The overarching objectives are to develop, investigate, and validate (for field and commercial deployment) robust pipeline treatments to prevent/minimize gas hydrate and other solid deposition in subsea oil flowlines. A robust pipeline treatment that is capable of preventing adhesion/deposition will be a major fundamental breakthrough in flow assurance science and engineering and to critical Deepwater field operations. This project will address the current major outstanding issues of mitigating gas hydrate, wax and asphaltene deposition in different pipeline conditions, a major outstanding issue that has not been solved to-date, despite previous attempts/studies.
Colorado School of Mines (CSM), Golden, CO 80401
Oceanit Laboratories, Inc., Honolulu, HI 96813
Gas hydrates are considered the major flow assurance problem during Deepwater offshore production and transportation of oil and natural gas, which if not addressed adequately can present severe production, environmental, and safety issues during operation (Sloan and Koh, 2007). The high pressure (depths of seawater) and low temperature (on the seafloor) conditions in Deepwater environments are ideal for providing thermodynamic stability of gas hydrates, thereby enabling gas hydrates to form and potentially plug Deepwater flowlines during oil and gas production and transportation. The formation of flowline blockages due to gas hydrates may result in rupture of the flowline, gas and oil spill and leakage, and hence catastrophic safety, economic, and environmental consequences. Costs for gas hydrate mitigation can exceed $1M/mile of pipeline, plus $100M/year in chemical costs for complete gas hydrate avoidance.
The conventional method of gas hydrate avoidance using thermodynamic inhibition (THI), e.g. using methanol or glycol, is becoming increasingly unfeasible from both an economic and environmental standpoint, particularly with Deepwater developments which present higher pressure conditions and hence more favorable conditions for gas hydrate stability, as well as maturing facilities in which the water content can increase significantly during the lifetime of the field. Thus, there is an imminent need for a new approach that allows operators to produce from wells where traditional gas hydrate mitigation is unfeasible. Low surface energy materials which can be applied in situ to operational pipelines represent a critical industry solution to gas hydrate mitigation, as these advanced treatments can repel gas hydrate adhesion to the wall, as well as repel the water layer that allows gas hydrates to form directly on the steel pipe surface. Initial testing indicated that gas hydrate adhesion could be decreased by over an order of magnitude, but larger-scale experiments to evaluate and advance coating performance and survivability need to be performed.
Similarly, to hydrates, wax and asphaltene solid deposits can disrupt and defer production as they build-up on pipe surfaces. Treatments for these other flow assurance solids can vary, such as chemical dosing or thermal treatments. In some cases, these treatments can interact unfavorably if multiple depositing species are present. A treatment option that can address multiple flow assurance concerns offers a unique and disruptive step forward in reducing maintenance costs and mitigating severe economic and safety risks caused by these flow assurance solids.
As oil and gas production wells mature, the water content and oil composition can change and increase the risk of gas hydrate, wax, and asphaltene deposition and blockages in flowlines, with the cost of complete inhibition becoming prohibitive. The ability to mitigate flow assurance risks in maturing flowlines can extend the life of the field as well as significantly reduce operational costs from inhibitor injection and prevent potential safety hazards to personnel and equipment. This research allows for a novel, cost-effective method of mitigating gas hydrate and other pipeline solids deposition/blockages in flowlines and extending the life of the field while being minimally disruptive to normal flowline operation. The omniphobic surface treatment developed in this work can significantly improve the economics of energy transport by providing flow assurance and limiting catastrophic blowouts.
CSM has extended their deposition loop system to allow for larger-scale and more detailed hydrate-phobic treatment testing under a variety of flow conditions including transient shut-in/restart conditions, which present significantly higher risks and safety hazards of gas hydrate pipeline plugging compared to steady-state operations. Oceanit has created coupons and pipeline coatings using its omniphobic treatment for use in CSM’s high-pressure rocking cell apparatus, flowloop, and larger-scale deposition loop for flow assurance solids (hydrates, waxes, asphaltenes) deposition mitigation testing. Material development and testing have demonstrated that DragX™ has diverse chemical resistance and long-term survivability.
The results so far are indicating critical disruptive breakthroughs in deepwater pipeline coating and deepwater flow assurance mitigation technologies. Specifically, the omniphobic treatment, which can be applied in situ to existing facilities, has been demonstrated to reduce and mitigate hydrate adhesion and deposition and delay hydrate nucleation for 5+ days while simultaneously preventing corrosion and reducing wax and asphaltene deposition (see Figure 1). Further larger-scale tests under simulated field conditions for hydrate deposition mitigation under transient conditions are underway, as is longer-timescale testing for wax and asphaltene deposition mitigation to test and validate the robustness of the coating. Field test planning for deployment of this disruptive technology, along with application logistics and long-term material survivability, are currently underway. This new technology would present a step-change for the industrial mitigation of major pipeline hazards for the industry. Internal and external project meetings have been held, including discussions with industry members and NETL to determine areas of interest and align the work with commercial goals during the project.