Oscillation Fishing System: A Novel Approach to Improve the Chances of Freeing Shallow Mechanical Stuck Pipe

Abstract

One of the most common and costly situations in drilling operations is stuck pipe recovery, as it results in significant non-productive time (NPT). Stuck pipe is often freed by applying axial jarring forces to the string to overcome the sticking force. However, becoming stuck at a shallow depth often results in insufficient pipe stretch in the string to generate enough energy to free the stuck pipe using a jar. In cases where it is not applicable to use a jar, the use of the Oscillation Fishing System (OFS) is a more effective technique and an optimal solution to free the stuck pipe. Using the OFS to free stuck pipe encompasses generating continuous oscillatory axial motion. Pressure pulsations generated within the tool are converted to steady axial oscillations using the springs in the tool. This continuous motion produces axial forces at high frequencies, which translates to continuous energy applied to the stuck pipe. The OFS is used in different fishing applications, such as vertical and directional well profiles. The technology is used to free stuck pipes in cased and open holes. Depending on the stuck situation, the OFS is either placed at the surface or downhole with conventional bottom hole assemblies (BHA). In the subject applications, the OFS was run at the surface to free both motor and slick rotary BHAs in large hole sizes, 22 in. and 16 in., in different scenarios. This paper will analyze four examples where the OFS was used in a similar application. In all these examples, conventional stroking tools (i.e., fishing jar) were not part of the system and jars were not used to avoid the potential hazards of impact forces affecting the rig floor. Moreover, activating jars at shallower depths is ineffective as it requires a longer length of pipe to generate enough energy to free the stuck fish. The OFS was used after unsuccessful attempts to pull and recover the string. When the OFS was activated at the surface, producing continuous axial movement, it successfully freed the stuck fish. A new application of the OFS in fishing operations was introduced by using it in the surface sections. Not only did the OFS eliminate the extra steps required to get closer to the stuck point, but also it saved rig time and drillstring components and prevented the need for sidetracking. This paper discusses the use of the OFS at the surface in three examples, including an analysis of the performance to free the stuck string.