Slideshow image
   
becpl
Mfg. of Water well Drilling Rigs, Dth Hammers and Button Bits...
 
phe
Water Well Drilling Rigs, Dth Drilling Rigs, Rotary Drilling Rigs...
 
phe
Blast hole Drills, Water Well Drilling Rig, Mud Pumps, Vertical Turbine Pumps...
klrsai deepagetechjcr
 

New Drill Bit Technology The Deep Trek Program

Drill-Bit
Rate of penetration (ROP) is a major issue in deep wells. Low ROP (e.g., 3-5 ft./hour) primarily is a result of the high compressive strength of the highly overburdened formations encountered at greater depths. Initially, the tricone bits with hardened inserts used for drilling hard formations at shallower depths were applied as wells went deeper. However, at greater depths, it is more difficult to recognize when a tricone bit’s bearings have failed, a situation that can occur with greater frequency when greater weight is applied to the bit in a deep well. This can lead to more frequent failures, lost cones, more frequent trips, higher costs and lower overall rates of penetration.

Fixed cutter bits with polycrystalline diamond compact (PDC) cutters were a solution to the problems inherent with tricone bit moving parts. The PDC cutting surface employs synthetic polycrystalline diamonds bonded to a tungsten-carbide stud or blade. First developed in the 1970s, this type of bit now holds the record for single-run footage in a well (22,000 ft.). PDC bits typically drill several times faster than tricone bits, particularly in softer formations, and PDC bit life has increased dramatically over the past 20 years. But PDC bits have their own set of problems in hard formations. For example, “bit whirl” is a problem that occurs when a PDC bit’s center of rotation shifts away from its geometric center, producing a non-cylindrical hole. This can result from an unbalanced condition brought on by irregularities in the frictional forces between the rock and the bit, analogous to an unbalanced tire causing vibrations that spread throughout a car at higher speeds. PDC bits are more susceptible to this phenomenon, as well as to “stick slip” problems, where the bit hangs up momentarily, allowing its rotation to briefly stop, and then slips free at a high speed. While PDC cutters are very good at shearing rock, they are susceptible to damage from the sharp impacts that these problems can lead to in hard rocks, resulting in reduced bit life and lower overall rates of penetration. New PDC bit designs include features that attempt to address these problems – force balancing, spiraled or asymmetric cutter layouts, gauge rings, and hybrid cutter designs, to name a few.

However, PDC bits still have some shortcomings when drilling in extreme environments. Sandia National Laboratories currently is working in cooperation with industry and university partners to improve the hard-rock, high-pressure, high-temperature drilling capability of PDC bits. After much testing and computer modeling of stresses, high temperatures, hydraulics and wear mechanisms, a reliable thermally stable polycrystalline (TSP) diamond bit is being developed.

Rate of penetration (ROP) is a major issue in deep wells. Low ROP (e.g., 3-5 ft./hour) primarily is a result of the high compressive strength of the highly overburdened formations encountered at greater depths. Initially, the tricone bits with hardened inserts used for drilling hard formations at shallower depths were applied as wells went deeper. However, at greater depths, it is more difficult to recognize when a tricone bit’s bearings have failed, a situation that can occur with greater frequency when greater weight is applied to the bit in a deep well. This can lead to more frequent failures, lost cones, more frequent trips, higher costs and lower overall rates of penetration.

Fixed cutter bits with polycrystalline diamond compact (PDC) cutters were a solution to the problems inherent with tricone bit moving parts. The PDC cutting surface employs synthetic polycrystalline diamonds bonded to a tungsten-carbide stud or blade. First developed in the 1970s, this type of bit now holds the record for single-run footage in a well (22,000 ft.). PDC bits typically drill several times faster than tricone bits, particularly in softer formations, and PDC bit life has increased dramatically over the past 20 years. But PDC bits have their own set of problems in hard formations. For example, “bit whirl” is a problem that occurs when a PDC bit’s center of rotation shifts away from its geometric center, producing a non-cylindrical hole. This can result from an unbalanced condition brought on by irregularities in the frictional forces between the rock and the bit, analogous to an unbalanced tire causing vibrations that spread throughout a car at higher speeds. PDC bits are more susceptible to this phenomenon, as well as to “stick slip” problems, where the bit hangs up momentarily, allowing its rotation to briefly stop, and then slips free at a high speed. While PDC cutters are very good at shearing rock, they are susceptible to damage from the sharp impacts that these problems can lead to in hard rocks, resulting in reduced bit life and lower overall rates of penetration. New PDC bit designs include features that attempt to address these problems – force balancing, spiraled or asymmetric cutter layouts, gauge rings, and hybrid cutter designs, to name a few.

However, PDC bits still have some shortcomings when drilling in extreme environments. Sandia National Laboratories currently is working in cooperation with industry and university partners to improve the hard-rock, high-pressure, high-temperature drilling capability of PDC bits. After much testing and computer modeling of stresses, high temperatures, hydraulics and wear mechanisms, a reliable thermally stable polycrystalline (TSP) diamond bit is being developed.


Drilling Today Contact