As long as a rig has the appropriate GPM and pressure ratings, it’s a YES. Let’s say for example a contractor has a rig with a pump rated at 150 GPM by its maker. The score is based on pumping water with a new pump. Realistically, we have a pump that will probably pump mud at 100 to 120 GPM. This suffices flow to power a 3- 1/2-in. Mud motor in its mid flow range requirements. At that circulation rate, we can inspect the engine’s efficiency curve and discover we have around 550 ft. Lbs. of revolution at 150 RPM. This will operate well enough in rock up to 15,000 psi. However, if the job is in rock that is 25, 000 psi, it will considerably reduce the penetration rate, decreasing the ROP to the point that it ends up being economically not practical. In this case, the specialist would require a larger rig with a bigger mud pump to power a bigger mud motor to succeed over the strength of the rock.
An important point to remember is that the contractor’s ability to recycle and clean the drilling mud. If you are pumping around 100 GPM, you will drain pipes 1, 000 gal mud blending system in 10 minutes, obviously, give the need to recycle drilling mud.
What errors do drillers make with mud motors?
Probably the most common error is what is done when mud motor stalls out? A stall-out takes place when the drill stops turning or working while pumping. We have three Mud Motor pump pressure readings we keep track of while using a mud motor:
1. Off-bottom pump pressure
2. The on bottom pump pressure
3. The stall pressure
Let’s state our specialist has an off bottom pressure reading of 500 psi and on the lower reading of 750 psi. While drilling, he applies excessive weight on the bit, triggering it to stop turning. The pressure now reads 825 psi, and at this point, most drillers pull the engine off the bottom and resume drilling. This approach will send reactive torque up the drill string and could trigger the motor or drill pipe to loosen. What is the correct method to take when a motor stalls are to do the following:
1. Turn the pump off.
2. Pull the motor off the bottom.
3. Restart the pump and proceed to bottom.
Another problem is the fact that you are doing your finding behind the mud motor. You have your drill bit, mud motor and crossover sub, then your steering system. It does not matter if you are using a wireline steering tool or a walkover system– if the rig is using a 4- 3/4-in. Mud motor, your steering system is 20 feet behind the drill bit. This causes the specialists or the driller to overreact and drill an S-curved pilot hole. He sees he is heading left of centerline, so he steers right, then he sees he is heading right, so he steers left so on and so on. This circumstance will fix itself as the operator ends up being used to drilling with a mud motor.