James P. Brill

A Comprehensive Mechanistic Model for Upward Two-Phase Flow in Wellbores

A comprehensive model is formulated to predict the flow behavior for upward two-phase flow. This model is composed of a model for flow-pattern prediction and a set of independent mechanistic models for predicting such flow characteristics as holdup and pressure drop in bubble, slug, and annular flow. The comprehensive model is evaluated by using a well data bank made up of 1,712 well cases covering a wide variety of field data. Model performance is also compared with six commonly used empirical correlations and the Hasan-Kabir mechanistic model. Overall model performance is in good agreement with the data. In comparison with other methods, the comprehensive model performed the best.

A Study of Oil-Water Flow Patterns in Horizontal Pipes

Oil-water flow pattern transitions in horizontal pipes have been studied both experimentally and theoretically. A new state-of-the-art, oil-water test facility was designed, constructed and operated. A transparent test section (5.013-cm inside diameter x 15.54-m long) can be inclined at any angle, to study both upward and downward flow simultaneously. Mineral oil and water were the working fluids (μ o /μ w = 29.6, ρ o /ρ w = 0.85 and σ = 36 dynes/cm @ 25.6 °C). Only horizontal flow tests were conducted. A new classification for oil-water flow patterns based on published and acquired data is proposed. Six flow patterns were identified and classified into two categories: Segregated flow and Dispersed flow. Stratified flow and stratified flow with some mixing at the interface (ST & MI) are segregated flow patterns. The dispersed flow can be either water dominated or oil dominated. A dispersion of oil in water over a water layer and an emulsion of oil in water are water dominated flow patterns. An emulsion of water in oil and a dual dispersion are oil dominant flow patterns. Conductance probe data and high speed photographs were found to be adequate flow pattern identification tools while wall pressure fluctuations are not. Pressure drop decreases when the transition to dispersed flow is crossed. Slippage is only relevant for segregated flow patterns. The oil-water flow pattern transitions for light oils are predicted using the two-fluid model and a balance between gravity and turbulent fluctuations normal to the axial flow direction. Linear and non-linear analyses reveal that the stratified/non-stratified transition must be addressed with the complete two-fluid model. Stratified flow is predicted by the viscous Kelvin-Helmholtz analysis while inviscid Kelvin-Helmholtz theory predicted the ST & MI flow pattern. Both the viscous Kelvin-Helmholtz analysis and structural stability criterion are satisfied simultaneously. For the dispersed flow pattern, the predicted drop sizes from the Hinze and Levich models are modified in order to account for the effect of the dispersed phase concentration. The controlling parameter for the coalescence phenomena is the water fraction. The model performance is excellent and compares well with published data.

Multiphase Flow in Wells

Multiphase flow can occur throughout the production system. The fluids involved in multiphase flow in the petroleum industry are multicomponent mixtures with complex phase behavior. Petroleum engineers are faced with the need to predict the relationships between flow rates, pressure drop, and piping geometry for reservoir fluids produced during the life of a field. This paper reviews the historical development of design tools used to address these unique multiphase-flow features. State-of-the-art technology is also presented.

Unified model for gas-liquid pipe flow via slug dynamics: Part 1: Model development

A unified hydrodynamic model is developed for predictions of flow pattern transitions, pressure gradient, liquid holdup and slug characteristics in gas-liquid pipe flow at all inclination angles from -90° to 90° from horizontal. The model is based on the dynamics of slug flow, which shares transition boundaries with all the other flow patterns. By use of the entire film zone as the control volume, the momentum exchange between the slug body and the film zone is introduced into the momentum equations for slug flow. The equations of slug flow are used not only to calculate the slug characteristics, but also to predict transitions from slug flow to other flow patterns. Significant effort has been made to eliminate discontinuities among the closure relationships through careful selection and generalization. The flow pattern classification is also simplified according to the hydrodynamic characteristics of two-phase flow.

Two-phase flow splitting in a tee junction—experiment and modelling

Abstract A model is presented for the prediction of two-phase flow splitting in a horizontal pipe tee for the stratified wavy and annular flow patterns. The model is based on a splitting mechanism which suggests that the preferential liquid flow is controlled by competing inertial and centripetal forces acting on the liquid phase at the tee junction. The model is compared with experimental data and gives reasoanble agreement.

Stratified three phase flow in pipes

Abstract The simultaneous flow of water, oil and gas is of practical importance for the oil and gas industry. Many oil and gas pipelines contain these three phases with varying degrees of concentration, depending on the particular situation. In this work the gas/oil/water holdups for stratified three phase flow are calculated. This information is usually the first step for analyzing the stability of stratified flow and for developing transition criteria. It is shown that one can obtain three theoretical steady state configurations for stratified flow, but only the configuration with the thinnest total liquid layer is stable and can actually occur. Taitel & Dukler (AIChE Jl22, 47–55, 1976) criterion for transition from stratified flow was applied to the three phase flow case and was found to yield good agreement for flow gas flow rates.

Wax deposition in single phase flow

A series of experiments on wax deposition from oil have been performed in a 50-m long by 43.4 mm ID jacketed flow loop at Tulsa University. Tests were performed on a 35°API crude oil from the Gulf of Mexico with a wax appearance temperature (WAT) of 120°F. The series of tests were designed to determine temperature and flow rate effects on the deposition rate and fraction of oil in the deposit. The deposit thickness in the flow loop was determined using five methods; pressure difference, energy balance, the spool piece volume change (LDLD), ultrasonic transit time, and direct measurement in a test section. Samples of the deposits were analyzed at the conclusion of each test for included oil. The effect of the difference in temperature between the oil and pipe wall showed a simple increasing deposition rate with temperature difference. The change in deposition rate was a weak function of oil temperature relative to WAT. The variation in deposition rate with flow velocity gave large differences between laminar and turbulent flow. Deposit oil contents decreased with increasing flow velocity. The fraction of oil in the deposit decreased with time in turbulent flow tests but did not change in laminar tests.

Simplified transient solution and simulation of two-phase flow in pipelines

A simplified transient formulation for calculating transient behavior of two-phase flow in a pipelines system is proposed. The formulation assumes a quassi-steady-stage gas flow and a local equilibrium momentum balance. The applicability of this method is demonstrated for the case of a pipeline system with horizontal, upward and downward inclined sections.

Severe slugging in a riser system: experiments and modeling

Abstract Previous analysis showed that “severe” slugging would exist in a pipeline—riser system when the liquid in the riser is unstable and gas penetrates into the riser. This would then result in an unstable blowout and a cyclic process. When the liquid column is stable, a steady state is assumed to exist. However, observations made on a small-scale test facility have demonstrated that when the liquid column is stable there is still a tendency for a cyclic process to occur. This cyclic process can be damped and become a steady flow or it can continue indefinitely. From these observations a new theory is developed for predicting the behavior in the stable region and is verified with experimental results. It is also shown that in the region predicted by the Boe criterion to be a steady flow, the flow can be unstable and lead to a severe slugging type of behavior.

Two-Phase Flow Through Chokes

Two-phase flow through wellhead chokes, including both critical and subcritical flow and the boundary between them, was studied. Data were gathered for air-water and air-kerosene flows through five choke diameters from 1/4 in. (6.35 mm) to 1/2 in. (12.7 mm), and results were compared to published correlations. A new theoretical model for predicting flow rates and the critical-subcritical flow boundary was tested against these data, as well as data from two published studies. The new model substantially improves the existing methods for predicting choke behavior in two-phase flow.