DRILLING MUD MOTORS RUNNING PROCEDURES
Making-Up Mud Motor
- Pick up PDM, put in slips, install collar clamp, unscrew lifting sub.
- Test dump valve operation by hand (using water hose and e.g. handle of sledge hammer).
- If testing PDM, make up bit first, use x/o and kelly/top drive. (PDM new from base should be O.K.!).
- If testing PDM with a bent sub, keep pumping time to absolute minimum. Pick up MWD collar. Make up float sub & bent sub (by hand) onto collar. Stab bent sub pin into box of PDM.
- Align scribe line towards drawworks (or v-door).
- Pull MWD collar over with tugger so that bent sub threads are in line with PDM box threads (i.e. horizontal).
- Put make-up tong on bent sub body.
- Rotate rotary table (and hence PDM) slowly counter-clockwise.
- When all threads are engaged, torque connections to API value using rig tongs. Torque all connections up to MWD collar.
- Measure angular offset from slick pin to bent sub scribe line. Bring up bent sub scribe line mark to top of MWD collar
- P/U NMDC(s), UBHO (if used) and PRS. Stab into box of MWD collar.
- Torque connections up to UBHO. Put UBHO in slips. Install collar clamp below UBHO screws.
- Back out NMDC(s).
- Align key of UBHO sleeve with bent sub scribe line. Lock in place using screws. Make up NMDC(s) and RIH.
Running In With Mud Motor
- Hole should be circulated clean before running PDM. Go slowly in open hole. Driller must be careful!
- If high Bottom-Hole Temperature (BHT), break circulation periodically. If using float valve (normally), fill pipe at regular intervals.
- Be especially careful near bottom (fill etc.).
Getting On Bottom With Mud Motor
- About 1 single off bottom, P/U kelly. Circulate. Wash slowly to bottom. Clean hole using expected flow rate. Rotate slowly only if required!
- If doing single-shot kickoff, rack back kelly & work torque out of string before orientation survey.
- If using MWD, work pipe with pumps on (rotary locked) before taking orientation survey.
- Orient tool face before drilling.
- For "blind" sidetrack, orientation is not absolutely necessary. However, we must keep a toolface reference. Inclination is built along an arbitrary direction before being dropped back to vertical.
Drilling With Mud Motor
- Record off-bottom circulating pressure.
- If the standpipe pressure (SPP) is calculated and does not increase as WOB is applied, itâs an indication that the dump valve has not closed. Pick up off bottom, surge the pumps. Try to force the piston to close.
- As bit is lowered to bottom and drilling begins, torque demand on PDM increases. Pressure differential across motor (P motor) increases in proportion. We must limit Pmotor to the value recommended for the particular motor (e.g. 360 psi for D500 Dynadrill).
- Drill with pressure gauge (WOB gauge normally not accurate in sliding mode). Maintain a constant SPP while drilling. This ensures a steady DWOB in homogeneous formation. It should also ensure a steady tool-face (provided no change in formation).
- For trouble-shooting with a PDM in the hole, please refer to the DD UOP or the ANADRILL PowerPak PDM Manual.
POOH With Mud Motor
- Use pipe spinner in open hole.
- Rotate string slowly if necessary.
- If dump valve ports clear, we should pull "dry".
- Dump valve less likely to "work" in soft formation (ports plugged with formation).
- Slug must be kept well above dump valve when pumped.
Lay Down Mud Motor.
If you don''t look after your mud motor, it won't work for you next time! Its a good idea to paint on body of PDM the number of D+C (Drilling + Circulating) hours done so far with this tool. This is especially useful for your relief DD!
DRILLING MUD MOTORS LIMITATIONS
Mud And Mud Motor
- The motor will operate in either air/mist or mud; however, air drilling will limit motor life and the power output of the motor. There are some motors that are specifically designed to drill with air, mist and foam.
- Some oil muds are not compatible with the nitrile rubber stator and reduce the useful life of the positive displacement motor. Aromatics such as aniline can swell and deteriorate nitrile rubber. The lower the aniline point of an oil, the more detrimental it will be on the rubber parts. Therefore, aniline points above 200ºF (93ºC) are recommended when using oil based muds.
- Diesel muds should be avoided.
LCM And Mud Motor
- Lost circulation material can be used with downhole motors but it should be medium or fine LCM. Larger LCM or poorly mixed LCM may plug the flow restriction into the bearings.
- Reduced flow through the bearings will lead to poor lubrication and will increase bearing wear. Subsequently, the motor life will be reduced.
Temperature And Mud Motor
- Most downhole motors have a temperature limitation. The rubber stator will get hard and brittle at temperatures above 300ºF (150ºC) and motor life will be limited.
- There are some motors available with high temperature rubber that can be used to a higher temperature.
- Additionally, as the temperature increases over 200ºF (93ºC), the rubber will swell causing less clearance between the rotor and stator.
- For high temperature applications, motors with more clearance between the rubber and stator are available
BHA And Mud Motor
- The basic drilling assembly for using a downhole motor consists of a full gauge bit, bent housing motor, mule shoe sub (if required), and MWD packaged in a non-magnetic drill collar.
- The bent housing tilts the bit and causes the motor to deviate.
- The downhole motor produces a continuous change in the wellbore course along a smooth arc of a circle. The arc or radius of curvature is defined by the bend in the motor, stabilizer size and stabilizer placement