Technology transfer and helping member companies implement the newly developed compact separation technology are important aspects of the TUSTP joint industry project. TUSTP and the supporting member companies aim at rapid deployment of GLCC systems in the field. Over 1050 compact separators, mainly GLCCs, have been installed in the field since 1992.
Recently, TUSTP personnel have been involved in several field application designs for member companies, as described in the following links:
Size Comparison of GLCC & Conventional Vessel Type Separators
The compact dimensions, smaller footprints and lower weight of compact separators have a significant potential for cost savings to the industry. This is especially true for deep-water offshore platforms for which production separators are usually the largest and heaviest equipment. For this application, platform space and weight-carrying capacity are very crucial. Thus, the reduction in size and weight of the compact separators is highly advantageous and can lead to considerable cost savings. A size comparison study has been conducted to aid in the decision making process of selecting an appropriate separator for a field application. They provided a comparison between the required size of the GLCC and conventional horizontal and vertical liquid-gas separators for a field operated by Chevron. The average expected flow rates in this field are qg = 70,000 Mscf/d and ql = 100,000 bbl/d at an operating pressure of 100 psig.
The linked figure shows the schematic results of this investigation. The size comparison between conventional vessel-type horizontal and vertical separators with a GLCC separator for the above mentioned field operations reveals a significant reduction in size when a GLCC is used. The GLCC design was based on the developed simulator, while the dimensions of both conventional vessel type separators are determined by a widely available program. For this case, the required GLCC internal diameter and height/length (5 × 20 ft) are about half of the corresponding dimensions of the required conventional vertical separator (9 × 35 ft), and about a quarter of those of a conventional horizontal separator (19 × 75 ft). Translating this dimension to weight of half-loaded separators, the GLCC weight is 1/8 and 1/64 of the weights of the conventional vertical and horizontal separators.
Multiphase Metering Loop
In this application, the GLCC is used as an integral feature of a multiphase metering loop. This type of measurement loop configuration affords several advantages over either conventional separation with single-phase measurement or non-separating multiphase meters.
The compactness of the GLCC allows the measurement loop to weigh less, occupy less space, and maintain less hydrocarbon inventory than a conventional test separator. Furthermore, complete or even partial gas-liquid separation can improve the accuracy of each phase rate measurement in a multiphase metering system.
About 80 6-inch diameter GLCC multiphase metering loops, such as the one shown in the linked figure from the Springer field of southern Oklahoma, have been installed by Chevron. This application is for an oil flow rate of 1,500 bbls per day and a GOR (gas-oil ratio) of 500. One such GLCC serves several wells simultaneously. It costs about $7,500 as compared to $25,000 for a commercially available conventional separator, for the same application.
Texaco tested the GLCC in a multiphase metering loop under field conditions at the Humble facility in Houston and installed a similar unit in the Eugene Island 354 platform.
PDVSA, Venezuela, recently commissioned a GLCC multiphase metering system on a Lake Maracaibo platform. The GLCC system, shown in the linked figure, is used to test 24 wells with flow rates ranging between 43 – 3,033 bbl/d and 683 – 4,597 Mscf/d.
Partial Separation
A compact GLCC is often very appropriate for applications where only partial separation of gas from liquid is required. One such application is the partial separation of raw gas from high pressure wells to use for gas lift of low pressure wells.
The GLCC is a central feature in the design for raw gas lift system operated by Chevron in Okan, Nigeria. The use of GLCC eliminated gas compressors and pipelines to and from the wells. Separating a significant portion of the gas will reduce fluctuations in the liquid flow and may result in improved performance and smaller units of other downstream separation devices.
Krebs Petroleum Technologies has conducted field studies on the use of a GLCC in series with other compact separation devices such as a wellhead desanding hydrocyclone in order to reduce the required size of the desander and improve its performance.
Recently, TUSTP designed a GLCC for Arco Alaska, to be used as a gas knockout to remove partially gas from a high GOR crude oil system upstream of a multiphase flow meter. This system, which reduces the size of the multiphase meter and improves accuracy, is now under construction.
GLCC as an External Pre-Separator
As an added apparatus upstream to an existing separator, the GLCC can enhance the performance of the separator and increase its throughput capacity.
Schlumberger, Etudes et Productions, France, a member company of TUSTP, is evaluating the possibility of incorporating GLCCs upstream of their test separators.
A GLCC has been designed for Petrobras, Brazil and installed upstream of an existing vessel-type separator located in a jungle, in order to attenuate the effect of slugging. This eliminated the need to replace the existing separator with a larger one, saving millions of dollars.
GLCC as a Primary Separator
GLCCs can also be used as primary full separators.
The function of GLCC as a full separator needs separate gas and liquid legs, without recombination. For such applications, liquid level control is essential for the GLCC in order to reduce or eliminate liquid carry-over into the gas stream or gas carry-under into the liquid stream.
The performance of the control system required for such application cannot be simulated directly using the existing TUSTP model. The control system simulation for this field application was carried out by analyzing the response of the liquid level for different conditions of constriction in the gas and liquid legs. This field application of GLCC as a full separator was designed for Unocal overseas. The GLCC is capable of handling liquid flow rate of 59,800 bbl/d and gas flow rate of 67,180 Mscf/d, at 600 psig. A relatively large GLCC, 26-in internal diameter and 10-ft height, is needed for this application.
World’s Largest GLCC
Caltex Pacific Indonesia (CPI), Minas, Indonesia
New GLCC field applications designed utilizing the TUSTP GLCC simulator, have been installed by Caltex Pacific Indonesia (CPI) in the Light Oil Steam Flooded (LOSF) project in Minas, Indonesia.
World’s Largest GLCC
Caltex Pacific Indonesia (CPI), Minas, Indonesia
The project was executed by Drs. Jack Marrelli from Texaco and Gene Kouba from Chevron. The largest GLCC (60-in ID) for bulk separation/metering and three 36-in ID metering GLCCs for well test metering applications have been recently installed.
The bulk separation/metering GLCC 5-ft ID and 20-ft tall is shown in the linked figure. The GLCC operates at 170 psia and 350ºF, handling liquid and gas production rates of 180,000 bbl/d and 71 MMscf/d, respectively. The GLCC is equipped with control valves on the gas and liquid legs and a sophisticated control system for liquid level control.
TUSTP personnel were closely involved in designing these GLCCs and the respective control systems. The 36-inch diameter well testing GLCC operates at 170 psi and 350ºF, handling liquid and gas production rates up to 7,000 bbl/d and 4.5 MMscf/d, respectively. The control philosophy for this GLCC was also developed by TUSTP.