What does the drilling process really look like?
Written and Edited by Raj Gautham Viswaprabhakaran
What is Drilling?
Drilling is process of create a hole in the earth to reach the desired hydrocarbons (oil & natural gas) in the ground.
First Step – Prepare the Location
This process includes building roads for access to the site, clearing the area for pad construction, and creating necessary infrastructure for water and electrical needs. Next, the pilot Hole is dug representing the location of the main hole. After that the mouse hole is dug close to the main hole. The function of the mouse hole is to hold pieces of pipe and other equipment during the drilling process.
Second Step – Surface Drilling
A large hole (50 -80 ft. deep below the water table) is dug before actual drilling starts. Conductor casing is then cemented into place, stabilizing the ground around the drilling rig and effectively isolating the hole from private water wells. After this step, air drilling is used to drill the hole to a depth of approximately 100-200 feet below freshwater zone.
Third Step – Intermediate Drilling
A 2nd layer of steel casing (surface casing) is installed in the newly drilled hole inside conductor casing. Cement is then pumped through the surface casing and up along the sides of the well to provide a proper seal and completely isolate the hole from any water wells. The BOP (Blowout Preventer) is then installed. It serves as the major safety precaution in regards to shutting the well to prevent a blowout. Next, a small drilling assembly is passed through the surface casing and drills down to the natural gas/oil target area. The drilling method utilized in this step is with drilling mud. The drilling mud serves to lift the rock cuttings out of the hole, stabilize the hole, cool the drill bit, and control down head pressure.
MWD (Measurement While Drilling) Specialist
This person monitors the progress of the well during the actual drilling process from a technical standpoint. He uses electrical signals and other frequencies gather information to pin point the actual location of the drill bit. This is particularly helpful when the driller is in the bend/horizontal drilling stage and they need to drill in the right direction.
Fourth Step – Bend/Horizontal Drilling
A few hundred feet above the target area, the entire drill string is retracted to the top to adjust the drilling assembly to install a new drilling tool. This new tool allows for horizontal drilling – letting the driller to gradually turn the tool bit. The turn rate of the drill bit is approximately 10 degrees for every 100 ft. drilled until a desired lateral plane is reached. After this point, the horizontal drilling continues for designated lateral distance. After reaching the lateral distance, all equipment including drill string is once again retracted out of the hole and a smaller diameter casing (production casing) is installed throughout total length of the well and cemented in. The cement serves to create a seal so that formation fluids can only be produced through the production casing. Next, pressure testing occurs to check the integrity of the drilled hole. All in all, there are 7 layers of protection from the fluid flow area to the surrounding earth.
The major benefit of Horizontal/Directional Drilling is that it calls for fewer wells to be drilled while still allowing greater production since the horizontal portions of the hole are in greater contact of the target area.
The process of pulling out all the piping and other drilling equipment is referred to as tripping out. Before tripping out, derrick hands “mud up” or circulate the drill string and hole with fluid too maintain the hydrostatic pressure equilibrium. The situation is similar to putting a pencil in a water bottle. When the pencil is put inside, the water level increases along with the pressure. Similarly, when the pencil is removed, the water level decreases along with the pressure. Thus, to maintain the same level of pressure throughout the tripping out process, the drilling mud is pumped and removed as needed. To prevent the clogging of the hole with solid chunks of mud, the mud is put through shakers to separate the solid pieces out. Gas Separators and centrifuges all serve to purify the mud for the drilling process. The solid chunks of the mud are mixed with lime and loaded into trucks for disposal. The gas from the mud is sent through pipelines and flared out. The remaining “pure” mud is recycled back into the drill string when needed. The two major people in charge of the Mud processes are the Mud engineer and the Solids Control Specialist. The Mud Engineer takes samples of the mud, tests the chemical properties of it and makes sure of whether the mud is in a an ideal condition to be used in the drilling process. The Solids Control Specialist serves as the supervisor of the centrifuge and the mud processing facilities.