A mechanistic gas kick model to simulate gas in a riser with water and synthetic-based drilling fluid

This paper presents a simple mechanistic model to describe a gas kick in a drilling riser with water- based mud (WBM) and synthetic-based mud (SBM). This model can estimate key kick parameters such as the change in the wellhead pressure, kick ascent time, and pit gain. In addition, this model also predicts the solubility of the gas kick in SBM at various depths in the annulus. We used the commercial chemical process simulation software, HYSYS, to validate the results of this solubility model. This paper also presents the gas kick experimental results from a 20-ft. tall vertical flow loop at Texas A&M University, Qatar. The base case investigates a gas kick in a vertical 10,000 ft. deep, 12.415 in. drilling riser with WBM. Our analytical model uses the Hasan-Kabir two-phase flow model and develops a set of equations that describe the pressure variation in the annulus. This computed pressure change allows estimates of pit- gain. Our experimental data comes from a 20-ft. tall flow loop with a 2.5 in. steel tube, inside a 4.5 in. Acrylic pipe, that simulates a riser. For these gas kick experiments, we injected specific amounts of gas at the bottom of the setup and recorded the bubble's expansion and migration. The mechanistic model predicted explosive unloading of the riser near the wellhead. A comparison between our model results and HYSYS values for methane liquid-phase mole fraction showed a maximum 8% deviation with complete agreement on bubble point (Pb) pressure and location estimates. Similarly, our model calculated the solution gas-oil ratio (Rs), with a maximum divergence of 3% from HYSYS estimates. From the comparison studies with other empirical Bo & Rs correlations, we note that the estimates of our model agreed best with those of O'Bryan's (Patrick Leon O'Bryan, 1988) correlations. Numerical kick simulators that exist today are notoriously time and power-intensive, limiting their on field utility. Our mechanistic model minimizes computation time through its simple, analytical form to describe kick migration. Our model offers another layer of novelty through the analytical, thermodynamic solubility modeling as opposed to empirical modeling sused by most of the current gas kick simulators.Contributions from the National Academy of Sciences' Gulf Research Program, grant NPRP10-0101-170091 from Qatar National Research Fund, and the International Research Collaboration Co-fund (IRCC) made this research possible. The authors are grateful for all the support they received from the NAS, IRCC, and the Qatar National Research Fund (a member of the Qatar Foundation). The contents of this paper are solely the responsibility of the authors, and not to be taken as the official views of any of the organizations listed above.Scopu

Comprehensive assessment and evaluation of correlations for gas-oil ratio, oil formation volume factor, gas viscosity, and gas density utilized in gas kick detection

For reliable gas kick detection modeling and simulation, the PVT properties of the gas must be predicted accurately. The property correlations available in open literature are developed mostly for certain regions and conditions, which usually over-predict or under-predict when applied to different regions and conditions. To assess these correlations and to determine their applicability and accuracy, a comprehensive evaluation is performed for 63 empirical correlations of four gas properties; gas-oil ratio GOR, oil formation volume factor OFVF, gas viscosity, and gas density based on published laboratory measurements. The GOR and OFVF correlations were evaluated on a regional basis and three best-fit correlations are recommended for each selected region including the Middle East, Central & South America, North America, Africa, and Asia. A universal new correlation for the GOR is developed in this study that can be used for any region in the world with better accuracy and wider range than all available correlations. Furthermore, based on the evaluation results, the most accurate correlations for gas viscosity and density at high-temperature and high-pressure (HTHP) conditions are recommended. The density-based models of the gas viscosity show close results within a minimum average absolute relative error (AARE) of 3.50% to a maximum of 4.45%. Further assessment for the equations of state based on real compositions of the gas kick is recommended for future work. The present work provides a comprehensive and one-stop source database for property correlations and measured data related to gas kick detection.This publication was jointly supported by International Research Collaboration Co Fund Grant [ IRCC-2019-012 ], Qatar University and Texas A&M University at Qatar. The findings achieved herein are solely the responsibility of the authors. This publication was also made possible by an Award [ GSRA7-2-0427-20027 ] from Qatar National Research Fund (a member of Qatar Foundation). The contents herein are solely the responsibility of the authors.Scopu

Investigation of gas-liquid flow using electrical resistance tomography and wavelet analysis techniques for early kick detection

Gas kick is a well control problem and is defined as the sudden influx of formation gas into the wellbore. This sudden influx, if not controlled, may lead to a blowout problem. An accidental spark during a blowout can lead to a catastrophic oil or gas fire. This makes early gas kick detection crucial to minimize the possibility of a blowout. The conventional kick detection methods such as the pit gain and flow rate method have very low sensitivity and are time-consuming. Therefore, it is required to identify an alternative kick detection method that could provide real-time readings with higher sensitivity. In this study, Electrical Resistance Tomography (ERT) and dynamic pressure techniques have been used to investigate the impact of various operating parameters on gas volume fraction and pressure fluctuation for early kick detection. The experiments were conducted on a horizontal flow loop of 6.16 mERT with an annular diameter ratio of 1.8 for Newtonian fluid (Water) with varying pipe inclination angle (0 - 10o) and annulus eccentricity (0 - 30%), liquid flow rate (165 - 265 kg/min), and air input pressure (1 - 2 bar). The results showed that ERT is a promising tool for the measurement of in-situ gas volume fraction. It was observed that the liquid flow rate, air input pressure and inclination has a much bigger impact on gas volume fraction whereas eccentricity does not have a significant influence. An increase in the liquid flow rate and eccentricity by 60% and 30% decreased the gas volume fraction by an average of 32.8% and 5.9% respectively, whereas an increase in the inclination by 80 increased the gas volume fraction by an average 42%. Moreover, it was observed that the wavelet analysis of the pressure fluctuations has good efficacy for real-time kick detection. Therefore, this study will help provide a better understanding of the gas-liquid flow and potentially provide an alternative method for early kick detection. CopyrightThis publication was jointly supported by International Research Collaboration Co Fund Grant [IRCC-2019-012], Qatar University and Qatar National Research Fund (NPRP10-0101-170091), Texas A&M University at Qatar. Furthermore, the authors would also like to acknowledge Heavy Oil, Oil shales, Oil sands, & Carbonate Analysis and Recovery Methods (HOCAM) for providing support and guidance without which this work would not have been possible. The findings achieved herein are solely the responsibility of the authors.Scopu