Micromechanical Analysis of the Rock Sanding Problem

Abstract

SUMMARYRock sanding in oil wells is an erosion process in which grains are disaggregated due to a combination of stress and fluid flow. This process is studied here using the finite element method with interface elements and explicit representation of the material microstructure. A cross-section of a small-diameter side perforation of the main well is considered. Within a circular region around the hole, the individual rock grains are discretized, while the space between the ring perimeter and the square domain limits is filled with standard triangular elements. The space within each grain is discretized using elastic finite elements, while the intergranular contact is represented with zero-thickness interface elements equipped with a fracture-based constitutive law. Numerical analyses start from the in situ stress state and contemplate the perforation process and drawdown pressure. Preliminary results obtained in this on-going study suggest that the evolution of cracking and fracture around the hole can be represented quite realistically with this approach. Also, the correct trend that seems to emerge is the dominant effects of the initial stress value and the size of the perforation diameter.Brought to you by | Purdue University Libraries Authenticated Download Date | 5/29/15 2:25 AM Vol. 16, Nos. 1-2, 2005 Micromechanical Analysis of the Rock Sanding Problem investigations, particularly those realized in cylindrical samples /1 /, 121, and 13/ and second, numerical modelling carried out by FEM or DEM calculations 13/, /4/, 76/ and /5/.Brought to you by | Purdue University Libraries Authenticated Download Date | 5/29/15 2:25 AM Vol. 16, Nos. 1-2. 2005 Micromechanical Analysis of the Rock Sanding ProblemThis study is in a preliminary stage and on-going efforts are directed at continuing the reduction of the hole inner pressure to complete the perforation stage. We also consider cases with non-isotropic initial stress state, K 0 * 1. A next stage of the study will involve a coupled analysis required to simulate reduction of the transient downhole fluid pressure, and the parametric study to finally reach quantitative predictions of sand production in oil wells.

A method for the calculation of inter-element stresses in 3D

“…(11), and the equilibrated inter element forces from Eq. (8). Note that, rather than 2 different minimizations, the same Eqs.…”

Application of zero-thickness interface elements to sanding prediction analysis

“…Nevertheless, the analysis in its present form can be used to predict the rock failure in consolidated rocks which is the first stage of sanding; if rock failure is avoided no sanding will occur. The methodology was originally developed for heterogeneous materials such as concrete (López, 1999;Caballero et al, 2006), and then its application has been extended to other materials including rock (Garolera et al, 2005(Garolera et al, , 2011. The numerical aspects of the micro-mechanical model employed are described in detail in Garolera et al (2019), while the present paper focuses on the application of the same model to the 2D analysis in plane strain of a thick wall cylinder crosssection, for comparison with thick wall cylinder (TWC) tests used for simulating failure of perforations (Fig.…”

Micromechanical analysis of sand production

“…For this purpose, a new methodology is proposed based on a mesomechanical approach, successfully used in heterogeneous materials such as concrete . The application of this approach to rock sanding was first proposed in the context of the PhD thesis of Garolera in order to obtain a realistic methodology for assessing the risk of sand production and provide a quantitative assessment. In particular, the present study focuses on a 2D analysis of a perforation cross section (Figure ).…”