Streamlines have been acknowledged as a powerful tool for modeling and optimizing waterfloods in oil reservoirs. Streamlines provide visualization of reservoir fluid flow and a unique way to conceptualize and quantify injector-producer well connectivity. Well allocation factors (WAFs) between injectors and producers as well as injection efficiency can be calculated and used to optimize water injection and reduce injection water cycling while focusing on maximizing oil recovery. The objective of this study was to develop a methodology, tool, and workflow for optimizing pattern waterflood management and to demonstrate application in a giant offshore carbonate reservoir. This methodology utilizes historymatched simulation models to generate streamlines from the pressure field and fluxes computed by a finite-difference reservoir simulator, EM power . A finite-difference simulator is more rigorous than streamline simulators in terms of its ability to model complex fluid flow, and therefore, provides a more realistic solution. The streamlines thus obtained take into account the detailed geology, well locations, phase behavior, and flow behavior of the history-matched models. This methodology utilizes the concept of pair "injection efficiency" (IE) and pair "voidage replacement ratio" (VRR) which was necessary for the subject giant oil field and is equally applicable to other fields.The optimization process is started by generating streamlines and associated WAFs at the current time using the simulation model. The injection efficiency is calculated and injector-producer well pairs are identified with high and low IE. New producer rates are then calculated by increasing producer rates in high IE well pairs and decreasing rates in low IE well pairs based on a weight factor. The injector rates are then calculated by applying a target VRR to each individual well pair. This results in redistribution of injection and production rates in a more balanced/optimal manner. The process is repeated at regular intervals (e.g., yearly or quarterly) while simulation is run in the prediction mode. Results show higher total oil production rates or lower water production and water injection rates. The WOR versus cumulative oil production clearly demonstrates that the overall injection efficiency increases as the optimization process is progressed.

Pressure core is the gold standard of reservoir saturation determination retaining gas and oil in an enclosed container preventing hydrocarbon loss to the mud system during retrieval of the core to surface. The technique is underutilized in the oil industry due to safety concerns, short coring lengths (3 to 7 feet) per trip and small core diameters (1.6 to 2.6 inches). A new elevated pressure coring system addresses these concerns. The system does not maintain true formation pressure but reduces the core barrel pressure to less than 1,000 psia for safer working conditions on surface. Upon arrival at surface, the core barrel and accompanying gas/liquid collection canisters are blown down and gas/liquid volumes measured and analysed. Free oil is gathered and stored for later analyses. Core diameter is 4 inches and core length is 10 feet. Zakum Development Company (ZADCO) operates a gas injection pilot in a large carbonate oil reservoir. There was a need to determine field remaining oil saturation after gas flood (ROSg) in a gas injection pilot. Pressure coring was selected as the best technology to obtain this data. This paper covers the planning and implementation of a successful elevated pressure coring operation in the U.A.E., the operational aspects, special core handling techniques, issues encountered and solved. Recommendations are made for future pressure coring operations. A follow up paper will cover the core and fluid analyses aspects.

Most reservoirs, especially in carbonate systems, are characterized by heterogeneities in pore systems, permeability, diagenetic imprints, faults and lineaments, fractures, fluid systems and displacement parameters. These variable set of conditions may result in significant differences in in-place volumes as well as life cycle production behavior from different regions of the reservoir when subjected to the same depletion scheme. To guide and control the reservoir life cycle development and management, and to leverage the full benefit of tailoring specific depletion designs suitable for specific areas of the reservoir, the asset owner has instituted a new set of guidelines on reservoir sectorization to govern all operated assets. Reservoir Sectorization could be defined as the process of outlining regions of the reservoir defined by prominent geologic features (structural, stratigraphic, diagenetic, fluid contacts, etc.) that control reservoir and well performance within which production targets can be defined, analyses conducted and surveillance plans designed. A large offshore carbonate reservoir operated by ZADCO, which is the subject of this paper, is impacted in several ways by the aforementioned geological complexities and was deployed as a pilot to test and fully implement the new guidelines on reservoir sectorization. Previously, the existing sector pattern for the candidate reservoir was based on a five-spot flood scheme which is no longer suitable in view of the change to the current field development concept of artificial islands and long MRC wells. Therefore, in addition to compliance with the new guidelines, the key business driver for re-sectorization is to ensure sector geometries that support a line drive system, avoid wells intersecting sector boundaries and provide flexibility to adapt well placement to evolving field development challenges. Advanced integrated workflows (analytical and simulation) were implemented and several sectorization schemes designed (1 or "no" sector, 3 sector, 4 sector, 4 quad, and 5 sector-patterns), assessed and benchmarked against defined criteria for success. Further optimizations through numerous dynamic model sensitivities led to adoption of a particular scheme that best complies with new guidelines on sectorization as well as meet the life cycle production target for the reservoir. This paper highlights the workflows implemented, the challenges encountered and the proposed best practices in working and adopting a reservoir sectorization scheme that best enables sustainable production and maximum recovery within the constraints of the asset owners' guidelines.

Significant advances in reservoir management have been achieved in recent years to address the many challenges in managing giant carbonate reservoirs. The advances are made possible due to culmination of three key elements working in harmony: Work Processes, Technology and People. Three major advances mentioned in this paper underpin this all important truth in reservoir management and surveillance. First is the development and implementation of a framework of recommended Integrated Reservoir Management Practices with detailed and structured multi-disciplinary workflows. Information Technology plays a key role in all these workflows via automation, data integration and visualization. Second is a new generation data integration and analysis tool facilitating data and work flow integration and providing a common platform for intelligent and interactive display, thus promoting collaboration to achieve synergistic benefits. Third is the application of advanced simulation-based streamline techniques whereby new technology and workflows are deployed, with full collaboration among stakeholders.The Integrated Reservoir Management Practices include a set of highly interactive workflows set in a continuous improvement loop: Data Gathering Requirements, Data QC/QA, Data Analysis, Integration and Visualization, Opportunity Generation, Execution and Monitoring. ZADCO is following these workflows with significant improvement in work efficiency and results. In the collaborative environment, open communication and sharing of knowledge is strongly encouraged among stakeholders to assess the problem from different perspectives. This often results in creative solutions being developed. The new generation integration tool further facilitates collaboration as it retrieves data from reservoir static and dynamic models, surveillance data such as cased-hole logs and pressure data, and displays them for interactive work sessions, including animated display to give extra insight on time dependent data. The streamlines enable model-based well allocation factors (WAFs) to be calculated to supplement analytically derived WAFs, guiding injection optimization and thus resulting in improved reservoir management.These advanced workflows and tools have helped ZADCO to make timely and informed decisions, resulting in significant savings to the company, and at the same time improving understanding of reservoir behavior and facilitating optimization of ongoing development plans. The advanced workflows and tools have been recognized by Shareholders as game changers greatly needed to better manage the complex giant carbonate reservoir.