Critical review & comparison of severe slugging mitigation techniques

Abstract

One of the common flow assurance issues in offshore production facilities is riser-based severe slugging. Severe slugging is a cyclic process that occurs in the late life of reservoirs when there is not enough energy available to push the liquid out of the riser. Severe slugging is highly undesirable as it results in large fluctuations in pressure, oil, and gas flow rates at the outlet of the riser. Several innovative techniques for severe slugging mitigation and elimination have been developed in the past few decades. However, most of these techniques are scattered in the published literature. Hence, at times, it is difficult to assess the status of the severe slugging mitigation technology. A thorough overview of this technology for selecting an appropriate slug mitigation technique is highly required.In this work, an exhaustive literature review has been conducted for severe slugging mitigation techniques. The review includes methods developed by researchers and innovative practices developed in the industry. Details of the experimental facilities used by various researchers for conducting severe slugging experiments have also been documented. Different definitions of severe slugging have been explained, and contemporary industry-oriented definitions are proposed in this study. Slug mitigation techniques can be broadly categorized into three different categories: (i) Topside chokes and control valves, (ii) Gas lift and combinations with others, and (iii) Passive & other hybrid techniques. The working principle of different slug mitigation techniques and their critical reviews, comments, advantages, and disadvantages, are provided. This work lays the foundation for developing screening criteria for selecting slug mitigation techniques. Such criteria are beneficial during the initial design phase of offshore production systems, where severe slugging is expected to occur at the late-life reservoirs or even when there is a remote chance that minimum provisions should be considered in the design due to uncertainties. In addition, the scope of potential future work for the development of new slug mitigation techniques has been proposed.