ABSTRACT:

Innovative completion rehabilitation techniques recently applied at Giovanna field, Adriatic Sea, Italy, allowed cost-effective rehabilitation of failed gravel packs in three wells - and extended the economical production life. The first time screenless completion techniques for sand control were used to complete virgin gas layers, left uncompleted in the past. These enabling innovations have resulted in more than several times production increase. Successful application of both novel technologies, a new polymer-free visco-elastic fracturing fluid (VES) and proppant flow-back control fibers, would provide confirmation that the new VES fluid and the screenless completion sand control technique could be applied to other wells throughout the area, whilst failure could arrest any similar future application. Both technologies and results achieved are being described in this paper. Many gas wells in the Adriatic Sea are either sanded up and shut in, or are under-performing due to plugged or failed gravel-packs and/or screens and which cannot currently justify the expense of an immediate and costive full rig workover rehabilitation. Limited rig availability adds to the problem. Objectives are to find improved and reliable completion rehabilitation techniques for the Adriatic fields to avoid or defer expensive full-scale rigbased workovers. Rigless rehabilitation has confirmed being an efficient solution and allows cost-effective production increase. Enabling technologies can be summarized as: Screenless sand control completion technology, allowing low cost development of any numbers of layers to be produced by the short string, which otherwise could not be drained using conventional sand control technologies without expensive re-completion. Similarly, a specific version of a visco-elastic fracturing fluid for use with seawater and process controlled surface mixing equipment enabled attainment of both execution and economic goals. To quantify the economical value of the performed rehabilitation program, an advanced economic analysis tools was used, considering tax analysis and investment. Sensitivity scenarios for production, gas price, operating and capital costs have been applied to provide detailed information for easier future decision making. Decline analysis, historical and forecasted production with fiscal modeling are presented to evaluate the financial value of treatment expenditures.

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