Deane Roehl

GEOMECHANICS APPLIED TO THE WELL DESIGN THROUGH SALT LAYERS IN BRAZIL: A HISTORY OF SUCCESS

The lessons learned on the geomechanical salt behavior and its application in subsalt wells design are described in this article. In addition, the developed methodology validation, through comparison between computing modeling results with measurements carried out in experimental panels, in the potash mine, and with measurements obtained in an experimental well drilled for the purpose of calibrating and optimizing directional drilling in salt layers are presented. These parameters and methodology have been used for supporting the design of the wells drilled in the Pre-Salt giant oil fields in Brazil with very successful results.

An adaptive strategy for elastic-plastic analysis of structures with cracks

This work presents a methodology for self-adaptive finite element analysis of two-dimensional elastic-plastic structures. The self-adaptive process is based on an h-type refinement, with a posteriori error estimation. Two types of error estimators are available. The first is based on effective stress (Lee and Bathe, 1994) and the second is based on a ratio of plastic work (Peric et al., 1994). In the non-linear adaptive process for incremental plasticity analysis, a technique for interpolating analysis variables across distinct meshes (Lee and Bathe, 1994) is adopted. The von Mises yield criterion, with isotropic hardening, is adopted. Fracture problems are used to evaluate the performance of the adaptive process. Keywords : finite elements, adaptive analysis, plasticity, cracks, error estimator

Design of Buried Pipes Considering the Reciprocal Soil-Structure Interaction

Finite element models have been surveyed for the numerical evaluation of the behavior of buried pipes with emphasis on soil-structure interaction. The following characteristics are recognized as defining finite element models: the material model for the soil and for the pipe; two or three dimensional geometry description; finite element type; contact conditions; and type of analysis which, according to the engineering problem and analysis purpose can be selected.

An efficient algorithm to generate random sphere packs in arbitrary domains

Particle-based methods based on material models using spheres can provide good approximations for many physical phenomena at both the micro and macroscales. The point of departure for the simulations, in general, is a dense arrangement of spherical particles (sphere pack) inside a given container. For generic domains, the generation of a sphere pack may be complex and time-consuming, especially if the pack must comply with a prescribed sphere size distribution and the stability requirements of the simulation. The primary goal of this paper is to present an efficient algorithm that is capable of producing packs with millions of spheres following a statistical sphere size distribution inside complex arbitrary domains. This algorithm uses a new strategy to ensure that the sphere size distribution is preserved even when large particles are rejected in the growing process. The paper also presents numerical results that enable an evaluation of the proposed algorithm.

Three dimensional elastoplastic contact analysis at large strains with enhanced assumed strain elements

In this paper, a model for elastoplastic contact analysis under large strain conditions is presented. Consideration of the impenetrability constraints follows through a penalty formulation. Due to the presence of large strains and to the impenetrability restrictions, special care by the choice of the finite element formulation is required. Here, the enhanced assumed strain concept is employed. Since this concept is based on the enhancement of the strain fields with no interelement continuity requirement imposed, the simple global structure of the displacement based model remains unchanged.

THE GEMA FRAMEWORK – AN INNOVATIVE FRAMEWORK FOR THE DEVELOPMENT OF MULTIPHYSICS AND MULTISCALE SIMULATIONS

This paper summarizes the GeMA (Geo Modelling Analysis) framework, a library intended to support the development of new multiphysics simulators and its integration with existing ones. GeMA uses software engineering techniques to allow engineers to focus on the programming of the physical simulation and letting the framework take care of data management and other necessary support functions to develop efficient, professional programs. These programs are capable of simulating complex problems that may involve multiple physics that interact in different spatial and time scales. GeMA architecture supports multiple simulation and coupling paradigms, with particular emphasis given to finite element methods. GeMA support includes the coupling of different physics, each one with possibly different spatial domain discretizations (meshes). It has functions to support efficient transfer of state variable values from one discretization to another. The framework also implements some important concepts of extensibility, through the combined use of plugins and abstract interfaces, configurable orchestration and fast prototyping through the use of the Lua language. In this paper, we also present some results of a 2D basin modeling test case that couples FEM non-linear temperature calculations, compaction and kinetic oil maturation and generation algorithms. This scenario includes a time evolving mesh and different time scales among physics.

Numerical Analysis of Metal Powders in Uniaxial Compaction

Powder consolidation constitutes an important step in the manufacture of products of high quality and precision. To obtain these components, with desired forms and final mechanical properties, it is of extreme importance to have knowledge about the processes to obtain powders, compacting and sintering. The objective of this work is to verify which model, obtained from the literature, better describes the compaction densification behavior of iron powder in closed-die. Doraivelu’s criterion was carried through the method of the finite elements with the implementation of an elastoplastic model with hardening. The influence of the yield function coefficient against the relative density was evaluated, as well as, the yield function in the hydrostatic space.