A New Potassium Based Mud System
Authors: Mondshine T.C. 
Published: December 2007

This paper was prepared for the 48th Annual Fall Meeting of the Society of Petroleum Engineers of AIME, to be held in Las Vegas, Nev., Sept. 30-Oct. 3, 1973. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The 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 to the Editor of the appropriate journal provided agreement to give proper credit is made.

Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers Office. Such discussion may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines. Copyright 1973

Laboratory-wellbore simulation tests and a shale stability index test illustrate the benefits of potassium based muds. These shale studies and other laboratory tests led to the development of a new potassium based mud system designed for drilling various types of troublesome shales.

The system is prepared with potassium chloride or other potassium compounds and contains a potassium lignite derivative for limiting shale hydration and reducing filtration. A special non-ionic surfactant is for controlling rheology.

Laboratory and field data substantiate features of the new mud, which include shale stabilization, versatility, solids tolerance, and thermal stability.

Introduction

The benefits of potassium ions in suppressing the hydration and swelling of clay minerals has long been recognized and applied in drilling and completions. Specially designed potassium muds have been used, from time to time over the years to avoid damaging clay-bearing productive sands and for improving borehole conditions. Usage of potassium muds has been limited, however, because of poor versatility.

More recently, potassium chloride polymer muds have been successfully used for polymer muds have been successfully used for shale stabilization. These polymer muds still lack the versatility needed for widespread usage and appear to be practical only when low solids concentrations can be maintained. The primary limitation of KC1/polymer muds has been the control of rheological and filtration properties, especially in the drilling of properties, especially in the drilling of mud-making shales. Temperature limitations and inability to meet medium and high density requirements present other obstacles.

A new, more practical potassium mud system suitable for shallow, intermediate and deep drilling conditions has been developed to exploit further the benefits of potassium muds. The system can be described as potassium muds. The system can be described as a potassium mud compounded with a potassium lignite derivative which serves as a colloid for restricting entrance of water into shale. A special surfactant is used to aid in the control of rheology.

The main features of the potassium mud are:Shale Stability - The mud minimizes osmotic hydration and suppresses clay swelling.Solids Tolerance - The mud tolerates high concentrations of clay solids and is nondispersive to shale cuttings.