Evaluation of Drilling Fluids Formulated from Coconut Oil, Melon Oil, and Commercial Ester: A comparative Study

Abstract

High cost of importation and processing of commercial ester for synthetic-based drilling fluid calls for the sourcing of local derived oil as alternative. In this work, oil was extracted from coconut fruit and melon seed for preparation of synthetic-based drilling fluid. Three drilling fluid samples of commercial ester (CE), coconut oil (CO) and melon oil (MO) were formulated with derived oil as based oil using the same concentration of the same additives. The physicochemical properties of the three base fluids (CO based, MO based and CE based) were determined. Also the rheological properties and electrical stability (ES) of the three samples of drilling fluid were tested and determined at different temperatures such as 80^oF, 120^oF, 150^oF, 170^oF and 200^oF. Similarly, other properties such as high-pressure-high-temperature (HPHT) fluid loss properties, chemical analysis and retort analysis of the three drilling fluid samples were tested and determined. The results from the three samples  show that the specific gravity and kinematic viscosity of CO and MO are greater than CE; all the three based fluids (CO, MO and CE) are acidic in nature; and the pour point, cloud point, flash point and fire point of CO and MO are higher than CE. Also, the rheological properties of the CO and MO drilling fluids at different temperatures are not as desirable as CE drilling fluid; however, only CO drilling fluid possesses acceptable ES at different temperatures; all the three drilling fluids have undesirable alkalinity and excess lime; in the same way all the three drilling fluids have acceptable oil-water-ratio (OWR) with MO drilling fluid being the best; and the CE drilling fluid has the best filtrate and filter cake thickness when compared with CO and MO drilling fluids. The observed viscosity of the CO and MO drilling fluids are very high compared to CE drilling fluid and in most cases as the temperature increases the rheological properties reduce; high kinematic viscosity of CO and MO resulted to high plastic viscosity, which can result to high pumping pressure during circulation. Also, the observed poor alkalinity and excess lime of the three drilling fluids might result from the acidic nature of the based fluids (CO, MO and CE) used in the formulation. It revealed that CO and MO drilling fluids are not as desirable as CE drilling fluid. However, reducing concentration of viscosifier (organophilic clay) from 4g to 2g may tend to reduce the viscosity of CO and MO drilling fluids. Similarly, increasing the concentration of lime from 8g to 10g will improve the alkalinity and excess lime of the three drilling fluids.