Exxon Mobil’s in-house lightweight proppant is “seeing wide use across the Permian Basin” as the company scales it up, a company engineer said last week at the Unconventional Resources Technology Conference in Houston.

The proppant is made with petroleum coke (petcoke), a low-value product of the refining process. It's a “viable low-cost lightweight proppant option for use in our uncon wells,” said Matt Spiecker, a research engineer in Exxon's technology and engineering unit. Among the advantages:

  • It increases conductive frac area and improves production, showing a gain of 7% to 18% in comparison tests;
  • It’s been compatible with all types of fluids in lab tests and feasibility trials; and
  • It can be safely transported and handled on location.

After testing in “tens of wells” last year, “the idea is to get to hundreds more wells throughout this year and into next year and the years to come as we're able to scale up our supply,” Spiecker said.

Exxon makes use of the supply chain from its downstream and upstream businesses to do so.

"We've used the technology capabilities of both our downstream and upstream businesses to help build our supply, build an understanding of this material as a proppant and use the competitive advantage to be able to take things from our refineries using our supply chains and put them into our wells and go downhole and ideally make good value out of this material that we're using.”

The pilot was conducted on around 50 Permian wells—mostly in the Delaware and northern Midland basins, or areas with higher Exxon Mobil working interests.

The key benefit is the lower density, Spiecker said.

“It’s about 60% the density of sand, which makes it more buoyant than sand would be in the fluids that we’re pumping, which is primarily produced water or recycled produced water,” he said. “It flows a lot easier than sand for the most part.”

Exxon tested the petcoke proppant for flow, strength, conductivity and more at its lab in Friendswood, Texas, Spiecker said. Physically, it’s a black sand.

“We did some additional tests outside of that to look at things like leaching, how does it behave in the presence of hydrocarbons, which you typically wouldn’t test necessarily with sand,” he said. “It’s almost completely inert to almost all conditions. It has sufficient strength to withstand the expected closure stresses.”

The first samples came out of the Imperial Oil refinery in Sarnia, Ontario, in Canada. (Exxon Mobil owns most of Imperial at 69.6%.) Then came the scale-up, supported by the resources of a giant multinational energy company.

The petcoke from Sarnia moved to an offsite sieving facility to remove the big and small chunks, which were sold to third parties. Then about 50 tons of material came by train to the Midland Basin in the Permian for field trials.

Josh Brown, an Exxon drilling fluids engineer, said the petcoke proppant outperformed the sand as it got farther from the well, as expected from the lab results. Also, the results were sustained over time.

After the successful results, Spiecker said, Exxon needed more rail cars.

“We started off with a series of hundreds of sand cars because they were readily available in the early 2020s” when the work began, he said. “We have since increased our rail car supply to be able to put material into multiple storage locations within the basin for all of our well operations that are under way now.”

Spiecker said Exxon is still learning how to make the most of the new proppant.

“We believe that it's best used in a place where there's room for that advantage to be observed or taken advantage of,” he said. “In a case where we've got pretty good spacing between wells, our addition of lightweight propping in that completion mix helps fill in the space better. It allows us to draw more producible hydrocarbons from that well in which we pumped it.”

Spiecker declined to give details on the proppant mixes Exxon is using. He did say the primary cost driver of the petcoke proppant is transportation.

“It’s not coming from just down the street like all of our regional sand or local sand,” he said. “We’re beholden to the rail for most of the material at this point. But overall, what we’re looking to do is deploy an economically thumbs-up good value. We're doing that by using an amount of material in our fracs that will ideally generate enough production uplift that we’re ultimately increasing value total for the corporation.”

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