Assessing the Rheological and Filtration Capacities of Rubber Seed Husk in Water Based Mud

Drilling operation efficiency is enhanced by the application of a drilling mud constituted with suitable additives. Numerous commercial fluid additives: carboxymethyl cellulose (CMC), polyanionic cellulose (PAC), among others are non-biodegradable, hence can cause harm to the environment, personal safety and affect the total drilling cost. Thus, there is need for alternative drilling fluid additives to reduce the amount of non-biodegradable waste disposed to the environment. This study investigates the effect of different particle sizes of a locally sourced rubber seed husk as an additive for the enhancement of density, pH, rheological and filtration properties of water based mud. The materials were prepared, ground and sieved to 125 and 250 microns. The mud formulation was based on the American Petroleum Institute (API) standard of 25 g bentonite to 350 mL of water. The results obtained showed that the mud density of the formulated water based muds increased with increase in the quantity of additives and fall within the API recommended range for density. The muds are similar in their rheological behaviours as both exhibited a rheological model similar to Bingham Plastic model. Rubber husk (125 microns particle size) decreased the pH from 7.70 – 6.50 while rubber husk (250 microns particle size) decreased the pH from 6.70 – 6.10, hence, both did not fall within the API specification for pH. Also, the filtration test of the formulated muds was performed using API recommended practice for static filtration test at low temperature - low pressure (LTLP) condition. The different particle sizes (125 and 250 microns) of rubber husk exhibited a good fluid loss control behaviour, such that, the fluid loss volume of both muds decreased with increase in the quantity of additives. Also, the results revealed that the filter cake thickness of rubber husk of 125 microns (particle size) at 5 g was within API specification for cake thickness whereas rubber husk of 250 microns (particle size) formed mud cakes of non-acceptable thickness. The mud filter cake characteristics exhibited by these particle sizes of rubber husk depicted that they have slippery, smooth and soft mud cakes, thus, a thin and soft cake of rubber husk of 125 microns is more preferable and can be used in consolidating the walls of the borehole during drilling operations.