Every machine or equipment requires maintenance and repairs from time to time. Similarly, any structure, be it a building or oil well, requires maintenance to improve its functionality. Workover is basically related to the repair and maintenance of an oil well.
Producing oil wells can only produce in good capacity if they are kept in good shape. Any problems need to be dealt with immediately to ensure the flow of crude oil into the wellbore. Over time, production can slow down due to a variety of reasons, and late or no maintenance is one of them.
So in this post, we’ll cover the topic of workover, which is a technical term used frequently in the oil and gas industry.
What is a Well Workover?
Workover or well workover refers to major maintenance or remedial processes of an oil well. It is an invasive process that uses invasive techniques such as wirelines, snubbing, or coiled tubing. This process mainly involves pulling out and apart the completion hardware to replace it or fix it, in order to increase the life of the well and keep the production levels optimal.
These techniques help avoid complete workover where the tubing is removed. This helps save time and money, but still, the overall process of workover is quite expensive.
Most importantly, workover requires that the well be killed, which means production temporarily stops. This, of course, has an impact on revenues as well, so companies try their best to make workover activities as efficient as possible to ensure the well is dead for a short time only.
Why is Workover Needed?
As workover is expensive and also stops production for a while, most companies only undertake it when it’s absolutely necessary. Of course, doing maintenance and repairs as early as possible is arguably more feasible but more often than not economic feasibility also comes into play.
Nevertheless, the main reasons for workover oil and gas are as follows:
For regular maintenance of a well, the tubing or pipe has to be removed. However, in some situations, this pipe might be stuck, which will require workover.
A pipe may be stuck because of a number of reasons, but the most common one is salt bridges.
If the rock formation has very salty water, salt bridges can form, especially if the well pumps oil in several cycles routinely. The water usually collects in annulus space when the well isn’t pumping. While it does drain out before pumping begins, it often leaves a salt residue.
Over time, the collecting and draining of saltwater, again and again, leave enough residue that can turn into bridges.
As a result, production may reduce or completely halt as these salt bridges become a barrier to the flow.
Even though the engineers use freshwater to dissolve and drain the salt, but if it’s too much, workover is the only option.
Similar to salt bridges, sand and limescale can also be obstructions in pipes.
Removing Parted Tube
Workover is needed when a tube is parted. This process can be painstakingly laborious and difficult. In fact, it also requires a custom tool to make the process easier. But before all that, impression blocks are run.
It’s a flat tool that goes downhole and the soft material at the bottom of the block is used to make the impression of the parted tubing. Usually, this material is soft lead. It goes all the way down to the hole, so it gives a complete impression of the tube.
Stripping well involves removing tubing and rod string of the well. Typically, the rod string is broken out, especially if the clutch is engaged.
This is a complex process, which can result in blow out. Blow out refers to oil spilling and rising from the well hole, which is often the case with stripping wells. Lighter oils can rise up even more easily.
So special equipment is needed, like swabbing, to ensure that oil doesn’t rise or spill out, ensuring safety for all on the site and the infrastructure.
More often than not, a workover is needed to stimulate more fluids and increase production. Production may reduce over time or perhaps wasn’t much, to begin with. Either way, workover equipment, depending on the type of well, can help increase production.
A well may produce lower because of some of the obstructions above or perhaps because the formation access is limited. Either way, workover equipment may be used to perform remedial procedures in order to stimulate more production.
Workover vs. Recompletion
Workover is different from recompletion in many ways. First of all, the workover process is carried out for working wells that need maintenance or repairs. On the other hand, recompletion is often carried out on inactive wells that have not been producing for a while.
While both workover and recompletion are invasive processes, workover is still somewhat lesser work than recompletion. Recompletion may involve different completion techniques, which is basically completing the well once again. Recompletion may take much longer than workover.
The primary goal of both is to increase production, but recompletion is also used for wells that have depleted accessible resources, but there are more resources underneath to extract.
Also, the equipment is different for these processes. Recompletion may require even more heavy machinery and raw materials to fix or improve the structure of the wellbore and reservoir. So workover is markedly different from recompletion of an oil or gas well.
Workover is an important process in the lifetime of an oil well, as it helps increase the production of oil and safeguard the well from damage that is beyond repair. Companies shouldn’t avoid workover activities for the sake of money or time, as these activities can ensure the well keeps producing for a long time.
The only big drawback of workover is that production temporarily stops. You can’t do workover activities and keep the production going too. It’s simply not possible.
Perhaps in the future, we could see less intrusive workover methods that take minimal time and get production back on track as soon as possible.