Combinations of bentonite drilling fluids and a variety of additives are widely used here in North America and around the world. As bentonite drilling mud manufacturers, we spend a considerable amount of time each year conducting classes both in classrooms and at drill sites with contractors in order to educate them on proper use of drilling mud and additives. Issues generally discussed often include: preparing make-up water for the best yield of drilling products, knowing soil conditions, and matching these conditions with the proper drilling mud and additives. Classes also include the various types of bentonite drilling fluids and the various polymers and additives available, along with the proper application of each. In water-based drilling fluids, many of products used are NSF-certified and are environmentally safe.

In recent years a new issue has been increasingly cropping up: How and where can these drilling products be safely disposed of after the drilling project is complete? We are seeing federal, state, and local regulations becoming much more numerous and stringent each year, especially in populated areas. Over the years, drilling mud spoils have been left at the drill site to solidify on their own. Sometimes drill cuttings, soil, sawdust, concrete or lime have been added to speed up this process. Use of these products does not always prevent leaching of drill spoils into surrounding soils. With the coming of tougher regulations, these practices are not as acceptable as they once were.

The most economical way of dealing with leftover drill fluids at the completion of the drilling project is to make sure fluids are clean with low solids, and reuse them on the next site. Fluids can be stored in tanks or mud cleaning units and transported to the next well site.

When that is not practical, there are several disposal methods that can be used. Some of these include:

  • Flocculating the solids and removing the liquid
  • Land farming or other land applications
  • Transporting the drill spoils to a landfill
  • Solidification of the drill spoils for burial on site or transportation to a landfill

Flocculating the solids could require the use of a centrifuge. These have high start-up costs, which makes this method expensive. The water in the fluid could be skimmed off the top, leaving only the solids. This is a process that takes time, several days or even weeks to complete, which is also not practical in many cases.

Land farming involves removing the spoils from the drill site and spreading them over wide areas. This method requires approval by regulating agencies and by the landowner. There is considerable expense in transporting the spoils and in spreading over land areas. Many states approve of this type of disposal as long as the landowner agrees. Regulations may also have limits on the type of land where this method cannot be used, such as on cropland. It is important to note that, while drilling fluids can be deemed safe by the manufacturer, drilling spoils contain the unknown addition of the soil added at the jobsite.

Transporting the spoils to a landfill has it problems as well, because many landfills are not able to handle disposal of liquids and drill spoils may be banned by regulating agencies. In cases where regulations allow such disposal, they may require the material to pass a paint filter test. A paint filter test involves placing a sample of the material to be disposed over a filter to measure the amount of liquid passing through. If any liquid passes the filter, the material is unacceptable for the landfill.

Over the past few years, new products have been developed that will help to solidify drill spoils in a minimal amount of time and are being successfully used as an alternative to other methods mentioned above. Solidification of the drill spoils makes them much easier to dispose of either on site or in transportation to a waste facility. These types of products actually tie up the free water in the drill fluid so that it will not leach out in to surrounding soils. Solidification products include:

  • Bentonite-based material
  • Super absorbent polymer-based material referred to as SAPs
  • Combinations of bentonite and super absorbent polymers

Bentonite-based products are the most economical and the easiest to mix. These products do not require high dosages, although they do require higher solids than SAP products or bentonite/SAP blends. Bentonite-based solidification agents can be spread over the drill fluid, which is contained in a pit, by using a backhoe or similar type of equipment. Solidification of the drill spoils usually occurs in 24 to 36 hours. These types of products can solidify a number of types of liquid and they absorb 7.5 times their weight in water. They are environmentally safe.

SAP-based products require very low dosages, sometimes as low as .5 percent, and will solidify drill spoils much more rapidly than bentonite-based solidification products. They can also be mixed with a backhoe or excavator; however to achieve the lowest dosage, a high shear mixer is the best option. SAPs are the most expensive option, but they are also the fastest way to solidify drill spoils.

Bentonite/SAP blends give the contractor the advantages of both bentonite- and super absorbent polymer-based solidification agents, resulting in a fairly low dosage rate and more rapid solidification than a straight bentonite. The blend is less expensive that the straight SAP solidification product.

Solidification agents are a great answer to the serious problem of disposing of drill spoils. Three different blends offer contractors a choice of economy versus speed in solidification. These blends make it possible to leave the spoils onsite if allowed, or to transport the spoils to landfills or waste disposal sites if that is the required option.

If you have questions on the above information, please contact me through the National Driller, or contact your bentonite manufacturer or distributor.

Bob Oliver is regional manager for CETCO Drilling Products.