Summary This paper presents a method for determining the fatigue behaviour of Drill String (DS) components under given environmental conditions. Over the past few years. field data for DS failures have been gathered from certain wells drilled in Italy. West and North Africa. Clearly, fatigue phenomena were identified as the main cause of most of such failures. Among the several factors that can affect DS element fatigue resistance are tensile load. makeup torque. material properties. corrosive environment. abrasive wear and so on. However, simply on the basis of the existing guidelines it is difficult to define the real cause of a failure under given operating conditions. Based on a comparative study of full-scale fatigue test results and field data. a new approach is suggested for the analysis of some of the drilling technology factors that can affect the DS fatigue behaviour. IntroductIon DS is subject to great stress variations during service such as different kinds of dynamic and static loading. mud corrosion. temperature and so on. This, in combination with high stress concentrations. makes DS susceptible to fatigue damage which is still a major concern for Oil Companies and Drilling Contractors. On the other hand. in the available literature it is possible to find recommendations on how to take fatigue into account. As a matter of fact. according to, DS fatigue resistance analysis, for drilling directional wells. is carried out by means of drill pipe (DP) combined loading curves or given equations. Published curves display stress as a function of combined tension and dogleg, and show regions of "no fatigue damage" and "fatigue damage". However. this approach is based on the knowledge of the cyclic load history which is usually very difficult to quantify. Current methods for evaluating the drilling equipment fatigue failure risk as well as analysing failures are usually based on full-scale fatigue test results. The results of such investigations show that all factors affecting the DS element fatigue resistance can be divided into two main groups that can be defined as construction factors and drilling technology factors. Construction factors refer to fatigue characteristics of the tubular goods as they leave the manufacturer, such as the following:- type and size of DS components;- material characteristics;- design parameters;- strengthening methods (SRF, CW and so on). None of these factors can be changed at the rig site. On the other hand. drilling technology factors can be defined as those that can be "worked on" at the rig site such as:- tensile load;- makeup torque:- abrasive wear;- mud corrosion;- tripping technique, equipment and so on. In other words, drilling technology factors depend on the drilling technology itself. In this paper, the terms construction and drilling technology factors, as described above, will be used extensively. Full-scale fatigue tests on DS elements have been performed for years and represent the basis for evaluating the effect of these factors on DS fatigue resistance. However. the existing specifications limit the possibility of changing the DS element construction thus making any change of construction factors while operating "unpractical".

This papar was prepared for presentamn at the lS9d SPE European Petroleum Confefenca held m MlIan, Italy, 22-24 October 199STtus paper was selecled for pres6Waticmw an SPE Prqram Committee following review of information ccataimd in an abstract subm-,itbdby the author(s). Ccalen!s of the paper, as presented, have not ken rev!ewd by lhe Sc.oeiy CJPetroleum Engineers and we subjsct!0 correction~the author(s). The material, as presented, does not necessarily retlect any psition of the SocIely of Petroleum Engineers, its officers, or membels. Papers presemti al SPE mm3tlng8are subj8ct to publiMion revmw by Edtiorial Committees of tfm S&5efy of Petroleum En@wers, Permissionm copy Is reslncted to an abstracf d not more Ihan S00 wards, Illustrallons may not tm copied. The absfract should contain conspicuous acknowledgnmt of where and by tiom the pa$w was presented. Wriie Liixarian, SPE. PO. Box 8338S8, Rrhardscm, TX 75083-3s36, u.S A., fax Of -2 14-952-943&

This paper was prepared for presentation at the 1999 SPE Annual Technical Conference and Exhibition held in Houston, Texas, 3–6 October 1999.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractAutomated directional drilling systems were amongst the key deliverables in a recently concluded joint development program between an oil company and an oilfield service provider. The two automated directional drilling systems as developed in the project have a certain degree of commonalty, however, there are also major differences in the way they work. The field experience described here was the first opportunity to run both tools together in the same well. Each of them was able to demonstrate it's specific and unique capabilities. The drilling strategy for Monte Enoc 9 required the use of a straighthole drilling system, SDD, in the upper hole sections and the rotary steering system, AutoTrak, in the 8 ½" hole size. By synergistically using the new automated tools, Monte Enoc 9 was drilled in a much more efficiently than offset wells, producing substantial time savings, a smoother hole trajectory, and less friction. The concluding 6" hole section of the well could be drilled and steered in a much easier fashion than expected because of the good conditions created in the vertical and curved hole sections. The drilling strategy as practiced in ME9OR will be further optimized to allow for even greater savings.

a-titiin n! MIII.O canwwtmn m the so&tv d Pntmlaum Enghmam and are su@l to correction by the authw(s). The =;~'~-~nb-,'& '~"=~;&;-~~"~=~~~-S~{Or"~fi;~w;~-=rn,-~r-~m-~~~"-s w-nt~at sp~l~m@n9s am Wb* m publ~tlr wbw by Edhodal Cemm12te8nof me SPE and v@C. Permb.$lon to copy is mwlcted to an abstract of not mare than WO wwds. Illustratbns may not be copied. The abstract should cmtaln conspkuc+m acknowledgment of where and by whom the paper b Presented. Write Ltiwisn, SPE, P.O. SoX 822626 Rk~ti~,~7~, U.S.A. Telex, 162245 SPEUT. AbstractManaging drilling operations requires a careful and skilled use of all the information available.In most cases, the information is processed by statistical methods. However, sometimes there is the risk of neglecting some par+ of the information, thus biasing the decision-making process.In our opinion, the reliability approach can overcome this problem.This paper aims at showing how it is possible to effectively manage the performance of the drillstring by constantly monitoring the reliability of every single drillstring component.