A Physicochemical Approach to the Prevention of Balling of Gumbo Shales

Abstract

ABSTRACT Gumbo-type shales have presented a multitude of problems in many drilling areas of the world, including "balled" bits, collars and stabilizers, plugged flow lines, and shaker screens. These problems can result in decreased drilling rate, lost circulation, stuck pipe, logging difficulties, and, in general, increased well cost. A study was made of the gumbo-type shales which exhibit plasticity and adhere to the drill string and other drilling equipment. This work revealed that the balling tendency of these shales could not be controlled effectively with conventional inhibiting electrolytes such as gypsum, lime, sodium chloride, potassium chloride, etc. Thus, the clay base exchange or cation fixation mechanisms have been only partially effective in preventing the drilling problems associated with gumbo. This paper describes a physicochemical approach to preventing the balling and sticking together of the massive gumbo shales. This approach is based upon the interaction of water with silica and alumina surfaces. This interaction produces a difference in proton density between the bound water on the clay surface and the pore or interstitial water. The electrostatic forces created by the proton density difference causes adhesion of clay masses. The adhesion resulting from clay-water interaction is believed to be the dominant factor in the stickiness and balling tendencies of these shales. An organo-aluminum complex has been synthesized, which strongly adsorbs onto a clay surface forming an organo-aluminum-clay complex. The formation of this complex decreases the interaction between the particle surface and water, thus greatly reducing the adherence factor. A number of test wells have been drilled successfully using this physicochemical approach in various parts of the world. Data and drilling performance criteria are presented in this paper, and a comparison with previous wells drilled with other fluids is given. INTRODUCTION The finding of new petroleum reserves to meet the increasing demand for energy has pushed exploratory efforts towards the various continental shelves and deltaic regions of the world. The cost of finding these new resources and producing them has reached enormous proportions, as evidenced by the recent exploration activities in the North Sea.