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313 results on '"Detournay, Emmanuel"'

2. Hydraulic Fracturing of Poorly Consolidated Reservoir During Waterflooding

Author

Detournay, Emmanuel and Hakobyan, Yera

Subjects
Physics - Geophysics
Abstract

This paper describes a KGD-type model of a hydraulic fracture created by injecting fluid in weak, poorly consolidated rocks. The model is based on the key assumption that the hydraulic fracture is propagating within a domain where the hydraulic fields are quasi-stationary. By further assuming a negligible toughness, the fracture is shown to grow as a square root of time. The asymptotic fracture propagation regimes at small and large time are constructed and the transient solution is computed by solving a nonlinear system of algebraic equations formulated in terms of the fracture aperture. At early time the fracture is hydraulically invisible and the injection pressure increases with time $t$ as $\log t$, while at late time leak-off from the borehole is negligible and the injection pressure decreases as $t^{-1/4}$. According to this model, the peak injection pressure observed when injecting fluid in weak, poorly consolidated rocks should not be interpreted as indicating a breakdown of the formation, but rather as marking the transition between two asymptotic flow regimes. The timescale that legislates the transition between the small and large time asymptotic regimes is shown to be a strongly nonlinear function of a dimensionless injection rate.

Published
2021

25. Fluid injection‐induced cavity expansion in dry porous medium.

Author

Kumar, Jithin S, Chaudhuri, Abhijit, Detournay, Emmanuel, and Kandasami, Ramesh Kannan

Subjects
POROUS materials, FLUID injection, EVOLUTION equations, FLUIDS, STRENGTH of materials, ELASTOPLASTICITY
Abstract

Fluid injection‐induced deformation around a cylindrical cavity is of particular interest in the area of subsurface energy extraction. In this study, a model is proposed to analyze the time‐dependent expansion of a cavity caused by fluid injection in an elastoplastic dry porous medium. This problem is characterized by the existence of two moving boundaries, a permeation front and an elastoplastic interface, which leads to distinct time‐dependent zones governed by different sets of equations. The interplay between these two boundaries leads to three phases of solution. The a priori unknown partitioning of the injection rate into the rate of change of cavity volume and infiltration in the porous medium necessitates the introduction of a time‐dependent permeation coefficient as one of the primary variables. The method of solution takes advantage of the quasi‐static and quasi‐stationary nature of the problem, which makes it possible to treat time as a parameter rather than a variable. It follows that the problem can be solved in two steps. In a first step, closed‐form expressions for the pore pressure, displacement, and stress fields in each zone are derived, with parameters in these expressions depending explicitly on four time‐dependent variables, namely the positions of the two interfaces, the cavity radius, and the permeation coefficient. In a second step, the rate equations governing the evolution of these variables during different phases are derived and solved numerically. The paper concludes with a parametric analysis of the influence of the stiffness and strength of the material on the solution. [ABSTRACT FROM AUTHOR]

Published
2024
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26. Finite domain solution of a KGD hydraulic fracture in the viscosity-dominated regime.

Author

Cexuan Liu, Detournay, Emmanuel, and Fengshou Zhang

Subjects
BOUNDARY element methods, HYDRAULIC fracturing, FLUID pressure, NONLINEAR equations, POROELASTICITY, ANALYTICAL solutions, FINITE volume method, FRACTURE mechanics
Abstract

This paper describes a numerical algorithm for solving the classic problem of a plane strain (KGD) fracture propagating in an impermeable elastic medium with zero toughness. The method, which takes advantage of the self-similar nature of the solution, combines a domain-based scheme to solve the elasticity equations and a finite volume method to solve the nonlinear lubrication equation. This work represents a first step towards developing a model able to account for pore pressure diffusion in the medium and corresponding poroelastic effects, noting that these processes are more efficiently solved using a domain-based rather than a boundary integral method. To enhance the efficiency and accuracy of the numerical scheme, the far-field crack asymptotics is embedded in the discretized elastic relationship between the fluid pressure and the crack opening, while the coupled fluid-solid tip asymptote is enforced in a weak form when solving the nonlinear lubrication equation. The proposed technique yields results that closely match the analytical solution, even with a coarse mesh. This approach offers potential for addressing more complex hydraulic fracturing problems in the future. [ABSTRACT FROM AUTHOR]

Published
2024
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32. Performance Analysis of a Downhole Regulator on Rate-Of-Penetration and Drilling Efficiency

Author

Aribowo, Arviandy, Aarsnes, Ulf Jakob F., Detournay, Emmanuel, van de Wouw, Nathan, Reimers, Nils, Dynamics and Control, Group Van de Wouw, EIRES, EAISI Foundational, EAISI High Tech Systems, EAISI Mobility, and ICMS Affiliated

Abstract

Over the last years, the use of autonomous solutions for balancing the loading on the drill-bit has increased annually. By 2021, downhole tools for this purpose have been used for more than 1,500 wells and these become possibly the fastest growing trend in drilling. Polycrystaline Diamond Compact (PDC) drill-bits represent a great potential for drilling economics when steady cutting is attainable. Deep drilling, however, typically involves long drillstring causing an array of dynamic instabilities preventing steady cutting conditions at the bit. Such behavior affects drilling performance in terms of the rate-of-penetration (ROP) and system damage and failure. This leaves a big potential for improvement of drilling performance. The first experiments with an autonomous downhole regulator constructed were completed at Ulrigg in Stavanger almost twenty years ago to tap into this potential. Several versions of similar tools have since developed using a variety of mechanical and hydraulic functions to modify and shift the forces acting on the drill-bit in order to improve drilling performance.The Norwegian operator Equinor has participated from the very start of this new automation trend. By 2020 they had deployed downhole regulators to a total of 93 well sections on the Norwegian Continental Shelf alone. In this paper, Equinor shares statistic plots from comparing these first 93 sections to well section with conventional BHA's. The data show how the continuous improvement of the regulator eventually led to gradual improvement of both ROP and footage - in addition to its initial task of reducing vibrations. By utilizing a variety of dynamic models, predictions and sensitivity analysis, it has been revealed that the downhole regulator could change the dynamic response of the bit such that the friction losses at the bit are reduced and the rock cutting efficiency is improved. In this paper, it is shown that such benefits can also be expected in real-life scenarios in which two key aspects play a role: 1) a PDC bit penetrating heterogeneous layers of rock formations, and 2) involving two frictional losses due to borehole - drillstring contact in deviated wells.This paper brings a unique insight to the fundamentals, advanced mathematical models, and statistical results from a new line of drilling technology. The autonomous regulators bring a combination of reduction in risk and time to drill that makes a significant impact on cost.

Published
2023

39. Dynamic modeling of drill-string systems for layered rock formations

Author

Aribowo, Arviandy, Wildemans, Roeland, Detournay, Emmanuel, van de Wouw, Nathan, Balachandran, B., Detournay, E., van de Wouw, N., Liu, X., Dynamics and Control, EIRES, EAISI Foundational, EAISI High Tech Systems, EAISI Mobility, and ICMS Affiliated

Published
2022

44. Application of wavelet to strength log from scratch test

Author

Zhang, He, Le, Jia-Liang, and Detournay, Emmanuel

Abstract

This paper proposes a methodology to construct logs of rock strength from the cutting force signal recorded in scratch tests conducted in the ductile regime. The approach, which is based on the application of discrete wavelet transforms, recognizes the existence of two length scales ℓcand ℓr. The strength length scale ℓcrepresents the length over which it is meaningful to measure strength, while the repeatability length scale ℓris related to the resolution at which the force signal must be observed to become insensitive to the stochastic micro-failure events triggered by the motion of the cutter. It is postulated that the original cutting force signal, assumed to be sampled at a high enough frequency, can be decomposed into a deterministic signal intrinsic to the rock and a stochastic one resulting from discrete rock failure events. The technique of multiresolution analysis based on the maximal overlap discrete wavelet transform is applied as a low-pass filter to the original cutting force signals so as to wipe out the high-frequency components associated with the stochastic rock failure events. A criterion to determine the optimum cutoff frequency of the low-pass filter and the corresponding repeatability length scale is discussed in terms of the correlation coefficients between different filtered signals. It is shown that the low-pass filtered signals obtained at the optimum cutoff frequency have two salient features: (i) repeatability over different tests conducted at the same depth of cut on the same sample, and (ii) variability along the cutting distance. The excellent repeatability reveals that the deterministic background trend of the original force signals is relevant to the rock strength property, and the variability of the background trend captures the spatial variation of the rock strength.

Published
2023
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