Motor Steerable (MS) assemblies are used globally in the majority of directional drilling applications. However, the limitations of MS systems are often highlighted as well paths, become more complicated and efficient drilling performance becomes more difficult to obtain. Tools that impart cyclic, axial oscillations into the drill string have been shown to extend the operating range of MS assemblies, particularly in slide-drilling mode, including coiled tubing applications (Robertson-2004). Adding the correct Axial-oscillation Generator Tool (AGT) to a drill string can dramatically improve slide drilling (Rasheed-2001); and significantly improve work over operations with coiled tubing as well (Tongs-2007). When evaluating the overall performance of a drilling system, it is necessary to determine the interaction between the AGT, Bottom Hole Assembly (BHA) and drill string as a whole. This paper will document the magnitude of the forces generated by the AGT and compare them to the specifications of other common drilling components. It will confirm that the correct selection and configuration of an AGT will impart benign forces into the drilling assembly, improving the effectiveness of the drilling system, and maintaining full compatibility with the entire drill string. Historically, measuring the actual forces transmitted by the AGT has been a challenge, as most downhole measuring devices record at sample rates significantly lower than the operating frequency of the oscillation tool. These recording devices often lack the necessary number of data channels required to fully describe the downhole dynamic environment. Furthermore, variations in bit type, BHA configuration, drilling parameters and formations make evaluating results from different wells difficult. To accurately measure downhole vibration and other drilling parameters, a Drilling Research Tool (DRT) was used. The DRT is a high-speed, sixteen-channel, downhole dynamics recorder. By ensuring identical BHA's, drilling parameters and formations, the differences in downhole activity can be attributed to the axial oscillation system. This paper will compare a number of field runs with and without an AGT and will quantify the actual downhole accelerations caused by adding the oscillation system to the drill string. The results will show that the addition of an effective axial oscillation tool positively influences drilling performance while maintaining compatibility with all drill string components. Introduction The effects of adding pressure pulses to drilling assemblies have been studied and is well documented. The practical benefit of adding the appropriate axial oscillation device to the drill string has often meant the difference between being able to slide drill and having to stop short of finishing a desired hole section. Recently, there has been research into how hydraulic vibrations (pressure pulses) can influence static friction of pipe against borehole walls (Barakat-2007). External, axial oscillation has also been shown to reduce friction more effectively than other oscillation types (Newman-2007). The results clearly show that hydraulic vibrations and axial oscillation can be helpful in reducing static friction. This paper expands on the laboratory tests that were performed and uses actual field data to quantify the performance benefits associated with an AGT system. In addition to evaluating the performance improvement, this paper also analyzes the compatibility of the AGT system with other elements of the drilling assembly; particularly Measurement While Drilling (MWD) tools and the dynamic influence the AGT could have on these tools.

With the discovery of shale plays around the world, there has been an increase in the prevalence of highly deviated wells and extended reach drilling. Both highly deviated wells and extended reach drilling present drilling challenges; modeling is required at various stages of the well and several considerations must be taken into account. In addition, detailed torque and drag analysis along with a comprehensive analysis of hydraulics programs must be performed to ensure the down hole equipment used for the application meets the challenging requirements. One of the most important considerations that should be taken into account is jar placement. The intricacies of jar placement are typically misunderstood and often over-looked. Good, sound technical recommendations on jar placement are generally hard to come by. Yet, legitimate technical advice on jar placement can ultimately ensure the use of optimal operational guidelines when drilling in highly deviated wells and using extended reach drilling. In these instances, conventional jar placement knowledge does not always apply. Highly deviated wells and extended reach drilling present unique drilling challenges such as the possibility of getting stuck in two different sections of the well bore. Computer modeling is currently used to predict any down hole loads that would hinder the operation of a drilling jar used in such an instance. This paper provides an analysis of jar placement in highly deviated wells and promotes the use of two drilling jars in the drill string. In addition, consideration is given to jar placement calculations which are further discussed in order to provide optimal impact and impulse result recommendations. A set of operational guidelines also has been included, ensuring that optimal results are obtained when using two jars in the drill string.

Jar technology has been around in the oil industry for several decades and its basic principles have remained primarily the same. As the oil industry moves forward in the exploration and development of unconventional hydrocarbon reserves, the demand for tougher, more reliable, and safer tools is more critical. Deeper wells and more complex well geometries are pushing the drilling envelopes, requiring tools to be engineered not only to withstand higher stresses downhole, but also to provide higher levels of safety on the rig floor. Through the engineering of simple but ingenious features, this paper describes how jar technology has been taken to a higher level. A jar has been designed acknowledging the most important features required in the current demanding drilling scenarios. The industry is not only looking for safer and more reliable tools, but also tools that will provide higher firing loads to increase the levels of success of freeing a drill string during a stuck pipe incident. The loads delivered during the first hours of a stuck pipe event can significantly improve the chances of retrieving the drill string safely to surface. The design features employed in this new technology maintain the same operating procedures of standard designs, but have increased the torque, tensile, and pressure ratings of the tool. In addition, current technology can suffer damage from excessive internal pressure build up when the over-pull rating of the tools are exceeded; particularly in deepwater applications where heave can be a contributing factor. A device has been engineered to protect the tool if such a condition is reached. The new jar also features a modular safety mechanism that will eradicate the use of the traditional safety collars eliminating the potential hazards of dropping objects on the rig floor. This paper will provide an overview of the innovative technology, plus review the initial field trials. Testing and field trials will demonstrate how this technology is a true step change, matching the growing demands of the drilling industry.

With almost 45% of wells drilled globally employing some form of hole opening technology, borehole enlargement has become commonplace. However, for many reasons it can still be very demanding, from both planning and execution points of view, particularly in the deep water basins being exploited today. To address the needs of these challenging applications, a variety of tools have been developed by many service companies. There are two primary borehole enlargement methods involving eccentric and concentric tools. Contained within these two general categories are many options: fixed cutter, roller cone, mechanical, hydraulic, hydro-mechanical, bi-center and so on. Factor in the different drive types available (rotary, positive displacement motor steerable, rotary steerable, coiled tubing) and the potential borehole enlargement options can quickly lead to a confusing, even circular, decision making process. With so many options, an important question must be answered by the drilling engineer: How does one select the appropriate borehole enlargement option for a specific application? With continually increasing costs and more difficult wells being drilled around the world, there is little room for error. Several factors must be weighed and evaluated before making the correct decision. Depending on the type of well being drilled and the formation characteristics, one must choose the optimal BHA and drilling parameters to obtain a successful borehole enlargement result. This paper reviews the decision making process that can lead to the best chance of success in many borehole enlargement applications. Understanding the application is critical in delivering a successful borehole enlargement operation. Based on results obtained over many years of industry experience with applications involving all types of borehole enlargement technologies available, a practical guide to hole opening solutions has been derived. It takes into account critical factors, including economics, borehole quality, equipment availability (including rig capacity), drive type, drilling parameters, the type of well being drilled, and formation characteristics. After a brief introduction and a description of currently available technologies, this paper will review the decisions that are made in determining which borehole enlargement tool to use and how to apply these in practice. This allows the drilling engineer to have a practical view of the available options and their versatility for proper tool selection.