OIL FIELD EQUIPMENT
UDO 622.276.5.05.002.56 © Group of authors, 2014
New multi-phase flow metering technology available for industrial measuring units in the oil and gas industry1
Новая технология измерений многофазных потоков, реализованная в промышленных измерительных установках для нефтегазовой промышленности
Р. Казимиро
(Шнейдер Электрик / Инвенсис, Фоксборо, США), М. Генри, М. Томбс (Оксфордский университет), А. Крошкин (Шнейдер Электрик / Инвенсис, Москва, Россия), А.Н. Лищук (Группа ГМС)
Адреса для связи: richard.casimiro@schneider-electric.com, alexeykroshkin@schneider-electric.com, lan@hms.ru
Ключевые слова: многофазный поток, кориолисовый расходомер, нейронные сети, измерительная установка, нефть и газ.
Рассмотрена новая бессепарационная технология измерения продукции нефтяных скважин, реализованная компанией Schneider Electric/Invensys в многофазном расходомере NetOil&Gas. Расходомер построен на базе общепромышленных средств измерений (кориолисового расходомера, датчика избыточного и дифференциального давления, преобразователя температуры, влагомера) и математического обеспечения, разработанного специалистами Технологического центра Инвенсис, базирующегося в университете Оксфорда. В изделии использована уникальная способность цифрового кориолисового расходомера Foxboro® сохранять работоспособность при высоком значении объемной доли газа. Для компенсации дополнительных погрешностей и моделирования многофазного потока применен математический аппарат искусственных нейронных сетей. Расходомер прошел сертификационные испытания на ГЭТ 195-2011 и полностью подтвердил соответствие метрологических характеристик требованиям ГОСТ Р 8.615-2005. Предприятием ОАО «ГМС Нефтемаш», входящим в Группу ГМС, разработана и сертифицирована промышленная измерительная установка МЕРА-МР на базе расходомера NetOil&Gas, имеющая как стационарный, так и передвижной варианты исполнения. Установка МЕРА-МР успешно прошла ряд опытно-промышленных испытаний на месторождениях Западной Сибири и Поволжья и получила высокую оценку специалистов нефтедобывающих компаний. К основным достоинствам технологии, помимо точности и достоверности результатов измерений, можно отнести снижение продолжительности теста скважины, минимальную потерю давления, получение данных в режиме реального времени, развитые средства передачи и отображения информации. Проведенный экономический анализ показал, что установка на базе технологии NetOil&Gas обеспечивает заказчику более низкую совокупную стоимость владения по сравнению с установками, построенными по традиционной технологии сепарационных измерений. В настоящее время ОАО «ГМС Нефтемаш» реализует первые коммерческие контракты на поставку установок МЕРА-МР заказчикам.
R. Casimiro
(Schneider Electric / Invensys, US, Foxboro), M. Henry, M. Tombs (University of Oxford, UK, Oxford), A. Kroshkin
(Schneider Electric / Invensys, RF, Moscow), A. Lishchuk
(HMS Group, RF, Moscow)
E-mail: richard.casimiro@schneider-electric.com, alexeykroshkin@schneider-electric.com, lan@hms.ru
Key words: multi-phase flow, Coriolis meter, neural net, measuring skid, oil and gas.
The last few years have seen oil production industry and state regulators bring forward increasingly strict requirements regarding well yield measurements. Conventional metering technologies, based on gas/liquid separation, do not necessarily meet the most recent requirements concerning accuracy, efficiency and validity of measuring data. This can be especially significant when applying modern "smart oil field" concepts, where a close interaction between instant measurement data, layer models and real-time control is pivotal. Furthermore, the old technologies require high levels of maintenance which means a high TCO (Total Cost of Ownership). Some alternative new technologies utilize radiation sources. These systems retain relatively high costs and attract even more rigorous safety requirements.
Given the current state of play, a relatively new multi-phase metering technology which avoids separation and which utilizes conventional industrial sensors such as Coriolis flow meters, water cut meters, and temperature and pressure sensors, is drawing widespread interest from the industry.
NetOil&Gas measuring skid
The NetOil&Gas measuring skid (from here on referred to as the Skid) is intended to measure the oil and gas flow rates and accompanying water in a three-phase well fluid. The Skid core technology has been developed by the Invensys Technology Centre located at Oxford University and now is commercially produced by Invensys Foxboro. The Skid is intended to replace three-phase separator measuring systems conventionally used for well testing and production monitoring in the field.
:Печатается в авторской редакции.
Fig. 1. NetOil&Gas skid design
Fig. 1 shows the design of the Skid. The pipework dimensions and internal diameter (50 mm) are the same for a range of Skid (Coriolis flow tube) DNs from 15 to 50 mm. The Skid with flow tube DN80 has an 80 mm pipework. The well fluid flow is conditioned to minimize slip through the rising and falling of the Skid pipework. The Coriolis meter is installed in the downward and outward leg of the Skid. The design has been developed through field experience with low pressure well applications, and helps to ensure that with low flow rates liquid passes through the Coriolis meter in relatively substantial slugs, which provides better measurement performance.
It is commonly believed that Coriolis meters are not applicable for liquid/gas mixtures. However, researchers at the Invensys Technology Centre have been studying this issue for over two decades, and developed a new fully digital Coriolis meter for liquid/gas operation. The first commercial version of the digital Coriolis meter was launched by Foxboro in 2002. Since then, this innovative Coriolis meter has found hundreds of successful two-phase applications in the chemical, oil and gas, food and beverage and other industries, and has become the heart of the NetOil&Gas Skid. While other vendors are now offering Coriolis meters with claimed two-phase performance capabilities, Foxboro are the market leaders in this field, as demonstrated by the introduction of this new, non-separating three-phase Coriolis-based metering system.
In addition to the Coriolis flow meter, the instrumentation on the Skid consists of a water cut meter and a multivariable pressure and temperature transmitter. The water cut meter is placed immediately below the Coriolis meter. The multivari-albe transmitter reads the fluid pressure at the inlet to the Coriolis meter and the temperature at the top of the Skid. The control unit, called the Net Oil Computer, acts as communication master for all the devices, using the Modbus RTU
industrial communication protocol. The control unit performs three-phase flow measurement calculations based on the data received, provides a human-machine interface (HMI) and also archives well test data files. Real-time data is available to the user's control system via a Modbus interface, with an update rate of 1 second. H
Several water cut meter technologies have been evaluated ^ for measurement accuracy when gas is present in the well fluid. The water cut meter operates using near-infrared absorption spectroscopy with several bands of infrared wavelengths measured simultaneously to distinguish water, oil, gas and other components. Recently an oleophobic and hydrophobic non-stick lens coating has become standard for the NetOil&Gas Skid water cut meter.
The hardware/software architecture of the Skid is shown in Fig. 2. The Display Computer provides three communication interfaces: an internal Modbus for the Skid instrumentation, an external Modbus to provide the user with final measurement values, and an Ethernet interface to enable remote configuration, monitoring and archival data retrieval. The Display Computer further provides a touch screen HMI to enable local configuration, data display, etc. Fig. 2 further shows an overview of the flow calculations. The uncorrected data from the instruments is gathered via the Modbus interface. Here, 'uncorrected' refers to the effect of multi-phase flow: the mass flow, density and water cut readings are calculated based on their single-phase calibration characteristics. The liquid and gas densities are calculated based on the temperature, pressure and water cut readings and configuration parameters provided by the user. Corrections are applied to the Coriolis meter mass flow and density readings based on the three-phase flow measurement models. Finally, the oil, gas and water measurements are calculated from the corrected mass flow, density and water cut readings.
Fig. 2. Hardware and software architecture
The primary technical challenge is to correct for the potentially large errors induced in the mass flow and density measurements of a Coriolis meter by the effect of a gas/liquid mixture. Error functions depend on flow tube geometry and orientation. For a fixed flow tube position, the most significant dynamic parameters are the liquid flow rate and the Gas Volume Fraction (GVF). Previous work, e.g. [1], describe how these errors can be modelled so that corrections can be applied based solely on parameters observable within the Coriolis meter itself. While a number of approaches are possible, here Neural Nets have been used for modelling purposes. A series of experiments have been carried out to create a range of mass flow, GVF and water cut conditions, where the resulting mass flow and density errors have been modelled based on internally observed parameters. Further details of the techniques used to model the multi-phase error surfaces are given in [2], such as handling the interaction between models of the Coriolis meter errors and the water cut meter error. This patent further includes the use of superficial velocity to model flow meter behavior where slip is significant.
NetOil&Gas Skid is specified for u
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