Abstract
Riser gas events appear during offshore drilling operations when there is a presence of gas in a marine riser above the subsea BOP, which has been recognized as a hazardous situation. The selection of pressure control methods during such events significantly impacts the safety and efficiency of riser gas handling (RGH). This paper performed a numerical simulation study on the fixed choke and constant outflow method as one of the most discussed and positively perceived pressure control methods for RGH currently in the industry. The processes of RGH with the proposed fixed choke and constant outflow method were simulated with a comprehensive riser gas influx simulator. The multiphase flow dynamics in a riser were simulated by a drift-flux model with the inclusion of various sub-models and coupled with a multiphase choke flow model. Measurement data (including distributed fiber optic sensing data) from a set of full-scale experiments conducted at the Petroleum Engineering Research, Training, & Testing (PERTT) Laboratory at Louisiana State University (LSU) was used for the calibration and validation of the developed simulator. The performance of the proposed method is evaluated based on the maximum gas and liquid outflow rates and the peak choke upstream pressure during RGH. A series of sensitivity analyses and a contingency case study was conducted to evaluate the applicability and the extendibility of the fixed choke and constant outflow method. The proposed pressure control method shows great potential in enhancing the safety of RGH for a wide range of riser lengths and gas influx sizes with the available managed pressure drilling (MPD) and riser gas handling equipment. The sensitivity analyses revealed that the selection of the initial circulation rates and choke positions has a significant impact on the safety and time efficiency of the RGH operations and should be carefully determined based on the influx and riser system status. This study deepens the understanding of gas influx movement and pressure behaviors in a marine riser during riser gas events. The numerical simulations in this study help to improve the design of riser gas handling strategies.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
