Study on the Model and Law for Radial Leakage of Drilling Fluid in Fractured Formations

Abstract

The economic loss caused by fracture leakage accounts for 90% of all leakage costs; thus, it is necessary to find the factors that affect the leakage and to study the leakage laws of fractured strata. The advantage of this article is that we introduced fracture index deformation and fracture tortuosity parameters to characterize fracture roughness and fracture characteristic parameters using the logging data analysis method. To explore the mechanism of leakage in essence, this paper, based on fluid mechanics, improves the radial leakage model by adopting the Herschel–Bulkey (H–B) flow type drilling fluid with high calculation accuracy and comprehensively considering the factors such as drilling fluid performance parameters, fracture roughness characteristic parameters, pressure difference between the wellbore and formation, and radial extension length of the drilling fluid. The advantage of the model is that it is solved in an absolutely stable backward Euler difference format. The numerical simulation is carried out by MATLAB. The simulation results revealed that the leakage rate increased as the fracture index deformation coefficient and the fracture opening increased. The leakage rate also increased as the fracture tortuosity parameters decreased and as the fracture smoothened. However, the leakage rate decreased as the drilling fluid consistency coefficient increased. Drilling fluid dynamic shear force had a minor effect on the leakage rate. The higher the pressure difference between the wellbore and the formation, the higher the leakage rate. As the drilling fluid intrusion depth increased, the leakage rate decreased until it reached 0. Two parameters were mainly controlled in order to control the degree of leakage: differential pressure and fracture static width, which has important guiding for adjusting the drilling fluid density and predicting leaks in the field. The solution method of the model in this paper has a certain reference value for the solution of other models in the future. The conclusion can provide reference for numerical simulation, laboratory test, and field application in the future.

Study on Radial Leakage Model and Law of Fractured Formation Drilling Fluid

“…For self-similar fBM, the current main method is to describe fractures as fractals, evolving Mandelbrot's fBM into fractal theory by characterizing fracture roughness with fractal dimensions D and Hurst index H. The Hurst index measures the degree of roughness of the fracture surface [25], and H approaches 0 as the fracture becomes rougher. Rough fracture surfaces can be generated using a random midpoint displacement method through numerical simulation software [26], as shown in the Figure 2 below. Many scholars have studied fluid dynamics in pipeline flow [27], combined with existing fractal models of relative roughness, and the morphology of fractures, using laminar flow of non-Newtonian fluids with low Reynolds numbers in cylindrical capillary models [28].…”

“…As the models continued to improve, scholars began to consider fissure deformation. Li Daqi et al established one-dimensional linear and two-dimensional planar fissure leakage models using non-Newtonian fluids [13][14][15]. Jia Lichun et al utilized the power-law model of drilling fluid to establish a two-dimensional fissure model while considering the characteristics of fissure deformation, inclination, and roughness [16].…”

Development and Application of the Anti-High-Temperature Delayed Crosslinking Polymer as a Gel Plugging Additive for Drilling Fluid

“…As oil and gas exploration and development deepen, the cost of well leakage treatment has significantly increased [1][2][3][4]. Formation leakage not only affects drilling efficiency but also leads to issues, such as unstable wellbores and even the blockage of permeable channels, resulting in reduced oil well production [4][5][6][7][8][9].…”

“…As oil and gas exploration and development deepen, the cost of well leakage treatment has significantly increased [1][2][3][4]. Formation leakage not only affects drilling efficiency but also leads to issues, such as unstable wellbores and even the blockage of permeable channels, resulting in reduced oil well production [4][5][6][7][8][9]. Currently, the plugging materials primarily used in drilling sites can reduce losses caused by well leakage, but their effectiveness is unsatisfactory when dealing with crack-type and cavern-type leakages [10][11][12][13].…”

Synthesis and properties of self‐healing hydrogel plugging agent

“…With the advancement of petroleum exploration and development, various challenges are frequently encountered during the drilling process, leading to a significant escalation in drilling costs. 1,2 Formation loss stands out as one of the most critical issues in drilling and completion operations, resulting in substantial losses of drilling fluid. Addressing this problem necessitates increased non-productive time and extended construction periods.…”