Laboratory tests and a field trial have demonstrated the technical and economic benefits of a revolutionary downhole chemical scale inhibitor delivery method. The method also has the potential to be used for other oilfield chemicals, for example corrosion inhibitors and gel breakers.
The method involves the controlled release of chemical from impregnated porous ceramic beads, manufactured with the necessary mechanical strength and size properties for direct substitution of proppant, gravel pack sand and prepacked screen beads.
This novel concept offers an economically attractive method of chemical delivery for both advanced wells and conventional wells when compared to conventional intervention based delivery techniques, such as squeeze treatments. The concept addresses many of the operational problems associated with chemical treatment of wells completed with multiple fractures, long horizontal sections with unfavourable pressure regimes, remote wells with high intervention costs, and multi-lateral type completions. In general, the concept offers reduced deferred oil costs through reduced well intervention and preservation of pack conductivity, and more efficient chemical use compared to squeeze technology.
Wells with fractures containing in excess of 100,000 lb of proppant have the potential for scale inhibitor treatments lasting a significant proportion of a wells lifetime. Prepacked screens containing 3,000 lb of chemically impregnated bead could provide treatment periods of 2 to 36 months.
The deposition of mineral scales, such as carbonates and sulphates, in oil producing wells is a recurring operational problem for conventional and advanced wells. Significant operational costs are incurred when applying preventative or remedial scale control strategies, for example chemical scale inhibitor squeeze treatments or re-perforation, respectively. This paper presents technical and economic details 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 control strategies, as applied to advanced and conventional well completions. The potential for applying other chemical types is briefly discussed. The method of delivery is applicable to production wells completed with propped fractures, gravel packs, prepacked screens, and other intermediate types where beads or proppant are placed in a well.
Several methods are currently used, or have been used, to deliver chemicals into produced fluids from oil wells.
Bullhead squeeze treatment
Coil tubing/bridge plug/packer squeeze treatment
Solid chemical placed in a "rat hole"
These methods have been primarily used for the placement of preventative treatments for phenomena such as scale deposition, or corrosion. The application of chemical scale inhibitors as squeeze treatments is a common operation in many oilfields worldwide. However, rapid advances in drilling and completion technology, and increasing pressure to reduce the cost and frequency of well interventions associated with chemical treatment, has provided the incentive for development of a revolutionary method of chemical delivery. P. 211