Hydraulic Fracturing for Reservoir Management: Production Enhancement, Scale Control and Asphaltine Prevention

Abstract

Productivity in the Scott reservoir, located in the Central North Sea, is subject to impairment by scale and asphaltine disposition in the near wellbore region. Several intervention options have been attempted to restore the production potential (ie. re-perforation, fractured re-perforation, scale dissolution). These techniques have proved largely unsuccessful since due to the severity of the damage mechanism. This left hydraulic fracturing as the final option to bypass the damage and reconnect the wellbore to the productive sands. A technical and economic success was particularly desirable given the high operating costs associated with offshore operations and was achieved through a combination of well analysis and novel enabling technologies which are described in detail within this paper. The target well identified (J9) was selected based on criteria of production potential, drainage, pressure support and wellbore access. The fracture orientation plane was identified using existing open hole imaging logs allowing perforations to be oriented along the preferred fracture azimuth to minimize near wellbore effects during proppant placement and production. Specialized scale inhibitor impregnated proppant was employed to ensure deep and long term productivity protection for the fracture and tubulars. Placing a fracture in the reservoir also assisting in mitigating the effect of asphaltine disposition within the formation matrix. The large production string necessitated a new approach to lifting out the excess proppant within the wellbore. This was accomplished by reverse flow up a coiled tubing string in a process which was engineered to be a safe and effective.