When Machine Learning Helps to Understand a Facies Controlled Two Ways Tilted Contact in a Large Carbonate Reservoir

Abstract

Abstract This case study presents an example of a large multibillion barrels in place carbonate reservoir where a two way tilted contact has been identified. Based on petrophysical analysis integrated with sedimentology studies and structural analysis, a tilted contact with two perpendicular directions (North-West / South-East and South-West / North-East) has been identified in this large structure. The mapped contact surface was found to be near parallel to the top depth structure, while the oil column thickness remained generally consistent throughout the field. During a recent drilling campaign, new cores have been cut in several wells. These cores cover the entire reservoir section from reservoir top to reservoir base, as well as across the depths of the measured resistivity-based contacts. Thus, a complete sedimentological core description as well as routine core analysis and special core analysis are available both in the hydrocarbon and water legs. Machine learning algorithms have been used here for two purposes. Firstly, using core plug permeability measurements to create a core based permeability model and then to propagate it throughout the field to the uncored wells. Secondly, using sedimentological core descriptions, a depofacies and a lithofabrics frameworks have been established and propagate to the entire field. This approach has been validated by means of production logs and correlation panels. A good correlation between the permeability profile, the facies distribution and the resistivity-based oil water contact (OWC) location has been observed. This suggest that the reservoir facies control the two-way tilted contact in this reservoir. Additionally, based on the regional tectonic’ setting of the area, a structural tilt is envisaged to have been active in geological time. This has likely contributed to a certain extend to this two-way tilted contact. The tilted contact orientation in two perpendicular directions identification has helped in sensitizing the hydrocarbon in-place and recoverable volumetric impact to support the present and future field development plan and the long-term sustainable production of this reservoir.