A New Low-Damage Drilling Fluid for Sandstone Reservoirs With Low-Permeability: Formulation, Evaluation, and Applications

Abstract

Drilling-induced formation damage is the key factor dominating the failure of development of hydrocarbon reservoirs with low-permeability. In this paper, a new low-damage drilling fluid was formulated, evaluated, and applied to well drilling operations in a low-permeability reservoir in the Shengli Oilfield, China. To formulate this low-damage drilling fluid, filter-cake forming agents were used to prevent fluid loss, inhibitors were used to enhance the shale inhibition of the fluid, surfactants were used to minimize water block, and inorganic salts were used to enhance compatibility. A holistic experimental approach combining Micro-CT, SEM, FT-IR, and XRD techniques was designed to identify the underlying interactions between the formulated drilling fluid and rock samples, demonstrating its significant mitigation on formation damage which mainly results from the hydration of clay minerals and the invasion of solid particles. The newly formulated low-damage drilling fluid is then extended its applications to well drilling operations with excellent performance. Not only can the new low-damage drilling fluid avoid non-fracturing stimulation, but also reduce the drilling operational costs and time, minimize the formation damage, and facilitate extending the reservoir life for a longer time.

An Experiment-Based Study of Formation Damage Using a Microetching Model Displacement Method

“…During the drilling fluid cycle, the drilling fluid infiltrates the formation rock through pores, thus blocking the pores in rock (Figure 1b,c) and reducing the permeability of the formation, resulting in a dramatic decline in oil and gas recovery efficiency [5][6][7]. In low-porosity and low-permeability sandstone reservoirs [8][9][10][11][12], the formation damage from drilling fluid is extremely complicated. Therefore, with the gradual advancement of exploration and the development of low-porosity and low-permeability sandstone reservoirs, the study of the microscopic mechanism of formation damage by drilling fluid has received increasing attention in recent years.…”

Performance Evaluation of an Octadecyltrimethyl Ammonium Chloride–Dimethyl Silicone Oil as a Waterproof Locking Agent in Low-Permeability Reservoirs

“… 10 − 12 Fluorinated surfactants are effective waterproof locking agents owing to their ability to reduce the surface tension of water from 70 mN·m –1 13 to less than 20 mN·m –1 , 14 thereby minimizing formation damage and extending the reservoir lifetime in low-permeability reservoirs. 15 Aminnaji et al 16 studied the wettability of carbonate and sandstone cores treated with fluorinated chemicals, using contact angle measurement, scanning electron microscopy (SEM), and energy dispersive X-ray analysis, and observed altered liquid wetting by increasing surface roughness and decreasing surface free energy. However, fluorinated surfactants are expensive, exhibit poor biodegradability, and readily accumulate in the environment.…”

“…When the core contact angle is greater than 90°, the resulting tension tends to outwardly repel the external body in the pore throat . This significantly weakens the self-imbibition effect of reservoir cores, reducing both the capillary force imparted on the solution and the self-imbibition of the pore throat, thereby alleviating the water-locking effect. − Fluorinated surfactants are effective waterproof locking agents owing to their ability to reduce the surface tension of water from 70 mN·m –1 to less than 20 mN·m –1 , thereby minimizing formation damage and extending the reservoir lifetime in low-permeability reservoirs . Aminnaji et al studied the wettability of carbonate and sandstone cores treated with fluorinated chemicals, using contact angle measurement, scanning electron microscopy (SEM), and energy dispersive X-ray analysis, and observed altered liquid wetting by increasing surface roughness and decreasing surface free energy.…”