1 Copyright © 2002 by ASME Proceedings of ETCE2002 ASME Engineering Technology Conference on Energy February 4-6, 2002, Houston, TX ETCE 2002/MANU-29103 PERFORMANCE AND CONTROL OF LIQUID-LIQUID CYLINDRICAL CYCLONE SEPARATORS Rajkumar Mathiravedu REDA Production Systems, Schlumberger Bartlesville, OK 74005 Shoubo Wang, Ram S. Mohan and Ovadia Shoham Petroleum and Mechanical Engg. Departments The University of Tulsa Tulsa, OK - 74104 Jack D. Marrelli, ChevronTexaco E&P Technology Company Houston, TX - 77082 ABSTRACT The feasibility of using Liquid-Liquid Cylindrical Cyclone (LLCC 1 ) as a free water knockout device for bulk separation of oil-water mixtures in the field strongly depends on the implementation of control systems due to its compactness, less residence time and possible inlet flow variations. In this investigation, the LLCC control dynamics have been studied extensively both theoretically and experimentally. A linear model has been developed for the first time for LLCC separators equipped with underflow watercut control, which enables simulation of the system dynamic behavior. A unique “direct” control strategy is developed and implemented, capable of obtaining clear water in the underflow line and maintaining maximum underflow rate. Dedicated control system simulations are conducted using Matlab/Simulink â software to simulate the real system dynamic behavior. Detailed experimental investigations are conducted to evaluate the system sensitivity and dynamic behavior of the proposed control strategy. The results demonstrate that the proposed control system is capable of controlling the underflow watercut around its set point by obtaining maximum free-water knockout for a wide range of flow conditions. (inlet water concentration of 40% and an inlet mixture velocity of 1.5 m/s). INTRODUCTION The production of water with oil continues to be a problem for the oil industry. Oil and gas companies are constantly searching 1 LLCC - Liquid-Liquid Cylindrical Cyclone - Copyright, The University of Tulsa, 1998. 2 GLCC - Gas-Liquid Cylindrical Cyclone - Copyright, The University of Tulsa, 1994. for more effective ways to handle produced water and to increase oil production. Since 1865, when water was co- produced with hydrocarbons, it has challenged and frustrated the industry on how to separate the valuable hydrocarbon (oil) from the disposable (water). Innovations over the years have led from the skim pit to installation of the stock tank, to the gun barrel, to the free water knockout device and most recently to compact separators. Compact separators such as Gas-Liquid Cylindrical Cyclone (GLCC ©2 ) and Liquid-Liquid Cylindrical Cyclone hold a key element in reducing the costs of production operation. These separators are simple, compact, low-cost, require little maintenance and are easy to install and operate. GLCCs that have already been installed and put to use in the field have demonstrated the pronounced impact that this technology is bound to have on the petroleum industry. Most of the studies have been carried out for gas-liquid separation. To further enhance the applicability of cylindrical cyclone, the technology is extended to design LLCC for oil-water separation. A schematic of the LLCC separator is shown in Figure 1. The LLCC is a vertically installed pipe mounted with a horizontal inlet pipe. The oil-water mixture is introduced through a tangential slot at the inlet. It has two exits, the upper outlet that is oil rich stream, and the lower outlet, that is clear water stream. It has neither moving parts nor internal devices. Separation occurs due to the centrifugal forces caused by the swirling motion and the gravity forces. The heavier water is forced radially towards the cyclone wall and is collected from the bottom, while the lighter oil moves towards the center of the cyclone and is taken out from the top. Thus, it provides an efficient alternative for oil-water separation as a free water knockout device. The performance of LLCC strongly depends upon the split of oil rich and clear water streams. Thus, the control system