Fixed Choke Constant Outflow Circulation Method for Riser Gas Handling: Full-Scale Tests in Water- and Synthetic-Based Mud with Gauges and Distributed Fiber-Optic Sensors

Summary Accurate estimation and prediction of gas rise velocity, length of the gas influx region, and void fraction are important for optimal gas kick removal, riser gas management, and well control planning. These parameters are also essential in monitoring and characterization of multiphase flow. However, gas dynamics in non-Newtonian fluids, such as drilling mud, which is essential for gas influx control, are poorly understood due to the inability to create full-scale annular flow conditions that approximate the conditions observed in the field. This results in a lack of understanding and poor prediction of gas kick behavior in the field. To bridge this gap, we use distributed fiber-optic sensors (DFOS) for real-time estimation of gas rise velocity, void fraction, and influx length in water and oil-based mud (OBM) at the well scale. DFOS can overcome a major limitation of downhole gauges and logging tools by enabling the in-situ monitoring of dynamic events simultaneously across the entire wellbore. This study is the first well-scale deployment of distributed acoustic sensor (DAS), distributed temperature sensor (DTS), and distributed strain sensor (DSS) for investigation of gas behavior in water and OBM. Gas void fraction, migration velocities, and gas influx lengths were analyzed across a 5,163-ft-deep wellbore for multiphase experiments conducted with nitrogen in water and nitrogen in synthetic-based mud, at similar operating conditions. An improved transient drift flux–based numerical model was developed to simulate the experimental processes and understand the gas dynamics in different wellbore fluid environments. The gas velocities, void fractions, and gas influx lengths estimated independently using DAS, DTS, and DSS showed good agreement with the simulation results, as well as the downhole gauge analysis.

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Handling Gas-In-Riser – Part II: Numerical Simulation of Riser Equilibrium Point (REP), Riser-Gas Tolerance (RGT) and Riser Unloading, and Validation of the 2023 IADC Deepwater RGH Guidelines Calculation Worksheet

de Sousa,

Gabaldon,

Kaldirim

et al. 2024

SPE/IADC Managed Pressure Drilling and Underbalanced Operations Conference and Exhibition

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Several tools can simulate gas-liquid flow under typical operational conditions. However, the rapid expansion of gas in the riser (GIR) as it approaches the surface represents a challenge for many of these tools, as flow conditions fall outside assumptions used in developing their numerical models. Tools able to simulate the full transient behavior of GIR require expert setup and extended run-times. This work uses these tools to run simulations to estimate REP, RGT and riser unloading. The simulation work shows that RGT is generally higher than what is perceived by the industry. This means risers can safely handle larger volumes of gas without exceeding their operational ratings, assuming the influx is circulated using the Fixed Choke, Constant Outflow (FCCO) method. The results also show that the riser equilibrium in WBM happens deeper in relation to SBM, all else remaining the same, and that riser unloading is more intense in WBM, with peak liquid and gas outflows surpassing those of SBM manyfold. The results are also used to evaluate the reliability and intended conservative nature of the RGT Worksheet. This work demonstrates through simulation that GIR can be safely handled with existing surface equipment in many rigs. This represents a significant reduction in NPT and minimizes risks. The authors also demonstrate that calculations performed using the simplified methods considered in the RGT Worksheet can give conservative safeguards to offshore operations.

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Fixed Choke Constant Outflow Circulation Method for Riser Gas Handling: Full-Scale Tests in Water- and Synthetic-Based Mud with Gauges and Distributed Fiber-Optic Sensors

Cited by 3 publications

References 56 publications

Scrutinizing the influence of an adaptive fuzzy sliding mode control strategy on the regulation of constant BHP control

Scrutinizing the influence of an adaptive fuzzy sliding mode control strategy on the regulation of constant BHP control

Comparison of Gas Signature and Void Fraction in Water- and Oil-Based Muds Using Fiber-Optic Distributed Acoustic Sensor, Distributed Temperature Sensor, and Distributed Strain Sensor

Handling Gas-In-Riser – Part II: Numerical Simulation of Riser Equilibrium Point (REP), Riser-Gas Tolerance (RGT) and Riser Unloading, and Validation of the 2023 IADC Deepwater RGH Guidelines Calculation Worksheet

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