A New Methodology To Safely Produce Sand-Controlled Wells With Increasing Skin

Abstract

Summary Monitoring deepwater Gulf of Mexico (DW GOM) wells with gravel-pack and frac-pack completions is an increasingly challenging task. Wells often experience increasing skin, adding to the risk of completion failure. Historically, sand-control completions have experienced a 15% rate of sand-related completion failure (King et al. 2003). The industry tends to evaluate safe target rates qualitatively as skin increases. Reducing the flow rate entirely on the basis of an increase in global skin can be too conservative and can overrestrict target rate. Thus, it is important to know which components of the increase in skin can cause the completion to fail. Furthermore, it is not well understood how to quantify a safe target rate with the increased skin. This paper will present a new methodology to evaluate the components of skin increase that could cause sand-control completions to fail. The failure mechanism we address is perforation plugging by movement of fines and sand. Our new methodology helps to quantify the risk and convert it into a safe target rate. This paper will also present case studies of oil and gas wells in the Na Kika asset in DW GOM where this methodology was applied successfully. The well completions are monitored with BP's flux-based approach (Tiffin et al. 2003; Stein et al. 2005; Keck et al. 2005). In all cases, the wells experienced increased skin, causing the engineers to choke back the wells. The analysis showed that some of the skin increase was because of multiphase effects as the reservoir pressure was below the saturation pressure. We also determined which skin components likely caused perforation plugging, thereby increasing the completion flux. Accounting for multiphase-flow effects resulted in a higher safe-operating rate limit than with a conventional analysis. The results allowed the Na Kika asset to produce these wells at their maximum allowable safe-operating rate with the higher skin while producing within BP's flux-based guidelines.