ABSTRACT

A brownfield adjustment project was initiated by China National Offshore Oil Corporation (CNOOC) in 2014 to improve the production and further increase its reserve recovery from two oilfields in the South China Sea, this project is also known as the new XJ district joint development project.

New development wells were drilled targeting at the remaining less than 5m thin oil column or pursuing highly heterogeneous sand bodies. The re-development and exploiting of these targets present technical and operational challenges. Not only the horizontal well needs to be optimally placed within complex target zone, the lateral also needs to be placed close to the reservoir top to keep it away from the unknown current fluid contact. Real-time evaluation of the horizontal section is needed to steer the well following better sand quality when formation properties changes laterally. Considering all the challenges presented, the team must ensure each well can achieve the target productivity index to attain technical and economic success.

Multiple cases will be discussed in the paper based on 10 wells drilled since the launch of this joint development project. Several key outcomes that have been observed will be highlighted, including:

  • Selection of logging tools to address well specific challenges

  • Using real-time bed boundary detection technique to optimize the standoff between horizontal section and top of formation

  • Real-time evaluation to appraise formation heterogeneity

  • Evaluate productivity index while drilling to optimize the horizontal section length

Based on the well performance result obtained from this re-development project, the implementation of the best practices in operation is the key enabler to effectively place the trajectory in the best place to drain the remaining hydrocarbon that increase ultimate recovery of a mature oilfield.

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