Completion and Types of Completion
Introduction
The oil and gas completion process is the final step to get the drilled well ready for production or injection. It entails installing the necessary equipment and technology to allow hydrocarbons (oil or gas) or fluids (like water or steam) to enter or leave the reservoir. Well completion is a crucial aspect of the well lifecycle, as it has a significant effect on well productivity, efficiency, and economic viability.
Completing the well is the key action to optimize the operation and safety, but also ensures maximum recovery from reservoir, therefore choosing the suitable completion method is a must. Indeed various types of completions suit completely different reservoir or production scenarios and operational restrictions. So this article addresses what are the completions, the different types of completions, its functions and applications in the oil and gas industry.
1. Open Hole Completion
There is no need for a casing of the specific zone that is being produced, so one of the well types is an open hole completion in which the productive zone is left uncased. To do that, specialty screens or gravel packs would have to read more
Advantages:
✔Increases contact with the reservoir, resulting in higher production.
✔Avoids costs for casing and perforation associated with completion.
✔Allows hydrocarbons to flow naturally.
Disadvantages:
✔Increased potential for formation breakdown and sand production.
✔Not able to manage reservoir areas flow.
✔Challenging to conduct well interventions or workovers.
Applications Open-hole completions are commonly used in formations characterized by stable rock properties with a minimal risk of borehole collapse; naturally fractured reservoirs are typical examples of open-hole completion applications.
2. Cased Hole Completion
They also are referred to as cased hole completions where casing or liner is run into the wellbore and cemented in place to isolate and stabilize the producing zones. When the casing is cemented in place, holes can be created through the casing and cement to the reservoir so that fluids can flow.
Advantages:
✔Enhanced control of fluid generation and reservoir control functions.
✔Excellent well integrity and minimal formation damage
✔Well-suited for high-pressure and complex reservoirs.
Disadvantages:
✔More expensive in the beginning cost casing, cementing, and perforation operations.
✔Potential damage to formation due to perforation & cementing process.
Applications: Cased hole completions are utilized in a range of reservoir conditions, including high pressure and deep reservoirs that need zonal isolation.
3. Tubing less Completion
Tubing less completions, popularly known as “barefoot completions,” is the installation of a casing or liner in the wellbore without the run of production tubing. Instead, the produced fluid flows directly through the casing or liner to surface.
Advantages:
✔Reduced installation and maintenance costs.
✔Low-complexity well design for shallow / low pressure reservoirs.
Disadvantages:
✔Lack of suitable well intervention methods
✔Less control of production rates and flow of fluids.
Applications: Employed in shallow wells, low-pressure reservoirs, and temporary production situations where there is not enough flow to warrant added tubing.
4. Tubing Completion
The production tubing is run inside the casing or liner in a tubing completion to transport fluids from the reservoir to the surface. This has much more operational flexibility for well production and maintenance.
Other Tubing Completions:
✔Tubing-Perforated Completion: Perforations have been made through the casing or liner for the fluid to enter the production tubing.
✔Tubing-Retrievable Completion: The production tubing is retrievable so that downhole equipment can be installed and retrieved without needing to pull the entire tubing string (packers, valves, pumps, etc.).
✔Dual Tubing Completion: Two distinct tubing strings are run inside the well bore, enabling flow of fluids from various zones or fluid injection while also producing hydrocarbons.
Advantages:
✔Offers improved control regarding well output.
✔Enables workovers and maintenance without wellbore interruption.
✔Improves reservoir management through selective production
Disadvantages:
✔Higher installation cost than tubing less completions
✔Many additional downhole equipment needed and maintained.
✔Application: High-production wells, deep reservoir, and well with frequent interventions.
5. Multi-Zone Completion
Multi-volume completions produce a single wellbore from more than one productive zone (this can be in the same reservoir or different reservoir). This can be accomplished by isolating and controlling the flow from each section separately with the help of packers, sliding sleeves, or any other downhole tools.
Advantages:
✔Accesses multiple zones in single wellbore, maximizing reservoir recovery.
✔Lowers drilling and completion costs from not requiring additional wells.
✔Allows for selective production and zonal isolation for improved reservoir management.
Disadvantages:
✔Advanced completion scheme that needs sophisticated downhole tools.
✔Increased risk of equipment failure from concurrently managing multiple zones
✔Higher operational complexity and need for monitoring.
Application: To optimize EI (economic interval or well-potential intervals) in multi pay reservoirs and high-cost drilling environment (offshore/high-cost reservoirs).
Conclusion
Completion methods are essential to the unlocking of the gas and oil well bursting to the complete potential of the oil and gas reservoir by creating for the fluid flow path from the reservoir to the surface. Choosing the right completion approach for particular reservoir attributes, production goals, and operational limitations allows operators to enhance well performance, maximize production rates, and guarantee the economic feasibility of their assets during the life of the well.
New completion technologies and methodologies will arise as the oil and gas industry advances to further improve well productivity, enhance efficiency, and lower operating costs. Whether using open-hole, cased-hole, tubing less, tubing or multi-zone completion, each process offers different benefits dependent on reservoir conditions, making completion engineering an essential step in successful hydrocarbon recovery.
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