Research Project Team on Carbonate Reservoir

Research Project Team on Carbonate Reservoir* aims to contribute to improvement of oil recovery particularly in heterogeneous and/or low permeable carbonate reservoir where numerous oil and gas are still to be produced. It is necessary to evaluate reservoir structure and properties properly to make optimum development plan, diminishing uncertainties and risks. However it is not straightforward to deal with such heterogeneous and/or low permeable carbonate reservoir in which unexpected fluid flow behavior such as early water breakthrough is frequently taking place. Our project team therefore aims to provide methodologies and workflows for such reservoir evaluation and characterization by adopting multidisciplinary approach, more specifically integrating following technologies;

• 3D seismic guided reservoir characterization
  ◊ Fault/Fracture characterization
  ◊ Reservoir property modeling
• Sequence stratigraphy
• Upscaling methodology
• Advanced laboratory measurements
• Micro flow simulation
• Water cut monitoring technology
• Technologies of improvement of oil recovery for low permeable reservoir

*Research Project Team on Carbonate Reservoir was established in February 2004 by merging two project teams, Research Project Teams, Heterogeneous Carbonate Reservoir and Carbonate Reservoir Characterization. It basically succeeded the research subjects of the former two subject teams.

Overall, the researches have been conducted, targeting for actual Middle East giant carbonate reservoir as a joint research program in collaboration with the local national oil company.

The research activities and results are highlighted as follows;

3D seismic guided reservoir characterization
1) Fault / fracture characterization
Detailed fault characterization was achieved by adopting structure dip and curvature analysis, as well as the optimal use of offset/azimuth and removing shallow anomaly effect by Prestack depth migration (PSDM) technique. In addition, the small fracture density and its preferred orientation were evaluated by cautious handling of seismic anisotropy application in the 3D seismic area.
⇒refer to;
Tamura, Y., Tsuneyama, F., Okamura, H. and Furuya, K., “Fault characterization by seismic attributes and geomechanics in Thamama oil field, United Arab Emirates” Vol19, No.2 P63-76 2004

2) Reservoir property modeling
Uncertainties of predicting the reservoir properties were successfully reduced using acoustic impedance and vp/vs volume data delivered by the seismic inversion technique collaborating with laboratory measurements.
⇒refer to;
Tsuneyama F., Takahashi I., Nishida A., Okamura H. “Vp/Vs ratio as a rock frame indicator for a carbonate reservoir” First Break Volume21, p53-58. 2003

Sequence stratigraphy
Sequence stratigraphic framework has been established with honoring all available rock evidences. It helped to characterize sub-seismic scale reservoir heterogeneity and subsequently improved understanding on depositional mechanism and distribution pattern of high- permeability layers

Upscaling methodology
The upscaling methodology based on the effective properties approaches has been developed to predict average flow properties of large-size simulation block from the data of small-size block components as well as whole-core-scale kro/krw curves from plug-core-scale data. In the process, the upscaling program, CAVULUP, which can handle both one and two phases flow properties under capillary limit or viscous limit, was developed and enabled fast and robust computation.
⇒refer to;
1) S. Takahashi, N. Tokuda, T. Nakashima “SCA2004-16 Upscaling Method of Relative Permeability from Core to Whole Core”
2) M. Nomura, “Fast Computation of Effective Properties for Two Phase Flow Problems”, paper SPE 77570
3) T. Nakashima, M.Nomura, “New Analytical Correction for Multi-Phase Flow Effect in Near-Well Regions of Coarse-Grid System” paper SPE 87067

The automated history-matching program
The automated history-matching program for water flood experiments under X-ray CT scanning monitoring, GEMAP was developed based on Genetic Algorithm. The GEMAP was successfully applied to the interpretation of the actual water displacement tests on several oil-wet carbonate plug cores to derived kro/krw and Pc curves of lithofacies.
⇒refer to;
N. Tokuda, S. Takahashi, “SCA2004-62: Development of Automated History-matching Program Based on Genetic Algorithm for X-ray CT Coreflooding Experiment

Advanced laboratory measurements
Our research project team is currently building the laboratory system under the concept of INCELA (Integrated Core Evaluation Laboratory) with advanced core analysis equipments such as X-ray CT scanner, MRI, Reservoir Condition Capillary Pressure Measurement System, Reservoir Condition Steady State Relative Permeameter in order to obtain more appropriate Kr/Pc data for reservoir simulation.

Micro flow simulation
As a part of the INCELA, a methodology of applying Lattice Boltzmann Method to pore scale flow simulation has been developed. In the process, the application program, LB-Pore, has been developed.
⇒refer to;
H. Okabe, M. J. Blunt “SCA2004-24 Predicting Permeability Through 3D Pore-Space Images Reconstructed Using Multiple-Point Statistics”

Water cut monitoring technology
Turbine type Multi Phase Flow Meters (MPFM) developed by JOGMEC were installed in the subject field. MPFMs contributed to continuous and intensive water cut monitoring proving its accuracy in measurement and durability.
⇒refer to;
Zh.Y. Li, H. Kitami, H. Kawaoto, T. Watanabe “A Turbine Flow Meter for Multiphase Flow” paper SPE 88741

Technologies of improvement of oil recovery for low permeable reservoir
As a part of the above mentioned joint research program, our research project team contributed to make an optimum development plan for the subject low permeable area by conducting the feasibility study of CO2 injection as an EOR project. The study has been conducted comprehensively by integrating laboratory experiments, reservoir simulation studies and CO2 recovery studies from flue gas. Our research project team is currently researching on the feasibility of hydraulic fracturing for horizontal well in the same area.

Integrated Reservoir Modeling
Our research project team will be presenting optimized reservoir sector model in the subject field, by integrating above mentioned reservoir characterization technologies and findings obtained from those technologies.