Mastering Clay Formations: Tips for Drilling Success
Certified Drilling Fluid Engineer Ken Sechrist - DrilRite Chem.
Drilling through clay formations can feel like navigating a minefield. With so many variables in play, even seasoned drillers can face challenges if they aren’t properly prepared. Clay, as you likely know, isn’t a one-size-fits-all material. Lean clays, with their low plasticity, are generally straightforward to drill, break down, and remove. Fatty clays, on the other hand, are a different beast entirely—they’re sticky, plastic, prone to swelling when exposed to water, and far more difficult to manage.
A common misconception is that detergents alone can solve the sticking problem. While detergents help reduce the surface tension, they won’t stop fatty clays from absorbing water and swelling. That’s where inhibitors come in. The right amount of clay inhibitor is critical to prevent swelling, maintain the borehole’s integrity, and avoid a situation where your bore wall closes in- shrinking the annulus and potentially sticking your pipe. My advice? Don’t skimp on inhibitors. It’s far better to have them in your mix and not need them than to discover you’re in trouble too late to fix it.
Mud Management: The Key to Success in Clay
One of the most important factors in drilling clay is maintaining the proper drill or ream rate and ensuring you’re pumping enough mud to do the job effectively. The biggest mistake I see in the field is what we call “outrunning the mud.” This happens when the driller either moves too fast or pumps too little mud, failing to break down and remove cuttings properly.
Here’s a crucial fact: it takes four to five times more water to remove clay than it does to remove sand or silt. That means drilling in clay demands higher mud volume and slower progress. Many drillers try to save on mud by reducing GPM (gallons per minute), and in some soils, that approach works—but clay will quickly change your mind. If you want to keep GPM low, you have to slow down. If you want to go faster, you must pump more GPM. It’s a balancing act and getting it wrong can lead to problems that are both time-consuming and costly to fix.
A Case Study in Clay Drilling Missteps
Let me share an example I see all too often. I was recently called to a job site where the crew had drilled a 6.5-inch pilot hole and was stepping up to a 14-inch reamer. They were pumping 20 GPM and moving at a rate of 1 minute per rod. By the science, they should have been drilling at 3 minutes per rod to effectively clean the borehole. Not surprisingly, they created several inadvertent returns (IRs).
On the ream pass, they stuck with 20 GPM to save on mud but slowed down to 5 minutes per rod due to the larger hole size. Within a few rods, they lost returns. Why? Pumping such a small volume of mud and going that fast wasn’t enough to clean the hole. To fix the problem, we tripped back out, restored flow, and adjusted their strategy.
Using the DrilRite HDD app, we recalculated. At 20 GPM, they needed to slow to 13 minutes per rod, but to save time, we upped the GPM to 40, reducing the drill time to 6 minutes per rod. With this adjustment, we maintained full returns and achieved a properly cleaned hole. The lesson here is clear: drilling or reaming at the right rate and GPM isn’t just about following best practices—it’s about avoiding costly downtime and ensuring the job gets done right the first time.
Work Smarter, Not Harder
Proper drilling techniques in clay formations save time and resources in the long run. Trying to cut corners by reaming too fast or pumping too little mud often leads to additional passes or stuck pipe, which ends up costing more in mud and labor. Take the time to get it right, and you’ll see the payoff in more efficient operations and smoother completions.
Partner with DrilRite for Clay Success
At DrilRite Chemical, we’re here to support you with the additives, expertise, and customer service you need to tackle any bore, regardless of size or ground conditions. Our HDD app, available in your app store, can help you calculate the optimal drill or ream rate for your job. Whether you’re working in lean clay or battling through sticky, swelling fatty clay, we’ve got you covered.
If you’ve been struggling with clay bores, we hope this advice helps you find the solution. Let us know how we can assist on your next project. Thanks for reading, and happy drilling!
