Incorporating outcrop observations and laboratory measurements in 3D reservoir models: An integrated study to enhance the workflow of modeling bioturbated carbonate reservoirs

Abstract

Although the common characteristics of bioturbated reservoirs are well-documented, the numerical modeling of such reservoirs remains poorly understood. This study aims to address this gap by introducing a workflow for modeling bioturbated strata in the Hanifa Formation, central Saudi Arabia. The workflow involves integrating sedimentological, stratigraphic, and ichnological observations, outcrop photogrammetry, petrophysical analysis, geostatistical modeling, and fluid flow simulation to numerically model burrow abundance (in burrow percentage [BP]), porosity, and permeability of bioturbated strata. A trend volume that mimics the distribution of the BP was generated to model the distribution of the porosity and permeability in 3D models of the outcrop. Three porosity models reflecting the porosity of burrow infills, porosity of the host rock matrix, and their summation were generated. Four scenarios of permeability modeling resulted in eight 3D permeability models, which were then used to generate eight cases of fluid flow simulation for a hypothetical reservoir similar to the bioturbated strata of the outcrop. The results indicated that the flow capacity of the 3D model strongly depends on the BP, whereas the storage capacity does not, due to the presence of microporosity in the host rock matrix, which is substantially higher than the infills porosity but reflects pores that are extremely smaller in size. The results of the fluid flow simulation indicated that production data is very sensitive to permeability models, emphasizing the importance of selecting the correct permeability modeling scenario to accurately simulate bioturbated reservoirs. The insights derived from these permeability modeling scenarios can aid in identifying crucial parameters and variables that affect the permeability and productivity of bioturbated hydrocarbon reservoirs and water aquifers. Refining and validating these scenarios with real-world data from subsurface reservoirs can lead to the development of more accurate models of these systems. The findings from these models can guide future investigations and support the creation of more effective strategies for managing hydrocarbon reservoirs and water aquifers.