Well Completion

What is a Well Completion?

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Well completion is a process of preparing the oil or gas well for production after drilling it. The main objective of well completion is to make a reasonable and effective hydrocarbon recovery. There are various steps involved in the well completion process, including the casing, cementing, perforation, gravel packing.

The decision to proceed with the well completion for production or abandon the well is entirely dependent on the formation evaluation results. When formation evaluation log analysis clearly indicates the commercial volume of hydrocarbons in a reservoir, only production casing and cementing are carried out.

What is the purpose of Well Completion?

There are numerous objectives that the well completion process solves by extracting hydrocarbon from the subsurface deposits to the surface. The most important purposes of well completion are as follows:

• Well completion connects the surface from the reservoir that enables it to produce from a well.
• The completion also provides a conduit for well treatments and stimulations.
• Well completion helps to isolate the problematic zones which hamper the production and make the process more complicated.
• Well completion also helps to maintain the integrity of reservoirs in unconsolidated formations.
• Well completions serve the basic requirement for a well testing operation.

What are the different types of Well Completion processes?

Well Completions can be classified into three main categories i.e. open hole completion, perforated casing completion, and liner completion. The perforated casing is the most common type of well completion technique that is extensively used globally. Let's have a look at the basic completion types briefly.

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• Open Hole Completion: Open hole completion is a technique in which no liner or casing is cemented across the production zone. The producing zone is left bare, with some sand control and flow control measures. Although the process is not common nowadays, it is still used in some situations like horizontal well completions in the Devonian shales of the Austin Chalk in Appalachia.
• Perforated Casing Completion: It is the most prominent and widely used well completion technique today. The major advantage of this technique is that the well can be logged and drilled to its total depth (TD) even prior to cementing production casing. It becomes relatively easy to estimate the volume of commercial deposits of hydrocarbon in the reservoir. Cementing is also easy in this process compared to liner completion.
• Liner Completion: The liner completion process is almost similar to the open hole completion, where the casing is set before intersecting the production interval. A liner assemblage is mounted across the pay section in this technique. Perforation expenses are very low in this case. The biggest advantage of liner completion is that the drilling mud can be changed, and a lower density mud can be used for pay interval.

Summary

• Well completion is a process of making the oil or gas well ready for a reasonable and effective hydrocarbon recovery after drilling it to a total depth.
• There are various objectives of well completion, ranging from providing a conduit for the well treatment and isolating problematic zones.
• Open hole completion, perforated casing completion, and liner completion are some of the most widely used techniques of well completion.

Frequently Asked Questions (FAQs):

What are the various steps involved in a Well Completion process?

There are several steps involved in the completion of an oil or gas well. Let us glance at some of the fundamental steps involved in well completions.

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• Well Casing: Well casing is the most primary step in a well completion process. After the drilling of a well, it has been cased to isolate the well from the impacts of formation fluids. A circular cross-sectional cylindrical pipe is inserted into the wellbore and cemented with the help of cement. The casing also helps to have a check on lost circulation.
• Cementing: After a casing is inserted into the borehole, it is cemented with the help of cement slurry and special additives to provide strength.
• Completion: After the cementing of the casing, the well is completed for production. The company can use any type of completion technique discussed earlier based on the well and reservoir conditions.
• Perforation: Case hole completion requires perforations to commence production. During perforation, perforating guns are fed into the wellbore with a wireline to reach the reservoir level. Once the level is reached, the guns are fired in the side of the hole, allowing hydrocarbons to enter into the wellbore.
• Gravel Pack: Most of the wells require a type of filtration to keep the stream clear. A gravel pack helps to resist sand entering the wellbore through the well stream. Gravel pack incorporates coarse size sand and gravels.
• Production Tree: This is the last step before the start of the production from a well. A production tree is mounted at the wellhead. The device incorporates various types of heads to provide surface controls while producing. Production tree is sometimes also referred to as Christmas tree.

What are the different components used in well completions?

There are several components that are used in well completion. The most important ones are briefly described below:

• Christmas Tree: It is an assemblage of valves that are mounted on the wellhead and controls the well flow.
• Production Tubing: A small cross-section pipe provides a conduit to transport hydrocarbons to the surface from reservoirs.
• Tubing Hanger: It a type of support to the production tubing. It sits on the wellhead and is made of rubber or polymer sealing rings.
• Wellhead: It is pressure control equipment present at the surface of a well where a Blowout preventer is installed.
• Production Packer: It is used to stop the flow of reservoir fluid through the full-length casing by isolating the annulus between the inner casing, tubing, and the foot of the well.