As deepwater fields in the Guld of Mexico and elsewhere around the world mature and primary production declines, many will begin producing under water flooding conditions to increase hydrocarbon recovery and support reservoir pressure. The success of the water injection program is critical to overall project economics, and a clear methodology, work-flow and attention to detail are needed in planning, designing and implementing deepwater waterflood projects.

By using an integrated approach to implementing the front-end engineering design (FEED), operators can optimize future field development strategires, injector design and facilities planning to maxiize the total value of their deepwater assets. The proposed method has been executed using an example Gulf deepwater field to efficiently interconnect elements related to surface facilities, topsides process, subsea architecture, subsurface equipment, water quality, well completion, downhole flow controls and target injection rates in a common context.

The workflow consists of cordinating the diverse elements of design in the project: facilities design (including pump requirements and water treatment options), subsea and topsides network flow design, injector design, drilling and well planning, and critical data gathering. Results of the simulations conducted provide reliable estimates of well injectivity, fracture lengths under various injection scenarios, the impact of thermal stresses on injectivity and fracture growth, injector completion design, surface injection pressure requirements, and subsea/subsrface network flow parameters.

Developing a comprehensive model that incorprates these elements allows major factors to be evaluated that can impact the fracture length, bottom-hole pressure and suface injection pressure based on parameters sud as inection rate, injection temperature, water quality, reservoir pressure, Young's modulus, abosolute and relative permeability to water, and rock thermal coeffieient of expansion for cased-hole perforated and fracture packed completions.

This methodology plas a crucial role in guiding the planning, design, evaluation and development of water injection systems details and specifications. The output generated fromt he process helps improve the overall understanding of a field, utilizing and linking valuable information and technologies that are available to the various subsurface and topsides design teams involved int he poject. Likewise the approach represents a tool to solve technical and buisness challenges associated with water follod project design.

The water used in injection wells-produced water or seawater, or a mixture of the two-is filtered through primary and/or secondary cartridges to obtain less than a few parts per million of solids concentration and particle sizes of less than a few microns in diameter. The water is also often deoxygenated, desulfonated, and treated to control bacterial growth and scale formation.