MODIFICATION OF RHEOLOGICAL AND FILTRATION PROPERTIES OF WATER-BASED DRILLING MUDS WITH LIGNITE NANOPARTICLES FOR OIL WELL DRILLING OPERATION

Abstract

ABSTRACT Drilling muds are heterogeneous mixture of water or oil, clay materials and chemical, that facilitate drilling operations. Muds are important in successful well drilling as they have common properties that enhanced safe and satisfactory completion of the well by its functions such as removal of rock cuttings to the surface, controlling high pressure zones and cleaning of bottom hole. The importance of drilling muds, cannot be over emphasized as the knowledge on drilling mud is essential in the rotary drilling operation in the petroleum industry and the demand for drilling mud is on increase side as a result of drilling operations ranging from oil wells to ground water bore holes that are being carried out frequently on a daily basis. The aim of this research work is the modification of rheological and filtration properties of water-based drilling muds using Nigerian nano lignite coal. The abundancy of local clay in Nigeria are not exploited in drilling mud because these local clays contains high level of impurities and are mainly calcium-based montmorillonite bentonite with low swelling capacity which results to substandard rheological and filtration properties challenge in their natural form when used for formulation of drilling muds. This necessitates the testing of clays and nano lignite coal used for formulation and modification of mud in this research work via the following method of analysis: TGA, XRD, SEM/EDX, FTIR, and physicochemical analysis. The method employed involved, the formulation of mud, beneficiation of mud using surfactants such as caustic soda (NaOH), soda ash (Na2CO3) and polyanionic cellulose (PAC) and modification of mud using different Nigerian nano lignite coal concentration at different temperature. The data generated from FANN 35 viscometer at different dia reading of 600,300 200, 100, 6 and 3 rpm respectively, were used for evaluation of rheological and filtration properties of spud, beneficiated and modified drilling mud. The results obtained deduced that the Nigerian nano lignite coal have a thermal stability at the temperature of 570 °C from TGA curve, the XRD, SEM/EDX and FTIR shows that the clays and nano lignite coal were crystalline in nature, contains both metal and nonmetal elements and strong (-OH) functional group. The power law rheological model results obtained deduced that the drilling muds all obeys non-Newtonian fluid with the flow behaviour index of all muds at different concentration of nano lignite coal and temperatures were less than unity (n<1), having the highest value of (n) as 0.4653 and 0.4151 for local and commercial bentonite clay respectively. Conclusively, the pretreatment with soda ash, enhanced the swelling capacities of the bentonites and easy dispersion when mixed with water. The characterizations carried out shows that the bentonites were crystalline in nature while lignite nanoparticles were semi crystalline, their internal structure were like spherical in shape. The results of the spud water-based drilling muds obtained shows that the values were below API rheological properties standard (≥ 8 cP for plastic viscosity and ≥ 15 cP for apparent viscosity) and above API filtration properties standard (≤ 15 ml for fluid loss). The use of micro size lignite particles is recommended in order to justify the effectiveness of lignite nanoparticles for modification of drilling mud properties. Chemical substance (metallic oxide) such as nano Fe2O3, TiO2, Al2O3, CuO and SiO extract from plants and solid waste combined with lignite nanoparticles for modification of rheological and filtration properties of drilling muds are recommended