Varied Applications of Invert Emulsion Muds

Abstract

Invert emulsion muds, compounded so as to have specific properties, can solve such divergent problems as are encountered in producing from water-sensitive pay zones; in drilling formations that dissolve, disperse and disintegrate in water; and in alleviating pipe corrosion. Introduction Within the last 7 years there has been a significant increase in the use of drilling and completion fluids having oil as the continuous phase. This extension in applications for oil-base muds has been due in large measure to the development of products designed to provide specific properties. Users are no longer provide specific properties. Users are no longer restricted to certain proprietary mixtures but can devise a suitable composition to satisfy the immediate requirements in much the same way as is done with water muds. "Oil mud" has oil as the continuous phase. AH oil muds after use contain some water. The term "invert emulsion" often is applied to oil muds having water as a component that has been added to produce a desired property. In this discussion, the term "oil mud" is applied without regard to specific water content, with the limitation that the filtrate is all oil under the conditions of use. Our purpose is to review briefly some of the varied applications for oil muds and thereby to demonstrate the wide adaptability of these compositions. Oil muds are not to be regarded as cure-alls for every type of drilling and completion problem. On the contrary, before the decision is made to use an oil mud, attention should be given to specific local conditions. Factors such as potential loss of circulation and rapid accumulation of drilled solids or inclusion of excessive amounts of water in the oil mud affect the economic practicability. Nor should oil muds be used without due regard to the importance of the rig equipment - specifically, facilities for mud mixing, removal of drill cuttings, storage, and the like. Qualified supervision is a necessity, of course. Oil Mud Additives for Specific Functions With the objective of affording oil mud compositions as versatile as water muds, products have been developed to control various properties. These products are:Gelling and suspending agents organophilic clays.Emulsifiers: anionic mixed calcium and sodium soaps of fatty acids; cationic amine derivative stable to salts and high temperature.Oil-wetting agent: organic phosphate.Filtration control agent: nonasphaltic oil- dispersible organic colloid. The development and characteristic properties of these materials have been dealt with in detail in several publications and will not be reviewed here. The selection of an oil mud for drilling or completion usually involves the recognition of a problem with water muds and the conclusion that savings will result from using the product of higher unit cost. Frequently, the use of oil mud to solve the basic problem brings equal or greater associated benefits. JPT P. 261