WorldWide Drilling Resource

Do Drill Cuttings and Water Make a Good Drilling Fluid? by John Christ J.C.’s Drilling Consultant To be blunt, NO! The formation is always changing, so your fluid will be also. What kind of cuttings do you make in sand, gravel, and rock? A lot of fine grains with porosity. Which means you will have water loss to the formation, leading to poor borehole stability. Really, the biggest reason is you can’t control or predict the properties of this kind of fluid. With a high-quality drilling fluid, you can do API (American Petroleum Institute) testing of your fluids. This will tell you the effectiveness of your fluid. It will also be another indicator of what’s going on down hole. Drilling fluids help you to stay out of trouble. One thing I can tell you, trouble always costs time and money! You can have the best drilling fluid, but if your drilling techniques are poor, then maybe water and drill cuttings are best. If anything, you will have an excuse for why things went bad! The very first drilling fluid as I have been told was having cows run through a patch of water to stir up the mud, then this mixture was poured down the hole. Well, there have been many advancements from then. Keep in mind, we are only talking about industrial applications in my arti- cles, so oil-based muds won’t be dis- cussed. There are three basic types of drilling fluids: water-based bentonite, polymer, and air. Air? Yes, air! If used properly it can accomplish some objec- tives of a drilling fluid, so therefore it’s a drilling fluid. Now this isn’t rocket sci- ence. You have the knowledge of your territory or can access logs of wel ls drilled nearby. Maybe a test hole was drilled? This kind of information makes it easier to come up with a drilling fluid plan. Sometimes things aren’t as ex- pected and your drilling fluid may need to be tweaked. Okay, what should drilling fluid do? Different applications will require differ- ent results. Basical ly, a dri l l ing fluid needs to get the cuttings off the bit and out of the hole to the surface; provide borehole stability to keep it from caving in; control the subsurface pressures dur- ing the drilling process; cool and lubri- cate the bit and dri l l string; prevent excessive fluid loss to the formation in permeable zones; transmit pertinent in- formation of the formation being drilled to the surface; and finally, to provide pro- tection to the zone providing production. Of course, several variables will dictate the properties your drilling fluid will re- quire. There is no universal drilling fluid, even though bentonite is thought to be the answer to just about everything. There are additives to address the differ- ent formation issues. Again, drilling fluids are only a part of the equation, poor drilling habits such as swabbing the hole rapidly with the pumping equipment turned on can lead to cave-in and hole instability. Drilling fluids, just like every- Christ cont’d on page 52. 38 JUNE 2017 WorldWide Drilling Resource ®