Bit designers use the well-established practice of placing depth-of-cut (DOC) control features at strategic heights from the cutter profile to selectively manage drill bit aggressiveness and to maximize drilling performance. But, until now, the elements used for depth-of-cut-control were a fixed part of the bit. An innovative new feature enables compact element replacement and/or adjustments at the rig site using a mechanical locking design. The driller can quickly adjust the bit responsiveness before each run, if wanted, to optimize performance factors such as rate of penetration and tool face control. This paper describes the benefits, ease of use, positive results and reliability of this new technology with examples from multiple applications for a variety of bit designs. The final design was selected and validated based on a number of evaluation methods including concept screening tests, simulated laboratory drilling tests and field tests. The initial screening tests evaluated the ease of compact installation and removal for various concepts using a test block. Full bit testing using a full-scale, high-pressure, downhole drilling laboratory evaluated installation, integrity and aggressiveness response changes using compact height adjustments. Finally, multiple field tests on wells in North American applications of the Eagle Ford, Marcellus, and DJ basin formations provided data to refine the mechanical design and improve manufacturing processes to achieve a robust technology. Field tests proved the new design to be highly reliable, with drilling performance that matched or exceeded the performance of bits with standard brazed compacts in the same fields. This new design provided the unique ability to rapidly optimize bit responses. This paper describes the technical lessons learned, guidelines for use and tools developed to maximize the benefit from this innovative new feature. This new method enables compact element installation and removal within fifteen minutes on the rig site for the purpose of repair or aggressiveness modification. In contrast, traditional methods of DOC control include long lead times to alter bit design, manufacturing and delivery. Drillers can reap the immediate benefits of improved bit performance by changing bit design on the rig site using direct feedback of bit aggressiveness and steerability between runs without needing multiple bits on site. Ultimately, this new bit technology provides improved drilling performance and greater efficiency for the operator.
Numerous veins are present in basalts recovered from Hole 462A, Leg 61 of the Deep Sea Drilling Project. Three mineral assemblages are recognized and stratigraphically controlled. These assemblages are (1) a zeolite-bearing, quartz-poor assemblage which occurs from Core 44 to the bottom of the hole and contains smectite, clinoptilolite, calcite, pyrite, ± chabazite, ± analcime, ± quartz, ± apophyllite, ± talc (?); (2) a quartz-rich, pyrite-bearing assemblage, found between Cores 19 and 29, which contains smectite, calcite, quartz, and pyrite; and (3) a quartz-rich, celadonite-bearing assemblage which occurs from Cores 14 through 17 and contains smectite, calcite, quartz, celadonite, and Fe oxide.These data are interpreted to represent two episodes of vein mineral formation with an oxidative overprint on the more recent. The first episode followed the outpourings of basaltic lavas onto the sea floor. Zeolite-bearing veins were formed at elevated temperatures under low P cθ2 » while the thermal gradient was high and before a cover of calcareous sediments had formed. The second mineralization episode followed injection of basalt and microdiabase sills into a thick layer of sediments, and produced all the vein minerals now occurring between Cores 14 and 29. These veins formed at lower temperature and higher Pco 2 tnan ^e zeolite-bearing veins. The presence of pyrite indicates a nonoxidative environment. After the initial formation of these veins, oxygenated seawater diffused through the sedimentary cover and oxidized the pyrite and smectite, forming celadonite and Fe oxides.
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