Shoubo Wang

Design and performance of passive control system for gas-liquid cylindrical cyclone separators

The performance of gas-liquid cylindrical cyclone (GLCC) separators can be improved by reducing or eliminating liquid carryover into the gas stream or gas carryunder through the liquid stream, utilizing a suitable liquid level control. In this study, a new passive control system has been developed for the GLCC, in which the control is achieved by utilizing only the liquid flow energy. A passive control system is highly desirable for remote, unmanned locations operated with no external power source. Salient features of this design are presented here. Detailed experimental and modeling studies have been conducted to evaluate the improvement in the GLCC operational envelope for liquid carryover with the passive control system. The results demonstrate that a passive control system is feasible for operation in normal slug flow conditions. The advantage of a dual inlet configuration of the GLCC is quantified for comparative evaluation of the passive control system. The results of this study could form the basis for future development of active control systems using a classical control approach.

Performance Improvement of Gas Liquid Cylindrical Cyclone Separators Using Integrated Level and Pressure Control Systems

The performance of gas-liquid cylindrical cyclone (GLCC ©1 ) separators for two-phase flow metering loop can be improved by eliminating liquid overflow into the gas leg or gas blow-out through the liquid leg, utilizing suitable integrated control systems. In this study, a new integrated control system has been developed for the GLCC, in which the control is achieved by a liquid control valve in the liquid discharge line and a gas control valve in the gas discharge line. Simulation studies demonstrate that the integrated level and pressure control system is highly desirable for slugging conditions. This strategy will enable the GLCC to operate at constant pressure so as not to restrict well flow and simultaneously prevent liquid carry-over and gas carry-under. Detailed experimental studies have been conducted to evaluate the improvement in the GLCC operational envelope for liquid carry-over with the integrated level and pressure control system. The results demonstrate that the GLCC equipped with integrated control system is capable of controlling the liquid level and GLCC pressure for a wide range of flow conditions. The experimental results also show that the operational envelope for liquid carry-over is improved twofold at higher liquid flow rate region and higher gas flow rate region. GLCC performance is also evaluated by measuring the operational envelope for onset of gas carry-under. @S0195-0738~00!00804-9#

Control System Simulators for Gas-Liquid Cylindrical Cyclone Separators

The control system performance of gas liquid cylindrical cyclone (GLCC©) 1 separators can be considerably improved by adopting suitable control strategy and optimizing the design of the controller PID settings. Dynamic simulators have been developed in this study, based on Matlab/Simulink® software for evaluation of several different GLCC control philosophies for two-phase flow metering loop and bulk separation applications. Detailed analysis of the GLCC control system simulators indicates that for integrated liquid level and pressure control strategy, the level control loop compliments the operation of the pressure control loop, and vice versa. This strategy is ideal for reducing the pressure fluctuations in the GLCC. At severe slugging conditions, the integrated liquid level control is more desirable because of its faster response. However, there is no control of the GLCC pressure fluctuations. The results also show that the simulators are capable of representing the dynamic behavior of real physical systems.

Oil-Water Separation in Liquid-Liquid Hydrocyclones (LLHC) -Experiment and Modeling

The liquid-liquid Hydrocyclone (LLHC) has been widely used by the Petroleum Industry for the past several decades. A large quantity of information on the LLHC available in the literature includes experimental data, computational fluid dynamic simulations and field applications. The design of LLHCs has been based in the past mainly on empirical experience. However, no simple and overall design mechanistic model has been developed to date for the LLHC. The objective of this study is to develop a mechanistic model for the de-oiling LLHCs, and test it against available and new experimental data. This model will enable the prediction of the hydrodynamic flow behavior in the LLHC, providing a design tool for LLHC field applications. A simple mechanistic model is devel oped for the LLHC. The required input for the model is: LLHC geometry, fluid properties, inlet droplet size distribution and operational conditions. The model is capable of predicting the LLHC hydrodynamic flow field, namely, the axial, tangential and radial velocity distributions of the continuous-phase. The separation efficiency and migration probability are determined based on swirl intensity prediction and droplet trajectory analysis. The flow capacity, namely, the inlet-to-underflow pressure drop is predicted utilizing an energy balance analysis. An extensive experimental program has been conducted during this study, utilizing a 2” MQ Hydroswirl hydrocyclone. The inlet flow conditions are: total flow rates between 27 to 18 gpm, oil-cut up to 10%, median droplet size distributions from 50 to 500 µm, and inlet pressures between 60 to 90 psia. The acquired data include the flow rate, oil-cut and droplet size distribution in the inlet and in the underflow, the reject flow rate and oil concentration in the overflow and the separation efficiency. Additional data for velocity profiles were taken from the literature, especially from the Colman and Thew (1980) study. Excellent agreement is observed between the model prediction and the experimental data with respect to both separation efficiency (average absolute relative error of 3%) and pressure drop (average absolute relative error of 1.6%).

Optimal Control Strategy and Experimental Investigation of Gas/Liquid Compact Separators

This paper was selected for presentation by an SPE Program Committee following review of information contained in an abstract submitted by the author(s). Contents of the paper, as presented, have not been reviewed by the Society of Petroleum Engineers and are subject to correction by the author(s). The material, as presented, does not necessarily reflect any position of the Society of Petroleum Engineers, its officers, or members. Papers presented at SPE meetings are subject to publication review by Editorial Committees of the Society of Petroleum Engineers. Electronic reproduction, distribution, or storage of any part of this paper for commercial purposes without the written consent of the Society of Petroleum Engineers is prohibited. Permission to reproduce in print is restricted to an abstract of not more than 300 words; illustrations may not be copied. The abstract must contain conspicuous acknowledgment of where and by whom the paper was presented. Abstract The deployment of the new technology of gas-liquid compact separators such as Gas Liquid Cylindrical Cyclone (GLCC 1) requires dedicated control systems for field applications. The control strategy implementation is crucial for process optimization and adaptation, especially when GLCCs are operated at wide range of liquid and gas flow conditions. In this study, a unique and simple control strategy, which is capable of optimizing the operating pressure and adapting to liquid and gas inflow conditions, has been developed. Detailed simulations and experimental investigations have also been conducted to evaluate the performance of the proposed control systems. The significant advantages of this strategy are: the system can be operated at optimum separator back pressure; the system can adapt to the changes of liquid and gas flow conditions; and the strategy can be easily implemented using simple PID controllers available in the market. This provides the oil and gas industry a simple, robust compact separator control technique which has the potential for offshore and subsea applications. Introduction Compared to conventional separators, compact separators, such as the Gas-Liquid Cylindrical Cyclone (GLCC) are simple, compact, possess low weight, low-cost, require little maintenance, and are easy to install and operate. GLCCs have been used to enhance the performance of multiphase meters,

Wet Gas Separation in Gas-Liquid Cylindrical Cyclone Separator

A novel gas-liquid cylindrical cyclone (GLCC

GAS-LIQUID CYLINDRICAL CYCLONE (GLCC ) COMPACT SEPARATORS FOR WET GAS APPLICATIONS

Gas-Liquid Cylindrical Cyclone (GLCC 1 ) separators are becoming increasingly popular as attractive alternatives to conventional separators as they are simple, less expensive, have low-weight, and require little maintenance. However, present studies focus on GLCC designs and applications at relatively lower gas velocities (below the minimum velocity for onset of liquid carry-over in the form of mist flow). With appropriate modifications GLCCs can be used for wet gas and high gas oil ratio (GOR) applications, characterized by higher gas velocities, to knock out the liquid droplets from the gas core. The objectives of this study are to design a novel GLCC capable of separating liquid from a wet gas stream; conduct experimental investigations to evaluate the GLCC performance improvement in terms of operational envelope for liquid carryover; and, measure the liquid extraction from the gas stream. Specific design guidelines for wet gas GLCC are also formulated based on the experimental studies. This investigation provides new capabilities for compact separators for wet gas and high GOR (exceeding 90%) applications.

Slug Detection as a Tool for Predictive Control of GLCC© Compact Separators

Current design and performance of the GLCC© separator is dependent on the prediction of the upstream inlet flow conditions based on available models. It is expected that early detection of terrain slugging (slug length, slug velocity and holdup) and controlling the liquid level in the GLCC using feed forward mechanism can improve the operational range of the GLCC, by decreasing the gas carry under and liquid carry over, and thereby decreasing the control valve dynamics. The conventional feedback control loops can seldom achieve perfect control considering the impact of huge slugs that are keeping the output of the process continuously away from desired set point value. The reason is simple: a feedback controller reacts only after it has detected a deviation in the value of the level from the set point. Unlike the feedback systems, a feed forward control configuration measures the disturbance directly and takes control action to negate the effect of the disturbance on liquid level in the GLCC. Therefore, a feed forward control system has the theoretical potential for perfect control if the slug detection and characterization are perfect. A strategy for GLCC predictive control has been proposed which integrates the feedback and feed forward loops to compensate for error due to modeling and slug characterization. A model has been developed for predictive control system design and simulated in MATLAB-Simulink®. Experimental results obtained demonstrate that the proposed strategy is a viable approach for GLCC predictive control.

Dynamic Simulation and Control System Design for Gas-Liquid Cylindrical Cyclone Separators

Gas-Liquid Cylindrical Cyclone (GLCC) separator performance can be considerably improved by adopting a suitable control strategy to reduce liquid carry-over into the gas stream or gas carry-under into the liquid stream. A dynamic model for control of GLCC liquid level and pressure using classical control techniques is developed in this paper for the first time. Detailed analysis of the GLCC control system stability and transient response indicates that liquid level control could be achieved effectively by a control valve in the liquid outlet for gas dominated systems or by a control valve in the gas outlet for liquid dominated systems. Based on the proposed linear control system model, the system performance is simulated using a suitable software design tool. The novel control system design approach presented in this paper forms a framework for the GLCC active control system optimization.

Experimental Investigation of Falling Liquid Film in Vertical Downward Two-Phase Pipe Flow

In this research the hydrodynamics of falling liquid film in a vertical downward two-phase flow (liquid-gas) is experimentally studied.The 4 inch clear PVC test section is 6.1 meters long, with a length to diameter ratio (L/D) of 64. The fluids utilized are compressed air, water, Conosol mineral oil (light oil) and Drake mineral oil (heavy oil). The superficial liquid velocities tested range from 12 to 72 cm/s while the superficial gas velocities range from 0.2 to 29 cm/s. The vertical facility is equipped with the state-of-the-art instrumentation for two-phase flow measurements, the capacitance Wire-Mesh Sensor (WMS), allowing two-phase flow measurements with conducting and non conducting fluids.Experimental results show that the liquid film thickness has a quasi-linear relationship with the superficial liquid velocity for the air-water case. For the air-oil cases, at superficial liquid velocities higher than 50 cm/s, the liquid film thickness trend is affected by the liquid droplet entrainment. Furthermore, it was found that the liquid droplet entrainment increases as the superficial liquid velocity increases or the surface tension decreases. Details of the liquid droplets traveling in the gas core, wave formation, wave breakup and film thickness evolution are observed in the WMS phase reconstruction.© 2012 ASME