Understanding Gas Kick Behavior in Water and Oil-Based Drilling Fluids

Abstract

A semi-analytical model to simulate the behavior of a gas kick in an annulus was developed utilizing various concepts, including gas solubility in oil-based drilling fluids. This simulator examines critical kick indicators such as Pit Gain and Wellhead Pressure with time. It models the gas behavior using a drift-flux approach with bubble rise velocity appropriate for flow through an annulus. It also uses the Peng-Robison equation of state, van der Waals mixing rules, along with binary interaction coefficients appropriate for drilling fluids, to account for gas solubility in oil-based mud. The simulation results predict that a five-barrel (bbl) gas kick, would reach the wellhead of a 10,000 ft deep, non-circulating, vertical well in approximately 78 minutes. But it would only take 35 minutes to traverse the same well, if the well is circulating at 702 gallons per minute. The simulations also predict that if there is a constant kick influx of 1 scf/sec, the first gas bubbles would reach the wellhead of the same, non-circulating well in 4.45 hours. But only take 52 minutes when it is circulating. Incorporating gas solubility into these simulations revealed that the choice of drilling fluid volume factor (Bo) correlation affects the results significantly. It also showed that some of the existing Bo correlations fail, for drilling fluid swelling calculations, at higher pressures and temperatures. Finally, the results indicate that a gas kick would take longer to reach the wellhead when it is soluble in the mud than when it is not, regardless of the choice of Bo correlation. Most of the existing kick simulators either partially or entirely overlook the effects of solubility on gas migration. This model accounts for the gas kick's solubility in Oil-based drilling fluids, an issue that is critical for off-shore drilling. Applicability of empirical two-phase flow correlations developed for flow in cylindrical conduits, to a gas kick situation is questionable. This simulator addresses this issue by using a semi-analytical approach for modeling two-phase flow in an annulus.

A drilling wellbore pressure calculation model considering the effect of gas dissolution and suspension

“…In addition to empirical models, the calculation method of solubility based on gas-liquid phase equilibrium is also commonly used, and the fugacity equilibrium method based on equation of state is the most widely used method. Feng et al (2019) conducted experimental research on the solubility of gas in various drilling fluids and found that the calculation method using PR equation of state combined with two parameter mixing rules has the best accuracy, and its model has been widely adopted by Manikonda et al (2019), Sleiti et al (2020), and other scholars. Sun et al (2017) found that the dissolution process of gas in the drilling fluid is essentially the diffusion of gas molecules in the gas phase into the liquid phase under the action of fugacity difference, and the dissolution rate is related to the diffusion coefficient and gas-liquid interface area.…”

Study on Pinhole Leaks in Gas Pipelines: CFD Simulation and Its Validation

“…Liu [6] studied an improved dynamic pressure waves method that localization of the leak in natural gas pipeline. We have performed numerical simulations and experiments for single phase flow [7]- [9], gas/liquid flow [10]- [14], solid/liquid [15], gas/liquid/solid flow [16], [17]. We have also previously conducted a critical literature review on onshore/offshore leak detection and single phase (crude oil and natural gas) leak detection computational fluid dynamics modeling [18].…”