924287 Phenomenological model for the drilling action of drag bits Detournay, E; Defourny, P lnt J Rock Mech ,~,lin Sci II29, N1, Jan 1992, P13-23

Investigation of the drilling response of PDC bits in terms of weight on bit, torque, rotation rate, and rate of penetration is presented. Analysis is first made for a single cutter. This makes use of an early (1957) suggestion by Fairhurst and Lacabanne that torque and weight on bit can be decomposed into rock cutting and frictional contact components. A signature for the existence of these two processes is proposed and tested against published experimental data. The model for the drag bit is built by integrating contributions for each cutter. Influence of bit design on drilling response is examined.

924288 Limestone, shale penetration rate equations developed Osman, M E; Mohammed, S A Oil Gas J V90, N1, Jan 1992, P78-81

The influence of a range of parameters in drilling of Abu Dhabi shales has been studied: formation depth and character- istics, penetration rate, rotary speed, weight on bit, bit condi- tions, drilling fluid properties, mud pump dimensions, and pump pressure. Penetration rate increases slowly with increas- ing weight on bit, more rapidly with increasing rotary speed. Penetration rate equations are developed for shale and limes- tone. Drillability homographs are also illustrated for predict- ing penetration rate on the basis of weight on bit, rotary speed, and Reynolds number.

924289 Downhole motor specifically designed for directional air drilling Shale, L Oil Gas J V90, N5, Feb 1992, P45-49

A positive displacement motor, specifically designed for use with air as the drilling medium, is illustrated. It overcomes the inefficiencies of using conventional mud motors with air. The steering device which allows drilling of deviated boreholes is shown. Performance is compared to that of mud motors in terms of work efficiency and motor life. Case histories are described where these motors have been used in various for- mations with lost circulation problems.

924290 Model of a pneumatic jackhammer system Pang, S S; Goldsmith, W Rock Mech Rock Engng V25, NI, Jan-Mar 1992, P49-61

A complete model of the jackhammer system has been devel- oped. Two preliminary experiments were carried out, to estab- lish the relation between piston impact velocity and pressures acting on the top and bottom surfaces of the piston, and to determine force-indentation behaviour of the bit-target sys- tem. The model can be applied to any type or size of jackham- mer and allows prediction of efficiency and target response, including penetration and fracture propagation. It has been validated against test data using a commercial percussive drill and Sierra granite.

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924291 Fragmentation monitoring of production blasts at MRICA Ouchterlony, F; Niklasson, B; Abrahamsson, S Proc 3rd International Symposium on Rock Fragmentation by Blasting, Brisbane, 26-31 Aug 1990 P283-289. Publ Parkville: AuslMM, 1990

12 production blasts at a quarry near the Mrica damsite on Java were studied to test correlation between fragmentation and specific charge as well as structure and strength of the rock. The rock mass is mainly a competent low porosity ande- site, penetrated by thin porous bands, plus larger areas with porosity up to 20% and correspondingly lower strength. The thin bands, not immediately obvious, form intact weakness planes in the surrounding rockmass. They govern fragmenta- tion, mean particle size being almost independent of specific charge in the range 0.3-0.56 kg/cubic m. This knowledge allows reduction in drilling and blasting costs.

924292 Rock drillability comparison by different methods Singh, S P Proc 2nd International Symposium on Mine Planning and Equipment Selection,Calgary, 7-9 No~ember 1990 P489-494. Publ Rotterdam: A A Balkema, 1990

Drillability, the resistance of a rock to penetration, is a key parameter for matching drilling equipment to a particular operation to achieve maximum productivity. An overview is presented of the various approaches to drillability. Rate of penetration of a granite by a standard percussion drill as mea- sured in the field is compared to that from four drillability prediction equations. Models of Paone et al and of Hustrulid are seen to be reliable in predicting drilling rates.

924293 Application results of a new type non-resharpening tungsten carbide button bit for light duty rock drifter Xue Qingpeng; Gong Xiujun; Wang Dezhi Proc 2nd International Symposium on Mine Planning and Equipment Selection,Calgary, 7-9 November 1990 P495-498. Publ Rotterdam: A A Balkema, 1990

A newly developed eccentric tungsten carbide percussive drill bit is described. Results of its use in coal and gold mines and rock quarries, across a wide spectrum of rock strengths, are given. Comparisons are made of drilling rate and service life with the new bit and with conventional chisel bits. Mine appraisals are also presented and the economic gains possible with the new bit are discussed.

924294 Penetration behaviour of rock formations during exploration drilling operations in Turkey Akun, M E; Karpuz, C Rock Mechanics as a Multidisciplinary Science: Proc 32nd US Symposium, Norman, 10-12 July 1991 P415-422. Publ Rotterdam: A A Balkema, 1991

Results of research conducted on drillability of rock forma- tions at the Zonguidak hard coal basin site and Manisa- Maldan lignite basin site, Turkey, are discussed. Holes of 897m and 764m at Zonguldak were continuously cored using surface set and impregnated bits. A 703m deep hole at Manisa was completed using both surface impregnated coring bits and non-coring rock bits. Drillability is analysed considering such factors as lithology, bit type, bit wear, penetration rate, and RQD. Technical problems of cake formation and water loss and their solutions are described.

© 1992 Pergamon Press Ltd. Reproduction not permitted