DOLOMITE AS AN ALTERNATIVE WEIGHTING AGENT IN DRILLING FLUIDS

A series of experimental tests have been conducted to assess the suitability of usingdolomite as an alternative weighting agent in drilling fluids. Currently, barite iswidely used as weighting agent in drilling fluids slurry to ensure proper weights areachieved. However, barite contains toxic materials which make it unattractive fromhealth and environment point of views. This is especially true when drillingoperations are offshore, where most of the used drilling fluids will be dumped backinto the sea. In this work, rheological properties of dolomite blend drilling fluidsslurry were studied. Dolomite rocks were first crushed to produce dolomite powder,before being mixed with water and bentonite at various proportions. A total of 10samples which contains various percentages of water, bentonite and dolomite werestudied. For each sample, its rheological properties were determined. Suchproperties include density from mud balance, viscosity from viscometer, filtrate lossfrom API filter press and gel strength. The effect of aging on the properties ofdrilling fluids was also studied. From the study, it is concluded that Sample E, whichconsists of 70% dolomite by weight, produces the most stable drilling fluids. It isalso observed that the amount of 336 g of dolomite in the sample shows the similarphysical and rheological properties to that of the 480 g barite in the sample althoughthe density for both samples is not same.