Well known in the oil and gas industry is the importance of understanding drilling system vibrations and bit-reamer weight transfer when drilling with hole openers. A field testing program was carried out on a full-scale experimental test rig in the state of Oklahoma, USA, with known lithological formations, in order to evaluate underreaming system designs. In this context, the underreaming system comprised the bit, the drive system, and the underreaming element. To fully understand how the system interacts with the formation and reacts to inputs from the surface, drilling mechanics measurements were taken above and below the reamer element. Drilling dynamics measurements were also taken at three places in the BHA, with two drilling dynamics packages spaced out below the reamer and one positioned directly above it. That way, dynamics on the bit and reamer could be studied separately to understand how bit and reamer performance affect each other and the overall system dynamics. The first well was directionally drilled with a rotary steerable system, concentric reamer, and vibration monitoring equipment set up in an industry-standard arrangement. This paper will describe how the findings and learning from the initial field test led to bit redesign and operational techniques implemented to enhance the drilling system stability. Another borehole was then drilled through identical formations with this improved system, offering a unique detailed comparison between the two field tests. The new bit design allowed the bit to control the drilling rate with better weight distribution between bit and reamer, significantly reducing vibration, and in this study, without impacting penetration rate. A concentric reaming tool new to the drilling industry was used in both wells as a part of this study and will also be described. This tool demonstrated good steerability with a rotary steerable tool system and operated properly, drilling closed, activating, reaming, and finally, closing for retrieval from the hole. Introduction The purpose of this paper is to describe testing done under downhole-controlled conditions in identical, side-by-side wellbores with heavily instrumented BHAs. The testing compared the results of drilling with a conventional bit/reamer system compared to a specially designed pilot bit synchronized to the reamer. In both cases, the BHA was designed with dynamics modeling software with the objective of minimizing vibration. The test results proved a methodology that matched the reamer and pilot bit to substantially reduce vibration.

Technological improvements of drilling and reaming methods continue to be evaluated and introduced to the drilling industry. This paper describes recent, controlled testing of new expandable concentric stabilizers and reamers, performed on a full-scale, highly instrumented drill rig. An inherent problem of drilling and reaming concurrently is that conventional fixed stabilizers run above expandable reamers can be no larger than the pass-through diameter of the restriction above it and thus cannot effectively stabilize the upper BHA, which often results in undesirable vibrations. However, recent controlled tests have been conducted in twin wells drilled from the same casing under a full-scale drilling rig, one well with only a concentric expandable reamer and the other with both expandable stabilizer and reamer. The testing has shown that utilization of this novel stabilizer produces significant gains in performance. BHA modeling predicted lower bending moments above the reamer when a concentric stabilizer was utilized. The well drilled with the stabilizer above the reamer resulted in higher ROP with lower downhole WOB and up to 35% reduction in drilling mechanical specific energy (MSE), as compared to the well drilled without the expandable stabilizer. The stabilized well had significantly better drilling efficiency, which is attributed to reducing buckling and whirl in the drill pipe and upper BHA, and reduced frictional losses against the borehole wall. Additionally, lower levels of whirl, lateral and stick-slip vibrations were recorded with the new expandable stabilizer. The paper describes the novel design features of this expandable stabilizer, which are credited with the step-change improvement in drilling efficiency. Monetary savings from increased drilling efficiencies and improved reliability are anticipated for operators and will be discussed in this paper. Introduction The following three passages from previously written technical papers introduce the subject of this paper and the inherent problem of stabilizing the BHA and collars above the reamer in the enlarged borehole. "Historically, concentric underreaming has been plagued by several challenges. Some reamers, especially earlier models used after drilling a hole, were not rugged and failed downhole, leaving parts behind to fish out. Some current industry concentric reamers have complex functionality, requiring a fine balance of WOB, flow, and pressure drops in order to activate and operate properly. Some have multiple sliding mandrels with close tolerances that have problems closing after use due to accumulation of solids. Some reamers require lower flow rates while drilling out the casing plug and then a higher flow rate to activate the reamer, sometimes failing to open and remaining closed the entire run. Some reamers utilize hydraulic pistons for cutter blades that are difficult to close and pull into casing after drilling with water-based mud. These hydraulic reamers had problems with blades closing under reaming of high-angle holes due to weight of the BHA. Some of the reamers in the market have had small and less-effective cutter blocks that only allowed a few PDC cutters, reducing their life and cutting efficiency." (Radford et al. 2008)

This paper introduces bending tool face, a new measurement with applications in directional drilling. The measurement is derived from two perpendicular bending moment sensors in the BHA and identifies the orientation of BHA bending with respect to gravity high side while drilling, both in rotating and sliding modes. The paper presents the underlying theory and motivation for the measurement, describes its implementation into a downhole MWD tool and shows measurement examples from field applications. Furthermore, the paper outlines the use of the data for directional calculations. The paper concludes with a discussion of applications in which the bending tool face information adds value, such as reducing uncertainty in casing exit applications and improving directional control in challenging 3-D well profiles. The discussion is supported with field results.

One of the many challenges for the industry is how to extend the limits from rig capacities without significantly increasing cost; this is a perpetual problem which will continue to challenge the industry as the perceived norms for well designs are driven forward, with the need to tap into ever deeper and more distant targets. A way to address this challenge is to use a lighter drill string. The objective of this investigation was to determine whether, by reducing string weight and changing the material properties of the drill string it is possible to extend the operational envelope of the drilling rig; without having a detrimental impact on the drilling process. A field testing program was carried out on a full-scale experimental drilling rig in Oklahoma, USA. To test this hypothesis, steel drill pipe (SDP) was exchanged for aluminum drill pipe (ADP). By utilizing this methodology, it is possible to greatly reduce the weight of the drill string without significantly reducing its mechanical integrity. Two representative, well-known geological sections on separate wells were drilled with a string containing ADP. Extensive surface and downhole datasets were obtained on these wells. Dynamic drilling data was recorded at three discrete points along the drill string. At two of these three points, mechanical drilling data was also collected. An advanced modeling package was used during the planning phase of these wells and during the post-drilling analysis of the datasets. Through interpretation of the results from the testing program and by extensive modeling, it was possible to extrapolate the extent to which the operating envelope may be extended. These models were then used to challenge Extended Reach Drilling (ERD) profiles and investigate if the drilling envelope could be extended by applying ADP to future projects.