How things have changed over the last 35 years in the drilling fluids industry!
As with most in my profession, my career started with a 10-year stint in the oil and gas side of our business, where I was exposed to a number of different types of drilling fluids. The wide range of drilling fluids used on the oilfield were developed to solve specific problems with drilling in difficult geologic conditions. With the demise of the oilfield in the 1980s, I was drawn into the small drill industry where the drilling fluids were pretty generic, relying mainly on extended bentonite and little else.
Slowly, the small vertical drill industry began to evolve with the need for more efficient drilling techniques and equipment. With that came a great demand for training not only on the equipment side but also to understand drilling fluids on a much higher scale. Now insert the explosive growth of the horizontal directional drilling market (HDD) into the drilling fluids industry and a new evolution began. This evolution began with some pretty generic fluids with extended bentonite and a few polymers, but all in all, was fairly basic. As bore lengths and diameters grew, it became evident the drilling fluids had to have some very specific properties to meet these new demands to help the industry move forward. While we all have our eye on the goal of longer and larger bores and new and better drilling fluids to reach that end, we as an industry are also looking in another direction — behind us, at the spent drilling fluids. We know as an industry we have to be proactive in dealing with the spent drilling fluids in order to sell our products into the future.
Solids Control Equipment
Steps are already being taken by the industry to minimize the amount of spent fluids generated, with a noticeable increase in the use of solids control equipment being the most evident. Cleaning and reusing the fluid whenever practical makes good sense, especially in areas where drought is limiting the availability of good makeup water. But unlike the cartoon world, that does not mean you can continue to use a drilling fluid forever. Eventually, the fluid does need to be disposed of and that is becoming more of a challenge every day. Education plays a critical role in getting regulations that are specific to the HDD industry and keeps us from being lumped into oilfield and industrial slurry disposal. Simply trying to identify what the disposal regulations are is sometimes a real chore.
Given the drilling fluids folks put these fluids together, it makes a bit of sense to look to us to help with disposal solutions. (You noticed I used the word “solutions” and not “solution” as one size does not fit all). As I noted earlier, drilling fluids systems are put together in a variety of ways to tackle different formations and, thus, may need to be treated differently when it comes to disposal. An example would be a dispersed fluid system that (using thinners and detergents) does not clean very well in a solids control system, allowing ultra-fine solids to build up making timely disposal a necessity. These systems are effective in some formations and relatively inexpensive to build but may limit our ability to minimize our total volume by solids control equipment and, thus, drive our disposal costs up in the end.
Another example would be an inhibited mud system (using clay inhibiting polymers) to shield the clay solids and allow the cleaning system to remove more of the clay, allowing the slurry to have a longer useful life thus minimizing the total slurry volume that must be disposed of. Just some food for thought when choosing the fluid system not only for performance during the drilling process, but for disposal, as well.
We just visited a bit of what is going on in the way of mechanical minimization of spent fluids, but when it comes time to get rid of the fluids, what is new? Here are a couple of things that are getting some attention at this time and, as noted above, they are not a one-size-fits-all scenario. First, let’s take the minimization of volume to an additional level by dewatering the spent slurry, which reduces the volume but also creates good quality make-up water as a byproduct. While the use of flocculants have been used for years, they have had some real limitations that make them difficult to deal with and less desirable to use “as long as I can dump it cheaper.” The main problem encountered was the amount of solids where the flocculants were effective was usually greater than 5 percent or about 9 lbs/gal mud. To achieve clear water usually required dilution of the spent fluid using the recovered water, pH adjustment, patience and something just short of a chemistry degree and thus was time consuming and costly. The industry now has some products that work well on spent slurries up to 10 lbs /gal (greater than 30 percent solids) without dilution or ph adjustment resulting in recovery of 30 percent of good usable makeup water. Again, how the fluid is put together will have a big effect on how we can take it apart.
Industry attention is also being drawn to a time honored tradition of solidification. In most cases, a solid material is much easier and less expensive to dispose of than a liquid so solidification starts to look pretty good in some cases. Solidification can take on many faces, depending on the location you are working. For example, if you are in Iowa, corn cobs may be there for the taking where sawdust may be prevalent near a sawmill or fly ash from the power plant; however, keep in mind if you are not disposing on the jobsite, what comes in must go out and bulking becomes a very real cost. Also, keep an eye on what the requirements of the disposal facility are with regard to pH, leach ability etc., while the drilling fluid may be benign, the solidification agent may not. We don’t want something that haunts us later in life.
Industry attention is being given to maximizing the efficiency of the solidification agent with the use of polymer blends and specialty equipment that simply haven’t been thought to be cost-effective until now. While the costs of the products should not be ignored, they need to be examined in the context of overall performance and total disposal costs, not just their purchase price. Currently, we see a couple of spent fluid types that must be dealt with. The first is a spent drilling fluid that is still flowable but may weigh as much as 11 lbs/gal. The other is the discharge from the solids cleaning equipment that is no longer flowable but still has free liquid and, as such, still is considered a liquid for disposal purposes. As long as the fluid can be pumped and these high efficiency solidification materials can blended thoroughly, addition rates of 2 percent can be achieved virtually, eliminating the bulking problems associated with some of the materials noted above. With the solids control system discharge slurries being non-flowable, similar results can be obtained with the use of a pug mill; however, simple mixing with a backhoe is also showing very good results at greater than 5 percent addition rates.
Again, just as the industry looks for solutions in new drilling fluids to drill tough formations, it is also taking the spent fluid disposal to a new level to offer predictable long-term solutions for disposal to allow us to work into the future.
Stewart Krause is sales manager at Wyo-Ben Inc., headquartered in Billings, Mont.