From Pore to Process: Novel Flow Assurance Approach to Suppress Severe Production Chemistry Issues by Flow Dynamic Characterization

Abstract

Dragon Oil operates the Cheleken field in the Caspian Sea offshore Turkmenistan. The production system consists of multiple wellhead and manifold platforms, a complex network of infield carbon steel and flexible flowlines to handle production from HP and LP systems and a 30" × 40 km TL to transport the produced fluids to the CPSF (Central Processing and Storage Facility) located onshore. In addition to the complexities of the flowlines network, the development has a number of unique features that pose challenges to the daily production operation activities such as: -Relatively low reservoir temperatures;-Waxy oil with high WAT (Wax Appearance Temperature) and Pour Point;-Complicated bathymetry of the 30" TL (Trunkline);-Complex reservoirs leading to uncertainty in rates;-Increasing water production;-Increasing sand ingress;-Necessity to commingle water from different sources in the flowlines;-Corrosion, erosion and emulsion occurrence; While management of any of the Flow Assurance issues is well understood on stand-alone basis; there is no definite guidelines to manage them simultaneously through understanding their impact on each other. Obtaining flawless understanding of the nature and extent of each of the impediments issues was a key element for Dragon Oil's team to innovate this approach to minimizing the overall negative impact on production operations. The approach has been developed based on balancing the hydrophobic, hydrophilic and molecular properties of the produced fluids in correlation with the physical criteria of each of the issues to minimize the impact on the others. This paper presents the key elements of a novel approach developed to control the impact of some issues and maintain the deliverability and integrity of the 30" TL. The approach consisted of the following activities:Conducted thorough and rigorous fluids’ analyses;Generated comprehensive operating pressure-temperature envelop during different operational and ambient conditions in the 30" TL;Constructed the occurrence envelops of Flow Assurance issues focusing on wax deposition and severe slugging;Ensured adequacy of slug catching capability at the CPSF and proper procedures to operate;Controlled gas rates to generate severe slugging in the 30" TL;Monitored the performance of the 30" TL (and eventually the system) through close observations to the changes in the key controlling parameters e.g. pressure drop, outcomes of pigging operations and efficiency of separation.