Economic and Technical Advantages of Revolutionary New Chemical Delivery System for Fractured and Gravel Packed Wells

Abstract

Economic and Technical Advantages of Revolutionary New Chemical Delivery System for Fractured and Gravel Packed Wells P.J.C. Webb, AEA Technology plc, T.A. Nistad, Saga Petroleum ASA, B. Knapstad, Norsk Hydro ASA, and P.D. Ravenscroft and I.R. Collins, BP Exploration Operating Company Limited Copyright 1997, Society of Petroleum Engineers, Inc. Abstract The deposition of scale, such as carbonates and sulphates, in production facilities represents a serious operational problem that can result in significant well productivity decline. Current scale control strategies can involve significant capital and operational expenditure. Development work, involving laboratory testing and a field trial, has demonstrated the technical benefits of a revolutionary method of downhole scale inhibitor delivery that can prevent scale deposition for a significant proportion of a wells lifetime. The method involves the slow release of scale inhibitor from porous proppants. Economic analysis indicates that significant benefits can be derived for a variety of field development and well completion types. The greatest economic benefits would be realised for subsea and minimum facility installations with high intervention costs, where squeeze delivery of inhibitor or mechanical workover are used for scale control. In addition, major economic benefits can be realised for horizontal wells with unfavourable pressure regimes, multi-lateral type completions, multiply fractured wells, and many conventional completion types. The new chemical delivery method offers cost reduction through reduced deferred oil, efficiency of chemical usage, and reduction workovers using coil tubing and intervention vessels. Economic analysis has indicated that for some conventional and advanced well types, fracturing a well and deploying proppant impregnated with scale inhibitor, is economically preferable to a conventional strategy of squeeze treatment in a unfractured well. An additional economic benefit of proppant impregnated with scale inhibitor is increased well productivity. The benefit is derived from the combined effect of improved gel breaking, and scale inhibition during well clean-up. This has been demonstrated in laboratory testing and would appear to be confirmed by field observations. A further benefit of applying scale inhibitor as chemically impregnated proppant is the immediate treatment of produced water when water breakthrough occurs. This feature avoids the formation damage that can occur before squeeze treatment mobilisation. In addition, for some applications involving large fractures there is the potential for lifetime well treatment. This paper describes the laboratory work, the field trial and the economic benefits of the new product. Introduction Production of hydrocarbons is often associated with the deposition of mineral scales from co-produced water. Mixing of incompatible waters, and changes of temperature and pressure can cause deposition of carbonate (CaCO3) and sulphate (Ba/SrSO4) scales in the near wellbore and tubing of production wells. Scale deposition is a recurring operational problem for many conventional and advanced wells worldwide. Preventative and remedial scale control operations often involve significant cost to an operator through equipment and personnel, and deferred oil costs. This paper presents details of the technical and economic features of a revolutionary method of scale inhibitor delivery developed by AEA Technology with the support of Saga Petroleum ASA, Norsk Hydro ASA, and BP Exploration Operating Company Ltd. The delivery concept has many advantages when compared to conventional scale management strategies, as applied to advanced and conventional well completions. The current status of the technology allows simple application in fractured and gravel packed field developments. The considerable potential for applying other types of oilfield chemical is briefly discussed. P. 523^