Well Drilling and Completion Process

Drilling and Casing Installation

• After drilling the surface section, the drill pipe is removed to lay the casing.
• Casing is necessary to seal off aquifers from hydrocarbons for environmental protection.
• Casing String: Made of many joints of the same size, screwed together at the collar.

Casing Selection Criteria

• Factors Influencing Selection:
  • Outer diameter
  • Wall thickness
  • Length
  • Weight per unit length
  • Grade of steel
• Considerations for Grade Selection:
  • Hole size
  • Rigosity of the drilled hole
  • Expected pressure of flowing hydrocarbons
  • H2S content
  • Economic factors

Cementing Process

• The casing is secured to the formation by pumping cement through the casing shoe at the bottom of the well.
• Cement must cure adequately before further operations can continue.
• Once cured, the cement establishes a seal for the aquifers.

Drilling to Total Depth (TD)

• Drilling continues through the wiper plug, casing shoe, and cement until reaching total depth (TD), where the pay zone is expected.
• Evaluation tools, such as logging while drilling and wireline logging, are used to assess the formation and economic feasibility of the pay zone.

Well Completion Process

• Completion Method: Involves inserting a casing string into the drilled hole to prevent wall caving.
• Cementing may have bonding issues, evaluated using a cement evaluation wireline tool.

Perforation of the Well

• A perforating gun is lowered to the target depth using wireline for short, light gun strings or tubing-conveyed perforating (TCP) for heavier strings.
• Charges in the gun are ignited to create pathways through the formation, cement, and casing to the production tubing.

Production Setup

• After perforation, production tests confirm the reservoir's commercial viability before installing the production string.
• A typical production string includes a tubing string with a packer near the bottom to control hydrocarbon flow.
• Final installation of wellhead equipment, known as a Christmas tree, occurs before the drilling rig is relocated.

Hydrocarbon Production

• Once completed, hydrocarbons are produced, filling storage tanks or pipelines until the production rate declines.
• Eventually, the well is plugged and abandoned.