Drilling in small diameters is not new : the mineral industry currently drills slim holes in hard rocks. In this context, the drill string rotates at high speed very close to the hole wall, which is in general of good stability.To transfer that drilling method to the oilfield and keeping high rotation speed and small annulus, many problems occur due to the sedimentary type of formations drilled, and hydraulics become crucial for following points of view : the lifting up of cuttings in the annulus (no ball i i up), the well bore stability, the cleaning of the bit, the differential mud pressure in the annulus, the hydrodynamic lubrication between rods and the well bore.Therefore, it is essential in slimhole to investigate drilling hydraulics, using basic theoretical equations derived from fluid mechanics.The developed model takes into account mud rheology, drill string rotation -and eccentric position of drill string. Outputs are annulus thickness, drilling parameters (including mud flow), and mud characteristics, all to be respected to reduce slimhole drilling problems. The final output is the compromise which integrates all these requirements for a successful operation. SPE 24596R. DELWICHE, M. LEJEUNE, P. MAWET, R. VIGHETTO Nomenclature AP annular pressure (bars), DP pressure losses (bars), ECD equivalent circulatin density (kg/m3>,

The growing interest in deeply buried reservoirs increasingly leads operators into extreme drilling conditions characterized by high hydrostatic pressure (over 20.000 psi) and high temperatures (over 300 °F), combined with hard formations (high CCS-40,000+ psi). Drilling in such environments requires specific adaptations of well design and in equipment selection. Additionally, these wells present multiple issues in well control, drilling and completion operations, and make the entire operation technically more complex and financially more risky.Referencing the specific example of drilling operations, the great depths and increased formation compaction leads to very low rates of penetration (ROP) and considerably extended operation time. These low ROPs equate to low depth of cut, and as a direct consequence the typical size of the drilled cuttings recovered at the shakers is extremely low (0.020 to 0.20 mm). This makes the cuttings irrelevant for the purpose of geological identification of the formations. This situation occurs with both impregnated diamond and PDC drill bits in these applications at low ROPs. If the downhole conditions (HPHT) exceed the MWD or LWD specifications, accessing critical geological information will necessarily require a challenging coring job, dramatically increasing the operation time and thus the cost of the well.

New bit technology was used to create a series of steel body bits which incorporate proven PDC bit design features for improved performance. The bits have achieved field records in fully one-third of the applications in which they were introduced. The technology described includes all aspects of bit application, including new manufacturing processes, advanced design engineering, a unique nozzle configuration and use of a computerized rock compressive strength analysis program to refine application. Field performance of steel body PDC bits is detailed and compared to conventional matrix body bits to illustrate the resulting performance improvements possible with proper steel body PDC bit application. P. 271

New steel body PDC bit technology is shown to enhance drilling performance in a range of applications previously limited to matrix body bits. Specific aspects of the technology are &taile& including various proven desigm features, and unique manufacturing and materials treatment. In addition. the paper addresses the impact of increasing energy available at the bit face through utilization of a new hydraulic jet technology in combination with the advanced features of steel body PDC bits. Case histories are included to describe the application range of the new steel body bits, in terms of Mh drilling performance and economic impact.

Copy flghl 1996 %x,ely of Petroleum Engineers, IncTh!s -r w= prqad for presentation at the lA@SPE Onlhng Cmferen6u heti m New Orbans, USA 12.15 Mafd! 1% l%m paper was salmed for Mascmtatlon ty m SPE Program COmmtiOO tollowmg mwaw cd mlormatlon contambd In an abstract by the author(s) Contents of Ihe paper, as presented, have nti Won mvmwmd by ihe .socmty o+ Pmrolaum Engineers and are subjected to mrrection by the autlmr(s) The tiewd, = Premented, doet not nemaawdy relkt any mwtmn C4the Sccmiy of Petroleum Engneem, is ofkem,orrmntws Pawn pmsantec al SW l?u3tlnq meWbpdadtoPhltitmnby Edd.nal Comrmtaes d the Smcdy O( Petroleum Engmews Pemmsmn to m q reotnctad to an alxtmd 01 nti mow Ihan 300 words Illuslrat!ons may not be ccpmd The abstract should contain conspmous acknowhdgement of wiwe and by whom the papvr was presented Wrae L[brarmn, SPE, P O BOX 632836 Rchwdson, TX 75CSXM36 U S A, fax 01-214.952-9435 ABSTRACTThe Iithology of the North West of Argentina presents two major portions where PDC bits have not succeeded in the past. The first~rtion was mainly made up of alternating sands and shafes with s~t zones of conglomerates erotically encountered. The second portion was made of dense shales and cemented sandstone stringers, with allemandes of limestones. In spite of acceptable performance on the top potion, conventional PDC bits faced premature failures when the compacted sandstones and limestones were faced. Reek bit performances were usually in the range of+ 6 to 7 m/h and the footage around 360 m. The section was drilled with five to six bits for a total drilling time of 220 hours. The introduction of a new generation of PDC bits aflowed to triple the ROP and increase by five times the potential footage. This paper desenbes the methodology and shows the efficiency of a good partnership between the operator and the service company; a good level of communication. a knowledge of muNat skitls and expectations. as well a!!a prompt reaction horn both sides led to the definition of a reliable product using the latest developments of the PDC bit technology : q the ability to control the quality of the PDC cutters, q the use of an advanced cutter lay out defined by 3-D software, q the use of CFD code for optimized cleaning and cooling, q the mastering of vibration reducing features, including spirafled blades etc, Savings in the range of 200,000$ per well were recorded at the fiist trial of a drifling program. Fine tuning of the technology and parameters now allow savings beyond 350,000$ per well. A 1 CT To As% 1w 448 4C6 5994