Down-hole scale control in Statoil's Åsgard field presents a particularly severe challenge. The field is producing from low permeability formations with a high draw down, through subsea templates. System pressure and temperature changes experienced during production promote the formation of carbonate scales, which have been identified in the near well bore area and perforated intervals. The high formation temperature and pressure, 165°C and 500 bars respectively, high chlorite content coupled to the water sensitive nature of some of the formations creates a challenging environment for downhole scale treatments.

This paper will describe possible formation damage mechanisms that were identified for this water sensitive formation and the treatment strategy adopted to minimize them. It also presents the extensive laboratory studies that were undertaken to develop a non-damaging, non-aqueous inhibitor/squeeze enhancer formulation suitable for deployment under these harsh conditions. An understanding of the mechanisms by which the squeeze treatment package prevented water block formation and clay mobilization under such severe temperature and reservoir constraints, coupled to the mechanisms of squeeze life extension are discussed. The paper will also highlight the manufacturing challenges that were overcome to improve the environmental profiles of the products.

The paper will finally discuss the two treatments, which have been performed to date with the non-aqueous products. Initial field data demonstrates that the application of this nonaqueous product package significantly reduced the potential for formation damage and allowed the successful treatment of these wells. Residual inhibitor returns remain significantly above MIC and a long squeeze life is expected for both wells.

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