Category Archives: Oil Field Knowledge

Wireline Tool Recovery and Junk Removal Equipment for Drilling and Workover

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In order to fish for wireline tools out of the hole, we must use different equipment than would be used for pipe recovery. Common wireline tool issues center around the cable being tangled or wadded in the hole, as well as the fact that attempts at fishing can pull the wireline out of the rope socket or part, further complicating tool retrieval.

Which Part is Stuck? Cable or Tools

As soon as a wireline assembly becomes stuck, the operator will need to determine whether the problem is in the cable or the tool. Usually, one would apply normal logging tension on the cable and allow it to sit for a few minutes. During this time, four things should be recorded:

  • Current depth of the tool
  • Type and size of the cable
  • Surface tension of the cable just prior to becoming stuck
  • Cable-head’s weakpoint rating.

The cable will be marked at the rotary table, and a T-bar clamp will also be securely fitted to the cable just above the table. Should the cable break, then the clamp holds on to the cable end at the surface, so that the whole cable does not fall down the hole and cause additional blockage. The operator will then need to apply 1000 lbf of tension on the cable, and make a note of the distance that the cable mark moves at the rotary table. This figure shows the stretch produced in the elastic cable. It is then possible to estimate the length of free cable, using a stretch chart or from prior knowledge of the cable’s stretch coefficient. Should the length of free cable be the same as the current logging depth, then the problem does not lie with the cable; rather, the tool is stuck, and not the cable. If the length of free cable is less than current logging depth, then the cable is stuck at some higher point in the hole.

If it is the tool which is stuck, and not the cable, then pulling on the cable will cause one of three results. The tool may come free, the weakpoint can break and the tool will remain in the hole but the cable can be removed, or the cable will break at the point of maximum tension. Continue reading →

Introduction to a Jack Up Rig

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A Jack Up is a type of offshore drilling rigs. It is made up of a hull, legs, and a lifting system and a jack up rig can be towed to the offshore site, and then lower its legs into the seabed to lift up the hull, providing a stable work deck which is strong enough to cope with the required environmental loads.

Another advantage of Jack Up rigs is that they can operate in high wind speeds and with significant wave heights, as well as in water depths reaching 500 feet. Since the Jack Up will be ultimately supported by the seabed, they are usually preloaded upon arrival at the intended site to simulate the kind of leg loads that they will be exposed to. This ensures that once the rig is fully jacked up and in operation, the seabed will be able to provide a strong foundation for the rig.

The offshore industry has made significant use of Jack Up rigs for over 60 years now. They are especially useful for exploration drilling since they are relatively easy to set up, and also provide ample production, accommodation, and maintenance areas. Over the years, Jack Ups have been pushed to their limits in terms of what they can do. This includes their deck load carrying limits both when afloat and when elevated, their environmental and drilling limits, and the soil, or foundation, limits. By pushing these limits, drilling companies have been able to explore deeper waters, drill deep reservoirs in harsh conditions, and even drill in areas with unstable soils and foundations. Continue reading →

Junk Removal Tools Used for Drilling and Workover Operation

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Junk refers to any objects or debris which have been dropped into or lost in the hole. Junk can include all manner of things, from downhole tools and bottomhole assembly components, to bit cones, or even hand tools which have been accidentally dropped into the hole. In some cases, it may be clear what the junk is, such as when something has been visibly dropped down the hole. On the other hand, though, it may sometimes be unclear just what is causing the problem. While drilling is taking place, junk can be detected by an irregular torque, or by the drill being unable to move ahead when a new bit has been run. In order to remove any junk from a well, junk removal tools will be used depending on a particular condition of junk and wellbore.

There are three main ways that junk can be dealt with; which method is chosen will depend on the size of the junk itself, and how hard the formation is. The junk can be recovered whole, split into smaller pieces so that these pieces can be recovered or that they are too small to cause any additional issues, or finally pushed into the side of a soft formation or the bottom of a formation with a large enough rathole. If none of these are possible and the junk continues to interfere with well operations, then the well made need to be sidetracked or abandoned.

The junk removal tools are as follows;

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Wireline Tool Recovery In Case of Wireline Tool Stuck

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Wireline tool such as logging tool, slick line tool can be stuck in the hole therefore we need to understand about wireline recovery tool. This article demonstrate typical wireline fishing / recovery tool.  Common wireline tool issues center around the cable being tangled or wadded in the hole, as well as the fact that attempts at fishing can pull the wireline out of the rope socket or part, further complicating tool retrieval.

Stuck Cable or Tools

As soon as a wireline assembly becomes stuck, the operator will need to determine whether the problem is in the cable or the tool. Usually, one would apply normal logging tension on the cable and allow it to sit for a few minutes. During this time, four things should be recorded:

  1. the current depth of the tool
  2. the type and size of the cable
  3. the surface tension of the cable just prior to becoming stuck
  4. the cable-head’s weakpoint rating

Continue reading →

What is Fishing Operation?

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In technical terms, a fish can be any object which has been lost or stuck in a borehole, and has a serious negative impact on well operations. Fishes can be anything, whether that is a drill string that has come away, a bit cone, or even a hand tool that has been inadvertently dropped into the well. To solve this issue, fishing involves the use of special tools and procedures to recover the fish and allow drilling to continue. While this article will deal solely with regular fishing, there is also an alternative method, which involves using through-tubing processes that make use of tools on a wireline or coiled tubing.

Virtually any object that is dropped into a well, or even run into it, may need to be fished out at some point. Furthermore, the need for fishing may arise at any given point during operations, and there are therefore a wide range of different tools and methods. There are three main technologies that these solutions are built around, though: pulling, milling, or cutting the pipe itself, and other downhole parts.

A fishing job is one option, but this will depend on the cost and likelihood of success. Other options include:

  • Leaving the fish where it is, and sidetracking or redrilling the well to follow an alternative path
  • Leaving the fish where it is, and completing the well in a shallower zone
  • Abandoning the well altogether

Preferably, the fish should be completely avoided in the first place, thanks to the right planning and proper drilling practices. However, it is important that a contingency plan is in place should the situation arise. Continue reading →