Ranging techniques are used in many oilfield applications, including heavy oil production and in positioning relief wells. In heavy oil production, two horizontal twin wells with a few meters of separation must be kept parallel so that steam can be injected into one and oil can be produced from the other. When a relief well is drilled to intersect an existing well, the position and relative distance of the drilled well with respect to the existing well must be determined. In general, existing techniques rely on wireline technology, which does not allow real-time decisions to be made.

This paper will present a novel technique for locating the relative position of one well with respect to another using a rotating azimuthal logging while drilling (LWD) electromagnetic tool. With this technique, the relative position between casing in an existing well and a rotating LWD electromagnetic tool in a second well can be determined in real time. Consequently, the relative position can then provide field engineers with calculated inter-well spacing and the path to position a blow-out relief well or to keep two wells parallel and properly spaced in a heavy-oil operation.

This paper discusses and explains the fundamentals of the new LWD ranging technique. Several cases were modeled and compared with experimental data collected in a water tank with conductive casing. The experiments successfully validated the computed responses, and the casing position and distance to the LWD tool were successfully determined. The LWD technique described presents an alternative to existing wireline ranging techniques and can be successfully used in heavy-oil applications and possibly in positioning blow-out relief wells.

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