Drilling/Production Shell patents new reservoir drainage concept

Shell Research B.V has patented a subsurface tie-in concept that reduces development costs of new gas fields near existing producing reservoirs.

The concept involves drilling or sidetracking a well to connect gas-bearing formations between two neighboring reservoirs (Fig. 1 [42481 bytes]). The two reservoirs could be separated by a sealing fault or an intervening formation.

The well connecting the two reservoirs would then be suspended or abandoned in such a way that the subsurface tie-in would remain intact, allowing gas to cross flow between the reservoirs. The tie-in could be cased, open-hole, multiple bore, fraced, or any variations of these. No new drilling or completion techniques would be needed.

Shell believes the tie-in could complement conventional developments where, for example, there might be a slot shortage on a platform or difficulties in conducting operations.

Concept development

The concept was originally developed and evaluated for producing small fields, but Shell says the system also could exploit large new fields through adjacent, and sometimes smaller, producing reservoirs. For example, the new reservoir could be under a city, national park, or military exclusion zone that prevents installation of surface installations.

Shell says tie-ins may not be the best method to produce such reserves but they may be the only method under the prevailing circumstances.

Reservoir management

Simulations by Shell indicate flow would continue through the tie-in as long as a pressure differential existed. This flow will recharge the main reservoir but the operator will not be able to control the flow rate. Stopping flow would require a well re-entry or drilling a relief well.

In a suspended well, periodic pressure tests could be run to assess reservoir performance.

Shell also believes the tie-in concept could apply to oil reservoirs.

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