Now that most of us are drilling in the 21st century, cuttings disposal is starting to become a much more important issue than it was. In the not-too-distant past, most of us just left the cuttings in a pile on location for the customer to worry about. I remember one lady who asked what I was going to do with all that “stuff.” I told her that it was her dirt, and if I hauled it off, it would be like stealing. We were lucky if jobs were on a new construction lot – the landscapers would just spread it out.

Now, it’s getting to the point that more and more customers are specifying a clean location, which requires a little more planning on our part. When air-drilling, it’s not too hard to put a blooie line on the diverter, and somewhat contain the cuttings. Sometimes, though, if the well makes a lot of water, run-off is a concern. Most areas don’t want water with much turbidity entering the waterways. This sometimes is accomplished with straw-bale filters, or large settling tanks – it takes room and planning.

Cuttings disposal gets a little more interesting when mud drilling. First, you have to separate the cuttings from the mud. If you are using dug pits, the cuttings hopefully settle to the bottom. (The big ones, anyhow; the sand seldom settles out of good mud without mechanical help.) Then you either bury them, or dig them out and restore the location. This takes time, and often leaves more mess than before – plus most landfills won’t take wet cuttings, so you are going to have to handle them again. The easier way is to plan the job ahead of time with handling the cuttings in mind. A good solids-control system pretty much will produce dry cuttings, and if it is designed correctly, it will deposit them in a tank or trailer for later disposal. Landfills that won’t take drill mud and slop usually will take dry cuttings.

The offshore drilling industry has been hauling off and disposing of cutting for years. I remember in the early days offshore, on permanent platforms, the drillers often would just jet the cuttings overboard. This eventually created a huge pile of cuttings at the base of the platform. It didn’t seem to do much harm, so we thought, and out of sight, out of mind. It changed when jack-up rigs became common. The LeTourneau-style rigs had spud cans on the end of the legs, and it wasn’t too hard to jet the legs out of a pretty good-sized pile. Then came mat-supported jack-up rigs. Drillers found out the hard way that you couldn’t jack the mat off the ocean floor with hundreds of tons of cuttings holding it down. A friend of mine who was pushing a mat-supported jack-up in the Gulf of Mexico tried. He jacked until he had the main deck of the rig 4 feet under water before he gave up.

Operators reluctantly started hauling their cuttings to shore. What really convinced them was the increased use of oil-based mud. Oil-based mud uses diesel fuel or other petroleum products as its base, and it cannot be allowed to enter the environment. At first, drillers just boxed up their cuttings and shipped them in. They figured out that they were shipping in a fair amount of valuable drill mud, so cuttings’ washers and driers came onboard. This recycled the mud and cut shipping costs of sending in the waste.

Land rigs are starting to get on the bandwagon. As locations get smaller, and environmental laws get stricter, cuttings disposals’ day has come. The newer, closed-loop mud systems are perfectly set up for this trend. The shaker discharge can be easily directed for haul-off. On the more modern units, the desander underflow also is screened, saving a lot of mud, and producing a dry discharge.

In most active oilfield areas, there are companies that will haul off the cuttings, wash them and find a suitable use for them. In the case of oil-based mud, the cuttings first are washed in a solution of detergent, similar to dishwashing detergent; then they are washed with water to remove the detergent. Even in water-based mud, the cuttings are washed to remove drilling additives, and because a lot of good mud has a high pH, the cuttings are pH-neutralized before drying and disposal. For instance, in Florida where limestone is common, many drillers use the cuttings for road-building material. If the cuttings are mostly sand, a gravel pit or cement plant may take them.

Fortunately, with solids-control technology improving every day, cuttings disposal just becomes part of the job, with the side benefit of leaving the customer with a much cleaner location.
ND