Drilling Now
Authors: Kelly John 
Published: December 2007

Distinguished Author Series articles are general, descriptiverepresentations that summarize the state of the art in an area of technology bydescribing recent developments for readers who are not specialists in thetopics discussed. Written by individuals recognized as experts in the area, these articles provide key references to more definitive work and presentspecific details only to illustrate the technology. Purpose: to informthe general readership of recent advances in various areas of petroleumengineering.

In recent years, the energy problem and the extraordinarily high pricesplaced on produced oil and gas by the OPEC nations have combined to make anunusual demand for drilling rigs and drilling personnel. In the U.S. alone, anestimated 64,628 personnel. In the U.S. alone, an estimated 64,628 wells weredrilled during 1980. This an increase of 26% over the number drilled in 1979.The prediction for 1981 is that more than 70,000 wells will be drilled. Theshortage of drilling figs and personnel has made the cost of drillingskyrocket. As a result, operators have focused on the factors involved indrilling in an effort to reduce the cost. Increased attention has been given toresearch on drilling problems and improvement of drilling techniques. Equipmentmanufacturers have concentrated on improvements in drillstring components, rigdesign, wellhead units, logging devices, cementing equipment, etc.Drilling-fluid service companies and operators with research departments areworking to improve the capabilities of drilling fluids; striving to extendtheir temperature limits and to improve their wellbore stabilizationcharacteristics. Courses developed to train new drilling personnel and toimprove the abilities of experienced personnel and to improve the abilities ofexperienced drilling people have appeared in operator and service companyprograms. Many are being presented by universities and consultant groups. Ibelieve some of the technology and equipment developed during the last year orso will have a significant impact on drilling operations now and in the future.Essentially all these advances relate to reducing the cost of drillingwells.

Measurement While Drilling. One of the most unusual developments to betested successfully and used recently is measurement while drilling (MWD). Thepotential use of this tool to reduce drilling costs is almost unlimited.Several types have been developed, including those requiring an electricallyconductive means of transmitting downhole signals and those using mud pulsingto accomplish signal transmission. Basically, the systems provide almostinstantaneous downhole survey data, bottomhole temperature and pressure, formation conditions and types, and perhaps pressure, formation conditions andtypes, and perhaps other parameters. However, none of the MWD systems now onthe market provide all these measurements. The value and potential of obtainingessentially continuous hole survey data have been described in a recent JPTarticle describing the use of an MWD tool in directional drilling on theClaymore platform. The authors reported significant direct time savings fromthe reduction in survey time achieved through the use of MWD techniques inplace of conventional wireline surveys. Their so-called second-tier benefitsappeared even more significant. These benefits included "reduced number oftrips, extended length of bit runs, and reduced number of mud motor correctionruns." In addition, they concluded that important benefits were obtainedthrough increasing the rate of penetration and reducing dogleg severity and therisk of penetration and reducing dogleg severity and the risk of differentialpressure sticking. A summary of these "non-direct time savings" follows. Thenumber of trips was reduced because (1) corrective directional action could beachieved by using weight on bit rather than by changing the bottomhole assembly(BHA), and (2) the optimal BHA could be determined sooner. Bit runs could beextended because fewer trips were made to change BHA's. Hence, the tendency tochange bits at the same time was reduced. Mud motor runs were reduced becauseearly detection of directional problems allowed the use of more conventionalmeans (weight on bit, rotary speed, and mud flow) to solve the problem.Improved penetration rates were obtained because directional data feedbackpermitted carrying more weight on the bit without affecting the direction.Better directional control reduced the frequency of doglegs and key seating andreduced the torque. The possibility of differential pressure sticking wasreduced because circulation of the drilling fluid (but not rotation of thepipe) could be continued while the survey was being made. Another MWD tool'sperformance recently reported depends on an electrical conductor to transmitthe data from the downhole instrument package to the surface. The parametersmeasured are package to the surface. The parameters measured are downholepressure, mud resistivity, temperature, and hole inclination. One of theadvantages claimed for the unit is that it appears to help detect a kick andevaluate the steps necessary to handle it properly. Note that most MWD toolsinclude some way to determine the directional parameters of the well beingdrilled. If a well drilled using such a tool later blows out, the directionalinformation will be invaluable in planning for intercept kill wells. Now indevelopment planning for intercept kill wells. Now in development is a seismicmethod of locating the drill bit in a drilling well by analyzing the noisegenerated. Such a system could provide important information to guide a bit toa specific target.

Developments in Bits. Probably the most dramatic development in bittechnology is the Stratapax TM drill blank made by General Electric Co. fromsynthetic diamonds and a disk of cemented tungsten carbide. These blanks havebeen included in bits designed by various companies, and their impact onpenetration rate has been nothing short of unbelievable. One company reportsthat using a Stratapax-type bit with a turbodrill produced an increase inpenetration rate amounting to four times that of comparable wells drilled withtheir best selection of rock bits.