Applications of Stress Field Modelling Using the Distinct Element Method for Petroleum Production

Abstract

Abstract The distinct element method was first introduced in 19711 and has been progressively developed over the past two decades. It is described as a finite difference distinct element, numerical modelling method (DEM). The method was implemented in the computer program UDEC (2D and 3DEC (3D)2 and its major application to date has been in the field of rock mechanics and mining engineering. In this paper we demonstrate the applicability of this method to the production of hydrocarbons. The method can be used to model 3D stress fields in a petroleum basin or field setting. It has been shown previously that stress field model data is consistent with actual borehole breakout data and hydro-fracturing measurements3. The modelling methodology can be used to calculate fluid potential and hence used to associate crustal stress, hydrocarbon migration and accumulation. By monitoring disturbances to the syn-production stress field estimation of the residual oil potential can be achieved. The work initially presents via sensitivity analysis the generic effect of faults and horizon boundaries on the mean local in-situ stress field. A case study is presented whereby the fault geometry for the Big Lake Field in the Cooper Basin of South Australia is modelled using DEM. Predictions of the spatial distribution of hydrocarbon accumulations and pressure gradients using the model were found to be accurate. Subsequently the model is adapted to account for production and the resultant pressure changes over time, which can lead to the prediction of residual hydrocarbon distributions.