NeXT Course_Practical Directional Drilling Problems and Solutions
Short Description
Course material for directional drilling problem and solutions...
Description
Practical Directional Drilling Problems and Solutions
Copyright 2010, NExT, All rights reserved
Practical Directional Drilling Problems and Solutions At the end of this lecture, YOU should be able to: 1.
List common problems encountered in directional drilling
2.
Propose solutions to these problems
Copyright 2010, NExT, All rights reserved
2
Problems and Solutions 1 Costs related to directional versus vertical well
Rule of thumb – 1.50 to 1.75 times the cost of vertical well
Proper planning and communication is essential to reducing costs
Large target will reduce total well cost.
Copyright 2010, NExT, All rights reserved
3
Problems and Solutions 2 Torque
Caused by dog-leg severity, keyseating, balled-up drilling assemblies, poor mud properties and well path.
Some corrective measures are: use HWDP, minimize dogleg severity, and maintain drill fluid properties (mud weight, viscosity, filtrate and lubricity).
Copyright 2010, NExT, All rights reserved
4
Problems and Solutions 3 Drag - related to torque
Clean hole properly
Make short trips to reduce total drag (trip every ~300 mtrs of drilled hole, or every ~18 hours of drilling time)
Optimize BHA design
Optimize drillstring design
Use drilling fluid lubricants
Control dogleg development and eliminate keyseats
Copyright 2010, NExT, All rights reserved
5
Problems and Solutions 4 Dog legs - lead to torque
Shorten interval between surveys when drilling with limber hookups. This takes more time to survey.
Do not assume that dog-leg is removed by reaming. Make sure by re-surveying at same depth.
Plug back and sidetrack well if an excessive dog-leg cannot be eliminated
Copyright 2010, NExT, All rights reserved
6
Problems and Solutions 5 Key seats - more problematic in soft formations
Keep dog-legs to minimum
Design well KOP either deeper in well or in firm formation
Use keyseat wipers (hard formations) and string reamers (soft formations)
Run stabilizer near top of drillcollars
Make daily wiper trips
Monitor tripping drag, do not pull into keyseat
Copyright 2010, NExT, All rights reserved
7
Problems and Solutions 6 Differential sticking (wall sticking) – a potential problem when drill string is stationary, for instance during surveys and sliding portion of motor runs
Add lubricant (oil, surfactant, gel, etc,) to the mud system
Minimize time pipe is stationary
Reduce wall contact area - Use HWDP and spiral DC
Use stabilizers to prevent wall contact
Use drilling jars
Locate casing points to reduce open-hole exposure time
Locate casing seats to prevent having under pressured formation in same openhole with higher pressured formation
Copyright 2010, NExT, All rights reserved
8
Problems and Solutions 7 Hydraulics
Reduce bit hydraulic energy while building angle in soft formation
Control erosion with nozzle design and nozzle type selection
High annular velocities may erode hole while jetting
Do not circulate without moving location of pipe, avoid keeping bit at same location while circulating especially at high flow rates
Copyright 2010, NExT, All rights reserved
9
Problems and Solutions 8 Lateral drift
Normally influenced by bedding planes, hence use geologic structural maps for pre-planning
Use true rolling-cone bit (zero offset)
Use rebel tool (azimuth control tool)
Jet with packed BHA
Lead hole direction to plan for right hand walk
Copyright 2010, NExT, All rights reserved
10
Problems and Solutions 9 Small Hole and Ream Vs. One Pass
Larger holes are more difficult to control the direction
Dog-legs for larger hole are often not uniform
Small hole needs to be opened up to larger hole and adds to drilling time
Two BHA assemblies may be needed adding to handling time and tool rental
Smaller hole may yield higher quality logs
Copyright 2010, NExT, All rights reserved
11
Problems and Solutions 10 Plan Vs Actual
Plan the well will a lead to the left so as to anticipate normal right hand bit walk
Design left hand lead so that if no walk occurs, only one deflection tool run will bring it back to desired direction/inclination
Rule of thumb “Never allow yourself to be more than one tool run away from the target area”
Copyright 2010, NExT, All rights reserved
12
Problems and Solutions 11 Weight on Bit and Rotary Speed
Variation is used to control angle & walk
Because WOB & RPM are reduced, this method is not always conducive to maximum penetration rates
Varying WOB or RPM may introduce doglegs
Plan to maximize ROP by designing for high WOB with proper BHA design
Copyright 2010, NExT, All rights reserved
13
Problems and Solutions 12 Off-bottom Rotation
Creates a ledge and may lead to sidetrack
Aggravates and initiates keyseating
Increases cyclic stress on drillstring and may lead to drillstring fatigue failure
Unless pipe is reciprocated may lead to localized erosion and hole washout
Copyright 2010, NExT, All rights reserved
14
Problems and Solutions 13 Well Collision Common consideration for multi-platform or drilling pads – develop structural plots (spider diagram) Project radius of uncertainty and traveling cylinder Curved conductors may be necessary Magnetic interference very likely, use gyro orientation survey and short course lengths between surveys Ensure all other wells are accurately surveyed Monitor pressures in all wells on pad/platform subject to potential intersection Copyright 2010, NExT, All rights reserved
15
Problems and Solutions 14 Target Definition - Hard & Soft Lines
Soft lines ( e.g. target radius, target intersection requirement, etc.) are preferred because hard lines cannot be changed, varied, or extended (lease or fixed areas). Select big target size
Copyright 2010, NExT, All rights reserved
16
Problems and Solutions 15 Casing Wear Use drillstring protectors on the drill string Slow rotary and tripping speeds Monitor torque and drag in casing Use ditch magnets to monitor wear rates Run casing inspection logs Reduce low gravity solids content in mud Design with lower KOP, control dogleg severity Consider potential for wear in casing design phase Copyright 2010, NExT, All rights reserved
17
Directional Drilling Problems and Solutions Now, YOU should be able to: 1.
List common problems encountered in directional drilling
2.
Propose solutions to these problems
Copyright 2010, NExT, All rights reserved
18
View more...
Comments
