By Oscar Gabaldon, Blade Energy Partners; Gavin Humphreys, Stena Drilling; Paul Sonnemann, Safekick; and Mario Teixeira, Equinor
In a landmark development for the deepwater drilling industry, the Gas in the Riser Subcommittee of the IADC Underbalanced Operations & Managed Pressure Drilling (UBO & MPD) Committee released its Riser Gas Handling Guidelines in August. These comprehensive guidelines have been incorporated as a stand-alone chapter in the IADC Drilling Manual, 12th Edition Revised.
The guidelines are tailored to address the challenges associated with gas in the riser in deepwater rigs utilizing surface backpressure (SBP) MPD or installed riser gas handling (RGH) systems, as outlined in the guidelines. The document provides practical recommendations for safely managing gas in the riser, offering enhanced operational capabilities and environmental protection.
De-risking riser gas handling
Without the right equipment and procedures, gas-in-the-riser events pose a severe risk and can potentially lead to uncontrolled riser unloading and adverse consequences for personnel and the environment. However, the introduction of SBP MPD/RGH equipment has provided operators with the means to manage riser pressure and control gas expansion in a safe manner.
The Gas in the Riser Subcommittee comprises seasoned drilling engineers and offshore drilling professionals, as well as dedicated research teams, who have collaborated for more than 10 years in discussing, analyzing, modeling and researching the challenges associated with gas in the riser. Their combined expertise has culminated in the development of these guidelines to offer a comprehensive approach to preparing deepwater rigs, equipped with the necessary tools, for effectively handling gas in the riser.
One noteworthy aspect of the subcommittee’s work is its commitment to continuous improvement. Committee members actively seek feedback from the deepwater drilling community and encourage collaboration from volunteers who are passionate about enhancing safe drilling practices. Interested individuals can visit the UBO & MPD section of IADC’s website to find additional information and contribute to this ongoing effort.
These guidelines equip drilling personnel with the knowledge and strategies necessary to mitigate risks and effectively handle gas in the riser. They provide the basis for developing rig-specific riser gas handling procedures, considering the equipment layout and possibilities of each installation. The release of the guidelines is a milestone for several reasons:
Enhanced Safety: Deepwater drilling operations are inherently complex and challenging. Gas in the riser can quickly escalate into a critical situation. These guidelines provide a structured approach to manage these scenarios, reducing the potential for accidents and improving overall safety.
Environmental protection: The drilling industry is under increasing scrutiny to minimize its environmental impact. Proper riser gas handling is crucial to prevent unintended discharges and protect marine ecosystems. The guidelines offer practical measures to achieve this.
Operational efficiency: Effective gas handling in the riser can contribute to more efficient drilling operations. By controlling gas expansion and maintaining stable riser pressure, operators can optimize drilling processes, reduce downtime and enhance overall efficiency.
Industry collaboration: The Gas in the Riser Subcommittee’s dedication to collaboration and continuous improvement sets a positive example for the industry. By actively seeking feedback and input, they ensure that the guidelines remain relevant and effective.
The science behind the guidelines
The development of the new guidelines involved consideration of the relative importance of aspects such as fluid compressibility, gas solubility, hydrate behaviors, flow patterns, etc. From the start, it was recognized that existing models that are useful for drilling and training purposes are unreliable for simulations of near-surface, low-pressure free gas behaviors.
While the team that developed the guidelines found ways to work around that problem, including the use of supporting theoretical and testing work at public universities and privately developed special use modeling, that problem still exists. But for the guidelines to be useful, there is a clear need to provide some means for users to recognize the logic underlying the new recommended procedure and its sensitivity to influx volumes, riser length, circulation rates, etc.
The Gas in the Riser Subcommittee has released a tool to do just that, along with explanation for the underlying logic. Eventually, the subcommittee still plans to put together an accessible description of the underlying physics. The new “Riser Gas Tolerance Worksheet,” available for download at the IADC UBO & MPD Committee’s webpage on IADC.org, is provided to promote awareness and discussion of riser system gas handling capabilities when utilizing the recently published IADC Riser Gas Handling Guidelines.
Version 1.0 is not intended to be a final solution but is offered to help quantify related gas behaviors in a way that promotes both a better understanding of the fixed choke constant outflow (FCCO) method, as well as stimulating further work toward developing reliable modeling and simulation techniques. DC