Sensors, Actuators

Oil terminal efficiency improved with high-capacity flowmeter

Coriolis flowmeters mitigate pressures placed on terminal, tank farm, and pipeline distribution facilities.
By Mark Thomas January 31, 2019
Courtesy: Endress+Hauser

Because of increased U.S. oil production, pipeline bottlenecks in Texas and New Mexico are leading to growing truck and rail car use to haul oil, leading to transportation challenges.

Increase in crude oil production also causes problems at tank farms, pipeline distribution facilities, and even oil terminals. In addition to increased U.S. production, the country still imports a large amount of crude. According to the American Geosciences Institute, the U.S. imports 10.4 million barrels of petroleum per day (MMBPD), with the largest amounts coming from Canada (42%) and Saudi Arabia (8%).

One main issue at oil terminals, tank farms, and distribution facilities revolves around restrictions in flow caused by conventional flowmeters.

At one new oil terminal, Coriolis flowmeters are proving they are better able to handle flows through larger pipes and thereby help address emerging challenges in crude oil production and distribution.

Domestic crude production

The Energy Information Agency (EIA) says the Permian Basin in West Texas and southeastern New Mexico will double production by 2023. Current production already exceeds pipeline capacity, so several pipeline projects are underway.

The Eagle Ford shale formation in Texas is another huge source of crude. According to the latest report from the U.S. Geological Survey (USGS), the land sits on billions of barrels of untapped oil and natural gas reserves. The USGS estimates these shale fields contain approximately 8.5 billion barrels of oil, 66 trillion cubic feet of natural gas, and 1.9 billion barrels of natural gas liquids.

In 2018, the USGS said the Wolfcamp and Bonespring formations in West Texas and New Mexico hold the most potential oil and gas resources ever assessed—more than twice as much as previously reported. The Permian and Delaware basins account for roughly one-third of all U.S. crude oil production. Estimates are now in the range of 46.3 billion barrels of oil, 281 trillion cubic feet of natural gas, and 20 billion barrels of natural gas liquids.

The International Energy Agency (IEA) said U.S. production of crude oil, condensates, and natural gas liquids will rise to 17 MMBPD by 2023, up from 13.2 million in 2017. Rising production means the U.S. may soon be energy self-sufficient, a huge shift from the recent past when the U.S. was the world’s largest oil importer. Someday the U.S. may even be a net crude exporter, something that has not happened in 75 years.

Crude oil imports have remained at 10 million barrels per day since 2015, but instead of importing much of the crude from OPEC countries, the U.S. is importing more from Canada via pipelines, railroad cars, and tanker trucks, most of which is bound for Gulf Coast refineries.

The challenge to oil terminals, tank farms, and pipelines is they are handling 2.5 million barrels per day of crude today, but this will increase to 4.0 million barrels per day by 2022. This will require more capacity at all facilities. And one bottleneck for all this increased capacity is the ability of flowmeters to handle the increased flow.

Flowmeter challenges

Mechanical meters with rotating vanes or gears were the workhorse of the pipeline flow metering business for decades. Such meters are large, heavy, must have upstream dirt filters, wear out expensive rotating parts, require regular maintenance, don’t work with gas, and are not “smart” instruments. Device accuracy is usually around 0.25%.

All mechanical meters share common limitations:

  • Maintenance due to moving parts and other issues
  • Reliable with lubricating and clean fluids
  • Sensitive to changes in process parameters
  • High installation cost.

Regular maintenance is required on mechanical meters to replace worn or damaged parts. Parts, such as bearings, must be lubricated, inspected, or replaced on a regular basis to ensure the accuracy and performance. Other parts—such as pistons, gears, and turbine blades—must also be checked for damage and replaced over time.

Maintenance is often overlooked on initial investment, but this is often the biggest cost in the lifecycle of a mechanical meter as maintenance requires extensive downtime and constant replacement of sometimes expensive parts.

Mechanical meters are sensitive to process parameter changes such as in temperature, pressure, and viscosity. Parameter fluctuations can affect meter accuracy, performance, and life of the meter.

More and more terminals are looking for compact flowmeters that can fit in tight areas, are easy to repair and maintain, and provide exceptional accuracy, while also looking at multiple parameters and advanced diagnostics features.

To address these issues, oil terminals and other midstream facilities are turning to Coriolis (figure 1).

Figure 1: A Coriolis flowmeter is shown. Courtesy: Endress+Hauser

Figure 1: A Coriolis flowmeter is shown. Courtesy: Endress+Hauser

Terminal chooses Coriolis

For example, one new Gulf region oil terminal receives Gulf crude oil and distributes it to five local refineries via pipelines. The terminal accommodates multiple oil tankers at a time using an appropriate number of unloading piers. It needed reliable and repeatable flowmeters having a wide turndown range, capable of handling increased flow capacities from 24-in. pipelines.

Endress+Hauser and its partners met with the terminal operator and management to discuss options for these high-capacity flowmeters. Coriolis flowmeters were recommended due to their ability to meet high-capacity crude oil flow rates, maintain a low pressure drop, and remain accurate with a wide turndown ratio.

The involved companies worked with a local engineering firm to design unloading skids. The skids were installed at the shore end of the piers where low sea levels meant soft soil, so weight minimization was important. The more weight, the more concrete was needed for the foundation. By reducing size and weight, the need for additional support structures could be reduced.

A lightweight large-capacity mass flowmeter helped reduce the skid’s weight. Each Coriolis meter was installed in a horizontal position with its underside facing up. This departure from the normal vertical mounting reduced the size of the skid by almost 50%.

The project called for ten 12-inch Coriolis flowmeters mounted on five skids to handle crude oil being unloaded from tankers. Using the Coriolis flowmeters, terminal operators confidently move and distribute crude oil at high rates, while decreasing the size and weight of the metering skids. The five skids and 10 Coriolis flowmeters handle a total of 167,000 barrels of oil per hour. With Coriolis meters applied in this high-capacity crude environment, the terminal reliably and accurately tracks the crude entering the facility, with proper allocation of oil to local refineries.

The four-tube Coriolis

Coriolis flowmeter capacity can be increased by making the measuring tubes larger. However, larger measurement tubes result in bulky Coriolis devices which can be demanding to install due to the weight and required space.

Rather than upscale an existing two-tube Coriolis design for higher capacity, a patented four-tube design was used. Instead of two large measuring tubes, each flowmeter uses four smaller tubes.

Figure 2: Cross-section shows major elements of a Coriolis flowmeter. Courtesy: Endress+Hauser

Figure 2: Cross-section shows major elements of a Coriolis flowmeter. Courtesy: Endress+Hauser

By doing so, 68% of the pipe’s cross-sectional area can be used, allowing a more compact design than a two-tube system. Four-tube Coriolis meters are now available in sizes up to 16-in. with a capacity of 720,000 barrels per day and accuracy of 0.05% with repeatability of 0.025%.

Advantages of a four-tube Coriolis flowmeter over mechanical meters include:

  • Measurement is independent of density, viscosity, and flow profile
  • Provides both volume and mass flow rate
  • Typically handles higher temperature and pressure
  • Better turndown
  • No regular maintenance required
  • No upstream piping
  • Best basic accuracy of any oilfield meter
  • Patented Reynolds Number corrections
  • Measurement of density and other fluid quality parameters
  • Advanced diagnostics, process monitoring, and built-in verification.

With these advantages in mind, four-tube Coriolis flowmeters are the measurement technology of choice in midstream oil and gas and other demanding applications.

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Mark Thomas
Author Bio: Mark Thomas is the Oil and Gas Industry Manager for Endress+Hauser USA. Mark is responsible for the overall business development and growth of the company position related to the Oil and Gas Industry. Mark is a 2003 graduate of Texas Tech University with a BA and achieved his MBA in 2008.