The Gas-Liquid Cylindrical Cyclone (GLCC(c)1) is an example of a compact separator which is simple, lightweight, and having low capital and operational costs. The GLCC(c) has a wide variety of potential applications, varying from only partial to complete phase separation. This paper presents a state-of-the-art simulator for GLCC(c) design and analysis, based on an improved mechanistic model, written in an Excel Visual-Basic(r) platform. The simulator has two components namely, design wizard code and performance code. The design wizard is used for performing the preliminary design of the GLCC(c), and the performance code enables detailed prediction of the complex hydrodynamic flow behavior in the GLCC(c). This user-friendly simulator incorporates the best available technology for the design of GLCC(c) separators for the industry. The simulator has been used to design over 100 GLCC(c) units operating in the USA and around the world. Details of successful field application of GLCC(c) separator for offshore Lake Maracaibo, PDVSA, Venezuela, (multiphase flow-metering loop), PETROBRAS, Brazil, (external pre-separation) ARCO, Alaska (gas knockout) and Minas, CPI, Indonesia (bulk separation/metering), are presented and discussed. These examples demonstrate the potential, advantages, and benefits offered by the GLCC(c) simulator for enhancing the utilization of compact separators in both offshore and onshore environments.1 GLCC(c) - Gas-Liquid Cylindrical Cyclone - copyright, The University of Tulsa, 1994.

The performance of gas-liquid cylindrical cyclone (GLCC©) 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]

Wet gas metering covers a variety of measurements in production streams with high to very high gas volume fractions. There is a need for direct measurement of gas under these conditions in such applications as gas condensate and high GOR fields as well as many production operations where gas from separation systems may contain liquid. More gas will be produced in the future from remote and subsea fields where production, capital investment, and operating costs must be optimized. For example, real time measurement of gas and liquid flow rate are critical in a subsea production system which will improve well allocation, optimize reservoir production, and enhance flow assurance. A number of wet gas metering strategies and systems have been developed to address these needs. This paper reviews the principle of operations of commercially available systems, and evaluates their strength and limitations in various applications. Available data from test loops, pilot and field installations are used to assess the performance and accuracy of these wet gas systems. The field installations are used to identify the types of applications as well as the application trends that have utilized these systems. The paper also assesses the potential benefits from the deployment of a wet gas metering system. The technologies employed in the current systems impose performance and accuracy as well as operational limitations. These limitations are outlined and evaluated in terms of operator expectations and requirements. The analysis is used to outline a list of issues that an operator has to consider in selecting and justifying a system for wet gas measurements in an asset development. New developments that are ongoing or must be undertaken to address the limitations of the current wet gas metering systems are also reviewed. The implications of these developments to extend the future applications of wet gas metering systems are discussed. Introduction More gas will be produced in the future from remote and subsea fields where production, capital investment, and operating costs must be optimized. As an example, gas production from deep waters in the GOM (1) has increased in the last 5 years as shown in Fig. 1. Real time measurement of gas and liquid flow rate are critical in a subsea production system to improve well allocation, optimize reservoir production, and enhance flow assurance. In many of the deepwater reservoirs, the economics developments dictate that several fields be commingled together and processed at a central facility. In such cases, it is critical to be able to measure the produced gas at the wellhead in order to be able to allocate the oil and gas assets to partners in each reservoir (2). These trends have provided much support to the development of more robust and accurate wet metering systems. Wet gas metering covers a wide range of measurements, which is necessitated by the specific applications and the definition of "wet gas". The definition of wet gas can vary depending on whether one is looking at the fluids from the perspectives of reservoir engineering, measurement systems, or commercial sales of the products (3). The lack of a common definition is partly to be blamed for some confusion and misunderstanding when facility engineers, operators and vendors have to communicate across these perspectives. In the following section an attempt is made to establish an acceptable definition, which could be used through the rest of this paper to facilitate our discussion of the wet gas metering systems.

Current design and performance of the GLCC©1 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.

The control system performance of gas liquid cylindrical cyclone (GLCC©) 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. [S0195-0738(00)00504-5]