ESP Trailers: What They Do and When Oilfield Operators Use Them

A well comes in after a frac, and the operator needs a lot of fluid out of the ground fast. A pump jack can only move so much. Here is a plain-English look at ESP trailers oilfield operators use, what they do, what’s on one, and when they make sense.

An ESP trailer is a mobile power and control package for an electric submersible pump. You see them on oilfield sites all over the Bakken and the Permian.

What ESP Trailers Do in the Oilfield

A pump jack works in two strokes. On the up stroke, it brings oil up. On the down stroke, it goes back down to get more. Half the time, it’s just resetting.

An electric submersible pump runs all the time. The flow is constant. Charlie Handley, a project manager at DSI who builds these trailers, puts it plainly: you get twice as much production, and probably more. “You might get three times as much as a typical pumping unit would produce.”

That is his field estimate from years of building these, not a promise for every well. But it explains why operators reach for an ESP trailer.

When operators use an ESP trailer in the oilfield

Charlie says it’s less about the well and more about the production the operator wants.

Most operators put an ESP on for initial production. The goal is to get a large amount of oil out early.

ESPs also help after fracking. A fresh frac leaves heavy water sitting in the well. Charlie’s example: a well putting out 600 barrels of oil might also bring up 150 barrels of water. An ESP gets that mix out faster, so more oil comes with it.

What’s on the trailer

The trailer is the power and control side of the system. The pump itself is thousands of feet down the hole. Here’s the basic path on the ESP trailers oilfield operators order:

• Power comes in at 480 volts and goes to a variable speed drive. The drive sets the speed of the pump.
• From the drive, the power goes to a transformer. The transformer steps it up to about 3,200 volts.
• A filter cleans up the power quality, and a vent box handles the medium-voltage connection.

Why 3,200 volts at the top? Because the cable runs down about 9,000 feet, and some voltage is lost on the way. By the time power reaches the motor, it’s closer to 2,300 volts, which is what the pump runs on.

How DSI builds ESP trailers for the oilfield

Here’s how the work splits up. The customer’s engineers decide what the trailer needs. DSI builds to that spec.

DSI’s fabrication shop starts with the bare bones: brackets for a 400-amp disconnect, brackets for the boxes, and steel plating under the trailer. The plating matters. Without it, heavy equipment is bolted into wood, and that wears out over time.

From there, DSI’s electricians do the wiring. Each trailer gets a disconnect on the drive, so there’s a clear point to shut power off. It also gets an interface box between the trailer and the well’s controls. Whatever limits and safeties the operator has at the wellhead can be wired into that box and run up to the controller.

On site, DSI brings the trailer in, hooks up power, hooks up controls, and connects it at the wellhead. Then the operator takes over.

Because it’s one team doing the fabrication and the electrical, the work stays in one place from the first bracket to the last wire. That’s how the ESP trailers oilfield operators rely on get built, start to finish.

What it takes to get one running in the field

Weather is the biggest challenge. Cables have to come out of the ground, so crews excavate. Sometimes those holes fill with water. You can’t pump that water into a neighbor’s field, so crews work with the producer’s ditch system to move it. In winter, equipment is set on ice and snow. Sometimes the crew has to go back in spring and straighten things out as the ground settles.

Charlie says it’s unforgiving country. Crews plan for it.

Built to code, and checked

Every DSI installation is inspected by a state electrical inspector. Charlie shared that one inspector told his boss he doesn’t have to worry about DSI’s work. “When you’re noticed by the state inspector, you know you’re doing things right,” Charlie said.

Standards matter here. Charlie described one customer that wouldn’t buy leased trailers from another company because they didn’t meet its standards or state electrical standards.

Charlie calls the work “an art that’s hidden.” Open up the panels and they look beautiful, but you don’t see that from the outside.

What to take away

An ESP trailer is a power and control package for a pump that can move a lot more fluid than a pump jack. Operators choose them for strong early production and to clear heavy water after a frac. The right setup depends on the well, and the operator’s engineers decide that. What the trailer needs to be is well built, wired right, and ready for the weather.

If you’re planning an ESP build and want one team handling the fabrication and the electrical, we’d be glad to talk it through. Learn how DSI builds electrical and fabrication together →

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