GEODYN: A Geological Formation/Drillstring Dynamics Computer Program

Abstract

This paper describes the initial development phase of a finite element computer program, GEODYN, capable of simulating the three-dimensional transient dynamic response of a polycrystalline diamond compact (PDC) bit interacting with a non-uniform formation. The ability of GEODYN to simulate response variations attributable to hole size, hole bottom surface shapes, and formation material non-uniformities is demonstrated. Planned developmental phases will address the detailed response of a bottom-hole assembly (BHA), a drill ahead (rock penetration and removal) simulation, and ultimately, the response of the entire string.

Finite Element for Simulating BHA-Casing-Rock Interactions

“…Figure (5) the side forces that determine the directional trajectory was displayed with time; also the displacement due to these forces was depicted in the same figure. Figure (6) demonstrated the rate of penetration and bit angular velocity along the distance bath. Figure (7) verify the BHA model results by computing side forces since formation anisotropy and other parameters were not considered.…”

“…In 1953, the pioneering work was developed by Lubinski and Woods and Williamson and Lubinski [1] with the same model. Many analytical and numerical models exist which are designed to analyze Bottom hole assemblies and/or predict wellbore trajectories [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. There are four basic mathematical models used for BHA analysis; the analytical model, FEM, finite difference model and weighted residuals.…”

Finite Element Modeling of Drillstrings

“…Of note is the GEODYN program developed in Sandia National Laboratories [4]. This program is designed to simulate the three-dimensional, transient dynamic response of a bit-drillstring system interacting with a geological formation.…”