Fracking, or hydraulic fracturing, is a process used to create fractures in underground rock formations to allow trapped oil or natural gas to flow more easily to a well.
The process occurs after a well has been drilled and steel pipe (casing) has been inserted in the well bore. This casing provides structural integrity and isolates different geological zones. Once the casing is in place, the next critical steps involve preparing the well specifically for fracturing the target zone.
Key Steps in Fracking an Oil Well
Fracking is a multi-step process that takes place deep underground. Here's a breakdown:
1. Drilling and Casing the Well
First, a wellbore is drilled down to the geological formation containing the oil or gas. Steel pipe (casing) is then inserted in the well bore. This casing is typically cemented in place to prevent fluid migration between layers.
2. Perforating the Casing
Before fracking fluid can reach the reservoir rock, holes must be made through the casing and cement sheath. The casing is perforated within the target zones that contain oil or gas. Small explosive charges or abrasive jetting tools are typically used to create these perforations. These holes act as pathways for the fracturing fluid.
3. Injecting Fracturing Fluid
Once the casing is perforated, a high-pressure pump forces fracturing fluid down the wellbore and through the perforations. When the fracturing fluid is injected into the well it flows through the perforations into the target zones. This fluid, primarily water mixed with sand or ceramic particles (proppant) and a small percentage of chemicals, is injected at pressures high enough to fracture the surrounding rock.
4. Creating and Holding Open Fractures
The immense pressure creates tiny cracks or fractures in the rock formation. The proppant (sand or ceramic particles) suspended in the fluid is carried into these new fractures. When the pumps are turned off and the pressure drops, the proppant remains in the fractures, holding them open.
5. Flowback
After fracturing, some of the injected fluid returns to the surface. This is called flowback fluid. The oil or gas, now able to flow through the propped-open fractures, travels up the wellbore to the surface for collection.
Summary of the Process
| Step | Description | Purpose |
|---|---|---|
| Drilling & Casing | Drill wellbore, insert steel pipe (casing), cement in place. | Create well path, provide structural integrity, isolate zones. |
| Perforating Casing | Create holes through casing and cement in target zones. | Allow fluid access to the oil/gas formation. |
| Injecting Fluid | Pump high-pressure fracturing fluid (water, sand, chemicals) into the well. | Create fractures in the rock. |
| Creating Fractures | High pressure cracks the rock; proppant holds fractures open. | Create pathways for oil/gas to flow. |
| Flowback & Production | Injected fluid returns; oil/gas flows through fractures to the surface. | Recover oil/gas from the reservoir. |
The overall goal of hydraulic fracturing is to increase the permeability of the reservoir rock near the wellbore, allowing oil or gas that was previously trapped to flow more easily and economically to the surface.
Learn more about well completion and production processes in the oil and gas industry.
