Impact of Fluid Distribution on Scale Inhibitor Squeeze Treatments in Pattern Floods and Fractured Wells

Abstract

The most common method for preventing scale formation in the well completions is by applying a scale inhibitor (SI) squeeze treatment. Near-well squeeze treatment models generally assume that the flow pattern around the well is radial. Although, this assumption may be reasonable in most scenarios, this paper investigates whether strictly non-radial flow patterns around the well have a major effect on the squeeze treatment.Sensitivity calculations were performed to identify the impact of waterflood patterns such as Two-Spot, Five-Spot, Line Drive, etc. on the squeeze treatment lifetime in vertical production wells. The second part of the project then continued the study of the impact of flow patterns in fractured vertical production wells. The outcome is that scale squeeze treatments initiated at the same watercut appear not to be impacted by the various flood patterns studied. However, investigation showed that fractured wells typically have longer squeeze lifetimes in comparison to non-fractured wells.Calculations show that for fractured wells, inhibitor adsorption on the face of the fracture itself has no impact on the treatment lifetime; the longevity of the squeeze is determined by the inhibitor adsorption in the matrix rock outside the fracture. The benefit a fracture brings is in terms of propagating the SI further from the well than would occur in an unfractured radial treatment. In the fractured well the inhibitor is then more greatly retarded by contact with rock over a greater distance than would occur in a matrix only radial treatment. Sensitivity calculations were performed to identify the impact of fracture length. IntroductionMineral scale precipitation is a significant problem in the oil and gas industry. Oilfield scales are inorganic crystalline deposits, which can precipitate in the reservoir formation, flow lines and/or surface facilities. This solids deposition can cause formation damage in the reservoir formation in addition to restriction/blockage in the wellbore area and in flow lines. Scale formation is due to three main mechanisms (Mackay et al., 2004):