First Movers in Eco-Drilling: What to Do with Those Pesky Drill Cuttings

South of the brushy desert area of Pecos, Texas, is a test site for a project to turn once-detested drill cuttings into eco-friendly road surfaces … and more.

Faced with historically difficult waste disposal challenges, researchers are now eager to make drill cuttings into road surfaces and construction materials, and even re-inject them back into the earth safely.

So far, so good, says project director David Burnett, an advisor with Texas A&M University's Department of Engineering. The road surface does not "disappear," like the roll-up durable mats did in the same pilot project, but they made an acceptable surface that goes back to the earth without any environmental consequences when the need for the road is done. Key advantages of using drill cuttings are that the road base material is much more durable than the typical caliche being used in lease roads in South Texas and that the drill cutting material could be installed by a four man crew utilizing road building equipment.

"I really like the concept of the road mats and the drill cuttings base roads", said Paula Maywald, restoration ecologist for Environmental Land Steward Consults in San Antonio, Texas. "Many of my landowner clients require remediation of well pads and lease roads after drilling. And the operator's remediation costs are much less, so they recover much of their investment in the removable roads and drill cuttings roads."

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Meanwhile, Scott Environmental Services Inc. (SESI) of Longview, Texas, also participated successfully in a pilot project at the Pecos test site. SESI makes its life's work finding earth-friendly ways to deal with drill cuttings and other waste from hydrocarbon production. The company developed a patented service called Firmus that takes different kinds of drilling wastes – including freshwater mud and cuttings, oil-based cuttings and some saltwater mud and cuttings – and treats them with a solidification and stabilization technology so the "muck" can be transformed into construction material. Among the finished construction products are lease roads, drilling pads, compressor station pads, tank battery berms and other load-bearing structures.

"We firmly believe that our treatment and reuse processes offers clients transparent and sustainable alternatives for handling drill cuttings," said SESI's President Blake Scott.

Productively "Wasteful" Building

The Scott Environmental Services process is typically broken down into two phases. The first involves reducing the plasticity of drilling mud and cuttings, as well as drying and preparing them for reuse. The resulting material is then transported to the construction site, where there's further stabilization and shaping of the material to meet the desired loads that it will bear.

The process provides a double-whammy environmentally, because it takes waste that is normally disposed of and recycles the material for the creation of structures that would need new raw materials to build. The process thus reduces the overall environmental footprint, and mitigates customers' future liability for complying with often-challenging waste disposal regulations.

From previous experience, "we have learned that [Firmus] is most effective when a customer has high contaminant levels, transports the waste offsite for disposal and/or has multiple wells to drill in a given area," according to a background paper by Scott Environmental Services.

The company has another proprietary service called Duro, which uses the same raw waste materials as the Firmus process and treats them for use as load-bearing structures for setting tanks in hydraulic fracturing or other equipment during or after completion.

This is typically accomplished by solidifying and stabilizing the mud and cuttings within the confined pit area, the company noted. The Duro service is similar to Firmus in that it prepares the mud and cuttings for use and then further stabilizes them to support loads, but the Duro process also immobilizes the contaminants to reduce their mobility in the environment. This process is most effective when the customer's waste has high contaminant levels and/or is being transported offsite for disposal, the company said.

A Shot to Mother Earth?

Cut the action from the desert region of Pecos, Texas to the rough-and-tumble scenery of western Colorado's Piceance field. In an effort to reduce the environmental footprint of drilling operations, ExxonMobil tried Colorado's first subsurface injection of drill cuttings back into the earth, with a lost-circulation zone in the Wasatch G formation as the injection zone.

During the first phase of the pilot project, the operator injected water-based mud and drill cuttings from four wells into a fifth well to test technical feasibility and the formation's response to the injection. The fifth well was suspended at the intermediate casing and perforated in the Wasatch G formation. More than 40,000 barrels of fluid were injected in vacuum conditions, with confirmed confinement to the target zone.

When phase one proved successful, the operator moved into phase two, which involved assessing what was required logistically to transport cuttings from multiple drilling locations to a central processing and injection site. The pilot project processed cuttings from three active rigs and demonstrated the capability to process cuttings from more than six rigs.

All in all, these projects are proving the old axiom "waste not, want not" to be true.