Scale inhibitor application in injection wells to protect against damage to production wells: When does it work?

Prevention of inorganic scale damage in the formation around production wells is usually achieved by batch squeezing the productions wells at risk. However, in Western Siberia protection of production wells is sometimes achieved by application of scale inhibitors in the supporting water injection wells. This technique relies on the effective displacement of the inhibitor across the reservoir from injector to producer. This is not generally considered a viable scale management option due to the extent of chemical retardation that is a necessary result of inhibitor retention on the rock matrix. However, for short inter-well distances, such as may occur in onshore developments, and where fracture conductivity is high enough that inhibitor contact with the matrix rock is minimal, then this technique can provide adequate protection against scale induced formation damage in production wells. This paper explores the range of reservoir scenarios under which this technique may be applicable, considering inter-well distances, the extent of fracture vs matrix flow, and the potential range of inhibitor retention on various rock substrates that may be encountered in fractured reservoirs. The approach is to use numerical modelling techniques to investigate the range of conditions under which this scale management approach may be applicable. This data may then be used identify when scale control may be adequately achieved using this technique, thereby reducing the need to shut in production wells for treatments, and when this approach would not provide adequate protection in actual field systems. Comparison is made of the potential for performing batch treatments in the injections wells, compared to continuous injection of scale inhibitor in these wells.