Saturation-Height Modelling of Oil and Gas-Capped Reservoirs

The oil and gas companies work hard to produce hydrocarbons economically. A sound production plan must be based on a good assessment of hydrocarbon volume in the reservoir. Currently, three dimensional geological reservoir models are used to first assess hydrocarbon volume, which are then up-scaled to simulation to make a production forecast. Various production scenarios are tested in these models to maximize recovery before they are implemented in the field. Saturation height models are an essential part of three dimensional geological models in which they are used to populate hydrocarbon saturations in the porous reservoir.;Three dimensional geological models characterize the reservoir by sedimentological facies. Each sedimentological facies contains a number of rock types or hydraulic flow units. A rock type is distinguished by its texture and it has a distinct porosity-permeability relationship. A hydraulic flow unit is a rock having same ratio of permeability to porosity. For each hydraulic flow unit, there is a mathematical relationship that describes hydrocarbon saturation at any place in the reservoir as a function of its petrophysical properties and height above a datum or the Free Water Level. A set of mathematical equations for all hydraulic flow units in the reservoir (usually 5 to 8) are called a saturation height model. I established these models by integrating core data to logs and fluids in a multidisciplinary work-flow. The hydrocarbon saturations based on these models compare favorably with resistivity derived saturations from well logs.;I determined hydraulic flow units present in a reservoir based on core data interpretation. After cores are placed on log depths properly, the log responses are related to petrophysical properties measured on core. I established a predictive relationship for hydraulic flow units using log responses. This relationship is used to predict hydraulic flow units in non-cored wells. Once that is done, permeability can be calculated in non-cored wells also using the predicted hydraulic flow units. Each hydraulic flow unit has a saturation versus height relationship, which is used to calculate hydrocarbon saturations.;A well calibrated saturation height model populates the three dimensional geological model with hydrocarbon saturations that are related to its sedimentological and petrophysical properties. The assessments of hydrocarbons in place using such models are more accurate than traditional mapping methods.