Flow assurance and mitigation technical concerns are some of the more critical components in the engineering, design, cost, and operation of offshore production facilities. While gas-hydrate handling typically dominates the thermohydraulic design, the mitigation of waxes, emulsions, asphaltenes, corrosion, scale, and salt; solids handling; slugging; and operability of tubing, surface chokes, and pipelines are all challenging issues that demand attention and considerable technical effort. Among these challenges, paraffin deposition (interchangeable with wax) in pipelines has gained importance in flow assurance. Reliable wax-deposition-prediction models based on specially designed flow-loop experiments are an available mitigation option. Alternative internal pipeline/flowline coatings or materials present another option to address flow-assurance problems. Addressing these challenges requires thorough technical investigation and development of advanced transient modeling. The three papers here discuss slightly different approaches to production continuity and oil/gas fluid-production assurance. All three have been scaled up either to demonstration stage or to actual field implementation and use.
Subsea production faces both fluid and flow-based challenges that eventually lead to shutdown, safety concerns, or flow intermittency in production. The oil/gas production pipelines typically operate at a high Reynolds number and low-wall-shear-stress conditions; however, current wax-deposition models are based on laboratory flow-loop data obtained at low Reynolds number and high shear stress. Paper OTC 27757 discusses a present study that decouples the effect of the hydrodynamic parameters with specially designed flow-loop experiments. From the results, the Reynolds-number effects are more dominant on the deposited-wax-mass density compared with the shear stress and aid in scaleup from the laboratory to field conditions.
Gas hydrates typically form at high-pressure and low-temperature conditions where free water and small hydrocarbon molecules exist together in sufficient concentrations. Once these thermodynamic conditions occur in oil/gas production flowlines/pipelines, solid hydrate plugs that greatly restrict flow usually form. One potential hydrate-mitigation technique involves using a low-adhesion, protective-surface internal coating to inhibit deposition. Paper OTC 27874 describes a study evaluating two different coatings, one a superhydrophobic, anti-icing coating and one an omniphobic and corrosion-resistant coating. Hydrate/surface interactions were studied using micromechanical-adhesion-force measurements in both liquid and gas bulk phases. The initial results suggest that the use of these coatings may be an effective mitigation technique at low water content and in significantly corroded flowlines.
The third paper presents the flow-assurance challenges and associated mitigation steps implemented in the high-pressure/high-temperature North Kuwait Jurassic (NKJ) fields. An offline transient-model adviser was built to mimic the hydrate mechanism and optimize the methanol injection. Paper SPE 182237 discusses the traditional methods of hydrate mitigation performed in the NKJ fields and the way the transient model was initially built and continually improved with more data. Currently, methanol is used for hydrate inhibition and an antiagglomerate is under trial.
Mitigation of flow-assurance problems continues to drive new production-technology applications and approaches. The three papers highlighted here focus on minimizing costs while providing safe, effective, and reliable operations. I hope you find them as interesting as I did, and I greatly appreciate the opportunity to offer these new options to you in this and future Focus sections.
This Month's Technical Papers
Wax-Deposition Experiments Decouple Hydrodynamic Parameters To Aid Scaleup
Low-Adhesion Coatings Provide Novel Gas-Hydrate-Mitigation Strategy
Transient Simulation for Hydrate Mitigation Aims for Optimal Production in Kuwait Fields
Recommended Additional Reading
SPE 181560 A Pigging Model for Wax Removal in Pipes by Qiyu Huang, China University of Petroleum, et al.
SPE 183055 Multiphase-Flowmeter Performance: A Critical Piece of an Offshore-Well-Management Toolkit by V.U. Okotie, Abu Dhabi Marine Operating Company, et al.
