Kikar Gum in Water-Based Drilling Fluid: Rheology, Filtration, and Ranikot Shale Interaction

Abstract

Water-based drilling fluids must provide enough rheological structure for solids transport while limiting filtrate invasion and interaction with reactive shale. This study evaluates locally sourced Kikar gum as a plant-derived additive in a barite-weighted water-based drilling fluid. Four Kikar-gum formulations (F1-F4) were compared with a polyanionic-cellulose (PAC) reference fluid to determine how gum concentration and bentonite content affect rheology, filtration, filter-cake properties, and interaction with Ranikot shale. Kikar gum was ground and sieved to 0.212 mm before use. F1 contained 0.40 g gum with 18 g bentonite, while F2-F4 contained 12 g bentonite with 0.40, 0.75, and 1.00 g gum, respectively. Fluid density and rheology were measured with a mud balance and rotational viscometer. Low-pressure low-temperature (LPLT) filtration was measured for 30 min at 100 psi, followed by filter-cake thickness and apparent permeability estimation. Ranikot shale was characterized by X-ray diffraction (XRD) and cation exchange capacity (CEC), and shale-fluid interaction was assessed by contact angle, 72-h pellet immersion, and rheology after shale exposure. All fluids had similar densities of 9.9-10.0 lbm/gal. F1 developed the highest low-shear structure, with a plastic viscosity (PV) of 8 cP, yield point (YP) of 29 lb/100 ft2, and 10-s gel strength of 17 lb/100 ft2. F2 gave the most balanced response and the smallest rheological change after shale exposure; its PV remained 6 cP, while YP changed from 5 to 4 lb/100 ft2. F3 produced the thinnest filter cake at 2.05 mm and the lowest apparent cake-permeability estimate at 0.00644 mD. The PAC reference gave the lowest 30-min filtrate volume at 19.0 mL, compared with 21.0-35.0 mL for the Kikar-gum fluids. Ranikot shale contained 30 wt.% clay, including 15 wt.% smectite, and had a CEC of 12 meq/100 g. F1 showed the best visible pellet retention after 72 h, although all pellets showed some loss of integrity. The results support Kikar gum primarily as a rheology and filter-cake modifier in water-based drilling fluids. F2 is the strongest starting formulation for further development because it combines moderate initial rheology with the most stable post-exposure response. A complete fluid system will require additional filtration-control and shale-control components, followed by thermal aging, HPHT filtration, salinity, solids-contamination, and quantitative shale-stability testing.