LOST CIRCULATIONMeasurable loss of whole mud (liquid phase and solid phase) to the formation. LOST CIRCULATION Lost circulation can occur at any depth during any operation

ADVERSE EFFECT ON DRILLING OPERATIONS SURFACE HOLE Loss of drive /conductor shoe. Hole cleaning problems. Hole bridge /collapse. Stuck pipe. Well control event. Loss of well INTERMEDIATE HOLE Loss of fluid level monitoring. Loss of formation evaluation. Hole cleaning problems. Hole bridge collapse. Extended wellbore exposure time. Stuck pipe. Well control event. Under ground blowout. Additional casing string. PRODUCTION HOLE Loss of fluid level monitoring. Loss of formation evaluation. Hole cleaning problems. Hole bridge collapse. Extended wellbore exposure time. Stuck pipe. Well control event. Under ground blowout. Additional casing string. Production zone damage.

LOST CIRCULATION MECHANISMSPRESSURE INDUCED FRACTURE NATURALLY EXISTING FRACTURES / HIGH PERMEABILITY Wellbore pressure exceeds the fracture pressure of the formation causing the rock to crack open (fracture)

Over balanced well bore pressure is exposed to a formation with unsealed fractures or high permeability.

CAUSES OF LOST CIRCULATIONPRESSURE INDUCED FRACTURE Excessive mud weight. Annulus friction pressure. Well bore pressure surges. Imposed / trapped pressure. Shut-in pressure. Low formation pressure. NATURALLY FRACTURES / PERMEABILITY Unconsolidated formation. Fissures / fractures. Unsealed fault boundary. Vugular / cavernous formation.

PRESSURE INDUCED FRACTURE CAUSE: Well bore pressure greater than formation fracture pressure. The formation fractures allows mud loss.

WARNING: Prognosed loss zone. Excessive mud weight. Low fracture strength. Poor hole cleaning. Well bore pressure surges. May begin with seepage loss. Possible total loss. Pit volume loss. Excessive hole fill-up. If shut-in, sudden loss of pressure. Reduce pump speed to . Pull off bottom, stop pumps. Zero stroke counter, fill annulus with water or light mud. Record strokes if / when the annulus fills up. Monitor the well for flow. Minimize mud weight/maximize solids removal. Control penetration rate. Minimize well bore pressure surges. Avoid imposed / trapped pressures.

INDICATIONS:

FIRST ACTION (TOTAL LOSS):

PREVENTIVE ACTION:

NATURALLY FRACTURES / HIGH PERMEABILITY CAUSE: Well bore pressure is over balanced to formation pressure. Mud is lost to natural fractures and /or high permeability.

WARNING: Prognosed loss zone. Lost circulation can occur at any time during any open hole operation.

INDICATIONS: May begin with seepage loss, total loss possible. Static losses during connections / survey. Pit volume loss.

FIRST ACTION (TOTAL LOSS): Reduce pump speed to . Pull off bottom, stop circulation. Zero stroke counter, fill annulus with water or light mud. Record strokes if / when the annulus fills up. Monitor the well for flow. Minimize mud weight Control penetration rate. Minimize well bore pressure surges. Pre-treat with LCM.

PREVENTIVE ACTION:

LOSS SEVERITY CLASSIFICATIONS SEEPAGE LOSS (< 20 BBLs / HR) Gradual losses. Operation not interrupted. Possible warning of increased loss severity. PARTIAL LOSS (> 20 BBLs / HR) Immediate drop in fluid level when pumping is stopped. Slow to regain returns after starting circulation. Operations usually interrupted. Remedial action required. TOTAL LOSS (NO RETURNS) Return flow stops immediately. Pump pressure decrease. String weight increase. Operation suspended. Remedial action required.

METHODS FOR LOCATING LOSS DEPTHSuccessful treatment of lost circulation depends greatly on locating the depth of the loss zone.

SURVEY METHODS Temperature survey. Acoustic log. Radioactive tracer. Spinner survey Pressure transducer. Hot wire survey.

PRACTICAL METHODS Offset well data. Geologist / logger identifies potential loss zone. Monitoring fluid level trends while drilling.

CONSIDERATIONS FOR SURVEY METHODS

always available. me required to run survey. large volumes of mud. n difficult to interpret. sing survey tool in the hole.

GUIDE LINES FOR LOST CIRCULATION SOLUTIONS ACTION MINIMIZE MUD WT RESULTS Reduced well bore pressure (The driving force pushing into the loss zone) Reactive clays of loss zone swell with water of WBM producing a plugging effect. Soft shale deforms with formation stress helping to heal the fracture. Effectively bridges, mats and seals small to medium fractures / permeability. CONSIDERATIONS More successful with pressure induced fractures. Possible well control event or hole instability problems. More successful with fresh water mud lost shale formations Better results with LCM Normal 6 to 8 hours wait time with string in casing Less effective with large fractures, faults. Ineffective with cavernous zones Increase LCM lbs./bbl with loss severity.

FORMATION HEALING TIME

LOSS CIRCULATION MATERIAL (LCM) SPECIALTY TECHNIQUES

A plug base is pumped into the loss Can be used in production zones zone followed by a chemical activator. Increased risk of plugging equipments. The two materials form a soft plug Plug breaks down with time. Cement slurry is squeezed into the loss zone under injection pressure. The slurry cures to a solid plug. In some cases the only practical solution is to drill without returns Provides a fit-to-form solid plug at or near the stress of the surrounding formation. Not a consideration where well control potential exist. Set casing in the first compentent formation

CEMENT

DRILLING BLIND

GUIDELINES FOR SUCCESSFUL LCM RESULTS

s zone and accurate pill placement is vital. Position the string +/- 100 feet above the t stop pumping until the pill clears the bit. mud viscosity will suspend the LCM volume added. Add fresh to a pre mixed LCM before pumping . fresh gel continues to yield after spotting. M bridges, mats and then seals the loss zone, particle size distribution and pill t satisfy these requirements. Consult the LCM product guide prior to applying the

sizes if the loss potential is high. Keep the string moving during pill spotting id stuck pipe.

LOSS CIRCULATION MATERIAL (LCM)MATERIAL

DEFINITION FINE (F) A portion of the material will pass through the shaker screens. MEDIUM (M) majority of material will screen-out at shakers COARSE (C) All material will screen out at shaker. Will plug jets and down hole tools. Recommended with open-ended pipe.

GRADES

FIBROUS & FLAKED

Non rigid materials that form a mat on the hole wall to provide a foundation for normal filter cake development.

GRANULAR LCM BLEND CELLULOSTIC CALCIUM CARBONATE SIZED SALT

A rigid material that bridge and plug the permeability of the loss zone. A combination of fibrous. Flaked and granular materials in one sack. Sized wood derived materials used to prevent seepage /partial loss. Sized limestone or marble (acid soluble) used for seepage /partial loss in production zone. Granulated salt (water-soluble) developed for seepage / partial loss in production zone.

SEEPAGE LOSS SOLUTIONS (< 20 BBLS/HR) FIRST ACTIONReduce ROP to limit cuttings load. Minimize mud rheology. Minimize GPM. Minimize well bore pressure surges. Minimize mud weight. Consider pulling into casing and waiting 6 to 8 hours.

RECOVERYAdd LCM pill in 5 10 PPB increments. Evaluate results over 2 circulations before increasing to next level of LCM concentration. Mix in 30 to 50 bbl batches dictated by hole size. Consider spotting LCM pill before POOH.

NON PRODUCTIVE INTERVALS WBMLCM Blend (F) 5 10 PPB LCM Blend (M) 5 10 PPB Flaked (F/M) 10 20 PPB

OBM / SBMCellulosic (F/M) 2 25 PPB

PRODUCTIVE ZONE EXPOSED WBMLimestone (F/M) 5 30 PPB

OBM / SBMCellulosic (F/M) 2 25 PPB Limestone (F/M) 5 15 PPB

THE LCM MIXTURES SHOWN HERE ARE INTENDED AS A GUIDE WHERE NO FIELD EXPERIENCE EXISTS. SOME SITUATIONS MAY REQUIRE 2 6 PPB LCM CONCENTRATIONS IN THE TOTAL MUD SYSTEM. CONSULT YOUR MUD COMPANY FOR AVAILABLE PRODUCTS AND PILL FORMULATION BEST SUITED FOR THE AREA.

PARTIAL LOSS SOLUTIONS (> 20 BBLS/HR) FIRST ACTIONReduce ROP to limit cuttings load. Minimize mud rheology. Minimize GPM. Minimize well bore pressure surges. Minimize mud weight. Consider pulling into casing and waiting 6 to 8 hours.

RECOVERYAdd LCM pill in 5 10 PPB increments. Evaluate results over 2 circulations before increasing to next level of LCM concentration. Mix in 30 to 50 bbl batches dictated by hole size. Consider spotting LCM pill before POOH.

NON PRODUCTIVE INTERVALS WBMLCM Blend (M) 15 25 PPB LCM Blend (C) 15 25 PPB Walnut (M/C) 10 20 PPB

OBM / SBMCellulosic (F/M) 10 25 PPB Cellulose (C) 10 25 PPB Walnut (M) 5 15 PPB

PRODUCTIVE ZONE EXPOSED WBMLCM Blend (F) 5 15 PPB LCM Blend (M) 5 15 PPB Cellulosic (M) 5 15 PPB

OBM / SBMCellulosic (F/M) 2 25 PPB Limestone (F/M) 5 15 PPB

TOTAL LOSS SOLUTIONS

FIRST ACTION

RECOVERY

Pull off bottom, keep Formulations for the specialty pill and cement are dictated by conditions of string each event. moving. Fill annuals with water or NON PRODUCTIVE INTERVALS light mud. Record strokes OBM / SBM if/when annulus WBM fills up. 40 PPB LCM pill 30 - -40 PPB LCM pill Consider pulling specialty pill specialty pill cement into the casing. squeeze cement squeeze Minimize well bore pressure PRODUCTIVE ZONE EXPOSED surges.

WBM40 PPB LCM pill specialty pill squeeze ADDRESS RESERVOIR NEEDS

OBM / SBM30 - -40 PPB LCM pill specialty pill cement cement squeeze ADDRESS RESERVOIR NEEDS

THE LCM MIXTURES SHOWN HERE ARE INTENDED AS A GUIDE WHERE NO FIELD EXPERIENCE EXISTS. SOME SITUATIONS MAY REQUIRE 2 6 PPB LCM CONCENTRATIONS IN THE TOTAL MUD SYSTEM. CONSULT YOUR MUD COMPANY FOR AVAILABLE PRODUCTS AND PILL FORMULATION BEST SUITED FOR THE AREA.

SEALING MATERIALS USED FOR LOST CIRCULATIONMaterial Type Description Concentration Lbs./bbl Largest fracture sealed (inches)

Nutshell Plastic Limestone Sulphur Nutshell Expanded percite Cellophane Sawdust Prairie Hay Bark Cottonseed Hulls Prairie Hay Cellophane Shredded Wood Sawdust

Granular

50% - 3/16+ 10 mesh 50% - 3/16+ 100 mesh 50% - 3/16+ 10 mesh 50% - 3/16+ 100 mesh 50% - 3/16+ 10 mesh 50% - 3/16+ 100 mesh 50% - 3/16+ 10 mesh 50% - 3/16+ 100 mesh 50% - 3/16+ 10 mesh 50% - 3/16+ 100 mesh 50% - 3/16+ 10 mesh 50% - 3/16+ 100 mesh 3/4" flakes 1/4" particles 1/2" particles 3/8 particles fine

20

0.2

Granular Granular Granular Granular Granular

20 40 120 20 60

0.2 1 1 0.2 0.9

Laminated Fibrous Fibrous Fibrous Granular

8 10 10 10 10

0.9 0.8 0.8 0.4 0.4

Fibrous Laminated Fibrous

3/8" particles 1/2" flakes 1/4" fibrous

12 8 8

0.4 0.5 0.3

Fibrous

1/6" particles

20

0.2

SPOTTING PROCEDURES FOR LOST CIRCULATION MATERIAL (LCM)

s zone. rrels of mud with 25 30 ppb bentonite and 30 40 ppb LCM. string +/- 100 feet above the loss zone.

ump of the pill into the loss zone. Stop the pump, wait 15 minutes and pump the pill. ugh the bit. Pump the entire pill and follow with 25 barrels of mud. t regained, repeat procedure. If returns are not regained, wait two hours and repeat

t regained after pumping three pills, consider the other options to regain circulation.

SPOTTING PROCEDURES FOR SPECIALTY PILL

hrough the loss interval. Pull out of the hole and return open ended. string +/- 100 feet above the loss zone. g pit thoroughly. Mix 50 barrels of desired specialty pill. drill string and place in the suspected zone. If annulus is not full, pump mud down e pumping pill down drill string. lls and squeeze in place, apply 150 200 psi on annulus. This will soft squeeze the loss zone.

SPOTTING PROCEDURES FOR GUNK PILL

hrough the loss interval. Pull out of the hole and return open ended. string +/- 100 feet above the loss zone. ement and 100 sx of bentonite with 50 barrels of diesel (slurry wt 11.5 ppg. Yieldper sack). drill string. 15 barrels of water -free diesel ahead and behind the gunk slurry. iesel spacer reaches the bit close the BOP and pump mud down the annulus. n down the string and 2 bbls/min down the annulus until the tail diesel spacer clears

string slowly. Do not reverse circulate. ng clear of the squeeze. Mix and place the squeeze with a cementing unit, if

or the gunk to cure, repeat procedure if returns are not regained. ary to drill out the gunk before repeating the procedure.

SPOTTING PROCEDURE FOR CEMENT

The cement slurry formulation should be tested by the cement company to determine the thickening time. hrough the entire loss circulation interval ole and return open ended drill pipe n-ended drill pipe approximately 100 feet above the loss zone. 0 100 bbls of cement slurry. y with a sufficient volume of mud or water to balance the u-tube. s and attempt to fill the annulus. edure if returns are not regained. ary to drill out the cement before repeating the procedure.

LOST CIRCULATION PREVENTION GUIDELINES

Prevention of lost circulation must be considered in the well planning, drilling and post analysis phases. g program to case off low pressure or suspected lost circulation zones. d weight to the minimum required to control known formation pressures. High mud the major causes of lost circulation. d system with LCM when drilling through known lost circulation intervals. ud rheology , treat are still sufficient to clean the hole l string when starting circulation helps to break the gel and minimize pump

slowly after connections and periods of non-circulation. GPM flow rate to clean the hole when drilling known lost circulation zone. own lost circulation zone to avoid loading the annulus with cuttings . pping speeds to minimize swab/surge pressure. culation at 2 to 3 depths while tripping in the hole. us restrictions. et sizes or TFA that will allow the use of LCM pills (12/32 jets+). plugging pump suctions. Pump discharge screen, drill string screens, etc. mud losses due to shaker screen plugging

PRECAUTIONS WHILE DRILLING WITHOUT RETURNS

Circumstances may dictate drilling blind until 50 feet of the next competent formation is drilled. Casing is set to solve the lost circulation problem. A blind drilling operation must have drilling manager approval. ate water supply is available. o drill and the other pump to continuously add water to the annulus. to monitor the flow line at all times. torque and drag to determine when to pump viscous sweeps. pump pressure while drilling for indications of pack-off . possible) at one joint per hour. om every 15 feet (3m) drilled to ensure the hole is not packing off. oving at all times. 500 bbl reserve of viscous mud ready to pump. g viscous on bottom prior to tripping or logging. d consider pulling to the show if pump repair is required. pe slowly and minimize pipe speed. g a viscous pill above the BHA prior to each connection. nnection. Circulate and wipe the hole thoroughly. eys when drilling blind. urns, stop drilling, raise the drill string to the shut in position . stop the pumps and or flow. ed, close the BOP and observe shut-in pressures. slowly circulate bottoms up through two open chokes. served- slowly circulates the kick with the circulation method and present mud for an under ground blowout condition. ll times to pump cement to the well.