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This paper demonstrates the application of a higher-order Godunov method and adaptive mesh-refinement to a three-phase, seven-component, micellar/polymer (MP) model and use in the simulation of an MP flood designed for North Sea conditions. Conventional one-point upstream weighting with globally fine mesh is too expensive for obtaining a reasonable level of accuracy for field-scale simulations. The use of higher-order Godunov method with adaptive mesh-refinement not only results in significant reduction in computational times but also reveals more numerical details of the displacement process due to higher- order accuracy. Comparisons are also made between the first- and second-order Godunov methods under field-scale design conditions with and without adaptive mesh-refinement. Introduction To speed up computations in reservoir simulation, the recent emphasis has been on developing streamline models, parallel codes, and the use of higher-order methods. The stream, line models are computationally fast and can be used for simulating entire reservoirs. However, they cannot adequately model the complex chemistry and physics typical of an enhanced oil recovery process. The higher-order methods provide more accuracy than lower-order methods for a given computational cost; however, a reasonable accuracy may still not be obtained using fixed uniform grids in practical cases. By employing adaptive mesh-refinement (AMR), it is possible to concentrate numerical effort near fluid fronts or wells where the highest resolution is required. The simulations employing AMR cost less to achieve a desired level of resolution than uniform fine grid calculations and thus, more simulations can be performed within a given computational budget. We envision a new generation of reservoir simulators that would combine higher-order methods with AMR and parallel computing and make the process of reservoir simulation more efficient and accurate than ever. The application of Godunov methods is relatively new to reservoir simulation. Recent applications to problems like waterflooding, black-oil model, miscible flooding, and polymer flooding have been very successful. The commonly used one- point upstream weighting and the first-order Godunov method are the same in the absence of gravity in one dimension. With the gravity included, these methods are very different because the former looks only at the flow within phases to determine a numerical flux, while the latter constructs an approximation to the local chromatography to determine the flux. On a regular mesh, comparisons with conventional singlepoint upstream weighting for polymer flooding problems where analytic solutions are available, show that the higher-order method can achieve the same accuracy with about one-tenth the number of gridblocks. In combination with AMR, the performance of the higher-order method improves even more. This is because single-point upstream weighting results in smeared fronts that require more refined mesh around the displacement fronts for a given accuracy. The overhead cost of AMR, i.e., time not spent on solving flow equations, is less than about 10% of the total simulation time and guarantees the desired accuracy throughout the problem domain. MODEL DESCRIPTION This is a seven-component, three-phase, three-dimensional, finite-difference model developed to simulate MP flooding and surfactant remediation of aquifers. The seven components include water, oil, surfactant, alcohol, polymer, anions, and cations, the first four of which are the volume occupying components. P. 531

The subject reservoir is a heterogeneous carbonate formation in a giant field located offshore Abu Dhabi. Five gas injection pilots were initiated in late 2001 in the Eastern, Central and Western parts of the field both as secondary and tertiary recovery methods to evaluate the benefit of gas injection for pressure support and for recovery improvement. With less than 10% of HCPV gas injection, the pilots to date have provided valuable insight on production performance and pressure support, gravity override, swelling effect and flow assurance issues (such as asphaltene deposition) in the field. Using a 3D compositional model, a sector modeling study was carried out for comprehensive evaluation of the pilot performance to date and to predict definitive results within reasonable time frame (3-5 years) which will have ramifications on long-term full field development decisions. Additionally, the objectives of simulation efforts were to evaluate different recovery processes (gas/water/WAG) and assess key reservoir uncertainty (volumetric sweep) due to reservoir heterogeneity (high permeability streaks). Initially, the sector model was history matched with nine years of pilot performance while both reservoir heterogeneity and well spacing sensitivities were tested in the model. The history matched sector model was utilized to predict performance under different operating conditions using both gas, water and water alternating gas (WAG) injection methods. This paper describes the pilot performance, field observations and results of a sector model study including history match, sensitivity and predictions under different injection scenarios on two of the pilots. Based on the performance and surveillance data gathered on the two pilots and sector modeling study, it was established that both pilots have met their objectives and can be concluded. Through the integration of field observations and sector modeling work, the study provided valuable insight on optimum recovery processes, well spacing and well completion requirements for long-term field development.

Previous pseudo-phase representations of micellar/polymer phase behavior have been highly successful in simulating enhanced oil recovery processes using conventional numerical methods. These models allowed for a variety of physical phenomena, such as the formation of one to three phases, the effect of salinity and co-solvents on the phase behavior, adsorption of several of the chemical species, capillary desaturation, and polymer shear thinning and permeability reduction. In order to extend these models to either higher-order simulation techniques or to contaminant transport problems, it is necessary to remove previous discontinuities in the model behavior and to improve the predictions as concentrations become infinitesimal. In this paper, we provide a complete description of a revised model that avoids the problems of the previous model, and we show how to implement the computations in a numerically stable fashion. Computational results from a North Sea pilot study are presented.

This conceptual study addresses the subject field which has a current expected operating life of more than 100 years, which exceeds the life of the existing facilities. As an alternative to continuing development with Well Head Platform Towers (WHPT’s), the concept of artificial islands holding drilling and production centers has been introduced [ref.1]. The island concept brings enormous flexibility in terms of managing future development uncertainties both subsurface and surface. The new subsurface development concepts include extensive utilization of ERD/MRC wells specifically designed and placed in conformance with geologically defined drainage areas. This strategy predicts significant improvement in plateau duration and sweep efficiency with fewer wells. The new islands based surface plan allows a phased installation of facilities, and space provisions to expand facilities to cater for subsurface uncertainties. It also handles the remnant life issues associated with the existing infrastructure (Wells, WHPT’s, pipelines and trunklines, satellites, central complex). This includes provisions for future requirements in terms of Water Injection, Artificial Lift and Gas Injection and other EOR applications.