NeXT Course_Practical Directional Drilling Problems and Solutions

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


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.


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).


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


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


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


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


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


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


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


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”


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


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


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


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


18

NeXT Course_Practical Directional Drilling Problems and Solutions

Recommend Documents