Oil and Gas Well Completion

Oil and natural gas are some of the most in-demand commodities in the world. Even with the introduction of electric cars and renewable energy plants, most of the world is heavily reliant on these minerals. This is where the oil and gas well completion comes in.

In the field of oil and gas, especially in the context of exploration and production, you’ll hear the term completion or well completion. What does it really mean? This article will focus on exactly that. 

Well Completion Meaning

Well completion refers to readying an oil or gas well for production. It can also be used when the well is ready for testing, and not yet commercial production. 

There are many stages between the discovery and production of oil from a field. After drilling, the most important operation is preparing the well for extraction. It can be a series of steps, depending on the type of well completion. 

So, in simpler words, well completion defines the various operations after drilling. It’s the part between drilling and production in the lifecycle of an oil well. The process may include cementing the casing, perforation, or simulation. 

Completion oil and gas doesn’t just refer to the mere preparation of the well but also optimizing it for maximum production and lifespan. Therefore, it’s a highly expensive process that utilizes a lot of cutting-edge technology to achieve favorable results. 

Oil and Gas Well Completion Process

The well completion process involves the following main three steps:


The initial step of completion is similar to the rig upstage of drilling. It basically involves gathering and preparing all the materials and tools for the fracturing, such as fluids, blenders, sand, chemicals, etc. 

At this stage, a mix of water and acid helps clean out the well before the frac. 


Stimulation involves hydraulic fracturing or just frac (commonly used in the industry). It comprises a perforation gun creating holes to reach the surrounding rock of the well. 

Typically a mixture of fluid and proppant is pumped at very high pressure. The pressure of the fluid cracks the rock within the range of 250 to 500 feet of the wellbore. As a result, the fissures open up, allowing the mineral (oil or gas) to flow to the wellbore. 

This is just a simplified walk-through of the process, as the actual process involved over a hundred individual steps. 

Drill Out

This stage involves the removal of materials used to isolate stages of the stimulation phase. This depends on the method of stimulation. Some drilling companies used dissolvable plugs, but the drill-out technique remains the most common to this day. 

Types of Oil and Gas Well Completion

There are many different types of well completion perfected over the years by engineers in the petroleum industry. Mainly, there are three types:

Open Hole Completion

Open hole completion is the oldest type of well completion, common in the olden days of petroleum extraction. In this type of completion, casing ran along with the drilling of the hole. When the stimulation phase was completed, drilling would stop, and the well would start production. 

Although this method was more common in the days of drilling with cable tools, it continued to be used even with the advent of rotary rigs. They would rubberize the formation at the wellbore when it was time to stimulate the rock. 

The apparent drawback of this technique is that the casing needs to be set before drilling. This leaves the risk of setting in the casing in a well that doesn’t ultimately reach production. In other words, the money and effort go to waste as it turns out to be a dry hole. 

Another problem is that sloughing zones can reduce the flow of the mineral to the surface. This is because the flow from the reservoir to the wellbore cannot be controlled. 

However, open hole completion can be viable in certain cases, such as horizontal wells. 

Liner Completion

Liner completion is similar to open hole completion in many aspects, but it helps make up for some of the drawbacks of the open hole. 

Even in this type, the casing has to be set before drilling. The main benefit, however, is that the drilling fluid system is changeable. Moreover, the use of non-damaging fluid makes this kind more cost-effective. 

There are three sub-types of liner completion:

  • Slotted Liner: Slotted liner hangs in the open hole interval, which prevents or minimizes the sloughing of the formation into the wellbore. 
  • Screen and Liner: It’s similar to the slotted liner, except both screen and liner are set up in the open hole of the wellbore. It’s more appropriate for unconsolidated formations and may result in restriction of the flow of the fluids in the reservoir, which essentially makes it pretty similar to open hole completion. 
  • Cemented Liner: This type of well completion in oil and gas comes in handy when intermediate casing needs to be set before reaching the total depth. It can help deal with isolated zones that may result in low-pressure intervals or lost circulation. It also allows to easily change the weight or composition of the drilling fluid. There are pros and cons to this approach as well, but that depends on the quality of the cement job. 

Perforated Casing Completion

Perforated casing completion is the most common type of oil and gas well completion these days. It allows drilling and logging to the total depth of the well before running the casing. It’s also more predictable of the production as one can obtain important information from the cores and logs of the producing interval. 

In comparison with cemented liner completion, it’s relatively easier to get a better cement job for the perforated casing. Most importantly, this type of completion is more adaptable, especially to multiple and alternate completions. 

Conclusion About Oil and Gas Well Completion

Completion or well completion is an elaborate process that requires complex engineering and a lot of materials and tools. Over the years, drilling companies have improved the well completion techniques, with the perforated casing completion being the most advantageous. 

As you can see, the type of well completion also impacts production, as some types may result in hindrances to flow. That, in turn, results in less production of barrels per day. 

If you have further questions about well completion, reach out to Ranger Land & Minerals here.