Bentonite Deposits in Kenya as Drilling Mud

Abstract

An evaluation of Bentonite deposits from Kajiado County situated in the southern part of Kenya was undertaken for possible use as drilling mud. The primary objective was to assess and evaluate the occurrence and extent of the deposits for use as an alternative to imported Wyoming drilling mud. Tests were carried out both on the collected ore samples, imported clays as well as the locally processed bentonite. The results indicate that the ore deposits have a slight chemical variation from the Wyoming clay. This is primarily due to contamination by gypsum which occurs contemporaneously with the clay deposits. The geological setting also contributes to the unique clay geochemistry and thus the quality of the ore deposits. However, the locally processed samples correlate fairy well with the Wyoming sample in terms of chemistry although variation in aluminum, calcium and iron is noted. The marsh viscosity of the processed mud is 34 seconds which falls within the range of typical drilling mud of 30 to 50 seconds. Thixotropic tests indicate that the locally processed clays have the capacity to form a homogeneous gel, an indicator of a good drilling mud. Investigations further reveal that the ore is deposited along paleo-riverine channels which indicate that the transport and sedimentation was due to the action of water. The thickness is about 1-4 m and may vary while the tonnage is quite large. Based on the surveyed area of about 29 square kilometers, the total mass is estimated to be about 29×106 tonnes however the total tonnage is much bigger since the formation associated with these deposits stretches to Konza which is 40 kilometers away. Based on the geochemical and physical results, test trial drilling using the locally mined and processed clays is recommended. Processed clays from Athi River Mining Company should be utilized, so as to test its performance during the drilling process. This will ultimately help in evaluating its viability as an alternative drilling mud.