Summary

Over the lifetime of a well, it is possible that several squeeze operations will be performed, depending on scaling severity. Downhole-squeeze operations have been performed for many years and have been an effective scale-management tool on the whole. However, the long-term impact successive squeezing has on treatment lifetime and well productivity has received little attention. This paper will address these issues by comparing the results from a unique sequence of long-term corefloods designed to replicate five successive treatments on the kaolinite-rich, Middle Tarbert core from the StatoilHydro-operated field Oseberg Sør. Relatively few squeeze treatments have been performed on this field, and the coreflood results have been upscaled to provide a potential prediction of the effects of long-term squeezing on well productivity on Oseberg Sør. Furthermore, the laboratory results have been cross checked by comparing them with the Heidrun field, which has been squeezed for many years. Heidrun is an analog of Oseberg Sør, with kaolinite-rich producing intervals, and has similar productivity issues related to kaolinite mobilization.

Introduction

In many respects, the opening sentence of Vetter (1973) is still valid 35 years after publication: "There are a number of gaps in our knowledge of the principles involved in the squeezing process." This paper will address one of those identified knowledge gaps, which is the effect well lifetime squeezing has on treatment performance and productivity. Depending on the scaling severity, a well can require squeeze treatment as often as every 10 days, as is the case for the Miller field (Wylde et al. 2007), or after several months [e.g., Oseberg Sør field (Fleming et al. 2007a)]. With regard to the latter field, a study was initiated to determine the long-term impact of squeeze treatment on well performance. This forms the basis for the paper. The laboratory results will also be compared to the StatoilHydro-operated Heidrun field that has been squeezed over several years.

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