Stuck Pipe

Chapter Table of Contents

CHAPTER

Exit

Index

Handbook Table of Contents

Topic Page

Menu

12

Stuck pipe Contents Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-2 Differential sticking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-2 ENVIRO-SPOT spotting fluid . . . . . . . . . . . . . . . . . . . . . . . . 12-4 DUAL PHASE spotting fluid . . . . . . . . . . . . . . . . . . . . . . . . . 12-5 Determining depth to stuck zone . . . . . . . . . . . . . . . . . . . . . . . 12-9 Packing off . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-9 Undergauge hole . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-11 Plastic flowing formations . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-11 Wall-cake buildup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-11 Keyseating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-12 Freeing stuck pipe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-16

Exit

Chapter Table of Contents

Handbook Table of Contents

Index

Topic Page

Stuck pipe

Overview In drilling operations, the drillpipe is considered stuck when it cannot be raised, lowered, or rotated. Stuck pipe can be caused by several different mechanisms. Typical stuck pipe situations are: C C C C

Differential-pressure effects Packing off Undergauge hole Keyseating

Differential sticking Most incidents of stuck pipe are caused by differentialpressure effects. Excessive differential pressures across lower-pressure permeable zones can cause the drillstring to push into the wellbore wall where it becomes stuck. See Figure 12-1. Differential sticking may be identified by the following characteristics: C C

Pipe sticks after remaining motionless for a period of time Pipe cannot be rotated or moved when circulation is maintained

12-2

Exit

Chapter Table of Contents

Index

Handbook Table of Contents

Topic Page

Baroid fluids handbook

At moment of sticking Drill collar

Mud cake

Isolated area

After short time lapse Original cake thickness

Slightly thickened mud cake and fillet

Isolated area

Figure 12-1: Differential-pressure effect. The difference in pressure between the hydrostatic head pressure and the formation pore pressure forces the drillpipe into the wallcake and sticks the pipe.

To avoid or minimize the risk of differential sticking, follow these guidelines: C C C C C C C

Revised August 1, 1997

Drill with the lowest practical mud weight. Maintain a low filtration rate. Keep low-gravity solids to a minimum. Never allow the drillpipe to remain motionless for any period of time. Ream any undergauge section. Add appropriate bridging agents. Change to an oil/synthetic-based mud.

12-3

Exit

Chapter Table of Contents

Handbook Table of Contents

Index

Topic Page

Stuck pipe

When differential sticking occurs, spotting fluid can sometimes free the drillpipe.

ENVIRO-SPOT

spotting fluid

Note: It is critical to have a spotting fluid readily available and apply it within six hours of the stuck pipe occurrence. Spotting fluids are designed to penetrate and break up the filter cake. To mix the ENVIRO-SPOT spotting fluid, start with the required volume of oil and add ENVIRO-SPOT, water, and BAROID in that order. Base fluids can be diesel, mineral oil, water, etc. See Table 12-1.

ENVIRO-SPOT spotting fluid formulation for 100 bbl 7.3 (0.87)

10.0 (1.20)

12.0 (1.44)

14.0 (1.68)

16.0 (1.92)

18.0 (2.16)

Oil, bbl (m3)

64 (10.3)

58 (9.2)

54 (8.6)

49 (7.8)

51 (8.1)

44 (7.0)

ENVIRO-SPOT, 55 gal drum

6 (.98)

6 (.98)

6 (.98)

6 (.98)

6 (.98)

6 (.98)

Water, bbl (m3)

28 (4.5)

26 (4.1)

22 (3.5)

21 (3.3)

11 (1.7)

10 (1.6)

BAROID, lb (kg)

n/a

14,000 (6,350)

25,000 (11,340)

35,000 (15,876)

46,500 (21,092)

57,000 (25,855)

Weight, lb/gal (sg)

Table 12-1: ENVIRO-SPOT formulation. ENVIRO-SPOT is a good all-purpose spotting fluid suitable for use in many different drilling regions.

12-4

Exit

Chapter Table of Contents

Index

Handbook Table of Contents

Topic Page

Baroid fluids handbook

DUAL PHASE

Density

spotting fluid

Make the spotting fluid density equal to the mud weight in use. PHASE ONE has a starting density of 14.2 lb/gal (1.70 sg) and can be increased with calcium chloride to as high as 15.1 lb/gal (1.81 sg). PHASE ONE can be reduced with seawater/drill water to the desired density. PHASE TWO has a starting density of 8.6 lb/gal (1.03 sg). Adjust the density of PHASE TWO, as needed, by additions of weight material.

Volumes Needed PHASE ONE - 50 bbl minimum PHASE TWO - 100 bbl minimum Note: Larger volumes may be required to ensure that the stuck point is covered by the spotting fluid.

Displacement 1. PHASE ONE should be mixed in the slugging pit. Adjust the weight to the drilling fluid density. Pump PHASE ONE into the drill string at the normal pump rates. 2. PHASE TWO should be mixed in the slugging pit. Adjust the weight to the drilling fluid density. Pump PHASE TWO into the drill string at the normal pump rates. 3. Pump the PHASE ONE through the bit leaving 10 barrels of PHASE ONE inside the drill string (If the drill string capacity is greater than the volumes of both PHASE ONE and PHASE TWO pills), mud should be pumped to complete the spotting procedure.12-4

Revised August 1, 1997

12-5

Exit

Chapter Table of Contents

Index

Handbook Table of Contents

Topic Page

Stuck pipe

Soak Time 1. Break circulation once per hour pumping one barrel of fluid. PHASE ONE should have a minimum soak/exposure time of nine (9) hours. 2. After nine hours of soak time, pump PHASE TWO into the annulus at a slow pump rate. Leave 15 barrels of PHASE TWO inside the drill string. 3. Break circulation every hour pumping one barrel of fluid. 4. When the pipe becomes free, pump all of the DUAL PHASE out of the hole and discard the DUAL PHASE and interface. 5. Once the DUAL PHASE has been discarded, the mud should be conditioned with deflocculating and fluid loss control additives.

12-6

Exit

Chapter Table of Contents

Index

Handbook Table of Contents

Topic Page

Baroid fluids handbook

DUAL PHASE WORKSHEET Date

________________

Pipe

OD

ID

Capacity/ft

Operator

________________

DC

Offshore Area

________________

HWDp ____________________

Block

________________

Dp 1

____________________

Last Casing Shoe

______

MD/ft

Dp 2

____________________

Total Depth

______

MD/ft

Dp 3

____________________

Bit Location

______

MD/ft

_____________________________

Bit Size

______

inches

Hole Data

____________________

BHA Length

______

feet

Annular Vol. DC/OH

____bbl

Drill Collar Length

______

feet

Annular Vol. HW/OH

____bbl

HW Pipe Length

______

feet

Annular Vol. Dp 1

____bbl

Drill Pipe Length

______

feet

Annular Vol. Dp 2

____bbl

Drill Pipe Length

______

feet

Annular Vol. Dp 3

____bbl

Drill Pipe Length

______

feet

Annular Vol. Dp 4

____bbl

Total String Length

______

feet

Annular Vol. bit-shoe

____bbl

Pump Data

PHASE ONE Volume

Pump

______

bbl/stroke

Stroke to bit

______

strokes

Placing PHASE ONE & TWO

Feet of coverage DC/OH

____ bbl

Feet of coverage HW/OH

____ bbl

Feet of coverage Dp/OH

____ bbl

Strokes to Spot

Feet of coverage Dp/OH

____ bbl

PHASE ONE____ bbl

______

Feet of coverage Dp/OH

____ bbl

PHASE TWO ____ bbl

______

Footage Covered PHASE ONE

____ bbl

Vol.

Table 12-2: DUAL PHASE worksheet. This worksheet can be used to calculate the volumes required to be pumped and a pump schedule.

Revised August 1, 1997

12-7

Exit

Chapter Table of Contents

PHASE ONE Desired Density, lb/gal

Index

Handbook Table of Contents

50 bbl

PHASE ONE bbl

CaCl2 80 lb Sacks

Topic Page

Stuck pipe

PHASE TWO Water bbl

Desired Density, lb/gal

100 bbl

PHASE TWO bbl

Water bbl

Barite sacks

15.1 43 79 15.5 53 20 332 15.0 43 71 15.0 53 22 370 14.9 44 62 14.3 58 20 332 14.8 45 54 14.2 56 22 325 Note: At 14.8-15.1 lb/gal-TCT is 63E F 14.0 57 22 315 14.7 46 43 13.5 65 15 300 14.6 47 32 13.0 68 15 255 14.5 48 24 12.5 73 12 222 14.4 49 15 12.0 75 12 193 14.3 49 9 11.0 80 10 147 14.2 50 0.0 10.5 82 10 120 14.0 48 2 10.0 83 10 100 13.5 44 6 9.5 95 0 74 13.0 40 10 9.2 98 0 35 12.5 35 15 8.6 100 0 0 12.0 31 19 11.5 27 23 11.0 22 28 10.5 18 32 10.0 14 36 9.5 10 41 9.0 5 44 Table 12-3: DUAL PHASE density table. This table can be used to calculate the required amounts of materials to achieve the desired density.

12-8

Exit

Chapter Table of Contents

Determining depth to stuck zone

Index

Handbook Table of Contents

Topic Page

Baroid fluids handbook

Measure the drillstring stretch to estimate the depth that pipe is stuck. The following formula locates the depth at which the pipe is stuck. The length of free pipe is based on the drillstring dimensions and the measured amount of stretch. EeW 40.8 P Where L '

C C C C C

L is the length of free pipe (ft) E is the modulus of elasticity (30 x 106) (psi) e is the stretch (in) W is the weight of pipe (per ft) P is the amount of tension applied (lb/ft)

Packing off Drilling-fluid systems with poor suspension characteristics exhibit strong packing-off tendencies (see Figure 12-2). Factors that can lead to caving of the formation include: C C C

Revised August 1, 1997

Pressure imbalance Shale hydration Bottomhole assembly striking the wall

12-9

Exit

Chapter Table of Contents

Index

Handbook Table of Contents

Topic Page

Stuck pipe

Packing off

Figure 12-2: Packing off. Massive particle caving sticks the drillbit.

12-10

Exit

Chapter Table of Contents

Index

Handbook Table of Contents

Topic Page

Baroid fluids handbook

Undergauge hole Undergauge hole is a condition where the borehole is smaller than the bit diameter used to drill the section. Undergauge hole can result from any of the following causes: C C C

Plastic flowing formations

Plastic flowing formations Wall-cake buildup in a permeable formation Swelling shales

A plastic flowing formation is a formation that is plastic (easily deformable when stressed) and can flow into the borehole. When these types of formations are penetrated by the bit, the hole is at gauge. However, when the hydrostatic pressure exerted by the column of drilling fluid is less than the hydrostatic pressure of the formation, underbalance results, the formation flows, and hole diameter decreases. Undergauge hole is a common problem when drilling a thick salt section with an oil mud. The salt can flow into the borehole and make the section undergauge. When plastic salt formations exist, they are usually below 5,000 feet. Spotting fresh water is the best way to free the pipe from a plastic salt formation.

Wall-cake buildup

Wall-cake buildup occurs when the drilling fluid has poor filtration control across a permeable zone. Excessive wall-cake buildup can also be caused by: C C

Revised August 1, 1997

High percentage of low-gravity solids High differential pressures (excessive mud weights)

12-11

Exit

Chapter Table of Contents

Index

Handbook Table of Contents

Topic Page

Stuck pipe

Keyseating Keyseating is a situation frequently encountered in deviated or crooked holes when the drillpipe wears into the wall. The normal drilling rotation of the drillstring cuts into the formation wall in deviated areas where the drillpipe tension creates pressure against the sides of the hole. Keyseating is diagnosed when the drillpipe can be reciprocated within the range of tool joint distances or until collar reaches the keyseat, while pipe rotation and circulation remain normal. See Figure 12-3 for an example of a keyseat effect in a crooked hole.

12-12

Exit

Chapter Table of Contents

Index

Handbook Table of Contents

Topic Page

Baroid fluids handbook

Keyseating

A

A Section A-A

Position of the pipe before keyseating

Position of the pipe after keyseating

Figure 12-3: Keyseating. The friction generated by drillpipe rotation against the borewall cuts a narrow channel, or keyseat, into the formation.

Revised August 1, 1997

12-13

Exit

Chapter Table of Contents

Index

Handbook Table of Contents

Topic Page

Stuck pipe

A preventive measure is to carefully control upper hole deviation and dogleg severity throughout the well path. This action will eliminate the force that leads to keyseat creation. Once a keyseat is formed, the best solution is to ream out the small-diameter portions of the hole with reaming tools. See the example of reaming action in Figure 12-4. This action will solve the immediate stuck-pipe problem, but the keyseat can be formed again unless preventive steps are taken.

12-14

Exit

Chapter Table of Contents

Index

Handbook Table of Contents

Topic Page

Baroid fluids handbook

Reaming the Key

B

B Section B-B

Drill collar in keyseat

Reamer action in enlarging keyseat

Figure 12-4: Reaming action. Attach a reamer to the drill assembly to widen the keyseat.

Revised August 1, 1997

12-15

Exit

Chapter Table of Contents

Index

Handbook Table of Contents

Topic Page

Stuck pipe

Freeing stuck pipe The following guidelines can be used to free stuck pipe:

Cause...

Steps to free...

Differential sticking

Reduce mud weight. Use spotting fluid.

Packing off

Back off and wash over.

Undergauge hole

Increase mud weight. Underream.

Keyseating

Ream the keyseat.

12-16