What is the process of casing in drilling?

Any invasive oil well intervention

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The term workover is used to refer to any kind of oil well intervention involving invasive techniques, such as wireline, coiled tubing or snubbing. More specifically, a workover refers to the expensive process of pulling and replacing completion or production hardware in order to extend the life of the well.[1]

Reason to perform a workover

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Workovers rank among the most complex, difficult and expensive types of well work. They are performed only if the well completion is terminally unsuitable for the job at hand. The production tubing may have become damaged due to operational factors like corrosion to the point where well integrity is threatened. Downhole components such as tubing, retrievable downhole safety valves, or electrical submersible pumps may have malfunctioned, needing replacement.[2]

In other circumstances, the reason for a workover may not be that the completion itself is in a bad condition, but that changing reservoir conditions make the former completion unsuitable. For example, a high productivity well may have been completed with 5½" tubing to allow high flow rates because a narrower tubing would have unnecessarily choked the flow, but declining productivity could lead to stable flow being unsupportable through such a wide bore.

Operation

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Before any workover, the well must first be killed. Since workovers are long planned in advance, there would be much time to plan the well kill and so the reverse circulation would be common. The intense nature of this operation often requires no less than the capabilities of a drilling rig.

The workover begins by killing the well then removing the wellhead and possibly the flow line, then installing a B.O.P. commonly known as a blowout preventer, then lifting the tubing hanger from the casing head, thus beginning to pull the completion out of the well. The string will almost always be fixed in place by at least one production packer. If the packer is retrievable it can be released easily enough and pulled out with the completion string. If it is permanent, then it is common to cut the tubing just above it and pull out the upper portion of the string. If necessary, the packer and the tubing left in the well can be milled out, though more commonly, the new completion will make use of it by setting a new packer just above it and running new tubing down to the top of the old one.

Workovers on casing

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Although less exposed to wellbore fluids, casing strings too have been known to lose integrity. On occasion, it may be deemed economical to pull and replace it. Since casing strings are cemented in place, this is significantly more difficult and expensive than replacing the completion string. If in some instances the casing string cannot be removed from the well, it may be necessary to sidetrack the offending area and recomplete, which is also an expensive process. For all but the most productive well, replacing the casing would never be economical.

References

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Engineers are continually challenged with the risk of hole collapse when faced with drilling through overburden and unconsolidated formations. That is why it is prudent to use drilling casings to drill through overburden while advancing the drilling casing and protecting the hole at the same time.

The aim of this blog is to tell you everything you need to know about this ingenious product so you can make an informed decision as to whether it is the right solution for your drilling program.

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After reading our guide, you will have an understanding of what casing advancement systems are, when and where to use them and which casing advancement systems are suitable for your project.

What is a drilling casing?

A drilling casing is a type of drilling tool that enables you to case and drill simultaneously. It can be used with rotary percussion drilling where the impact of the hammer drives the casing down the wellbore.

Installing casing, while drilling, minimizes the risk of holes collapsing and enables projects to be completed faster and more efficiently. For this reason, casing advancement systems add value whether installing foundations, support elements, or casing a hole in formations where hole collapse is possible. 

Casing advancement systems, or drilled casings, are used when ground conditions make it difficult to drill, such as in loose formations or drilling through highly fractured rock.

Where to use drilled casings?

Ninety percent of the earth’s ground conditions are loose, unconsolidated, and rocky. Drilling in these formations is often challenging and the risk of collapsing, hole deviation, and failure to reach the intended depth is a real concern for drilling contractors.

Installing drilling casing as the hole is drilled helps to stabilize loose, or unpredictable formations, and shore up the hole. This is particularly the case when penetrating clay, silt, sand, gravel, cobbles, boulders, and fractured rock.

Casing and drilling simultaneously improve drilling efficiency. If you need to speed up drilling time, adding a casing advancement system to your drilling toolbox will go a long way to improving productivity and the drill time on your project.

How to select the right Casing Advancement System

Selecting the right system will depend on the drilling application or purpose. There are several factors to consider: the ground formation and type, the drilling method, whether a permanent or retrievable casing is required, the outside diameter of the casing, the wall thickness, the ring bit ID, as well as the casing and rock socket depth. Armed with this knowledge, we can then specify the appropriate system.

Below are examples of the most common applications:

Geothermal well drilling

The use of geothermal heating in houses has become increasingly popular as it provides both economical and environmental advantages for the user.

Casing advancement systems are useful when drilling a geothermal well as they keep the hole open during installation of the heat exchange system and minimizes any impact on the surrounding structures. It also prevents the collapse of the well during drilling where ground conditions are unstable.

Water well drilling

Water well drilling is commonly done in urban areas where drilling at speed is necessary to minimize disruptions to residents, as well as in the developed area where drilling is taking place.

The company is the world’s best Casing Drilling System supplier. We are your one-stop shop for all needs. Our staff are highly-specialized and will help you find the product you need.