Honeywell: Flow Measurement for Fiscal Metering – How Data Becomes Digital Intelligence
By Tim Vogel, Product Marketing Manager – Gas Metering, Honeywell Process Solutions
Today’s oil, gas and petrochemical industries must balance a number of factors – including declining crude prices, rising capital costs, and a continuing demand for high-value products. Improving their performance in this changing environment is critical and dependent upon implementing effective technologies for measuring and controlling process variables. Operations need to obtain accurate measurements from a wide range of field instrumentation, including flow measurement devices.
But beyond the task of precisely monitoring the production and transfer of petroleum products, today’s advanced flow metering systems also need to provide robust data that can be transformed into digital intelligence. This supports improved decision-making by enabling industrial personnel to capture, manage and analyze the right information at the right time.
Background
Industrial organizations worldwide are under pressure to reduce operating costs, minimize risks, and integrate technology from multiple vendors. Due to the current business climate, they seek standardization along with integration of plant systems and work practices that will improve capital efficiency, optimize production and meet challenging deadlines.
Fiscal measurements for allocation and custody transfer are of particular concern to petroleum-related firms. Metering large volumes of product requires highly accurate instruments. Even a very small measurement uncertainty in the derivation of bulk flow rate measurement of gas or materials being transferred can cost a company millions of dollars in one year (See Fig. 1).
Custody transfer (i.e. fiscal metering) takes place any time fluids are passed from the possession of one party to another (e.g., from producer to pipeline, pipeline to plant, or pipeline to storage facility). What makes custody transfer unique among flowmeter applications is that substantial sums of money changes hands, and thus uncertainty requirements are more stringent than they are for most other applications. As such, fiscal metering systems are more than just flowmeters and they represent a combination of highly-engineered flow measurement systems for the intended application.
An accurate and reliable fiscal measurement system not only defines the point at which ownership changes hands for the product being measured based on regulatory standards, but also helps maximize overall production and movement efficiency.
Today’s Operational Challenges
Throughout the petroleum-producing sector, the variety and availability of operational data is dramatically increasing in quantity and complexity, yet finding the expertise to filter and interpret data in a timely manner is a challenge.
In particular, the energy industry needs better solutions for measuring gas and other product flows between companies, making it easier to document and calculate transactions involving the transport of physical substance from one operator to another, as well as the documentation of appropriate customs and revenue tax payments.
Oil and gas producers and processors must precisely determine the amounts of product going into a pipeline, or onto a truck, barge or ship. In recent times, they have used disparate, bespoke systems for such measurements. But today’s faster changing and cost-constrained environment requires a new approach to metering — one that provides all the benefits of a centralized solution such as commonality and scalability, but also improved monitoring, management and reporting processes that supplies accurate data to the entire operation (See Fig. 2).
Many oil and gas operations are seeking to replace their old-generation flow computers with new, integrated automation solutions. This upgrade is an important step towards meeting regulatory requirements for fiscal reporting of emissions; simplifying integration of raw meter data in accounting and reporting systems; and enhancing performance where control and sequencing-type tasks are of utmost importance.
Growth of Process Data
At the core of intelligence for oil and gas companies is raw data. Within these organizations, there has been an exponential increase in available plant/process data stored in various databases and historians. This growth in data has come from many different sources.
The first source is the general growth in process automation as the Distributed Control System (DCS) replaced manual controls. Another source has been from the advancement of predictive and preventive maintenance in petroleum facilities. As digital communications have spread throughout the design architecture of new facilities, more data is more easily accessible, and this has led to significant increases in available data sources or inputs. Finally, in the current state of interactive human/non-human controls, significant data is collected through alarm systems designed to assist operations when the process is outside of the normal bounds of control.
In addition to the growth in field data collected, volumes of data from the many components that make up modern oil and gas operations are available as resource information. This data sometimes includes initial checkout and testing data, preventive maintenance requirements, maintenance records, and equipment operating curves.
Over the years, through the efforts of control professionals, process controllers have gradually become more and more intelligent. Proportional-Integral-Derivative (PID) control was first improved by adding external reset, decoupling, dead time and dynamic compensation, gain scheduling, feed forward and auto-tuning. Then came the Linear Quadratic Gaussian (LQG) regulator, Kalman filter, Model Predictive Control (MPC), adaptive control, repetitive control and optimization.
Rise of Artificial Intelligence
In modern field measurement systems, data is collected by hardware but organized and presented by software. Substantial increases in hardware accuracy are no longer attainable, so the main driver of business results is now the data itself — organizing it, collecting it alongside information from elsewhere in the plant, presenting it in a way that makes sense to operators, and then using the data to improve overall performance.
Most field measurement and metering units currently monitor a single process element and present it individually. Companies are looking for intelligent solutions to integrate disparate assets throughout the process, so data is fed into a central hub where it can be utilized to make highly informed production and business decisions.
In the vocabulary of control engineers, Artificial Intelligence (AI) is a relatively new term. With this approach, individual process variables of flow, pressures and temperatures can be treated as constraints to control and maximize the efficiency of unit operations by multivariable controllers. AI allows technology to make the logical leaps and intuitive assumptions that people are now relied upon to perform during many process operations.
Emerging AI technologies are enabling oil and gas and petrochemical firms to turn data from field devices into digital intelligence. This helps operators make critical decisions faster by capturing, managing and analyzing the right information at the right time (See Fig. 3).
Whereas decision-makers once had to be highly technical experts to make sense of the data in front of them, the objective now is to minimize personnel training requirements with intelligent software solutions bridging the gap in expertise by presenting data in a more user-friendly way.
Utilization of artificial intelligence not only allows robust information to be presented to operators, but also supports informed advice/suggestions on appropriate actions when data is delivered. These suggestions are backed up by decades of historic data and previous decisions and outcomes.
Latest Metering Technology
From one end of the plant to the other, everything in a typical oil and gas or petrochemical facility is flowing — and these flows must be measured for safe and efficient operation.
Ultrasonic meters are considered a preferred technology for many flow applications, particularly measurement of gas where it enters a refinery or plant. These meters provide volumetric flow rate and typically use the transit-time method, where sound waves transmitted in the direction of fluid flow, travel faster than those traveling upstream. The transit time difference is proportional to fluid velocity. Ultrasonic meters have negligible pressure drop, have high turndown capability, and can handle a wide range of applications.
The current generation of ultrasonic flowmeters employs robust transducers generating repeatable pulses (amplitude and frequency), as well as high-speed electronics complete with an accurate clock. This clock can detect, resolve and time transmission/reception of sonic pulses with sufficient time domain resolution. The transducer and electronics configuration allows for high pulse transmission rates, and transit time measurement enables fast integration of fluid flow velocity so accurately measured values can be reported once per second (See Fig. 4).
Perhaps the most important development in ultrasonic flowmeter technology has been the advent of multipath meters, which are designed to average axial velocity components over the cross-section of a closed pipe.
A key advantage of ultrasonic meters over other flow measurement solutions is the availability of diagnostic information beyond just delivering pulses or signals proportional to gas volume. New ultrasonic meter designs employ electronics that optimise internal diagnostics, flow velocity calculations, signal processing, data storage, interface to flow computers and Supervisory Control and Data Acquisition (SCADA) systems, and field service diagnostics tools (See Fig. 5).
The most advanced ultrasonic flowmeters provide stability during flow perturbations due to innovative “direct-path” technology, which utilises multiple measuring paths on different levels. Precision adjustment/echo measurement techniques also reduce measurement uncertainty attributed to in-situ auto calibration of system delay (tw) after field replacement of transducers.
Furthermore, ultrasonic meter designers have developed detection algorithms extending signal amplitude for a high Signal-to-Noise Ratio (SNR) compared to traditional intrinsically safe transducers. Qualitative analysis techniques evaluate the meter’s pulse envelope and identify ultrasonic pulses, while still maintaining high firing rates. Such innovative detection algorithms enable greater insensitivity to noise in many installations.
Value of Integration
Organizations in the oil and gas and petrochemical industries can significantly impact their growth and profitability when they have the ability to make fast, smart business decisions. This starts with streamlining data collection, validation, surveillance, and notification processes from field assets like ultrasonic flowmeters. It also requires an integrated operations platform delivering both operational intelligence and field system and engineering application integration for improved operational performance.
The original technology assumptions that accuracy, safe measurement and reliability required a separate, closed system are no longer valid. Open systems technology can now provide added benefits in a modernized operation.
Industry operations are now looking for integrated metering solutions, instead of separate, higher-cost dedicated systems. A solution that integrates the metering function into the control system architecture provides the basic answer. An added benefit comes from the cost-effectiveness of such a solution, from installation, simple configuration and support/upgradeability over the long-term.
Flow computation in petroleum facilities has traditionally been handled by disparate flow computer devices, and more recently by Programmable Logic Controllers (PLCs) and “virtual” flow computers. Unlike standalone metering systems, new solutions integrated with Distributed Control System (DCS) platforms provide flow calculation for greater cost efficiency, extended lifecycle support and improved control.
Thanks to the latest centralized metering technology, users can better meet regulatory requirements for fiscal reporting of carbon emissions; simplify integration of raw meter data in accounting and reporting systems; and optimize control of liquid, loading and proving systems where control and sequencing-type tasks are critical. They can also benefit from flexible reporting, Web-based access, and integration with wireless and fieldbus transmitters in the metering function.
With a DCS-embedded metering solution, fiscal/allocation metering functions are integrated in robust and sustainable controls, rather than held in custom flow computers, metering supervisory devices, or SCADA systems. This approach utilizes a redundant process controller as the fiscal point. Additional flow computing calculations are easily configured in software, which links new instrument inputs to results (Fig 6.)
With fewer systems to maintain, less training is required. With more functions inside the control system there is no external system and custom interface to maintain. This eliminates a separate database, configuration and graphics building effort.
In addition, modern control processors support a wide variety of I/O, including analogue, remote, FOUNDATION fieldbus and HART, allowing metering to follow the chosen approach to I/O. Users can also load ISO, American Gas Association (AGA) and American Petroleum Institute (API) calculations into the controllers and upgrade them, allowing the metering system to easily keep up with changing business and regulatory requirements.
By integrating fiscal flow measurements and centralizing the calculations, data becomes more accurate, more manageable, and ultimately more transparent to operators, partners, and regulatory authorities. Integration with the DCS platform also allows for advanced database maintenance, graphics building, trending, management reporting and Web-based intranet access.
Conclusion
While petroleum-based products have historically been regarded as precious commodities, today’s business outlook has made the need to accurately measure production values and product custody transfers all the more critical. Oil and gas and petrochemical companies are finding new ways use digital intelligence from fiscal metering systems to make faster and smarter decisions affecting their operational and business performance.