Drilling an oil well is a complex process. But the basic idea is straightforward: you want to punch a hole through thousands of feet of rock to reach oil trapped underground. Here is how it works, step by step, in plain English.
Step 1: Get a Permit
Before anyone drills in Texas, they must file a permit application with the Texas Railroad Commission. The application includes the location of the well, the name of the operator, and the target formation. The commission reviews it to make sure the well won't threaten groundwater or nearby property. Once approved, drilling can begin.
Step 2: Prepare the Location
A flat piece of land called a drill site or pad is prepared. Trees and brush are cleared. A gravel or dirt surface is laid down for the rig. Tanks are brought in to hold water and drilling fluid. Access roads are built. This preparation can take a week or two.
Step 3: Set Up the Rig
A drilling rig is a massive machine. The tall tower you see is called a derrick. It can be 150 feet or taller. The derrick holds the drill pipe and gives workers room to add new sections of pipe as the hole gets deeper. The rig also has engines to power the drill and pumps to circulate fluid. A modern rig costs tens of thousands of dollars per day to operate.
Step 4: Drill the Hole
Drilling starts with a drill bit at the bottom of the drill pipe. Think of it like a giant corkscrew with teeth made of tungsten carbide or industrial diamonds. The bit spins and grinds through rock as the drill pipe is pushed down. The entire drill string can be several miles long when you add it all up. Drill string means all the pipe sections connected together from the rig floor to the bit at the bottom of the hole.
As the bit grinds through rock, drilling mud is pumped down through the inside of the pipe. Mud isn't just actual mud. It is a specially engineered fluid that can contain water, chemicals, and heavy minerals. The mud does several jobs at once: it cools the bit, it carries rock cuttings back up to the surface so the hole stays clear, and it creates pressure inside the well to prevent blowouts — sudden releases of oil, gas, or water.
Step 5: Case the Well
After drilling a section of the hole, drillers lower steel pipe into it. This pipe is called casing. Think of casing like a metal straw inside the hole. Once the casing is in place, cement is pumped down the pipe and up through the outside of it. The cement fills the space between the casing and the rock wall. When it hardens, it seals the well. This keeps freshwater aquifers — underground water sources — safely separated from the oil-bearing rock below. This step is required by the Railroad Commission for every well drilled in Texas.
Step 6: Drill Horizontally
Most modern wells in Texas are not drilled straight down. After reaching the target depth, drillers use a special tool called a mud motor to steer the drill bit sideways. The bit gradually curves until it is drilling horizontally through the target rock layer. A typical horizontal section is 5,000 to 10,000 feet long — nearly two miles. Drilling horizontally exposes the well to far more oil-bearing rock than drilling straight down would.
Step 7: Complete the Well
After drilling is finished, the rig moves off. A different crew comes in to complete the well. First, they perforate the casing. That means shooting small holes through the steel pipe and cement and into the rock. They use a device loaded with shaped explosive charges, called a perforating gun. The holes let oil and gas move from the rock into the well.
Step 8: Hydraulic Fracturing
For shale formations — tight rock that doesn't flow easily — perforation alone isn't enough. Hydraulic fracturing, or fracking, is used to crack the rock and create pathways for oil to flow. A fleet of high-pressure pumps forces water mixed with sand and chemicals down the well at enormous pressure. The pressure cracks the rock. The sand stays in the cracks and props them open so they don't close back up. This process is typically done in many stages along the horizontal section of the well. A modern Eagle Ford or Permian Basin well might have 40 to 60 fracking stages.
Step 9: The Well Starts Producing
After fracking, the well is allowed to flow. Oil, water, and gas come to the surface together. They are separated at a piece of equipment called a separator. The oil goes into tanks or a pipeline. The gas goes into a gas line. The water — called produced water — is usually re-injected into a disposal well deep underground. The Railroad Commission regulates all of this, from the first permit to the final plugging of the well when production ends.