In a private seminar organized by Pico Integrated Solutions, Expert Sam Metcalfe, Blackwatch Petroleum Services discussed the case history of a North Sea oil field developed with horizontal wells

During the seminar held in Cairo Capital Club (CCC) on the development of horizontal wells, Metcalfe illustrated the case history of a North Sea oil field, in England, developed with horizontal wells.
Concerning the Gamma reservoir solutions, horizontal wells were found to be the only viable option to effectively drain the Gamma reservoir whilst meeting corporate investment metrics. Gas lift, using gas supplied from the export side of the host facilities was found to be the best artificial list option, providing long-term operability / high reliability. In addition, long horizontal wells maximise sweep and deliverability and minimise drawdown (assuming they contribute along their entire length). A subsea multiphase flow meter, on a test header located on the subsea production manifold was determined to be the best option for monitoring production rates from individual wells. While the individual well list gas metering and lift gas rate control was installed on the subsea manifold to enable wells to be optimised for gas lift. Each well had a permanent downhole gauge installed to aid in well and reservoir management. As for the well depth relative to GOC, it is possible to steer up and down by more than 10 feet to avoid shales, without significantly impacting recovery.

Well Placement Recommendations:

  • The effect of contributing length is more important than skin or well depth.
  • Contributing length can be impaired by:

-Not drilling and completing the full wellbore as planned.
-Shale intervals along wellbore.
-Poor clean-up zones along wellbore.

  • It is worthwhile to:

-Make the best effort to drill and complete the wells as planned.
-Geo-steer to avoid shale intervals.
-Use good completion practices to ensure the best possible clean-up is achieved.

Gamma development well objectives are locating well bores to avoid shallow gas hazards, suspending wells to minimise damage and in a condition to allow production start-up into subsea facilities and finally meeting host fluid entry specifications. The Gamma wells are designed to minimise the water coning, minimise attic oil, and to effectively drain the Gamma structures with the minimum number of wellbores.
Well placement (17ft below GOC) to mitigate gas and water coning. While steering decisions, the ROP should be low while making and carrying out decisions in order to give the BHA a chance to respond. And for reporting, better dissemination of information to the rig. Whilst, PeriScope tool response in the thin beds cannot accurately resolve boundaries in them.

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