Combining Geomechanical and Heat/Fluid-Flux Simulations to Better Understand Burial Dolomitisation in Carbonate Reservoirs

Abstract

Diagenesis is a major control on the petrophysical properties of carbonate reservoir rocks. Numerical simulation that uses information from core observations and measurements, diagenetic studies and a structural analysis of the basin development, is used to estimate these diagenetically-altered petrophysical properties away from well/cores out into the reservoir. Heat and fluid-flux simulations informed by both geomechanical and basin system analysis (basin modelling) simulations were applied to an offshore carbonate reservoir. This reservoir has been dolomitised during burial and has a complex permeability distribution that does not have an obvious depositional relationship. Basin modelling establishes the geological framework, the background state of rock compaction and the thermal state with time. The geomechanical simulation uses the appropriate geometry, rock properties and mechanical (tectonic) loads for the time of interest. It depicts fault-zone rock damage which locally creates potential flow pathways, depending on the distribution of the dilation and compaction zones within the fault zone. The conjecture is that fluid convection associated with the fault zone perturbs the temperature distribution and may introduce magnesium by fluid flow. This concept is tested by the heat- and fluid-flux simulations. The analysis provides a sequence of geometries, evolved rock mechanical properties, plus fluid and heat-flow patterns that allow us to infer the causes and consequences of the dolomitisation event affecting this reservoir. This workflow is generic and can be applied to any carbonate reservoir to enhance understanding of the relationship between fault-zones (i.e. dilation and compaction distributions) and fluid-related heat and solute transport in order to understand the diagenetic history of the reservoir and the resulting porosity and permeability distribution.

AAPG Datapages/Search and Discovery Article #90216 ©2015 AAPG Annual Convention and Exhibition, Denver, CO., May 31 - June 3, 2015