What are the best practices for mitigating bit balling and bit plugging issues?

From a PDC bit design perspective: 1) Make sure there's CFD analysis on the bit you're buying; flow doesn't always go exactly where the nozzles are pointing. While it's pretty readily available these days the software costs around 3x CAD and It'll add a day to design time so there are commercial reasons not to do it. 2) Make sure that fluid gaps diverge as distance from centreline increases; a secondary/partial blade getting too close to a primary blade is asking for balling. 3) Is it balling tripping in or out? If the later, no face design feature is going to help. 4) Make sure cutters aren't buried in the blades; any cutting ribbon pushed off the non-cutting side of a cutter should go into fluid, not blade.

Bit balling is the sticking of cutting to the bit surface when drilling through gumbo, water reactive clay and shale formations with high CEC. How to plan to avoid or reduce bit balling 1. Select bit with maximum cutting structure projection also steel tooth bits are better than insert bits as the steel tooth have greater teeth intermesh. 2. High flow tube or extended nozzles aren't recommended and some jetting must be directed onto the bit cutting structure (tilted nozzles). For bigger sizes bits use center jet bit that flush all cutting more effectively. 3. Good hydraulics Good practice to have HSI more than 2.5 for better clean the bits. 4. Use drilling fluid additives such as PHPA and 3-4% glycol for WBM.

Fundamentally, bit balling is a function of the clay type being drilled. Weight on Bit (WOB) Rate of Penetration (ROP), Fluid flow (PP) and Mud properties and additives are all primary variables to consider. Bit design is important if you know it will happen ahead of time.

In my experience, the Bit Balled up caused by 1- Driling in clay minerals formations and sticky Argillaceous Limestone, Marl, Shale 2- Mud properties especially if used WBM 3- Bit design should have a wide slot and a high jet for cleaning through it 4- Recommended 5 blads 19mm for PDC bit

Best practices for mitigating bit balling and bit plugging issues involve optimizing drilling fluid properties, using anti-balling agents (Drilling detergent), adjusting weight on bit (WOB) and rotary speed, employing effective cutting removal mechanisms, and employing advanced drilling technologies to minimize the impact of sticky formations. Regular monitoring of drilling parameters and adapting strategies based on real-time conditions contribute to successful mitigation of bit balling and plugging challenges during drilling operations.

I totally agree with this point. If we are to avoid bit balling and possible stuck pipe situations, the drilling fluid quality is paramount.

- If ROP decreases with increased WOB, it could indicate bit balling. Lower WOB and clean the bit. - Higher RPM spins cuttings around the bit, aiding removal. - Higher flow rate provides more fluid to clean the bit and carry away cuttings. - Hydraulic Horsepower per Square Inch (HSI) should be above 2.5 for good bit cleaning. - Use mud additives like PHPA to prevent clay swelling and improve lubrication. - If you suspect bit balling, stop drilling and implement cleaning procedures like increasing RPM, pumping high-viscosity pills, or pulling off bottom.

Adjust the TFA of the bit to yield an HSI value to above 3 or more whenever possible. Once we had an ROP issue on RSS in WBM due to the TFA settings had to follow the RSS requirements. The formations were predominantly soft and sticky claystones with layers of loose sandstones. Initially we were running RSS on OBM and no issues, however when we switched to WBM, the ROP dropped from 80-100 m/hr to only 25-30 m/hr. We suspected the bit must have suffered micro balling during the course of the run. Then we switched to a steerable motor BHA (with WBM) as it gives more flexibility for TFA to yield HSI of above 3. The end result the ROP was back to where it was before (80-100 m/hr).

Plugged bit or plugged downhole equipment issue will require additional expensive tripping activity to clean the drilling tool at surface. One day, a mud motor was plugged by the sand content of drilling mud (freshwater) when drilling in Total Lost Condition. The sand content increased due to the water source was flooding, resulting sandy river water. Thus, solid content inside drilling mud is one of the controllable parameter to avoid string plugging. Mud engineer should be adaptive and aware to the weather that may influence the mud properties, especially for onshore drilling with a natural river as the water resource.

When drilling, two common problems are bit balling and bit plugging. Bit balling happens when sticky materials, like clay or mud, get stuck to the drill bit, making it less effective. Bit plugging, on the other hand, occurs when the drill bit gets jammed with cuttings, slowing down or stopping the drilling process. To avoid these issues, it's important to choose the right drilling fluid and add special substances for lubrication. Keeping the drill pressure and speed in the correct range helps, and taking breaks to clean the drill prevents problems. Modern drill types are less prone to these issues, and monitoring the drilling process in real-time helps catch and fix any problems quickly.