or polymers are required for fluid loss control although they may be added to increase viscosity and solids carrying ability of the fluid. The non-damaging nature of the additive is demonstrated by laboratory formation damage tests and the results of well treatments. Introduction In recent years, considerable effort has been directed toward the development of new techniques and materials to minimize formation damage during workover and completion operations. Many workover fluids previously in common use have been replaced by previously in common use have been replaced by newer non-damaging systems. Solids free brines are finding increased use. These brines are designed to minimize formation damage and can be weighted by the addition of high concentrations of inorganic salts. Sodium chloride, potassium chloride, calcium chloride and calcium bromide are often used as weighting agents. Brine densities of up to 15.1 pounds per gallon are possible using mixtures of calcium chloride and calcium bromide. A commonly encountered problem in the use of solids free workover brines is loss of the fluid to the formation.