Reducing Safety Incidents While Lifting and Handling Drilling Jars: A Case Study
Authors: Evans Chad D. , Reitsma Rienk , Ramsay Euan Matthew 
Published: March 2015

The handling of drilling jars can present safety hazards when they are being serviced, transported, loaded or unloaded, handled on the rig floor, run in hole or racked in the derrick. Dangers are especially prevalent if the drilling jar is not equipped with a mechanical locking device. These tools present a potential hazard to personnel because of the possibility of inadvertently activating the jar.

Previously, this issue has been addressed by using an externally installed clamping device which is attached to the jar to lock it open and prevent an unplanned activation. If the clamping device is not properly installed, it can become a dropped object hazard. In response to the potential hazard of a dropped object from the derrick, some drilling contractors have elected to lay out jars from the Bottom Hole Assembly, BHA, on every trip. This in itself adds time to the operation and additional exposure to personnel.

The drilling jar safety clamp has evolved in design and material selection. The industry has evolved to a composite design, which reduces the element of operational error thus reducing the chance of a dropped object in the derrick and improved handling.

The composite design is much more reliable and easier to handle but has failed to eliminate the dropped object hazard. Following extensive risk analysis of the existing clamp, an innovative approach has been conceived in the form of an internal latch mechanism which can eliminate the requirement for an external clamp and provide more effective control of the jar while eliminating a possibility of an object being dropped in the derrick.

In this paper, the authors will review the safety hazards associated with the handling of drilling jars. They will describe the evolution of the external clamp, which is the main device in use. The paper concludes with a detailed discussion of the internal latching device that has been developed in the continuing effort to enhance the safety of drilling operations.

Introduction

Drilling jars provide a means of supplying a powerful upward or downward force to a stuck drill string. Mechanical jars are preset to a specific load for activation in the repair and maintenance center while the force for hydraulic jars varies with the applied load from the drill string. In vertical or low inclination wells, both types of jars should be run in the well in tension, which is mandatory for mechanical jars and advisable for hydraulic jars. Where inadvertent cocking and subsequent activation of the jar can occur such as in directional wells, jars can be run in compression. A jar should be handled with care in all aspects of every operation, from assembly and testing, to transportation to and from the rig location, picking up, to running in the well, racking back in the derrick, or laying the jar down when no longer in-use.

The possibility of inadvertent cocking and subsequent unexpected activation of the jar can present a hazard to personnel and other equipment. Of the various operational situations which may occur, perhaps the most dangerous is when the drilling jar is racked in the derrick. It is extremely important that when racking the jar in the derrick, the jar is positioned at the top of the stand of drill collars or heavy-weight drill pipe with the mandrel clamp installed. If this maxim is not adhered and the jar is racked at the bottom of the stand without a mandrel clamp, the weight above the jar can cause the jar to energize and create a force which could dislodge the stand from the derrick and fall to the drill floor.