For Drilling Jobs, Preparation and Planning Prevent Poor Performance
That statement was mentioned to me often by my sales mentor, Bob Mielke, as we both worked for Baroid IDP early in my career. He learned that phrase from his time in the military.
Bob was stationed in Germany during the Cold War as our military stood ready for an attack that they thought might come at any moment. The military called it the five “P’s”: Proper Planning Prevents Poor Performance. The concept is very simple, and it is just as applicable to drilling as it is to the military.
In my travel to drilling sites around the world, I often see poor planning followed by poor performance. No one sets out with the goal of poor performance in mind; it just happens. Asking the right questions and anticipating potential problems helps drillers avoid the pitfalls that lead to poor performance.
Begin by asking the important questions, such as:
- What manmade obstructions might be encountered during setup?
- What manmade subsurface obstruction might be encountered during drilling?
- At what depth is the drill expected to encounter water or water producing formation?
- What are the different types of geological formations from surface to total depth?
- What geologies could the rig potentially encounter that will be reactive or nonreactive?
These five essential questions will properly plan a drilling project for the best results possible.
As they say, proper planning prevents poor performance.
Before we can drill down, we need to know what is up above. That phrase might sound like a children’s riddle (“before we can go down, we must look up”), but it is good advice. What utilities or obstructions are overhead? What substructures or building code right-of-way might interfere with the installation of the borehole?
A few years ago in northeast Ohio, I arrived at a jobsite 10 minutes after a top head rig raised its derrick into a 1,000-volt residential power line. This action knocked the operator off the drill platform, severely injuring him. It also wreaked havoc with the electrical components on the rig and set the rear tires on fire. Was this action dumb luck or poor planning?
Before the start of a new job, it should be a habit to walk the off-road path that the rig will travel. Next, a driller should stand exactly where the borehole is to be drilled. This gives the driller time to look for obstructions and possible points of danger. The 15 minutes the driller mentioned above saved by skipping the pre-drill walk was all lost when it took six weeks to fix the rig. Consult your local and state regulations for proper right-of-way setbacks and minimum distance of setup near power lines.
Once the sky is clear, it is time to start looking at the surface. Jobsite soil type and structure is a great place to start. If the jobsite has a porous soil, then the potential for rig destabilization and blowouts will increase. A jobsite with a fine, permeable soil type will be more stable, but the chance to encounter sticky clay and standing water increases. Rig stability is critical to drill a straight and gauge hole.
Drilling beyond the topsoil is where the real mystery starts. Utility locators can help solve these mysteries. It is a matter of life and death to contact utility locators to detect gas lines, electric lines, communication lines and sewer lines. Dangers may lurk beneath a seemingly benign open field.
In 2006, for example, a 27-year-old man struck a high-pressure gas line just 4 feet below the surface in the middle of a cornfield. The explosion killed him and left a 60-foot crater in the ground. The high-pressure gas line pumped gas from Texas to Michigan.
Be sure to use 811, the designated call-before-you-dig number for the United States. The 811 service will directly connect you with a local call center that can schedule a locating company. Look for it online at www.call811.com.
Sadly, locating companies can only locate known utilities. In my career, I have watched drillers encounter old cement septic tanks, basements, railroad boxcars and a forgotten gravesite at a Huntsville, Texas, prison. All of these subsurface obstructions have different characteristics that do not become evident until drilling begins.
A company drilling in northwest Indiana once encountered an obstruction that seemed to drill like steel. The bit cut through the hard surface eight minutes later and the drilling team experienced a complete loss of drilling fluid. The driller was able to lower the drill bit another 8 feet without resistance before hitting a similar steel-like formation. Later in the day, they learned from a city-planning official that the drill site had been used as a railroad junkyard 75 years earlier. The lesson the team learned that day was not how hard it is to drill through an old boxcar but how difficult it is to trip rods and bit out of two sections of punctured steel.
Subsurface surprises are very common with geothermal drilling in inner cities and urban areas. It is advisable to take the first 20 feet of drilling very slowly, increasing speed only once stable ground is located. The last ice age and significant natural disturbance ended about 10,000 years ago, so easily drilled ground that looks like it was disturbed was most likely disrupted by man.
Reclaimed jobsites drill easier than compact undisturbed ground. The ground will seem to have more porosity and drilling fluids will lose return easier. Unfortunately, there is no 811 number to call to learn about lost substructures. Your best bet is to talk with local residents before drilling. People are your best resource for local history and their input can help you prepare for the use of surfacing casing or even relocating the drill site to an undisturbed area.
Perhaps the hardest lesson to learn on urban jobsites is when it might be more profitable to turn down a project, rather than bidding it with the hope of ideal conditions.
Now that we have looked up and down 20 feet, it is time to consider the actual ground formations or lithology that may be encountered when completing a hole. When I train new drillers or interns, I like to conduct our first lesson at the bottom of a rock quarry. I ask the students to look at the ground and tell me what they see. The obvious replies are dirt, rocks and haul trucks.
Next, I ask the new drillers to consider the sidewalls of the quarry and tell me what they see. The responses are different layers of sand, gravel, rocks, voids and some flowing water followed by vastly changing variations of the same formations in different order for hundreds of feet. We then discuss drilling a 100-foot hole in one spot and then moving 15 feet and drilling the same hole. The idea is to understand how quickly ground formations change.
I designed the rock quarry lesson after working with Ortman Drilling during the first phase of the Ball State University geothermal project in Muncie, Ind. Ortman Drilling, along with their partners, drilled the first 600 holes of south field phase one. The area was laid out in a grid with holes every 15 feet on center.
Drilling a hole every 15 feet allowed the drillers of the south field to experience an unusual loss zone that would pop up every few holes without warning when the driller reached a depth of about 100 feet. A rig could drill 10 holes straight north without hitting the zone and then move over 15 feet to the west and encounter total fluid loss. We solved the unpredictable loss circulation problem by preparing a pre-mixed pill of different loss circulation material and only pumping it when needed.
The first phase of the Ball State project taught those of us involved many lessons, including the importance of proper logging of a test hole and the importance of consulting past drilling logs. Ortman Drilling had proven their ability to finish projects on time with more than 80 years of drilling experience in Indiana. While not every company has 80 years of experience from which to draw, they can obtain useful data by evaluating drilling logs from the area in question.
In the United States, there are many resources available to help drillers understand an area where they are about to drill. Government agencies such as the Water Bureau, Department of Natural Resources and the Department of Environmental Quality can provide water well drilling and geotechnical logs. These records may go back many decades and can be an excellent starting reference. The United States Geological Survey is another valuable resource for technical data from around the country and the world.
Several questions need to be answered once a drilling log is selected. First, determine the depth to water and what type of aquifers will be encountered. It doesn’t matter whether the drilled hole is considered a water well or borehole. Every precaution necessary should be taken to protect the groundwater intersected while drilling.
Three steps can be taken to protect groundwater production zones and maintain good borehole stability:
- Use appropriate drilling methods
- Use NSF/ANSI Standard 60 approved drilling fluids
- Maintain good properties for drilling fluids
Proper drilling methods can maintain good borehole stability in porous areas that produce water. Having the ability to use various drilling methods such as mud rotary, air rotary or reverse circulation is invaluable. It is like pulling the proper tool out of your toolbox to install a screw. A hammer will get the job done, but how much damage will be caused?
NSF/ANSI Standard 60 approved drilling fluids are recommended for use in potable water zones. The NSF/ANSI Standard 60 designation means that the product will not create an impact on drinking water if used to drill a water production zone. Although these approved products are designed to not have an impact on water quality, it is not a good drilling practice to leave large amounts of drill fluid in the water production zone. Therefore, a well-maintained drilling fluid with low solids content and a low filtrate is the best way to drill in a water production zone.
Low solids content and filtrate can be monitored using a mud test kit. Ideal solids content is anything below 8.8 pounds per gallon, and a reasonable filtrate is anything below 15 milliliters over 30 minutes in a full area filter press. When the three steps are used, it is easy to prevent contamination of the aquifer and maintain stability when drilling through a water producing formation.
The drill log can also tell drillers what other problematic ground formations might be expected. The rest of the log can be categorized into two types of formations: reactive and non-reactive. A good practice is to highlight the reactive zones and note at what depth they will be encountered. Then a driller can prepare for those zones by mixing an inhibitive polymer, such as EZ MUD Gold, for a reactive clay or plan for a drilling method change before encountering several hundred feet of rock.
Before every water well job my father would say, “Well drilling is the only job that starts from the top.” In order to be successful, we need to focus on the unknowns.
Drilling is 80 percent knowledge and 20 percent luck. That 20 percent fluctuates between good and bad luck. Good luck happens when a driller can drill 100 feet with just water and set casing all the way to the bottom. Bad luck happens when a driller encounters the unexpected, like a buried junkyard full of old boxcars.
Total success is achieved when all given information can be answered before the first turn of the bit, eliminating luck altogether.
Brock Yordy is product manager and drill trainer for GEFCO, an Astec Industries Company.