I'm fascinated that you can bore a hole vertically down 2,5km into the ground then steer it to go horizontal.
My curiosity is such that I'm going to have to do some reading about directional drilling.
to change to directional drilling we install a Downhole motor, now if you know what a Mono pump is than the Downhole motor is similar in design except we vary the amount of lobes we use depending on if we want high speed low torque or low speed high torque, generally we use a 3 or 4 lobe motor
Straight behind the drill bit we install a bent sub that we can change the bend on but for a fairly standard angle of build would be around 1 3/4 to 2 degrees, then the Downhole motor and behind that we have an MWD which is a Measurement While Drilling tool which is very expensive
Motor and MWD would measure in at around 14-18 meters overall length together depending on what other kit we bolt on as well
At surface before running in hole we orientate the axis of the bent sub to a compass reading and tell the MWD unit where it is pointing and then we run in hole
We don't just blindly start drilling, team of rock doctors (Geologists) and the Drilling Engineers have plotted the path we need to follow before we start drilling
At surface we have a large wall mounted compass on the drill floor and when the Mud pumps are on the MWD unit sends pulses back through the mud column to a transponder on surface telling us what the inclination of the hole is and at what compass bearing the drill bit is facing
We turn the drill pipe at surface manually to obtain the compass reading we want by watching the compass readout on the drill floor
Can turn the pipe with a pair of Stillsons at surface until the build angle gets to high, we also add another 15-25 degrees to counter the reactive torque, then with Mud Pumps on we lower the drill string on to the bottom, at this point only thing spinning in hole is the drill bit
When the bit hits bottom you will see the string turn back slightly which is the reactive torque and then by watching Weight on Bit and the Mud pump pressure we "slide" the pipe down the hole, when "kicking off" the drill string is not turning
We then depending on how fast or slow we wish to build angle we will say "slide for 3 meters, rotate for 3 meters which is when we actually rotate the entire drill string and then "slide" again and repeat until we build to the angle we wish to get to
It may be that the well design is vertical to 2,500 meters, build angle to 45 degrees and than hold that 45 degrees through to say 3,750 meters and than start building again to horizontal and which point we need to push the drill string to the end of well
If we wish to get really technical we can also install a LWD tool behind the MWD and that stands for Logging While Drilling so that really expensive piece of kit is sending back to surface again by various pulses through the mud column to another tricky transponder on surface a whole pile of downhole data, Sonic Log, Gamma Ray, Neutron Porosity, Density Caliper, Resistivity, Formation Pressure and a number of other logs we can record depending on how much the client wants to pay
By running a LWD, MWD and DHM we can stay within an oil or gas bearing reservoir by seeing the LWD data at surface and we can see when we are about to drill out of it either at the top or the bottom of the reservoir by the change in rock formation so we roll the bit over to either drill up slightly or down slightly to follow the contour of the formation
In Siberia we generally drilled horizontal for 3-4,000 meters at a vertical depth of between 3-3,500 meters, depending on what part of the field we were in
So TMD or Total Measured Depth would be around 6,500 meters at a TVD or Total Vertical Depth of say 3,000 meters
If we are running LWD, MWD and a DHM look at a total cost of around US$2,500,000 just in those 3 tools and the LWD will nearly always have a radioactive source on board so if you lose that downhole, big issue
In Ukraine we had to drill through a super hard formation for nearly 1,000 meters vertical, went from around 3,500 meters through to 4,500 meters and we used Downhole Turbines that are high speed motors and Diamond Impregnated 12 1/4" drill bits that cost us US$115,000 each
Drill bits were manufactured in Belgium and Maxene and I visited their facility when we were on break, fascinating visit
Serious drilling in Ukraine wells were HTHP, "High Temperature, High Pressure" and all vertical, deepest we drilled was 6,480 meters and if we lost the well we would have seen well over 15,000 psi at surface
Now I just build Laverda cranks, my life has gone to shit
