Abstract

In this paper we present details of the approach utilized to optimize the completion and stimulation campaign in the continued development of a large gas carbonate field in the Middle East. A new acid diverter was deployed along with a revised placement model, field calibrated to more accurately predict treatment pressure responses, to optimize treatment design and to maximize diversion in this layered reservoir. Results presented include typical stimulation treatment plots alongside model post treatment pressure history matches, pre and post stimulation production logs, clean up data and well test interpretations. We also present details on how this new approach facilitated the execution of simultaneous drilling and well intervention operations.

We describe high permeability, multi zone treatments with a bullheaded matrix acid technique. We observed through large bore tubing treatment pressures in excess of 3000 psi, far above what is typically observed in this field. A degradable fibrous material was incorporated into an in-situ self viscosifying surfactant based acid formulation to effect the diversion responses and we observed negligible returns of fibres during clean up operations. We observed uniform inflow profiles, validating the technique and provide evidence that the use of such a fluid system is capable, in certain circumstances, of reconnecting to natural fracture and loss zones. We have also observed significant benefits in reduced flaring requirements for well clean up.

We conclude that this technique has facilitated enhanced diversion and promoted uniform zonal depletion. We have also found operational benefits in deploying the system in that commingled zones, normally perforated and stimulated in several stages can now be easily and effectively stimulated using a one-stage technique.

The stimulation of thick carbonate intervals presents several challenges if the long term well and field productivity is considered. Overcoming these challenges without additional well interventions such as setting retrievable bridge plugs or the introduction of ball sealers, requiring slick line re-entry to ensure no interference with surveillance activities, significantly reduces operational risk and well site exposure.

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