Advanced Semianalytical Geomechanical Model for Wellbore-Strengthening Applications

Abstract

Drilling depleted reservoirs often encounters a host of problems leading to increases in cost and nonproductive time. One of these problems faced by drillers is lost circulation of drilling fluids, which can lead to greater issues such as differential sticking and well-control events. Field applications show that wellbore strengthening effectively helps reduce mud-loss volume by increasing the safe mud-weight window. Wellbore-strengthening applications are usually designed on the basis of induced-fracture characteristics (i.e., fracture length, fracture width, and stressintensity factor). In general, these fracture characteristics depend on several parameters, including in-situ stress magnitude, in-situ stress anisotropy, mechanical properties, rock texture, wellbore geometry, mud weight, wellbore trajectory, pore pressure, natural fractures, and formation anisotropy. Analytical models available in the literature oversimplify the fracture-initiation and fracturepropagation process with assumptions such as isotropic stress field, no near-wellbore stress-perturbation effects, vertical or horizontal wells only (no deviation/inclination), constant fracture length, and constant pressure within the fracture. For more-accurate predictions, different numerical methods, such as finite element and boundary element, have been used to determine fracture-width distribution. However, these calculations can be computationally costly or difficult to implement in near-real time. The aim of this study is to provide a fast-running, semianalytical work flow to accurately predict fracture-width distribution and fracture-reinitiation pressure (FRIP). The algorithm and work flow can account for near-wellbore-stress perturbations, far-field-stress anisotropy, and wellbore inclination/deviation. The semianalytical algorithm is modeled after singular integral formulation of stress field and solved by use of Gauss-Chebyshev polynomials. The proposed model is computationally efficient and accurate. The model also provides a comprehensive perspective on formation-strengthening scenarios; a tool for improved lost-circulation-materials design; and an explanation of how they are applicable during drilling operation (in particular, through depleted zones). Sensitivity analysis included in this paper quantifies the effect of different rock properties, in-situ-stress field/anisotropy, and wellbore geometry/deviation on the fracture-width distribution and FRIP. In addition, the case study presented in this paper demonstrates the applicability of the proposed work flow in the field.

Laboratory Research on Fracture-Supported Shielding Temporary Plugging Drill-In Fluid for Fractured and Fracture-Pore Type Reservoirs

“…Loss of circulation was encountered in the low-pressure layers when the high pressure layers were drilling. Therefore, the bearing capacity of this kind of easy leakage formation must be considered [16][17][18][19][20][21]. In addition, there must be a larger pressure difference to ensure highly efficient cementation; thus, it was necessary to test the temporary plugging strength of the filter cake during drilling and other operations.…”

Geomechanical analysis of lost circulation control in tight formations

“…modeling, the analytical/semi-analytical model is more accurate in predicting the fracture aperture and stress intensity factor at different conditions and more computationally efficient. The semianalytical method has been widely applied to the calculation of the stress intensity factor and fracture width in fracture models (Warren, 1982;Shahri et al, 2014;Shahri et al, 2015;Xu et al, 2017;Xu et al, 2020). Mehrabian and Abousleiman.…”

A Numerical Study on the Application of Stress Cage Technology

“…However, the effect of temperature variation on the results of stress cage technology is not investigated [24]. Shahri et al (2015) provided a semi-analytical model to predict fracture width distribution and fracture re-initiation pressure, considering near well stress distribution, in situ stress anisotropy, and directional trajectory of the well. Using the results of the proposed model, the authors investigated the effect of different parameters on the design of lost circulation materials.…”

“…Using the results of the proposed model, the authors investigated the effect of different parameters on the design of lost circulation materials. Authors did not include the temperature effect in the semianalytical model [25].…”