For whatever your measurement job, there are a slew of meters available out there. In the oil field, knowing whether you need a turbine, Coriolis, vortex, positive displacement, ultrasonic, magnetic or other type of meter depends on really understanding your process and what’s going through your meter—planned or unplanned.
But perhaps more important than that is just understanding that you actually need a meter in the first place. At Marathon Oil, they found that the impact of inaccurate allocation measurements at their dynamic tanks amounted to close to $15 million a year.
“We were very reliant on a truck driver to come out to a facility, draw product from the tanks, and tell us how much he was taking,” explains Kevin McDaniel, SCADA coordinator for Marathon. “We had no way of challenging them on the volume of product they were putting on the truck.”
At the Well Site Automation for Unconventional Oil & Gas conference this week in Houston, McDaniel explained the types of inaccuracy issues they were seeing at Marathon, their impact, and how they tackled them with metering solutions. “Measurement is all about planning and designing upfront. If you don’t have a good plan, I guarantee you’re going to fail with that meter,” he says, adding that it’s important not only to know what kind of physical design makes the most sense, but what you want to do with the data you get from the meter.
McDaniel detailed a number of inaccuracy issues Marathon has seen in its operations—key among those being that meters get out of spec. “Probably the No. 1 issue I’ve seen is meters that don’t get proven often enough,” he says. “Make sure you have a routine proving process for whatever your operational scenario is. It’s not the same for every meter. A lot of it depends on how much volume we’re putting through that meter.”
There are also issues with following standard procedures, McDaniel says. “There are a whole lot of people talking about API and MPMS, but don’t assume everyone knows and follows API and company procedures,” he says. Be sure to communicate and train your people on the procedures, check and repeat. “They’re there for a reason.”
There are several issues that might seem small for any given incident, but can really add up over time, like discrepancies in S&W (solids and water) percentages, temperature readings, volume calculations and density measurements.
“Pressure is another one that people often overlook,” McDaniel says. Although it doesn’t have a huge impact on volume calculations, it can have an impact over time, he adds. “You’re not talking about millions of dollars today, but you’re talking about millions of dollars over time. That’s how they impact you, is over time.”
Certainly, with its dynamic tanks, Marathon was facing such measurement discrepancies. For example, depending on when and how the sample was taken, McDaniel says, temperature could be off by 10 degrees and S&W could be off by 0.5 percent. In a 190-barrel load, the measurement could be off by as much as 6.8 barrels. Based on 100 loads a day, at $60/barrel, that meant money lost by the oil company of $14.8 million a year.
Static tanks stabilize tank volume and enable measurement per API, but there’s still room for error. The impact is still considerable at $5.33 million a year.
Marathon has implemented a truck LACT (lease automatic custody transfer) system that has taken that risk down to just $440,000 a year. Although they won’t necessarily install a LACT at every well, it has become a viable solution in some locations, McDaniel says.
It’s certainly easy to justify, based on the results. “The cost of the project was under three-quarters of a million dollars, but the value was huge,” McDaniel says. Marathon has eliminated risk and losses to the tune of $19.7 million a year.
In December alone, 44 LACTs produced 7,237 tickets representing 1.2 million barrels of oil. The project has simplified truck driver interaction, eliminated manual entry of tickets, and reduced the manpower needed to deal with ticket entry and correction (they were previously entering 3,000+ manual tickets per month and growing fast).
And, of course, measurement accuracies have improved significantly. “I can tell you down to a hundredth of a barrel because that’s how accurate our system is now,” McDaniel says. “And the truck driver’s interaction with the system is greatly simplified. We still have them doing an S&W sample, so there’s still a vulnerability to our measurements. However, I do at least have a means of checking that.”
Once Marathon got a good system in place for its oil transfer system, they even began looking at what such a system could do for water transfer. “We have to pay for water to be taken away,” McDaniel explains. Although it’s not a huge expense, they decided to do a pilot program to see what would come of it, so they took the same concept and put it on one meter at one facility.
What they found was a discrepancy of eight to 10 barrels in one load. Granted, that’s only a difference of $25 per load, so not a big deal in itself. But over the course of a year, and extrapolated out over other sites, it meant a difference of $1.5 million a year. “It justifies itself,” McDaniel says. “You do one pilot to try it out, and the next thing you know you’re doing it enterprise-wide.”
As McDaniel asserts, “I guarantee, if you install a meter, you’ll find a value to get out of that meter.” McDaniel says.