China National Offshore Oil Corporation (CNOOC), Shell and Phillips China Inc. (PCI) are partners in the development of XJG oilfields located in the South China Sea. The XJG fields are considered to be in the mature phase and challenging PCI (the field operator) with lifting and surface treatment problems due to high water cuts, and the limited amount of slots available in the existing platforms for infill drilling.

A sandstone reservoir with average permeability over a Darcy and strong bottom water drive aquifer support is experiencing water breakthroughs from high permeable layers leaving hydrocarbons pockets behind. Typical completions include sand control devices such as gravel packs and Fracpack inside 9–5/8" casing.

The following list briefly summarizes the main challenges presented by the XJG fields at this stage:

  • Total production close to the limit of surface treatment facilities: 550,000 BFPD.

  • No more slots available for infill drilling, only 1 left reserved for an ERD well.

  • Sand production aggravated due to wells producing at high water cuts.

  • Overall oil recovery still below expected objectives.

PCI created a team including engineers from a service company working toward the common objective of "Maximizing Oil Recovery" in XJG fields making use of state of the art simulators, tools and innovative technologies specially tailored by technology centers to provide reliable answers in South China Sea completions and formation environments.

Reservoir modeling enabled the team to successfully identify remaining hydrocarbon areas in the fields. Resistivity measurements confirmed formation fluid saturations through the relatively large casing with high level of confidence. Reservoir modeling and resistivity measurements behind casing along with the innovative Geosteering tools and techniques helped plan and execute drilling new wells or sidetracking existing wells with high water cuts, effectively increasing oil rates and ultimate field oil recovery.

Encouraging results from this project along with other actions taken by PCI in the field have achieved an outstanding increase of 28 % in oil production of the new sidetracks while reducing the total amount of water at surface (in excess of 17,000 BWPD), saving PCI major expenditures on fluid treatment and/or upgrading platform facilities; benefiting from teamwork implementing innovative techniques in existing assets maximizing oil field recovery at effective cost.

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