31/01/2026
𝗧𝘆𝗽𝗲𝘀 𝗼𝗳 𝗪𝗲𝗹𝗹𝘀 𝗶𝗻 𝗣𝗲𝘁𝗿𝗼𝗹𝗲𝘂𝗺 𝗘𝗻𝗴𝗶𝗻𝗲𝗲𝗿𝗶𝗻𝗴
In petroleum engineering, a well is a drilled hole in the ground designed to access oil, gas, or water reservoirs. Wells are classified based on purpose, trajectory, production type, and completion method. Understanding well types is crucial for designing drilling programs, selecting equipment, and planning production.
① Based on Purpose
1️⃣ Exploration Wells
Drilled to discover new hydrocarbon reserves.
Typically shallow-to-medium depth depending on seismic data.
Example: Wildcat wells drilled in untested formations.
2️⃣ Appraisal Wells
Follow-up wells drilled after a discovery to define the size and quality of the reservoir.
Provide data on porosity, permeability, and fluid characteristics.
3️⃣ Production Wells
Designed to extract hydrocarbons efficiently.
Equipped with casing, tubing, and completion systems to maximize flow.
May be designed for primary, secondary, or tertiary recovery.
4️⃣ Injection Wells
Used for enhanced oil recovery (EOR) or reservoir management.
Types:
Water injection wells – maintain reservoir pressure.
Gas injection wells – CO₂ or natural gas for pressure support or miscible flooding.
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② Based on Trajectory
1️⃣ Vertical Wells
Traditional wells drilled straight down.
Simpler design, low deviation.
Common in onshore, shallow reservoirs.
2️⃣ Deviated / Directional Wells
Wells drilled at an angle from vertical to reach specific reservoir targets.
Used to avoid obstacles or reach multiple targets from a single pad.
3️⃣ Horizontal Wells
Wells drilled to follow the reservoir formation horizontally.
Increase contact with the reservoir, improving production rates.
Common in shale gas, tight oil, and extended reach wells.
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③ Based on Production Type
1️⃣ Oil Wells
Designed primarily to produce crude oil.
May produce associated gas as a byproduct.
2️⃣ Gas Wells
Designed to produce natural gas, sometimes with condensate.
Typically require gas handling facilities at the surface.
3️⃣ Water Wells
Mostly for water injection or disposal, not hydrocarbon production.
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④ Based on Completion and Equipment
1️⃣ Open-Hole Wells
The production zone is not cased, and the reservoir rock is exposed.
Requires sand control methods to prevent formation material from entering the well.
2️⃣ Cased and Perforated Wells
Production zone cased and cemented, then perforated to allow fluids to enter.
Most common in conventional reservoirs.
3️⃣ Gravel Pack Wells
Cased and perforated with gravel packs to prevent sand production in unconsolidated formations.
4️⃣ Horizontal / Multilateral Wells
Complex wells with lateral branches from the main bore to maximize reservoir exposure.
Used in tight formations, offshore reservoirs, or shale plays.
