Clay Chemistry And Drilling Fluids
Authors: Browning W.C. , Perricone A.C. 
Published: December 2007

Publication Rights Reserved
This paper was presented at the First University of Texas Conference on Drilling and Rock Mechanics in Austin on January 23 and 24, 1963, and is considered the property of the Society of Petroleum Engineers. Permission to published is hereby restricted to an abstract of not more than 300 words, with no illustrations, unless the paper is specifically released to the press by the Editor of the Journal of Petroleum Technology or the Executive Secretary. Such abstract should contain conspicuous acknowledgement of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon request providing proper credit is given that publication and the original presentation of the paper.

Introduction
The drilling of oil and gas wells demands ingenious engineering, utilizing the best mechanical and chemical principles. It is obvious that many aspects of the so-called borehole stabilization problem are mechanical and can best be dealt with by mechanical means. Some aspects of borehole stabilization problems are primarily chemical, however, and may be alleviated by proper attention to the chemical factors involved. It should be clear if any feasible chemical means can be employed to make drilling more efficient, or to facilitate coping with the mechanical problems of well drilling, full advantage should be taken of such chemical means. By so doing, it is possible to continue to increase the efficiency and minimize the cost of oil well drilling. The subject matter of this paper is concerned with the relationship of the colloid chemistry of clays to drilling fluid design when water is the continuous phase. It is also concerned with the promotion of more efficient drilling techniques by utilization of principles derived from increased knowledge of the colloid chemistry of clays. The data given in this paper emphasize certain aspects of clay chemistry pertinent to drilling technology that are not dealt with or are inadequately dealt with in earlier literature. The subject matter of this paper is specific and deliberately limited in scope. It does not purport to be a comprehensive treatment of drilling technology and clay science.
It is believed that the study of clay-water chemistry with respect to drilling fluids is of value at the present and will continue to be so in the future, although some recent trade literature implies that oil phase drilling fluids solve all our drilling problems. it should be noted that oil phase drilling fluids are not new to drilling technology. oil muds began to be used in the middle 1930's even before the use of starch in water base muds. The non-swelling of Wyoming bentonite in oil makes anyone concerned with drilling technology consider the use of oil as a drilling fluid.
It was soon found, however, that the mere presence of a continuous oil phase did not necessarily eliminate all borehole problems. Farrand and Clark reported in 1944 that some shales were found to slough in the presence of oil base fluids. Recent experience indicates that borehole problems continue even into the present with the newest oil phase fluids. The foregoing comment is not to be construed as an argument that water base muds are better than oil base muds for drilling and, therefore, has to be supported in this paper by rigorous experimental evidence. The point of digression is this: the use of oil as a continuous phase in a drilling fluid is not new to drilling technology. The use of oil does not automatically eliminate downhole problems, but it is automatically more expensive than water.
Irregardless of interest in oil phase drilling fluids the fact remains, however, that water base fluids can be further improved.