A fully implicit EOS based compositional two-phase transient flow simulator in wellbores

Modeling the simultaneous flow of gas and liquid or two-phase gas-liquid flow in pipes is a key aspect in petroleum production. These models can enhance our ability to estimate fluid properties, predict pressure loss, liquid holdup, and flow pattern, and to see the effects of introducing concepts such as heat transfer to the system. Modeling two-phase flow phenomenon also allows visualization of the interaction of one property or parameter to another. The understanding of heat transfer in two-phase gas-liquid flow is important for economic and optimized operations.;This work focuses on the design of a PC-Based Software for modeling the effect of convective heat transfer on flow patterns in two-phase gas-liquid flow in pipes at all inclinations from -90° to +90° from horizontal, with the utilization of a temperature and pressure traverse along the length of the pipe. The implementation of this model in a computer program involves substantial calculations and correlations, some of which require iterative procedures.

The characteristics of two-phase flow in a vertical pipe are investigated to gain a better understanding of vibration excitation mechanisms. An analytical model for two-phase flow in a pipe was developed by Sim et al. (2005), based on a power law for the distributions of flow parameters across the pipe diameter, such as gas velocity, liquid velocity and void fraction. An experimental study was undertaken to verify the model. The unsteady momentum flux impinging on a ‘turning tee’ (or a ‘circular plate’) has been measured at the exit of the pipe, using a force sensor. From the measured data, especially for slug flow, the predominant frequency and the RMS value of the unsteady momentum flux have been evaluated. It is found that the analytical method, given by Sim et al. for slug flow, can be used to predict the momentum flux.

This study describes the development and validation of an improved simplified model for transient two-phase flow for any pipe inclination. The simplified model proposed has been validated with field-scale test well and laboratorial data, and also compared to the state-of-the-art commercial simulator for transient two-phase flow in pipes. The results of the simplified model showed an agreement within the range of ±30% for the holdup predictions for 65% of the scenarios, and an agreement within the range of ±30% for the pressure predictions for 82% of the scenarios considered in this work. In the oil and gas industry, transient two-phase flow is present in many production and drilling operations, such as in well unloading, well control, and managed pressure drilling. There are many commercial transient multiphase flow simulators available, which use complex numerical procedures to describe multiphase flow in pipes and estimate variables of interest, such as pressure, temperature, phase fractions, and flow regimes discretized in space and time. Many of the transient flow scenarios encountered in the industry are considered slow transients and a rigorous transient simulator may not be necessary in these cases. With a few simplifications of the fundamentals equations, less complex models can be deployed in such cases without significantly compromising the accuracy of the results. With this consideration, and taking the fact that acquiring a license of a commercial software can be prohibitive for small operators and consulting companies, an easy-to-use and open source simulator was implemented based on the simplified transient model discussed in this work.

This paper presents a simplified model for transient two-phase flow in pipes of any inclinations, for slow transients. Such simplified model facilitates its use for real-time monitoring and machine leaning implementations. An improved correlation for the drift flux parameters is adopted in the model, which enables the utilization of the model for simulating transient flow scenarios for any pipe inclination and extends its applicability to a wider range of conditions. From the formulation, an equation has also been proposed to quantitatively define the application of the concept of slow transient. This equation indicates if a case of interest can be classified as a slow transient, which consequently implies that the use of the proposed model would likely provide accurate results. The model has been validated with experimental and field data, and also compared to the state-of-the-art commercial simulator for transient two-phase flow in pipes. The results showed an agreement within the range of ±30% for the holdup predictions for 65% of the scenarios, and an agreement within the range of ±30% for the pressure predictions for 82% of the scenarios considered in the validation data set. The model performance evaluation with data from a well in the GOM showed a maximum error of 30% in terms of predicted bottomhole pressure and an average error of 9% for the simulation of two years of transient flows.

Correlation of heat transfer coefficient for two-component two-phase slug flow in a vertical pipe

Godunov‐type algorithms are very attractive for the numerical solution of discontinuous flows. The reconstruction of the profile inside the cells is crucial to scheme performance. The non‐linear generalization of the discontinuous profile method (DPM) presented here for the modelling of two‐phase flow in pipes uses a discontinuous reconstruction in order to capture shocks more efficiently than schemes using continuous functions. The reconstructed profile is used to define the Riemann problem at cell interfaces by averaging of the components of the variable in the base of eigenvectors over their domain of dependence. Intercell fluxes are computed by solving the Riemann problem with an approximate‐state solver. The adapted treatment of boundary conditions is essential to ensure the quality of the computational results and a specific procedure using virtual cells at both extremities of the computational domain is required. Internal boundary conditions can be treated in the same way as external ones. Application of the DPM to test cases is shown to improve the quality of computational results significantly. Copyright © 2001 John Wiley & Sons, Ltd.

CFD Simulations of Abnormal Flow in Horizontal Pipes for Offshore Hydrocarbon Transport

Numerical modeling of wavy stratified two-phase flow in pipes

An experimental investigation on the fluid–structure coupling in horizontal pipes conveying two-phase intermittent flow

Dynamics of two-phase flow in vertical pipes

Flow structure and bubble characteristics of steam–water two-phase flow in a large-diameter pipe

This study describes the concept of Liquid-Assisted Gas-Lift (LAGL). This concept includes three main parts: two-phase downward flow in annulus, two-phase flow through orifice Gas-Lift Valves (GLVs), and upward two-phase flow in pipes. The latter part is well described in the literature and will not be investigated in this work. However, there is a lack of studies on two-phase downward flow in annulus and through GLVs. Therefore, these two topics are investigated in this work. An experimental and numerical study on two-phase flow through orifice GLVs is presented. The experimental results are compared to predictions using a numerical model published in the literature for two-phase flow through restrictions. It is observed that the mechanistic model could successfully characterize two-phase flow thorough gas-lift valves with errors lower than 10%. A flow regime map of downward two-phase flow in the annulus is used to analyze the flow regimes observed during field-scale experiments of LAGL unloading. It was concluded that the intermittent and bubbly flow are preferred to minimize injection pressure during LAGL unloading operations. A commercial flow simulator is used to perform sensitivity analysis of the LAGL system and to perform unloading of a well using the LAGL concept. The unloading simulation results indicated that the use of LAGL has the potential to decrease the injection pressure requirement in more than 50% when compared to the conventional single-point gas injection. The simulation model is shown to be a useful tool to perform system analysis and optimization of LAGL.

A simple friction pressure drop correlation for two-phase flow in pipes

Fluid flow monitoring is essential in many industrial processes. However, some flow measurement methods may not be feasible in a few applications such as the ones in potentially explosive atmospheres or under presence of intense electromagnetic fields. In this study, we present the construction and evaluation of an optical fiber transducer, which is suitable for flow monitoring in industrial environments pipes. Besides single-phase flow, which has been already monitored by similar techniques in the past, we also present in this paper the measurement of two-phase gas-liquid flows. Working principle is based on the measurement of the force induced by the streaming fluid into a cantilever whose deformation is indirectly and optically monitored by means of fiber Bragg gratings. Static and dynamic tests were performed for transducer calibration and validation. In static calibration, sensor sensitivity to force corresponded to 2.34 nm/N. The transducer was successfully applied to measure single-phase flow rate in the range of 0 $\text{m}^{{3}}$ /h to 6.68 $\text{m}^{{3}}$ /h, presenting maximal uncertainty of 0.3 $\text{m}^{{3}}$ /h. Finally, the transducer was applied in two-phase gas-liquid flow, being able to correctly identify gaseous and liquid phases since the cantilever is exposed to different forces during the passage of the gas and liquid. In this way, the developed transducer may be well applied to two-phase flow monitoring.

Experimental investigation of two-phase flows is important in many areas of research and industrial application. We introduce a probe based on electrical impedance and Fiber Bragg Grating-based strain measurements, which is able to monitor two-phase flow in pipes. The prototype probe presented consists of an optical fiber with a FBG for sensing encapsulated by a hollow stainless-steel cylinder, which is interrogated for strain and conductance measurements. Raw data is converted to flow parameters such as gas bubble length and velocity. Initial results in a two-phase flow test bench show that the combined optical-electrical technique is feasible and promising to be applied in two-phase flow monitoring.