SIMULTANEOUS DRILLING AND PRODUCTION ON OFFSHORE PLATFORMS

Abstract

Simultaneous drilling and producing on offshore platforms is a standard worldwide practice and can be conducted safely with significant attendant benefits. These include timely procurement of critical reservoir data to ensure proper reservoir development and improvement in reservoir development economics related both to and near term production acceleration and potential improvement in ultimate recovery.

Qualitative and quantitative assessments show that incremental risks associated with simultaneous drilling and production are small compared to the basic risks involved in offshore development drilling. The assessments have led to the identification of various specific safety practices which are recommended for simultaneous drilling and producing operations.

The possibility of intersection between a drilling and a producing well is considered to be one of the major areas of concern in concurrent drilling and production. A statistical approach, based on probable directional survey errors, has been developed for determining the minimum safe measured separation between drilling and producing wells as a function of depth. All producing wells falling within this minimum safe distance from a drilling well must be shut-in below the deepest point of potential interference.

Where possible the use of surface controlled subsurface safety valves (SSVs) for shutting-in completed and perforated wells to meet the minimum safe distance criterion is preferable to the more traditional practice of using wireline set tubing plugs. In addition to being much cheaper, the SSV method should render simultaneous drilling and production considerably safer by minimising the number of wireline operations; accordingly, directional well planning and the setting depth of SSVs should be such that the SSV is located below the deepest point of potential interference in as many cases as possible. In instances where the SSV is located above the deepest point of potential interference, tubing plugs will have to be set.