Steps and Phases for Drilling Oil and Gas Wells
This deliberation aims to provide a very high-level perspective on the various stages involved in a project to drill an oil or gas well. It is a simple and broad list of steps not meant to provide a detailed, in-depth view. Deep technical discussions on various aspects of oil and gas well drilling can be found in other sections of Drillopedia.
1. Planning and Preparation
Site Selection: Identify and evaluate potential drilling sites based on geological and geophysical data. Numerous surveys are carried out with painstaking data interpretation to identify a bottom-hole target and a feasible surface location for drilling a well.
Permitting and Regulatory Approvals: Obtain all necessary permits and comply with environmental and safety regulations.
Well Design: Develop a detailed well plan, including well trajectory, casing program, and mud program. Consider the well profile, such as Vertical, Directional, Horizontal, Multilateral, and Extended Reach Drilling (ERD).
2. Mobilization
Rig Selection: Define drilling rig specifications to fulfill well requirements. Select the appropriate rig from the current fleet or contract a new rig.
Site Preparation and Mobilization: Clear and prepare the drilling site, prepare access roads and necessary infrastructure, and mobilize the rig to the drilling site.
3. Drilling Operations
Spudding: Start the drilling process by drilling the initial surface hole.
Installing Conductor Pipe: Set and cement the conductor pipe to provide a stable foundation for the well.
4. Drilling Surface Hole
Drilling: Drill to the first casing point, typically a few hundred meters below the surface.
Running and Cementing Surface Casing: Install and cement surface casing to protect shallow aquifers, cover unconsolidated shallow formations, and provide well integrity.
Lost Circulation: If lost circulation occurs (loss of drilling fluids into the formation), use lost circulation material (LCM) to seal the loss zones or adjust the drilling mud weight and properties.
Hole Instability: If hole instability occurs (collapse of the wellbore), increase mud weight just enough to stabilize the formation.
5. Drilling Intermediate Hole
Drilling: Continue drilling to the next casing point, which may involve navigating various geological formations. Multiple sections as per well design may be drilled before reaching the next stage of drilling a production hole.
Running and Cementing Intermediate Casing: Install and cement intermediate casing to isolate troublesome formations and provide additional well integrity. Multiple casings or liners may be installed in this stage to isolate different sections based on well design.
Hole Deviation: If hole deviation may be required depending on the well design, the well could unintentionally deviate from the planned trajectory many a time. Directional drilling tools like stabilizers, downhole motors, or rotary steerable systems are deployed to ensure the well is drilled per the planned trajectory.
4. Drilling Production Hole:
Drilling Production Hole: The production hole is the final section of the well. Drill the final section to the target depth (Total Depth or TD). This section contains the reservoir that is targeted to produce formation fluid.
Well Logging: Several wireline or tubing-conveyed logs are run to evaluate the geological formations and determine the presence of hydrocarbons.
Running and Cementing Production Casing: Install and cement the production casing or a liner per the well design. This is the conduit for hydrocarbons to flow from the formation to the wellbore. Sometimes, an uncemented slotted liner may be run, or this section may not be cased off if the well is planned to be completed as an open hole.
5. Completion Operations
Perforating: Create perforations in the production casing to allow hydrocarbons to flow into the wellbore. Perforating guns are run either on wireline or tubing with explosives spaced out as per the well-completion plan.
Stimulation (if needed): Perform hydraulic fracturing or acidizing to enhance the flow of hydrocarbons.
Running Completion Equipment: Install necessary completion equipment, such as packers and tubing, to facilitate fluid flow from formation to the surface.
6. Testing and Evaluation
Well Testing: Conduct well testing by flowing the formation fluid to the surface. Measure the flow rates and record pressures to evaluate reservoir potential.
Evaluation: Analyze test data to assess the well’s production potential and economic viability.
7. Production
Production Start-up: Initiate production by opening the well to flow hydrocarbons to the surface.
Surface Facilities Installation: Set up surface facilities, such as separators, storage tanks, and pipelines, to handle and transport produced hydrocarbons.
8. Well Monitoring and Maintenance
Regular Monitoring: Continuously monitor well performance and production rates.
Maintenance and Workovers: Perform required maintenance and workover operations to ensure sustained production and well integrity.
9. Plug and Abandonment (P&A) (if needed)
P&A Planning: Develop a plan to safely plug and abandon the well when well test objectives have been completed, or the well is no longer productive or economically viable.
P&A Execution: Execute the P&A plan, which includes setting plugs, cementing, and removing equipment.