There are many benefits to reducing friction along the drill string while drilling directional wells. Higher rates of penetration (ROP), improved tool-face control, reduced drag, and reduced stick/slip are only some of the benefits documented in previous technical papers. There are generally two types of downhole tools used to generate benign vibrations within the drill string and/or bottom-hole assembly (BHA) to reduce friction: axial oscillation tools (AOTs) and lateral vibration tools (LVTs). This paper reviews the benefits and drawbacks of each of these types of tools and presents the results of mathematical modeling and field data to conclude which type of tool is more effective at reducing friction in horizontal wells. Axial oscillation tools typically employ a valve driven by the mud flow to generate pressure pulses. A shock tool is run above or incorporated into the AOT to convert these pressure pulses into an axial oscillating motion. This motion travels up and down the drill string to reduce friction between the pipe and the borehole wall. Lateral Vibration Tools (LVTs) typically employ one or more eccentric rotating masses driven by the mud flow. This creates a vibration in the lateral direction, perpendicular to the long axis of the tool, creating motion between the tool and the borehole wall and thereby reducing friction. To investigate the potential benefits of each type of tool, a mathematical model of a BHA and drill string was created and, using finite element methods, the friction reduction effect (in terms of drag reduction) was compared between the AOT and LVT. In each scenario evaluated in the study, a benchmark calculation was first made with no oscillation. Then, the oscillation for each tool was applied and the response of the system evaluated with respect to the improvement in weight transfer along the drill string. Afterwards, the results were compared to an actual case study for verification. The research concludes that axial oscillation tools provide significantly more effective friction reduction, which enhances drilling performance in horizontal wells. The paper also provides several additional examples of comparative field results.

Vitamin D plays a major role in bone health and probably also in multiple extraskeletal acute and chronic diseases. Although supplementation with calcifediol, a vitamin D metabolite, has demonstrated efficacy and safety in short‐term clinical trials, its effects after long‐term monthly administration have been studied less extensively. This report describes the results of a 1‐year, phase III‐IV, double‐blind, randomized, controlled, parallel, multicenter superiority clinical trial to assess the efficacy and safety of monthly calcifediol 0.266 mg versus cholecalciferol 25,000 IU (0.625 mg) in postmenopausal women with vitamin D deficiency (25(OH)D < 20 ng/mL). A total of 303 women were randomized and 298 evaluated. Patients were randomized 1:1:1 to calcifediol 0.266 mg/month for 12 months (Group A1), calcifediol 0.266 mg/month for 4 months followed by placebo for 8 months (Group A2), and cholecalciferol 25,000 IU/month (0.625 mg/month) for 12 months (Group B). By month 4, stable 25(OH)D levels were documented with both calcifediol and cholecalciferol (intention‐to‐treat population): 26.8 ± 8.5 ng/mL (Group A1) and 23.1 ± 5.4 ng/mL (Group B). By month 12, 25(OH)D levels were 23.9 ± 8.0 ng/mL (Group A1) and 22.4 ± 5.5 ng/mL (Group B). When calcifediol treatment was withdrawn in Group A2, 25(OH)D levels decreased to baseline levels (28.5 ± 8.7 ng/mL at month 4 versus 14.4 ± 6.0 ng/mL at month 12). No relevant treatment‐related safety issues were reported in any of the groups. The results confirm that long‐term treatment with monthly calcifediol in vitamin D‐deficient patients is effective and safe. The withdrawal of treatment leads to a pronounced decrease of 25(OH)D levels. Calcifediol presented a faster onset of action compared to monthly cholecalciferol. Long‐term treatment produces stable and sustained 25(OH)D concentrations with no associated safety concerns. © 2023 Faes Farma SA. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

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