Stuck Pipe

STUCK PIPE DEFINITIONS STUCK PIPE

TIGHT HOLE

Planned operations are suspended when down hole forces prevent pulling the string out of the hole. Down hole forces restrict string movement above normal operating conditions (a usual warning indicator of a stuck pipe event).

TYPES AND CAUSES OF STUCK A. B. C. D.

Key-Seating. Caving. Under gauge hole. Differential stuck.

A. Key-Seating: This usually occurs in deviated holes when the drill pipe wears into the wall of the hole. Since the drill pipe is the smallest diameter in the drill string, the larger diameter tool joints and drill collars can get stuck when making a trip. Key-Seating is recognized by the following characteristics: 1. Still having circulation. 2. Can rotate pipe. 3. May be able to move drill pipe down. Solution: Once the Key-Seating has been formed, the smallest diameter portion of its configuration must be reamed out with some sort of reaming device. B. Caving in: Causes: 1. Insufficient mud weight. 2. Wetting shales causing sloughing. 3. Insufficient carrying capacity of the drilling fluid. 4. Tectonically stressed and brittle shales. Caving is recognized by the following characteristics: 1. Can not circulate. 2. Can not move the pipe(sometimes the pipe can be moved down words but not up. 3. Can not rotate the pipe. Solution: 1. Increase mud weight to balance formation pressure if possible. 2. Use drilling fluid that will not wet or hydrate the shales and at the same time stabilize shales such as Kcl-Polymer Mud. 3. Increase the carrying capacity of the drilling fluid by increasing YP.

C. Under gauge hole: Causes: 1. Under gauge drilling assembly. 2. Plastic following formations(such as salt or soft formations) caused by overburden pressures. 3. Flocculated mud and aggregated mud causes thick filter cake. 4. Wall cake build upon a porous formation in an already gauge hole. 5. All of these can be complicated by additions of drilled solids to the drilling assembly, commonly refereed as (Bit Balling). Solution: 1. Check the gauge of the drilling assembly. 2. Increase mud weight to control formation pressures. 3. Reduce filtration to form a smaller wall cake. 4. Reduce bit balling by : • Change to inhibitive mud. • Add surfactants (detergent). • Slugs (having nut plug + caustic soda + spersene). • Redicoat. NB: When bit is balled, getting high torque, no progress. D. Differential Sticking: Differential sticking is defined as the sticking of pipe at one side of hole against a permeable formation because the drilling fluid pressure exceeds the pore fluid pressure of the formation, which causes break of the formation, which by turn will cause a complete loss. And thus the tendency of sucking of drill string to any side of pore hole is possible. Differential sticking may occur in any area of drilling but mostly occurs where deep wells are drilled with high density mud. Differential sticking is characterized by: 1. Drill with lowest mud weight practical. 2. Maintain low filtration rate. 3. Use lubricate. 4. Do not allow the pipe to remain motionless for any period of time. 5. Use square, hexagonal, or spherical drill collars. 6. Change to INVERMUL. 7. USE a spotting fluid (ENVIRO-SPOT). ENVIRO-SPOT spotting fluid formation for 100 bbls WEIGHT 7.3 10 12 14 16 18 (PPG) OIL 65 58 54 49 51 44 (BBL) ENVIRO-SPOT 6 6 6 6 6 6 55 gal Drum WATER 28 26 22 21 11 10 (BBL) BARITE _ 140 250 350 465 570 100 lb. bag Start with required volume of oil, add ENVIRO-SPOT, water and barite in that order

MECHANISMS STUCK PIPE MECHANISMS DISCUSS IN DETAILS

H OLE PACKOFF/BRIDGE SETTLED CUTTINGS

DIFFERE NTIAL STICKING DIFFERENTIAL FORCE

WELL BORE GEOMETRY STIFF ASSEMBLY

SHALE INSTABILITY

KEY SEAT

UNCONSOLIDATED FORMATIONS FRACTURED FORMATIONS CEMENT RELATED

MICRO DOGLEG

JUNK

UNDERGAUGE HOLE

LEDGES MOBILE FORMATIONS

CAUSES: HOLE PACK-OFF / BRIDGE MECHANISM HOLE PACK-OFF: Formation solids (cuttings, cavings) settle around the drill string and pack of the annulus resulting in stuck pipe. HOLE BRIDGE: Medium to large piceses of hard formation, cement or junk falls into the well bore and jams the drill string resulting in stuck pipe.

HOLE PACK-OFF CAUSES

HOLE BRIDGE CAUSES

SETTLED CUTTINGS SHALE INSTABILITY

SHALE INSTABILITY

• • • • •

• •

REACTIVE SHALE GEO-PRESSURED SHALE HYDRO-PRESSURED SHALE OVER BURDEN STRESS TECTONIC STRESS

OVER BURDEN STRESS TECTONIC STRESS

UNCONSOLIDATED FORMATIONS

UNCONSOLIDATED FORMATIONS

FRACTURED FORMATIONS

FRACTURED FORMATIONS

SOFT CEMENT

CEMENT BLOCKS JUNK

CAUSES OF SETTLED CUTTING HOLE CLEANING IS AFFECTED BY 6 BASIC FACTORS FACTOR

AFFECT

•

RATE OF PENETRATION

•

•

HOLE STABILITY

•

Determines the cuttings volume in returning mud Cavings load added to the returning mud

•

ANNULAR VELOCITY

•

Lifts the cuttings

•

MUD RHEOLOGY

•

Suspend and carry the cuttings

•

CIRCULATING TIME

•

Transport the cuttings to surface

• •

HOLE ANGLE

•

Reduces the ability to clean the hole

SETTLED CUTTINGS, NEAR VERTICAL WELLBORE (< 35) CAUSE: •

DRILLED CUTTINGS ARE NOT TRANSPORTED OUT OF THE HOLE DUE TO LOW ANNULAR VELOCITY AND/ OR POOR MUD PROPERTIES. WHEN CIRCULATING IS STOPPED, THE CUTTINGS FALL PACK DOWN THE HOLE AND PACK OFF THE DRILL STRING. FIGURE.

WARNING: • • •

HIGH ROP, LOW PUMP RATE, LITTLE TO NO CIRCULATING TIME AT CONNECTIONS, TORQUE, DRAG AND PUMP PRESSURE INCREASE. OVER PULL OF SLIPS, PUMP SURGE TO BREAK CIRCULATION FILL ON BOTTOM.

INDICATIONS: • •

LIKELY TO OCCUR ON CONNECTIONS, POSSIBLE DURING TRIPS. CIRCULATING RESTRICTED OR IMPOSSIBLE.

FIRST ACTION: • • •

APPLY LOW PUMP PRESSURE (200-400 psi) Apply torque and jar down with maximum trip load. Circulate clean to avoid recurrence.

PREVENTIVE ACTION: • • • •

CONTROL, ROP, MAXIMIZE ANNULAR VELOCITY. MAINTAIN SUFFICIENT GEL STRENGTH AND YP. CIRCULATE 5 TO10 MINUTES BEFORE CONNECTIONS. CIRCULATE HOLE CLEAN BEFORE POOH.

FIGURE

SETTLED CUTTINGS HIGH ANGLE WELLBORE (>35) CAUSE: • •

DRILL CUTTINGS SETTLE ON THE LOW SIDE OF THE HOLE AND FORM A CUTTING BED. THE CUTTINGS BED BUILDS AND SLIDE DOWN AND THE HOLE PACKING OFF ON THE DRILL STRING. WHILE POOH, THE CUTTING BED IS DRAGGED UPWARD BY THE BHA AND PACKS OFF THE DRILL STRING.

WARNING: • • • •

HOLE ANGLE GRATER THAN 35 deg. DRILLING WITH A DOWN HOLE MOTOR. HIGH ROP, LOW PUMP RATE, INCREASE IN TORQUE AND DRAG, INCREASE IN PUMP PRESSURE. INCREASE OVER PULL ON TRIPS.

INDICATIONS: • •

LIKELY TO OCCUR WHILE POOH, POSSIBLE WHILE DRILLING. CIRCULATING PRESSURE RESTRICTED OR IMPOSSIBLE.

FIRST ACTION: • • •

APPLY LOW PRESSURE ( 100 – 400 PSI ). JAR DOWN WITH MAXIMUM TRIP LOAD. APPLY TORQUE WITH CAUTION. CLEAN HOLE TO AVOID RECURRENCE.

PREVENTIVE ACTION: • • • •

RECORD TREND INDICATORS FOR INADEQUATE HOLE CLEANING. CONTROL ROP, MAINTAIN MUD PROPERTIES, CIRCULATE AT MAXIMUM RATE, MAXIMIZE STRING ROTATION. CIRCULATE HOLE CLEAN BEFORE POOH, ESTABLISH AN OVER PULL LIMIT. USE LOW VIS/HIGH VIS SWEEPS.

INDICATIONS OF SETTLED CUTTINGS DRILLER TRENDS

•

DRILLING

♦ CONNECTI ON

DRAG Increasing,erratic

 BACK REAMING  PUMPING OUT

Over pull off slips. Increasing,erratic



TRIPPING OUT TRIPPING IN

Increasing,erratic

Over pull off slips Increasing,erratic Over pull off slips Increaseing set down weight. Over pull off slips. Over pull off slips. Erratic over pull



TORQUE

PRESSURE

OTHER

Increasing

• •

Surge to start circulation

♦ Back pressure before breaking connection. ♦ Back flow.

Pressure surges Gradual decrease in ROP



Increasing,erratic

Increasing

Increasing

Swabbing



Begins with BHA below depths of 35 hole angle

     

Surge to start circulation. String pistoning. Loss of fluid possible. Surge to start circulation. String pistoning. Loss of fluid possible

RIG TEAM INDICATIONS SHAKER TRENDS

Low cuttings return rate for penetration, Erratic cuttings returns, No cuttings return, High cuttings return on fine shaker screen and desilter / mud cleaner.

LOGGER TRENDS

Rounded Reground cuttings.

MUD TRENDS

Increasing PV & YP. Increase in low gravity solids, Possible mud weight increase.

PREVENTIVE ACTION • • • • • • • • • • •

Maintain the required mud properties. Circulate the maximum recommended GPM for hole size. Place more emphasis on annular velocity when designing the hydraulics for 12.25” and larger hole sizes. Consider using a riser booster line when drilling 8.5” and smaller hole sizes. Do not allow the penetration rate to exceed the ability to clean the hole. Record torque and drag trends for symptoms for inadequate hole cleaning. Consider a wiper trip after a long section with a down hole motor. Wipe the hole at full circulating rate as long as possible (5 – 10 min.) before connections, Rotate at maximum RPM when possible. Maximize string motion when circulating the hole clean. Use maximum practical RPM, rise the drill string slowly (5 min/std) and slack-off at a safe but fast rate (1 min/std). Consider pumping high-vis sweeps in low angle wells (35). DO NOT STOP CIRCULATING UNTIL ALL SWEEPS RETURN. Circulate until the hole is clean, if the last sweep brings up excessive amounts of cuttings, continue with hole cleaning operations. Several circulations may be necessary.

MINIMUM GPM MINIMUM GPM VERSUS HOLE SIZE AND HOLE ANGLE HOLE SIZE

26”

17.5 –16”

12.25”

8.5”

ANGLE INTERVAL 0 – 35 deg

700 GPM

35 - 55 deg

1250 GPM

55 + deg

500 GPM

400 GPM

300 GPM

950 GPM

650 GPM

450 GPM

1100 GPM

750 GPM

500 GPM

MINIMUM ROP MAXIMUM ROP VERSUS HOLE SIZE AND HOLE ANGLE HOLE SIZE

26”

17.5 –16”

12.25”

8.5”

110

155

240

75

85

125

60

75

100

ANGLE INTERVAL 0 – 35 deg

60

35 - 55 deg

40

55 + deg

Penetration rate guidelines are based on adequate mud properties. MINIMUM STROKES MINIMUM CIRCULATING STROKES FACTOR (CSF) TO CLEAN HOLE HOLE SIZE

26”

17.5 –16”

12.25”

8.5”

ANGLE INTERVAL 0 – 35 deg 35 - 55 deg 55 + deg

2 2.5

1.7

1.4

1.4

2.5

1.8

1.6

3

1.2

1.7

PROCEDURE: 1. 2. 3.

Separate the wellbore into sections by hole angle from interval above. Multiply each hole section length (Sect. Lth) by CSF and totasl the adjusted measured depth (MD). Calculate the minimum circulating strokes to clean the hole.

Total Adjusted MD X Bottoms-Up Stks Minimum Circ. Stks = ---------------------------------------------------Measured Depth EXAMPLE CALCULATION: CALCULATE THE MINIMUM CIRCULATING STROKES FOR 12 ¼” HOLE HAVING THE FOLLOWING PROFILE. 1. FROM 0 FT TO 4500 FT ( 4500 FT ) HAVE 0 – 35 deg. 2. FROM 4500 FT TO 6500 FT ( 2000 FT ) HAVE 35 – 55 deg. 3. FROM 6500 FT TO 13000 FT ( 6500 FT ) HAVE 55+ deg. MULTIPLY EACH HOLE SECTION LENGTH BY CSF AND TOTAL THE ADJUST MEASURED DEPTH. ADJUSTED MD = ( SECT. LTH X CSF ) + ( SECT LTH X CSF ) + ( SECT LTH X CSF ) = ( 4500 X 1.4 ) + ( 2000 X 1.8 ) + ( 6500 X 2 ) = 6300 + 3600 + 13000 = 22900 TOTAL ADJUSTED MD.

CALCULATE THE MINIMUM CIRCULATING STROKES REQUIRED TO CLEAN THE HOLE. Total Adjusted MD X Bottoms-Up Stks Minimum Circ. Stks = ---------------------------------------------------Measured Depth 22900 X 15000 =

-------------------13000

=

26423 STROKES.

HIGH ANGLE HOLE CLEANING GUID LINES ( > 35 deg ) DRILLING • • • • • • • • • •

Maintain sufficient mud weight to stabilize the wellbore as hole angle and/or formation pressure increases. Use proper low-end rheology for hole size and angle to maximize hole cleaning. Circulate at maximum rate for hole size and hole angle. Limit the ROP for the maximum recommended for hole size and angle. Back ream each stand (or ½ stand) drilled with a down hole motor Rotate at a high RPM (160+). Raise the drill string slowly (i.e.. 5min/stand). Lower the drill string at a safe but fast rate (i.e.. 1min/stand). Continue back reaming if hole conditions dictate. Consider a wiper trip after drilling a long section with a down hole motor to mechanically agitate and remove cuttings bed. Pump a sweep pill if hole conditions do not improve. Consider low-vis / high-density tandem sweeps. Optimize sweep type, volume and frequency pumped. Consider reducing ROP or stop drilling and circulate until hole conditions improve.

CONNECTIONS • • • •

Start and stop drill string slowly. Ensure adequate back reaming at a full circulation rate prior to connections. Prepare crew and equipments to minimize connection time. Record free rotating weight, pick-up weight, slack-off weight, off bottom torque, and circulating pressure for trend indications of inadequate hole cleaning. Pull the slips and slowly rotate the drill string first, then increase pump speed slowly. Carefully lower the drill string to bottom.

TRIPPING • • • • • • • •

Circulate 1 to 3 joints off bottom while cleaning the hole to avoid dropping bottom hole angle. Consider sweeps (pills) to aid hole cleaning. Rotate at high RPM (160+) while cleaning the hole. Raise the drill string slowly (i.e.. 5min/stand). Lower the drill string at a safe but fast rate (i.e.. 1min/stand). Ensure recommended minimum circulation strokes for hole size and angle be pumped. 2 to 4 times normal bottoms-up may be required. Circulate until the shakers are clean. Consider pumping a sweep (pill) to determine if additional circulation time is required. Inform the Driller of the measured depth and stand count when the top of the BHA reaches the deepest anticipated cuttings bed. Maximum cuttings bed thickness is likely between 45 and 65 hole angle. Determine an over pull limit prior to pulling out of the hole (the lesser of ½ BHA weight or 30,000lbs). If overpull limit occurs, run in 1 stand and repeat hole cleaning guidelines from present bit depth. When the shakers are clean, continue pulling out of the hole. If the overpull limit is again reached, repeat procedure.

CAUTIOUSLY BACK REAM OR PUMP-OUT STANDS WHEN A CUTTINGS BED IS PRESENT!! Be patient, several hole cleaning cycles may be required to safety pull the drill string out of the hole. • Record depths and stand count of high pick-up weights during the trip. Compare these to the drilling pick-up weights for the same depths to determine value of over pull.

SHALE INSTABILITY The shale formation becomes unstable, breaks apart and falls into the wellbore CHEMICALLY STRESSED

MECHANICALLY STRESSED GEO-PRESSURED SHALE

HUDROPRESSURED SHALE

OVERBURDEN STRESS

TECTONIC STRESS

REACTIVE SHALE

CHEMICALLY STRESSED SHALE REACTIVE SHALE CAUSE: • Water sensitive shale drilled with little or no mud inhibition. • Shale absorbs water and swells into the wellbore. • Reaction is time dependably. WARNING: • Funnel viscosity, PV, YP, CEC increase. • Torque & drag increase. • Pump pressure increase. • Clay balls and/or soft (mushy) cuttings at shaker. • Over pull & swabbing. • BHA balling (mud rings) INDICATIONS: • Generally occurs while POOH, possible while drilling. • Circulation impossible or highly restricted. FIRST ACTION: • Apply low pump pressure (200 – 400 psi). • If POOH, torque up and jar down with maximum trip load. • If POOH, jar up with maximum trip load, DO NOT APPLY TORQUE. PREVENTIVE ACTION: • Use an inhibited mud. • Maintain mud properties. • Plan wiper trips. • Minimize hole exposure time.

INDICATIONS OF REACTIVE CUTTINGS DRILLER TRENDS

•

DRILLING

♦ CONNECTION

DRAG Increasing Smooth

TORQUE Increasing,Smooth

TRIPPING OUT

Increasing,Smooth. Over pull off slips



TRIPPING IN

Increaseing set down weight. Over pull off slips.

 BACK REAMING

Over pull off slips.

 PUMPING OUT

Increasing,Smooth. Over pull off slips.

Increasing

Surge to start circulation

Over pull off slips



PRESSURE

OTHER

• • • ♦

Pressure surges Gradual decrease in ROP Mud loss possible Back pressure before breaking connection. ♦ Back flow. 



Increasing,Smooth

Increasing

Increasing

      

Swabbing

Begins at depth of problem formation. Mud loss possible Surge to start circulation. String pistoning. Loss of fluid possible. Surge to start circulation. String pistoning. Loss of fluid possible

RIG TEAM INDICATIONS SHAKER TRENDS

Soft clay balls. Wet “ mushy “ clay ( Gumbo ). Flow line plugging.

LOGGER TRENDS

Large quantity of hydrated shale cuttings. High value on shale swelling test.

MUD TRENDS

High funnel vis. & yp, increasing pv, low gravity solids & CEC. Possible mud weight increase. Low inhibitor content.

PREVENTIVE ACTION • • • • • • •

Addition of various salts (potassium, sodium, calcium, etc.) to reduce the chemical attraction of water of the shale. Addition of various encapsulating (coating) polymers to reduce water contact with the shale. Use oil and synthetic base mud to exclude water contact with shale. Minimize open hole time. Plan regular wiper / reaming trips based on time, footage drilled or or the warning signs of reactive shale. Ensure adequate hydraulics for bit and hole cleaning. Maintain required mud properties and minimize low gravity solids.

GEO – PRESSURED SHALE CAUSE: • •

Drilling pressured shale with insufficient mud weight. The stressed shale fractures and caves into the wellbore.

• • • • •

Signs begin to occur as shale is drilled. Mud logger trends indicate increasing pore pressure. Torque increase and drag on connections. Hole fill on connections, bridges on trips, splintery shale caving. Possible background gas increase.

• • •

LIKELY TO OCCUR ON TRIPPING, POSSIBLE WHILE DRILLING. COMPLETE PACK-OFF LIKELY, HOLE BRIDGING POSSIBLE. CIRCULATION RESTRICTED OR IMPOSSIBLE.

• •

Apply low pump pressure. Apply torque, jar down with maximum trip load.

• • • •

Adjust mud weight before drilling known pressured shale. Slowly increase mud weight to stabilize shale. Minimize swab / surge pressures. Minimize open hole exposure time.

WARNING:

INDICATIONS:

FIRST ACTION: PREVENTIVE ACTION:

HYDRO-PRESSURED SHALE CAUSE: • • •

Over time, shale pore pressure becomes charged by hydrostatic over balance. Drill string motion and wellbore pressure surges stress-cracks the unstable shale. The shale falls into the wellbore and jams the string.

• • •

Generally follows a mud weight reduction. Torque and drag increase. Shale caving at shakers.

• • •

Possible while drilling or tripping. Hole bridging or complete pack off possible. Circulation restricted or impossible.

• • •

Apply low pump pressure (200-400 psi) Apply torque, jar down with maximum trip load. Circulate at maximum rate once circulation is established.

• • •

Use OBM, SBM, or GLYCOL base mud if problem is suspected. If a mud weight reduction is necessary, reduce gradually over several circulations. Minimize wellbore pressure surges.

WARNING:

INDICATIONS:

FIRST ACTION:

PREVENTIVE ACTION:

OVERBURDEN STRESS CAUSE: • • •

Mud weight is insufficient to support the overburden. Mud weight in not adjusted as hole angle increases. Stressed shale fractures and falls into the wellbore.

• • •

Hole cleaning problems. Torque and drag increase. Shale caving at shakers.

• • •

Can occur while drilling or tripping. Hole bridging or complete pack off possible. Restricted Circulation or no circulation possible.

• •

Apply low pump pressure (200-400 psi) Apply torque, jar down with maximum trip load.

• •

Use mud weight needed to stabilize to overburden. Increase mud weight as hole angle increases.

WARNING:

INDICATIONS:

FIRST ACTION: PREVENTIVE ACTION:

TECTONIC STRESS CAUSE: • • •

Naturally occurring lateral forces in the formations. Stressed shale fractures, falls into the wellbore and jams the drill string. Sandstone squeezes in causing undergauge hole.

• • • • •

Mountainous location. Prognosed tectonics. Erratic torque and drag. Blocky shale caving. Creates elliptical wellbore.

• •

Possible while drilling or tripping. Circulation restricted or impossible.

• •

Apply low pump pressure (200-400 psi) Apply torque, jar down with maximum trip load.

• • • •

Increase mud weight if possible Circulate high density sweeps Minimize wellbore pressure surges Minimize open hole exposure time.

WARNING:

INDICATIONS: FIRST ACTION: PREVENTIVE ACTION:

INDICATIONS OF MECHANICALLY STRESSED SHALE DRILLER TRENDS

DRAG

TORQUE

PRESSURE

OTHER

•

•

DRILLING

♦ CONNECTION

Increasing erratic

Increasing,erratic

Surge to start circulation

Over pull off slips



TRIPPING OUT

Increasing,erratic. Over pull off slips



TRIPPING IN

Increaseing set down weight.

 BACK REAMING

Over pull off slips.

 PUMPING OUT

Increasing,erratic. Over pull off slips.

Increasing

Increase ROP followed by gradual decrease pressure surges.

♦ Hole fill 



Increasing,erratic

Increasing

Increasing

      

Swabbing

Begins at depth of problem formation. Hole fill on bottom. Surge to start circulation. String pistoning. Loss of fluid possible. Surge to start circulation. String pistoning. Loss of fluid possible

RIG TEAM INDICATIONS SHAKER TRENDS

Large, splintery or blocky shale caving. Large volume of caving.

LOGGER TRENDS

Large quantity of splintery or blocky shale caving with striations. Possible indications of increase in formation pressure. Prognosed mechanically stressed shale.

MUD TRENDS

Possible slight increase in mud weight and plastic viscosity.

PREVENTIVE ACTION • • • • •

Consider offset well data and/or computer models which simulate failure limits when planning the mud weight for each hole section. Mud weight increase with hole angle and TVD specific to the area to maintain hole stability. Exploration wells, consult the Mud Logger for changes in formation pressure. Increase the mud weight cautiously until symptoms are no longer observed. If possible, increase the mud weight slowly ( 0.1 – 0.2 ppg per day ) until the desired density for a given depth is reached. This will maintain an overbalance against the hydrostatically sensitive shale. Avoid mud weight reduction after 1+ day exposure to hydrostatically sensitive shale. If mud weight reduction is necessary reduce the mud weight gradually over a time frame equal to the time of exposure.

• • • • • •

Use the Shaker Handover Notes to determine trends of cutting volume, size and shape. Maintain mud properties to ensure hole cleaning. Use sweeps to help clean the hole. Stop drilling until the hole is circulated clean. Minimize open hole exposure time. Plan contingency to case-off the problem.

UNCONSOLIDATED FORMATION CAUSE: • • •

Little or no filter cake. Unbonded formation (sand, pea gravel, etc) can not be supported by hydrostatic overbalance. Sand/pea gravel falls into the hole and pack off the drill string.

• • • • •

Likely to occur as the formation is drilled. Seepage loss likely. Increase torque and drag, pump pressure fluctuations. Hole fill on connections, and trips. Shaker & desander over load.

• • • •

Generally occurs in surface hole. Can occur while drilling or tripping. Sudden pack off without warning. Circulation impossible.

• • •

Apply low pump pressure (200-400 psi) Jar down with maximum trip load. Apply torque with caution.

• • • • •

Control fluid loss to provide an adequate filter cake. Control drill suspected zone. Use high vis sweeps. Spot a gel pill before POOH. Minimize trip speed.

WARNING:

INDICATIONS:

FIRST ACTION:

PREVENTIVE ACTION:

INDICATIONS OF UNCONSOLIDATED FORMATION DRILLER TRENDS

•

DRILLING

♦ CONNECTION

DRAG Increasing erratic

TORQUE Increasing,erratic

TRIPPING OUT

Increasing,erratic. Over pull off slips



TRIPPING IN

Increaseing set down weight.

 BACK REAMING

Over pull off slips.

 PUMPING OUT

Increasing,erratic. Over pull off slips.

Increasing

Surge to start circulation

Over pull off slips



PRESSURE

OTHER

•

Pressure surges.

♦ Hole fill 



Increasing,erratic

Increasing

Increasing

      

Swabbing

Begins at depth of problem formation. Hole fill on bottom. Surge to start circulation. String pistoning. Loss of fluid possible. Surge to start circulation. String pistoning. Loss of fluid possible

RIG TEAM INDICATIONS SHAKER TRENDS

Large volume of sand over shakers. Sand trap and desander over load.

LOGGER TRENDS

Large quantity of sand in samples. Prognosed unconsolidated formation.

MUD TRENDS

Increase in mud weight and plastic viscosity. High % sand content.

PREVENTIVE ACTION • • • • • • • •

Provide an effective filter cake for the hydrostatic overbalance to “ push against “ and stabilize the formation. If possible, avoid excessive circulating time with the BHA opposite unconsolidated formations to reduce hydraulic erosion. Slow down tripping speed when the BHA is opposite unconsolidated formations to avoid mechanical damage. Start and stop drill string slowly to avoid pressure surges to unconsolidated formations. Control drill the suspected zone to allow time for filter cake build up, minimize annulus loading and to minimize annulus friction pressure. Use sweeps to help keep the hole clean. Be prepared for shaker, desilter, and desander over loads. Minimize seepage loss with fine lost circulation material through these intervals.

FRACTURED FORMATION CAUSE: • Naturally fractured formations. • Pieces of formations fall into the wellbore and jam the drill string. WARNING: • Prognosed fractured limestone, shale and/or faults. • Likely to occur as formation is drilled. • Mud logger formation evaluation. • Blocky caving at shaker. • Hole fill on connections and trips. INDICATIONS: • Likely during trips, possible while drilling. • Sudden and erratic torque and drag likely just before sticking. • Circulation may restricted. FIRST ACTION: • Do not apply torque. Jar down with maximum trip load. • Circulate high density high viscosity sweeps. • Spot acid if stuck in limestone. PREVENTIVE ACTION: • Circulate hole clean before drilling ahead. • Minimize seepage loss. • Slow trip speed before BHA enters suspected zone.

INDICATIONS OF FRACTURED FORMATION DRILLER TRENDS

•

DRILLING

♦ CONNECTION

DRAG Sudden, increasing erratic

TORQUE Sudden, erratic

Over pull off slips



TRIPPING OUT

Increasing,erratic. Over pull off slips



TRIPPING IN

Increaseing set down weight.

 BACK REAMING

Over pull off slips. Increasing, erratic

 PUMPING OUT

Over pull off slips, Increasing,erratic.

PRESSURE

OTHER

No change No change

♦ Hole fill

  Increasing,erratic

No change No change

Begins at depth problem formation. Hole fill on bottom.

 Drag increase when pumping.  Drag increase when pumping..

RIG TEAM INDICATIONS SHAKER TRENDS

Blocky or angular rock fragments.

LOGGER TRENDS

Same as shaker trends. Possible offset well data clues. Prognosed fractured.

MUD TRENDS

No change.

PREVENTIVE ACTION NOTE: With fractured formations, maintaining a good quality filter cake can help to support the formation in some cases. Generally fractured formations require time to stabilize. Prior to this, the problem must be controlled with adequate mud properties, sweeps and sufficient circulation time to keep the hole clean, Other recommendations: • Circulate the hole clean before drilling ahead. • Restrict tripping speed when BHA is opposite fractured formations and fault zones. • Start and stop drill string slowly to avoid pressure surges to the wellbore. • Anticipate reaming during trips. Ream fractured zone cautiously. • Be prepared for the potential of lost circulation when drilling fractured formations. • Problem likely to stabilize with time.

of

CEMENT BLOCKS CAUSE: • Cement becomes unstable around casing show, open hole squeeze plug or kick off plug. • Hard cement chunks fall into the wellbore and jams the drill string. WARNING: • Excessive casing rat hole. • Cement squeeze job. • Cement kick off plug. • Cement caving at shaker and/or in mud logger samples. INDICATIONS: • Problem can occur any time. • Sudden, erratic torque and drag just before sticking. • Circulation possible. FIRST ACTION: • Attempt to break chunks with jarring and torque. • Jar in the opposite direction of string movement prior to sticking. • Apply jarring force & torque gradually. • Circulate high density, high viscosity sweeps. PREVENTIVE ACTION: • Minimize casing rathole. • Allow sufficient curing time. • Ream casing show and open hole plugs thoroughly before drilling ahead. • Slow trip speed before BHA enters casing show or plug depth.

PREVENTIVE ACTION • • • • • • •

Limit casing rathole to minimize a source of cement blocks. Several squeeze jobs at the casing shoe increases the potential for cement blocks. Allow sufficient cement curing time before drilling out. Ream casing rathole and open hole cement plugs slowly and thoroughly before drilling ahead. Maintain sufficient distance between the paths of platform wells to reduce the possibility of cement blocks. Reduce tripping speed when BHA is entering the casing shoe or opposite open hole cement plugs. Start and stop the drill string slowly to avoid pressure surges to the wellbore.

SOFT CEMENT CAUSE: • Circulation is attempted with the bottom of the drill string in soft cement. • Pump pressure causes the cement to flash set. • High penetration rate when cleaning out soft cement. WARNING: • Tripping in hole after setting an open hole cement plug or after a cement job. • Set down weight occurs above the theoretical top of cement. INDICATIONS: • Occurs as pump pressure is applied. • Circulation highly restricted or impossible. FIRST ACTION: • Bleed trapped pump pressure. • Jar up with maximum trip load. PREVENTIVE ACTION: • Known cement set time. • If set down weight is observed while RIH, pull 2 stands before circulating. • Start circulation 2 stands above top of cement. • Control drill when cleaning out cement.

PREVENTIVE ACTION • • • • • • •

Know the calculated top of cement ( TOC ) before tripping in hole. Do not rely on the weight indicator to find the top of cement. Begin washing down 2 stands above the theoretical top of cement. If set down weight is observed when tripping in hole after cement operation, set back 2 stands before attempting circulation. Pre-treat the mud system with chemicals prior to drill out cement. Verify cement compressive strength with the cement company before drilling out. Control drill when cleaning out soft cement.

JUNK CAUSE: • Poor house keeping on the floor. Hole cover not installed. • Down hole equipment failure. • Junk falls into wellbore and jams the drill string. WARNING: • Junk sticking can occur at any time during any operation. • Metal shavings at shaker. INDICATIONS: • Generally occurs when BHA is in hard formation or inside casing. • Sudden and erratic torque and drag likely just before stricking. • Missing floor tool or equipment. • Circulation unrestricted, depending on type of junk. FIRST ACTION: • If moving up when sticking occurred, jar down with maximum trip load. • Apply torque if progress is made. • If moving down, jar up with maximum trip load. Do not apply torque. PREVENTIVE ACTION: • Good house keeping on floor. • Inspect handling equipment. • Keep hole covered. • Inspect down hole equipment.

PREVENTIVE ACTION • • • • •

Inspect slip and tong dies regularly. Use good house keeping practices on the rig floor. Install drill string wiper rubber as quickly as possible. Keep hole covered when out of hole. Maintain rig floor equipment in good operating condition.

DIFFERENTIAL STICKING A sticking force developed when differential pressure ( overbalance ) forces a stationary drill string into the thick filter cake of a permeable zone. PERMEABLE FORMATION

FILTER CAKE A cake of mud solids develops on the hole wall due to fluid loss.

Sandstone / fractured limestone. OVERBALANCE Well bore pressure greater than formation pressure.

High fluid loss increase filter cake thickness. FIGURE Thick filter cake increases sticking potential.

STRING CONTACTS FILTER CAKE Angle well bore / un stabilized BHA increases potential.

STATIC FILTER CAKE FIGURE

Static filter cake increases cake thickness. The static filter cake seals HSP from the backside of pipe.

STRING MOTION STOPPED No string motion or circulation develops static cake.

Differential force begins to develop.

FIGURE LOW PRESSURE AREA

TIME DEPENDENT

An area of low pressure develops between the pipe & filter cake.

With time, the area of pipe sealed in the filter cake increases.

Over balance pressure across the contact area determines the differential force.

Immediate action is required to free the drill string.

DIFFERENTIAL STICKING CAUSES: • • •

Drill string contacts a permeable zone. When string movement stops, a static filter cake develops. High over balance applies a differential sticking force to the drill string contact area.

WARNING: • • •

Prognosed low pressure sands. Long / un stabilized BHA sections. Increasing over pull, slack off weight or torque to start string movement.

• • •

Occurs after a period of no string movement. String can not be rotated or moved. Circulation unrestricted.

• •

Apply torque and jar down with maximum trip load. Spot a pipe-releasing pill if the string does not jar free.

• • • • •

Maintain minimum required mud weight. Keep string moving when BHA is opposite suspected zones. Minimize seepage loss in low-pressure zones. Minimize unstabilized BHA sections, use spiral D/C & HWDP. Control drill suspected zones.

INDICATIONS:

FIRST ACTION: PREVENTIVE ACTION:

INDICATIONS OF DIFFERENTIAL STICKING DRILLER TRENDS

•

DRILLING

♦ CONNECTION

DRAG Possible increase

TORQUE No change

Increasing over pull off slips.



TRIPPING OUT

Increasing over pull off slips.



TRIPPING IN

Increasing over pull off slips.

 BACK REAMING

Increasing over pull off slips.

 PUMPING OUT

Increasing over pull off slips..

PRESSURE

OTHER

No change No change

No change

No change No change

RIG TEAM INDICATIONS SHAKER TRENDS

No change

LOGGER TRENDS

High overbalanced. Permeable formation depth. Permeability data to estimate stricking potential.

MUD TRENDS

Increasing mud weight. Increasing plastic viscosity and low gravity solids. High API water loss.

PREVENTIVE ACTION • Design the casing program to minimize overbalance to shallower hole formations. • Limit mud weight to minimum required for hole stability and well control. • Maintain fluid loss within specifications. • Minimize BHA length when possible. • Limit the length of un stabilized BHA. Use spiral drill collars. KEEP THE STRING MOVING. Consider rotating the string during drilling and tripping connections while BHA is potential sticking zones. • Preplan to minimize the down time for operations that require the sticking remains static (surveys, minor repairs. Etc.). • In zones with high sticking potential, minimize seepage loss with plugging agents. • Keep a pipe-releasing pill ready at the well site when differential sticking potential is high.

WELL BORE GEOMETRY Hole diameter and/or angle relative to BHA geometry and/or stifness will not allow passage of the drill string. BHA CHANGE

DIRECTION / ANGLE CHANGE / HOLE ID DECREASE

STIFF ASSEMBLY

KEY SEAT MOBILE FORMATIONS.

MICRO DOGLEGS

LEDGES UNDERGAUGE HOLE

STIFF ASSEMBLY: CAUSE: •

The stiff BHA can not negotiate hole angle / direction changes and becomes jammed.

WARNING: • • • •

Doglegs present. Pulled stabilizers out of gauge. A new BHA design is picked up. Sudden set down weight.

• • •

Most likely to occur when RIH. BHA at direction / angle change depth. Unrestricted circulation.

• •

If moving down when sticking occurred , jar up with maximum trip load, do not apply torque. If moving up, torque up and jar down with maximum trip load.

• • • •

Minimize BHA changes, consider a reaming trip. Limit dogleg severity. Slow trip speeds before BHA enters suspected zone, plan to ream. Limit set down weight.

INDICATIONS:

FIRST ACTION:

PREVENTIVE ACTION:

KEY SEAT CAUSE: • • •

Abrupt change in angle or direction in medium soft medium hard formations. High string tension and pipe rotation wears a slot into the formation. While POOH, the drill collars jam into the slot.

• • •

High angle dogleg in upper hole section. Long drilling hours with no wiper trips through the dogleg section. Cyclic over pull at tool joint intervals on trips.

• • • •

Occurs only while POOH. Sudden over pull as BHA reaches dogleg depth. Un restricted circulation. Free string movement below key seat depth possible if not stuck.

• •

Apply torque and jar down with maximum trip load. Attempt to rotate with low over pulls to work through dogleg.

• • • •

Minimize dogleg severity to 3 deg/100’ or less. Limit over pulls through suspected intervals. Plan reamer and/or wiper trips if a dogleg is present. Run string reamer or key seat wiper if suspected.

WARNING:

INDICATIONS:

FIRST ACTION: PREVENTIVE ACTION:

MICRO DOGLEGS CAUSE: • • •

Hard/soft interbedded formations. Frequent corrections in hole angle or direction. BHA becomes jammed in the successive micro doglegs.

• • • •

Prognosed hard/soft interbedded formations. Frequent angle direction changes. Drilling/sliding with down hole motor. Erratic torque and drag on connections.

• •

Likely when picking up for a connection. Possible on trips. Circulation un restricted.

• •

If moving up when sticking occurred, apply torque and jar up with maximum trip load. If moving down, jar up with maximum trip load, do not apply torque.

• • • •

Minimize BHA changes. Minimize direction / angle changes. Back ream frequently when drilling hard / soft formations. Slow trip speed before BHA enters suspected zone.

WARNING:

INDICATIONS: FIRST ACTION:

PREVENTIVE ACTION:

LEDGES CAUSE: • • •

Interbedded formations. Soft rocks – wash out, hard rocks – in gauge. Fractured / faulted formations. Stabilizer blades and tool upsets become stuck under ledges.

• • •

Prognosed hard / soft interbedded formations. Prognosed fractured / faulted formations. Sudden erratic over pull.

• • • •

Generally occurs when tripping. Possible when picking up for a connection. Generally associated with micro doglegs. Circulation un restricted.

• •

If moving up when sticking occurred, apply torque and jar up with maximum trip load. If moving down, jar up with maximum trip load, do not apply torque.

• • • •

Minimize direction / angle changes. Minimize BHA changes. Plan reaming trips, ream with caution. Slow trip speed before BHA enters suspected zone.

WARNING:

INDICATIONS:

FIRST ACTION:

PREVENTIVE ACTION:

MOBILE FORMATIONS CAUSE: • •

Over burden weight squeezes plastic salt or shale into the well bore. The BHA becomes jammed in the under gauge hole.

• • •

Prognosed salt or plastic shale. Sudden increases in over pull or set down weight. Sudden torque increases with fast moving plastic formations.

• • • • •

Generally occurs while POOH. Possible when RIH after a long period out of the hole. Possible while drilling if formation moves fast. Sticking occurs when BHA at plastic zone depth. Circulation un restricted or slight restriction possible.

• • •

If moving up apply torque and jar down with maximum trip load. If moving down, jar up with maximum trip load, do not apply torque. Spot fresh water if in salt. (consider well control).

• • • • • •

Select the correct mud system. Maintain sufficient mud weight. Plan frequent reaming/wiper trips. Consider eccentric PDC bits. Slow trip speed before BHA enters suspected zone. Minimize open hole exposure time.

WARNING:

INDICATIONS:

FIRST ACTION:

PREVENTIVE ACTION:

UNDERGAUGE HOLE CAUSE: • • •

Drilling hard abrasive rock wears bit gauge protection. Cored hole section undergauge. New bit is jammed into the undergauge hole section

• • • •

Prognosed abrasive sands. Pulled bit and stabilizers are undergauge. When PDC bit follows roller cone bit run. Running in hole after coring.

• • • •

Occurs only when RIH. Sudden set down weight. Bit stuck near bottom or at top of core hole section. Circulation un restricted or slightly restricted.

•

Jar up with maximum trip load. Do not apply torque.

• • • •

Gauge pulled bit and stabilizers. Never force the bit through tight spots. Ream the last 3 joints to bottom. Begin reaming 3 joints above core hole section. Slow trip speed before BHA enters suspected zone.

WARNING:

INDICATIONS:

FIRST ACTION: PREVENTIVE ACTION:

The indications of wellbore geometry problems are observed only when BHA is moving in the hole section with the geometry problem.

INDICATIONS OF WELLBORE GEOMETRY PROBLEMS DRILLER TRENDS

•

DRAG

DRILLING

TORQUE

Increasing, erratic

♦ CONNECTION

Increasing, erratic

Increasing, erratic

PRESSURE No change Surge to start circulation



TRIPPING OUT

Increasing, erratic over pull with BHA at problem zone.



TRIPPING IN

Increasing, erratic. Set down weight.

 BACK REAMING

erratic

 PUMPING OUT

Increasing, erratic over pull

erratic over pull

OTHER

•

Momentary over pull & set down

♦ Momentary over pull & set down 

Momentary over pull & set down



Begins at depth of problem formation.

No change

 Momentary over pull

No change

 Momentary over pull

RIG TEAM INDICATIONS SHAKER TRENDS

No change

LOGGER TRENDS

No change.

MUD TRENDS

No change.

PREVENTIVE ACTION • • • • • • • • • • • •

Optimize BHA design (run only what is required ) and when possible, minimize BHA stiffness. Plan a reaming trip if new BHA is locked up and/or a hole geometry problem is suspected. Slow down trip speed before BHA enters kick off or doglegs depth, depth of micro dogleg and/or ledges, mobile formation. Minimize dogleg severity to 3 deg/100’ or less. Minimize rotating hours below a sharp dogleg without a wiper or reaming trip. Consider using key seat wipers or drill string reamers if a key seat is suspected. Limit the length of rathole to avoid key seating the bottom of the casing. Do not start angle building operations too close to the shoe. Minimize sharp, frequent well bore course changes. Avoid prolonged circulation in suspected micro dogleg section to prevent hole wash out and forming ledges. With mobile salts consider using a slightly under saturated mud system to allow a controlled wash out. If necessary increase the mud weight to help slow down salt intrusion. Consider drilling mobile salts with eccentric PDC bits. Plan regular wiper trips to keep the hole section open. Use hard faced stabilizers and select bits with extra gauge protection if abrasive formations are drilled. Gauge the old bit and stabilizers as well as the bit and stabilizers picked up.

•

Begin reaming 1 joint above a cored hole section. As standard. Practice, ream the last stand or 3 joints back to bottom on all trip.

STUCK PIPE FREEING WORKSHEET SUMMARIZATION: SUMMARIZATION FOR GENERAL INSTRUCTION TO BE FOLLOWED IN CASE OF STUCK PIPE INITIAL ACTION 1. If sticking occurred while moving up apply torque and jar down with maximum trip load. If sticking occurred while moving down, do not apply torque and jar up with maximum trip load. 2. Stop or reduce circulation when cocking the and when jarring down. NOTE: Increase pump pressure will INCREASE the hydraulic jar up – below & DECREASE the down – below. 3. Continue jarring until the string is free or an alternative decision is made. Jarring for 10+ hours may be necessary. SECONDARY ACTION •

Spot acid if stuck in lime stone or chalk. Spot fresh water with mobile salt.

WHEN THE STRING COMES FREE:  Increase circulation to maximum rate, rotate and work the string .  Ream / back ream the hole section thoroughly.  Circulate the hole clean.

STUCK WHILE MOVING UP OR WITH STRING STATIC ACTION TO ESTABLISH CIRCULATION  Apply low pump pressure (200-400 psi). Maintain pressure if restricted circulation is possible.  DO NOT JAR UP !!!APPLY TORQUE !!! Slack off to MAXIMUM set down weight. Allow sufficient time for a hydraulic jar to trip (4-6 min for long cycle. See jar manual).  If the string does not come free. DO NOT JAR UP!! Jar DOWN until the string comes free or an alternative decision is made. Jarring down for 10+ hours may be necessary. WHEN CIRCULATION IS ESTABLISHED:  Slowly increase pump speed to maximize rate. When possible work the string and circulate the hole clean from bit depth.  Ream the section until the hole is clean.  If POOH to log and / or run casing, return to bottom and circulate the hole clean.

SUMMARIZATION FOR GENERAL INSTRUCTION TO BE FOLLOWED IN CASE OF STUCK PIPE WHILE MOVING UP OR WITH STRING STATIC INITIAL ACTION 1- circulate at maximum allowable rate. 2- Work MAXIMUM limit torque down to the stuck depth and hold the torque in the string. 3- Stop or reduce the pump speed to minimum. 4- Slack off to MAXIMUM set – down limit. 5- Allow sufficient time for a hydraulic jar to trip (4-6 min for long cycle. See jar manual). 6- If string does not come free, hold torque in the string and continue jarring down with maximum trip load. SECONDARY ACTION •

If the string does not come free after 5 – 10 jar below, continue jarring while preparing a pipe releasing pill.

WHEN THE STRING COMES FREE:  Rotate and work the string .  Circulate at maximum speed.  Check the poor mud specifications.

STUCK WHILE MOVING DOWN ACTION TO ESTABLISH CIRCULATION  Apply low pump pressure (200-400 psi). Maintain pressure if restricted circulation is possible.  DO NOT JAR DOWN !!!APPLY TORQUE !!! Apply MAXIMUM over pull to jar. Allow sufficient time for a hydraulic jar to trip (4-8 min for long cycle. See jar manual).  If the string does not come free. DO NOT JAR DOWN!! Jar UP until the string is free or an alternative decision is made. Jarring up for 10+ hours may be required. WHEN CIRCULATION IS ESTABLISHED:  Slowly increase pump speed to maximize rate. When possible work the string and circulate the hole clean from bit depth.  Ream the section until the hole is clean.  Continue RIH until excessive set down weight is observed, circulate the hole clean.

NOTE: Since there are many causes of the drill string becoming stuck in a bore hole. Identifying the cause will be the key to determine the quickest and most economical method of getting the pipe free. The following is a list of the various ways pipe may become stuck: 1) Differential pressure sticking. 2) Cuttings and/or weight material settling. 3) Bridging due to an unstable well bore. 4) Key-seating. 5) Soft clay or salt packing off the annuls. 6) Mud or cement solidification. 7) Jamming bit into under gauge hole. 8) Junk dropped into the hole. 9) Collapsed casing.

COMMENTS: The first six ways of pipe becoming stuck are directly or indirectly related to the drilling fluid being used. The last three ways are purely mechanical. Of all the causes listed above, differential pressure sticking is normally the most frequent and requires special attention. It is also the only cause that normally requires the assistance of a mud engineer to prepare and spot a soak solution.

IDENTIFYING DIFFERENTIAL PRESSURE STICKING: 1) 2) 3) 4) 5) 6)

The drill string was stationary when it became stuck. A permeable formation is exposed in the well bore. The hole can be circulated with normal pump pressure. The drill string can not be reciprocated or rotated. The mud has high solids and high fluid loss. The mud weight has been increased recently.

METHODS OF FREEING DIFFERENTIALLY STUCK PIPE: The following information will deal with the remedies available to free differential pressure stuck pipe. The area of contact increases as the filter cake with time, thus produces greater sticking forces. Because of this, a quick determination of the cause followed by an immediate remedial step is imperative. 1) Spot a PIPE-LAX soak solution quickly. The probability of freeing differentially stuck pipe is inversely proportional to the time between actual sticking and final spotting of the solution. 2) Work pipe by tripping the jars both up and down if possible. 3) Reduce mud weight if possible. 4) Run a drill stem test tool and relieve pressure. 5) Pump a slug of water down the drill string and let it u-tube. 6) Pump some air to reduce the hydrostatic head.\

NOTE: Soak solution equivalent in weight to the drilling fluid will help prevent migration, and help keep the spot in proper placement. b. Proper placement of soak solution to cover the stuck zone with enough remaining in the drill string to move at least ½ barrel every ten minutes for several hours is essential. c. Attempts to wash over i differentially stuck can involve high risk. If all attempts within few hours of sticking fail, consider tracking. a.

PIPE- LAX: A PIPE LAX soak solution may be prepared with oil, LVT mineral oil or an oil mud as carrier fluid. A ratio of at least one-gallon PIPE-LAX to one barrel of carrier fluid is recommended. Soak solution equivalent in weight to the drilling fluid will help prevent migration, and help keep the spot in proper placement.

FREE POINT PROCEDURE: 1) Apply more hook load pull (25,000 lbs.) over the weight of the drill string and record this pull in pounds. 2) Mark a reference point on the Kelly or pipe. 3) Pull an additional 25,000 lbs. 4) Measure of pipe caused by additional pull in inches. 5) Calculate the free point using Eq. 10.4.2 or figure 10.4.3 FREE POINT EQUATION

(735,000) (DP Wt) L Fp = ▲F Where: Fp = Free point, ft DP. Wt. = Unit weight of drill pipe, lbs./ft, e.g. 16.6, 20.0, etc. L = Pipe stretch inches. ▲F

= Differential pull pounds.

FREE POINT CHART: EXAMPLE: Given: Drill pipe = 4 ½” X 16.6 lbs./ft X 12,000 ft. Drill Collar = 6 ½” X 2 ¼” X 800 ft. 8 ½” open hole to 12,800 ft. 9 5/8” casing to 9,300 ft. MW = 14 ppg.

The buoyant weight of the pipe was 154,000 lbs. To make the pipe in tension , the initial pull 160,000 and reference point was marked. An additional pull of 40,000 pounds was made and the pipe stretched by an amount of 39.7 inches. Calculate the free point? SOLUTION:

(735,000) (16.6) (39.7) Fp =

= 12,100 ft. (40,000)

Or Using fig. 10.4.3 1) Enter the chart with 40.000 pounds differential pull as left vertical scale. 2) Move horizontally to the right until the 4 ½” (16.6) is reached. 3) From above intersection, move vertically down and read 305 ft/inch. Fp = (305) 39.7 = 12,108 ft. CALCULATIONS FOR SPOTTING PIPE-LAX SOAK SOLUTION 1) After determining where you are stuck , with strong indications that you are differentially stuck , a calculation must be made to determine how much soak solution to mix. One would normally want to mix enough to cover the entire stuck area and leave enough the drill string to move at least ½ barrel every 30 minutes for several hours, to make sure you keep the stuck zone covered. 2) We must also make calculations so that the soak solution will be spotted properly. 3) We should also anticipate additional or excess pump pressure if we are spotting a lighter soak solution than the mud in the hole. EXAMPLE Given: 1) 8 ½” open hole to 12,800’. 2) 4 ½” (16.6) D.P. 12,000 long. 3) 800 ft. of 6 ½” X 2 ¼” drill collars. 4) Stuck below 12,100’ so we want to cover entire drill collar interval. 5) We want enough soak solution left inside the drill string to move ½ barrel every 30 minutes for 10 hours. 6) Pump output is 0.13 bbl/stk. 7) Surface lines from pits to rotary table holds 5 bbls of mud. 8) Soak solution weights 7.2 lb./gal and mud weight 14 lb./gal. 9) Pump pressure while circulating 14 lb./gal at 40 SPM is 1,200 psi. pressure drop inside the drill pipe is 30 psi/1000 ft. while inside the drill collar is 36 psi/100 ft. Find: 1) Barrels of soak solution needed = - - - - - - - bbls 2) Pump stroke required to spot the leading edge of the PIPE-LAX soak solution at the top of the collars = - - - - - - - strokes 3) Maximum pump pressure while moving soak solution down drill string at 40 SPM.

Solution: [ (8.5)2 – (6.25)2 (800) 1)

A) Volume around drill collars =

= 25.8 bbls. 1029

B) Volume inside the drill string = (1/2 bbl / 30 min) (60 min / hr) (10 hrs) = 10 bbls C) Total solution needed = 10 + 25.8 = 36.0 bbls 2) A) Capacity of surface lines = 5 bbls. B) Capacity of D.P. = (0.01422 bbl/ft) (12,000 ft) = 170.64 bbls. C) Capacity of D.C. = (2.252 / 1029) X 800 X 3.94 bbls. D) Annular capacity around D.C. (above) = 25.8 bbls. E) Total fluid to move to spot = 205.38 bbls. 205.38 bbls F) Pump strokes to spot

=

= 1,580 stks 0.13 bbl/stk 3) A) Maximum pump pressure will occur when soak solution is longest inside drill string, which will occur when the drill collars are full and the remainder is in the drill pipe. From 2.C. we find the capacity of the drill collars is 3.94 bbls, therefore if we have 36 bbls of soak solution we must have 36 – 3.94 = 32.06 bbls inside the drill pipe. B) C) D)

32.06 bbls / 0.01422 (bbl/ft) = 2,255 ft. of soak solution in the drill pipe. Total length of soak solution = 2,255 ft. + 800 ft. = 3,055 ft. Differential density between mud eight and soak solution weight = 14 – 7 = 6.8 lb./gal. E) Length of soak solution times differential density times 0.052 = (3,055 ft.) (6.8 lb./gal) (0.052) = 1,080 psi , which is the differential hydrostatic pressure F) Decrease in pressure loss due to the length of soak solution = (30) (2255/1000) (6.8 / 14) + (36) (800/100) (6.8/14) = 173 psi. G) The expected pump pressure when the soak solution reaches the bit = 1577 + 1200 – 173 2604 psi. NOTE: If we stopped pumping with the leading edge of the soak solution at the bit , we should see 1,577 psi on the stand pipe gauge.

PREVENTIVE MEASURES Both a positive differential pressure and a contact area, for this pressure to work on, are necessary for pipe to become differentially stuck. Therefore, any thing that will reduce contact area or differential pressure will help considerably to minimize or prevent differential sticking. 1) Keep mud weight to a safe minimum. 2) Keep solids content and fluid loss to an economic minimum 3) Minimize the time during which the drill string is not being rotated or reciprocated. 4) Use a good mud lubricant such as LUBE 153. 5) Use spiral or square drill collars 6) Use heavy weight drill pipe to compensate for loss of weight by using smaller or shorter drill collars. 7) Use good drilling and pipe handling practices.

8) Optimize stabilizer placement to minimize the contact area between the BHA and the side of the well bore.

FIGURE 1. STUCK PIPE CAUSES AND RECOMMENDED FREEING METHODS . STUCK PIPE CAUSE

Mechanical

Key Seating

Differential Sticking

Wellbore Geometry

Inadequate Hole Cleaning

String Jammed

String Jammed

Hole Packed Off

Work String Down & Rotate

Work String Up if RIH Work String Down if POOH

Work String Down to Establish Or Improve Circulation

Junk or Collapsed Casing

String Jammed

Work String Down & Up

Cement Related

String Jammed

Work String Up or Down Pump Acid if Available

String Jammed

Slump String & Rotate Reduce Mud Wt Utilize Spotting Fluid