Papers by Author: O.A. Olafuyi

Abstract: When a reservoir is subject to edge water drive mechanism, well completion for the purpose of optimizing oil production becomes a critical objective. Achieving this objective will require a comprehensive knowledge of fluid movement in the reservoir. Effective well spacing and design, production or injection, transient test analyses possibilities and rate scheduling are additional benefits that can be derived from knowledge of fluid movement and dynamics. Source and greens functions are utilized in deriving the appropriate dimensionless pressure expressions for the reservoir system. Finally, dimensionless pressure derivatives are computed based on the dimensionless pressure expressions. Two-edged lateral water encroachment pattern is assumed for a centrally located horizontal well, occurring both at the toe and at the heel of the well. Influences of both reservoir and wellbore properties are investigated for infinite conductivity wellbore condition. Results show on the derivative that, flow is characterized first by infinite acting flow (constant value of 0.5) before a mandatory rapid decline to zero for all well and reservoir dimensions considered. The period of infinite activity, that is, period of clean oil production, is extended if the reservoir is much larger than the length of the well. Furthermore, dimensionless time of attainment of steady state for all well design is strongly dependent on the reservoir external extent and reservoir anisotropy under constant rate regime.

Abstract: This paper presents the results of drainage capillary pressure and relative permeability measurements made on cores having different bulk volumes ranging from 0.5 to 12 cm3. The aim of the experiments was to provide reliable experimental data which can be used to validate the predictive value of micro-CT based network models for capillary pressure and relative permeability. The micro-CT based network models use realistic networks constructed from the X-ray images of the rock samples having a typical bulk volume of 0.3 cm3. Experimental data for drainage capillary pressure were obtained using the centrifuge technique. The results of the largest cores were verified by the data obtained on the same sample using the porous plate technique. Relative permeability data were obtained by history matching the unsteady state displacement data. Homogeneous model sandstones (Berea and Bentheim) and carbonate (Mt. Gambier) were used in the experiments. Air-brine and oil-brine fluid-systems were used for drainage capillary pressure and relative permeability measurements, respectively. The relative permeability data were compared with those predicted from empirical and geometry based models using capillary pressure data. Good agreement was obtained for the drainage capillary pressure measured on all samples used. The residual saturations obtained from the cores used in the displacement experiments were also in good agreement. The models were found to predict relative permeability of oil and water with varying degrees of success. For water relative permeability, the Pirson model predicts the experimental data successfully while the Corey, Corey-Brooks/Burdine and van Genuchten/Burdine models predict the data of oil relative permeability better than the others. The results demonstrate for the first time that reliable drainage capillary pressure and relative permeability measurements can be made on small model sandstone and carbonate cores of representative scales used in micro-CT-imaging.

Abstract: Advances in micro-CT imaging of porous materials provide the opportunity to extract representative networks from the images. This improves the predictive capability of pore scale network models to predict multiphase flow transport properties. However, all these predictions need to be validated with laboratory experimental data. The experimental data for such validation may either be from the literature or newly conducted laboratory experiments on same outcrops. This paper presents the review of some of the available Pc – Sw experimental data available in the literature for validating the predictions made by network models.

Abstract: This paper presents comparisons between drainage capillary pressure curves computed directly from 3D micro-tomographic images (micro-CT) and laboratory measurements conducted on the same core samples. It is now possible to calculate a wide range of petrophysical and transport properties directly from micro-CT images or from equivalent network models extracted from these images. Capillary pressure is sensitive to rock microstructure and the comparisons presented are the first direct validation of image based computations. The measured data include centrifuge and mercury injection drainage capillary pressure for fired Berea, Bentheimer and Obernkirchner sandstones and unfired Mount Gambier carbonate. The measurements cover a wide range of porosities and permeabilities. The measurements were made on core samples with different diameters (2.5 cm, 1.5 cm, 1 cm and 0.5 cm) to assess the effect of up-scaling on capillary pressure measurements. The smallest diameter samples were also used to obtain the 3D micro-CT images. Good agreement was obtained between the experimental measurements and direct computations on 3D micro-CT images.

Abstract: This paper compares the pressure drop profiles of both horizontal well producer and injector in a 5spot waterflood pattern. Dimensionless pressure distributions for each pattern were utilised. All computations were limited to conditions of unit mobility ratio; i.e., before water breakthrough condition. Results show that a normal 5-spot flood pattern, with a horizontal well producer, offers higher pressure drops, but early water breakthrough tendencies, than as an injector for the same reservoir and wellbore conditions. An inverted pattern, under the same conditions, produces clean oil for a longer time, before water breakthrough possibilities.