Abstract
Drilling mud is a key component in drilling operations and in accessing oil and gas reservoirs. Bentonite is applied as a viscosifier, fluid loss control agent, and as a weighting material in water-based drilling mud. The type of bentonite used in drilling mud formulation is sodium bentonite due to its high dispersion properties and high swelling capacity. Nigeria has a huge bentonite clay deposit resources which can be evaluated and enhanced in order to be utilized as drilling mud. However, bentonite clay from different parts of Nigeria was investigated and found to be calcium bentonite which is not suitable for drilling mud, because it has low swelling capacity and poor rheological properties. In this study, local bentonite obtained from Afuze, Edo state was used to formulate different samples of drilling mud with each treated using thermo-chemical beneficiation process with sodium carbonate and cassava starch, and then undergo characterization to identify the changes in physical properties and finally, draw comparison with API values for standard drilling mud. The results obtained from this study indicates that, the flow and rheological properties of the beneficiated drilling mud developed through thermo-chemical treatment, showed significant improvement compared to the untreated mud. Therefore, pure calcium bentonite from natural deposits in Nigeria can be modified to sodium bentonite and sufficiently used in drilling mud formulation.
Highlights
As one of the largest oil producers in the world, the present consumption of bentonite clay in the drilling operations in Nigeria alone is over 100 thousand tons a year [1]
Local bentonite obtained from Afuze, Edo state was used to formulate different samples of drilling mud with each treated using thermo-chemical beneficiation process with sodium carbonate and cassava starch, and undergo characterization to identify the changes in physical properties and draw comparison with American Petroleum Institute (API) values for standard drilling mud
The results obtained from this study indicates that, the flow and rheological properties of the beneficiated drilling mud developed through thermo-chemical treatment, showed significant improvement compared to the untreated mud
Summary
As one of the largest oil producers in the world, the present consumption of bentonite clay in the drilling operations in Nigeria alone is over 100 thousand tons a year [1]. Due to the high calcium content and low sodium content compared with foreign bentonite, it does not meet the API drilling standards Due to these or more difficulties, Nigeria’s bentonite used in drilling activities is mainly imported into the country [6]. To the mud formulation to help in improving drilling mud properties such as; free swell volume (FSV), gel strength, yield point, weight, specific gravity, viscosity, fluid loss These additives help minimize formation damage, maintain well integrity, reduce logging analysis problems, protect water-sensitive shale, reduce fluid loss in the protective formation, and reduce well washout for better results, lining and cementing work [15] [16]. Its geographical coordinates are longitude 6.04254 ̊7'E latitude 6.96945 ̊N and elevation of 440 ft (134 meters) and this is 533 ft (162.5 meters) below average elevation of Nigeria
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