8. diamond coring system—roller cone bits ......diamond coring system—roller cone bits 9.875...

Storms, M. A., Natland, J. H., et al., 1991Proceedings of the Ocean Drilling Program, Initial Reports, Vol. 132

8. DIAMOND CORING SYSTEM—ROLLER CONE BITS AND ASSOCIATED HARDWARE1

G. L. Holloway2

EXECUTIVE SUMMARY

Design changes were made on conventional ODP rotary corebarrel bits to allow deployment with the Diamond Coring System(DCS) hardware. Two of the more significant changes allowed fora latch-in center bit to be run. These changes included: (1) enlarg-ing the throat diameter of the bit and (2) removing the core guidewhile still maintaining the same size roller cones. The center bititself was a completely new design utilizing two small TungstenCarbine Insert (TCI) cones. The position of the center bit withinthe primary bit was adjustable so that the center bit could be runahead of the larger cones or behind them. This was accomplishedby placing spacers between the latch and the center bit. The centerbit was held in place with a modified Extended Core Barrel (XCB)latch which allowed recovery via a wireline.

The roller cone bits held up remarkably well against the youngfractured basalt encountered at the Bonin back-arc location.Though not as abrasive as some locations investigated on previoushard rock legs, it still challenged the bits to penetrate and survive.All the holes were spudded with a Positive Displacement CoringMotor (PDCM). Several holes had the additional benefit of beingconfined within the diameter of a casing hanger and run in con-junction with spiral bladed stabilizers. There was no excessivewear or damage reported to any of the larger four-cone bits.Several of these bits were rerun on other holes at the Boninback-arc location. One washout was reported on a center bit after21 hr of rotation. Overall, the bit performance and quality wasrated extremely high.

BACKGROUNDOne of the primary objectives of Leg 132 was to provide a

cased hole to isolate unstable formations in the upper portion ofthe hole and allow the smaller DCS to be deployed. This wasaccomplished by drilling-in and backing a Bottom Hole Assembly(BHA) composed of the larger API drill pipe and/or drill collarsalong with a modified version of ODP's rotary core barrel bit. Inorder to provide a greater degree of flexibility in the drillingprogram, two different sizes of core bits were designed to com-plement the two sizes of BHA also being developed. It had beenlearned on previous legs that the smaller the hole diameter drilledinto fractured formations, the more likely the hole was to remainstable. However, this fact had to be balanced with the size of theroller cones themselves so that bit life could be preserved.

Two bit manufacturers were approached with the idea of re-designing ODP's roller cone bit in order to allow the DCS tubingand core bits to pass. After several discussions with each manu-facturer and review of the preliminary concepts presented, Secu-rity was chosen to pursue the design to the final stage ofdevelopment.

1 Storms, M. A., Natland, J. H., et al., 1991. Proc. ODP, Init. Repts., 132: CollegeStation, TX (Ocean Drilling Program).

2 Ocean Drilling Program, 1000 Discovery Drive, College Station, TX 77845-9547, U.S.A.

Since three locations were to be investigated on this leg, eachwith different types of formation, two cutting structures wereincorporated in the roller bit cones. This allowed a total combi-nation of four types of bits which could be run. It was felt thatwith this selection there was sufficient coverage for any of theformations expected during Leg 132. These formations rangedfrom young fractured basalt to reefal limestones. Figure 1 illus-trates the different bit sizes and BHA combination that wereavailable for Leg 132.

The conventional bits of this type used by ODP were normallyrun on a core barrel to catch the core cut by the four roller cones.However, for this application where tubing was to be run insidethe API drill pipe and out the bottom of the bit, conventional corebarrel hardware could not be run. Therefore, a whole new BHAand enlarged bit throat were required. To ensure that core wouldnot enter the bit and BHA while drilling in the back-off assembly,the bits had to be further modified to accept a removable centerbit.

DESIGN MODIFICATIONSTwo of the more significant design modifications to the bits

manufactured for Leg 132 included removing the core guide andopening the throat of the bit to a diameter of 4.05 in. Thismodification was required so the diamond coring bits/core barreland tubing string used with the DCS could pass freely out thebottom of the BHA. Several ideas pertaining to the center bitdesign were investigated prior to selecting a wireline retrievablecenter bit. These included: (1) drilling out a welded-in center bit,(2) retrieving a latched-in center bit, and (3) drilling through atri-cone bit with the DCS diamond bit.

Before a decision was made as to the direction to pursue in thedesign of the center bit, several attempts were made to drillthrough a conventional core bit and a tri-cone bit with the DCSdiamond bits. Full-scale field tests were performed in Salt LakeCity, Utah, to determine the feasibility of the concept. The resultswere promising but not conclusive. Several diamond bits wereneeded to penetrate completely through existing ODP roller coneor tri-cone bits. It was also felt that the time taken to drill throughthe more conventional bits, coupled with the trip time for the DCStubing and the possibility of leaving inserts, diamond matrix,and/or cones in the hole, was not in the best interest of testing theDCS. This scenario also involved sacrificing several diamond bitsbefore even beginning a hole. Since manufacturing time wasrunning out, it was decided to focus the design on adapting aretrievable center bit using a modified ODP downhole latch as-sembly.

The two sizes of bits manufactured were 11-5/8 and 9-7/8 in.with cutting structures designated as M84F and H87F. The Mdesignation describes bits with tungsten carbide inserts for me-dium to hard formations. The inserts are shaped for moderateextension with a closely spaced chisel design. The H designatestungsten carbide inserts for hard to extra hard formations. Insertsselected for these bits used a short extension of closely spacedconical design. Both sizes used Securities patented sealed journalbearing and gauge inserts along the shirt-tails with hardfacing on

211

G. L. HOLLOWAY

Gimbal device

Mini-hard rockguide base \ 1

Mechanicaltensioning tool

Matingreceptacle

BHA landingseat

DCS hydrilstring

Reentry cone

16 in.casing

DCS hydrilstring

Hard formation concept Soft formation concept

Figure 1. Bottom hole assembly options.

the leading edge. The journal bearing on the larger size bit useda 7-7/8 in. bearing with the smaller size bit using a 6-1/2 in.bearing. A schematic of this type of roller cone bit is presented inFigure 2.

CENTER BIT DESIGNSecurity was again selected to pursue the manufacturing of the

center bit option because of their innovative design, willingnessto work with ODP, and the cost competitiveness of their product.Also, due to the time restraints of manufacturing, it was felt thata single bit manufacturer would be less apt to make dimensionalmistakes or errors in compatibility between the two bit designs.

Therefore, along with the large roller cone bits, Security wasto provide the center bits. These bits were to be positioned in thethroat of the larger roller cone bits to provide a cutting structureto remove any material not broken up with the four outer conerollers. Because of the small size required for the center bit, onlytwo cones could be incorporated into this design. A schematicdrawing of the center bit is presented in Figure 3.

These bits were made in an assembly which latched into thebladed spiral stabilizers attached immediately above the largerbits. A modified version of the XCB latch was adapted for holdingthe center bits in position (Fig. 4). Besides providing a positivelocking mechanism, the latch also allowed three different lengths

of spacers to be added so that the center bit elevation within thelarger roller cone bits could be changed for the different forma-tions encountered. This allowed for several different combina-tions of bits to be run until an optimum penetration rate could beestablished for the formation encountered. The elevations were:(1) 1.5 in. behind the roller cones, (2) flush with the roller cones,or (3) 1.5 in. beyond the roller cones. Figure 5 illustrates thedifferent elevations at which the center bit could be positionedwithin the larger roller cone bits. The TCI's used on the smallcenter bits were HI OOF. These inserts were for very hard toabrasive formations with a short 120° double conical shape. Thecenter bit's body was slightly smaller than the cavity providedinside the large bit. Four centralizing tabs approximately one-eighth of the circumference were used to align and prevent wobbleof the center bit inside the throat of the larger roller cone bit. Thesepassageways provided additional flow paths to help in flushingthe face of the center bits. Besides these flow paths, a single 3/16in. hole was provided above each roller cone for the drilling fluidto cool and clean the individual cones.

SET-UP/FIELD ASSEMBLYThe assembly of the modified XCB latch and the adaptation to

the two-cone center bits were not without some minor problems,as normally would be expected on any prototype design. These

212

DIAMOND CORING SYSTEM—ROLLER CONE BITS

9.875 in./11.625 in.diameter

A-A

Figure 2. Roller cone bit design.

problems amounted to several small machining errors not checkedbefore the parts were shipped. The first was that the length of theslots in the latch body for the latch dogs had to be increased byapproximately 1 in. in order to latch properly. It was also discov-ered that the center bits were 3 in. longer than the design calledfor. This made the spacers provided to adjust the position of thecenter bit ineffective. Thus, the center bit without any spacersprotruded from the end of the roller cone bit by approximately1.75 in.

It was originally thought that the conditions at the Bonin sitewould necessitate the center bit be recessed. However, it wasdecided not to invest the time to remachine the center bits but torun them as they were originally manufactured. This decisionproved to be correct at least for the unsupported spud-ins, in thatthe center bit acted as a pilot and eliminated the bit skating overthe seafloor. It also provided a more severe test of the center bitlatch assembly and center bit itself. Other than the small omis-sions mentioned above, the center bit latch assembly workedperfectly. Retrieval of the center bit was effortless on everyattempt made with the overshot.

The XCB latch with the center bit attached was required to beloaded into the lower stabilizer before the bit was installed. Thiswas necessary due to fact that the latch had been modified so thatit could only operate in one direction. Loading the center bit wasaccomplished by tens^oning the XCB latch first and locking thelatch dogs down with a C-clamp. The bit could be pushed insidethe cavity, oriented, and latched in. The C-clamp would be re-moved as soon as the latch dogs were held shut by the I.D. of thestabilizer.

PERFORMANCE

Boreholes 809A And -BTwo test holes were performed at the Bonin back-arc location

to determine the performance of the different size bits. These testswere conducted to evaluate which type bit would provide the bestpenetration rate, hole cleaning characteristics, and stability, andalso retain its integrity in the young fractured basalt expected atthe first location. Both bits were rotated approximately the samelength of time (7 hr for the 11-5/8 in. M84F and 8.25 hr for the9-7/8 in. M84F). However, the actual penetration of the smallerbit nearly doubled that of the larger bit (13.4 m to 8.3 m). It wasgenerally thought that the smaller size bit performed better since

video inspection of the seafloor from the VIT revealed a cleanerhole. Also, the torque reported by the driller and stalling of thePDCM was less of a problem than on the first borehole. Resultsfrom the PDCM runs showing weight on bit, flow rate, anddrilling times are presented in Tables 1 and 2. It should be noted,though, that the first borehole was stopped several times in orderto view the spudding and to confirm that the bit was indeedpenetrating the seafloor. This most likely contributed to some fillfalling back into the borehole, confirmed by the amount of redrill-ing necessary on this borehole each time the PDCM was stoppedfor observation. Another factor is that the two boreholes wereapproximately 100 m apart and, consequently, material variabilitycould have played a much larger role in the changed drillingcharacteristics than the size of the bits. However, it was generallyfelt that the material was consistent over the area.

Visual inspection of the roller cone bits and center bits re-vealed that both bits had very little wear. There were no chippedor broken inserts, all the cones were intact, and the bearingsappeared to still be tight and functional. This was true for boththe center cone bits and the larger roller cone bits despite the factthat the center bits took the majority of the wear by being runahead of the roller cone bit.

Boreholes 809C, -D, -E, And -FBoreholes 809C through 809F were all conducted through the

mini-hard rock guide base (HRB) (Fig. 6) for spudding the DCSholes. All of these BHA's were restrained by the landing seatinside the lower section of the casing hanger (Fig. 7) attached tothe HRB. Also, all the center bits run on these holes were recessed1.5 in. behind the cones of the larger roller bits. Penetration ratesaveraged 10-12 m/hr for Holes 809D and 809F. The drilling ratesfor the two other sites (809C and 809E) were considerably greaterand cannot be grouped into the same category as the other twolocations. This was because a considerable amount of torque didnot reach the bits but was lost by the BHA rotating against theside of the casing hanger. This occurred when attempting to spudand drill the boreholes at an angle greater than the reentry conescould compensate for.

The most notable difference between these holes (809Cthrough 809F) and the unsupported spud-in holes (809A and809B) was the penetration rate. Since two of the variables werechanged in the spudding technique, it is not clear how much each

213

G. L. HOLLOWAY

Top view

3.750 in.diameter

4.000 in.diameter

Figure 3. Center bit design.

Latch dogs (2)OP4473

Modifiedpulling neck

OQ2526

Hexagonalhead boltOD7240

Landing shoulder capOP4479

Figure 4. Modified XCB latch assembly.

contributed to the faster drilling. Good arguments can be madefor both. However, it was felt that a significant improvement overbare rock spudding can be realized when the bit is restrained fromrolling around/skating on the seafloor.

The two holes drilled at an angle (809C and 809E) and abortedprior to reaching the designated termination depth allowed betterobservation of bit wear. It was observed that material encounteredat the Bonin location was not representative of that expected atEast Pacific Rise or what was found at the Mid-Atlantic Ridge on

Washers (2)OQ2524

Modifiedlatch bodyOQ2522

Legs 106 and 109. However it is felt that improvements in thesebits over those used previously are a step in the right direction.

One of the 11-5/8 in. bits rotated for 21 hr showed little signof wear. However, the accompanying center bit with the samenumber of hours produced a wash out on one of its legs and lossof one insert on the gauge. The other 11-5/8 in. bit was rotatedless than 2 hr and also showed relatively little wear. Typicalweight on bit ranged between 2 and 8 kip. Tables 3 through 7provide the bit record for flow rates, weight on bit, and penetra-

214


Figure 5. Center bit elevations.

Table 1. Coring motor runs, Hole 809A.

Runno.

1234567891011121314151617181920

WOB(1000 lb)

0-50-50-52-52-52-52-52-52-52-52-52-52-52-52-52-52-52-52-52-5

Flowratea

(gpm)

250325325325370315310310320340345350350370370370420410415415

Operatingpressure

(psi)

250300300400500500450450500500500500500500500500550550550550

Stallingpressure(psi)

5005505508008008008008008008008008008008008008001000110011001100

Pene-tration(m)

0.000.001.001.802.002.203.003.504.004.505.005.806.006.106.106.507.007.508.308.30

Time(hr)

04300435044505450600061506500730075008150830091009150925094510301045110511451215

a Gallons per minute divided by 5 equals strokes per minute.

tion. A complete summary of the bits run and their performancein terms of hours run and meters drilled is presented in Table 8.

Another important point is that all the bits were manufacturedwith a consistent quality control. Threads were all cut to gaugeon both the larger Hycalog threads and the smaller and moredifficult ODP CX thread on the center bits. There were no re-ported bearing failures on any of the bits other than the center bit,which experienced a wash out and all the welds held up withoutlosing any arms.

Table 2. Coring motor runs, Hole 809B.

Flow Operating Stalling Pene-Run WOB ratea pressure pressure tration Timeno. (10001b) (gpm) (psi) (psi) (m) (hr)

1234567891011121314151617181920212223242526

0-50-50-50-50-50-50-50-50-50-50-50-50-50-50-50-50-50-50-50-50-50-50-50-50-50-5

325210210260270320330335370360360360360410420420415420420420420450450455450450

300200200300300350250350350700250400700450400400500500450400800500500475500500

500

—700

700700

—

200

0.001.002.003.003.004.004.505.005.305.506.006.006.006.007.007.607.608.009.0010.0010.3011.0012.0013.0013.4013.40

23452350240000200030010001200145020002100230024002550300034504000400042004350445052005500610065507050710

Gallons per minute divided by 5 equals strokes per minute.

215

G. L. HOLLOWAY

Side view

Figure 6. Mini-hard rock guide base.

216


Innerpipe

(jay-latch)

Lowerbody

Trunnions

Innerlanding

seat

16 in.buttressthread

12 in. I.D.

15.125 in.

21.75 in.

Landing

Kseat keyrestraint

Rotational. restraints

Mini-HRB type

Figure 7. Modified casing hanger.

HOLE 810D

A 9-7/8 in. H87F bit was run at this location. The formationconsisted of soft calcarious oozes to firmer chalk down to a depthof 127.1 mbsf (417 ft). A hard chert layer was located at this depth.This was confirmed by a wash-in test (no rotation) conductedearlier at this site to determine the depth to which it would bephysically practical to set 16 in. casing. The test, which limited

Reentry cone type

the weight on bit to only 5000-10,000 lb, produced a penetrationof 60 m (197 ft) in a little less than an hour. A reentry cone wasthen deployed at this site to establish a conduit for the BHA to bedrilled through (Fig. 8). However, due to a problem with thecasing hanger itself, casing was not run. Since casing was not run,it was decided to drill the BHA (consisting only of drill collars)to 112.63 mbsf (369 ft). This was accomplished in a little less than3 hr with the PDCM. However, because the BHA did not back off

217

G. L. HOLLOWAY

Table 3. Coring motor runs, Hole 809C. Table 5. Coring motor runs, Hole 809E.

Runno.

12345678

WOB(1000 lb)

2-52-52-52-52-52-52-52-5

Flowratea

(gpm)

210350400400410405410410

Operatingpressure

(psi)

300350400400300300300300

Stallingpressure

(psi)

500600-700600-700

600

—

Pene-tration

(m)

0.00

2.00

3.00

4.004.10

Time(hr)

12201230123512501300133013451410


Table 4. Coring motor runs, Hole 809D.

Runno.

123456789

101112131415161718

WOB(1000 lb)

52-52-52-52-52-52-52-52-52-52-52-52-52-52-52-5

Flowratea

(gpm)

225300300300350350350350350350350350350350350250

Operating Stallingpressure pressure

(psi) (psi)

200-250 —250-350 —250-350 —275-350 —325-400 —325-400 —

350 —350 —

350-450 —425-600 —425-600 —400-500 —450-500 —375-400 —200-250 —100-125 —

shut down pumpspull out of cone

Pene-tration

(m)

0,000.50LOO1.502.002.503.003.504.004.505.005.506.006.306.306.30

Time(hr)

061006170622062406250627062806290631063306370639064406470649065106570708

Comments: Good run, drilled to total depth, and backed off as designed.a Gallons per minute divided by 5 equals strokes per minute.

as it was suppose to, it was retrieved for inspection. This scenariooccurred two more times before actually leaving the BHA in theseafloor.

As would be expected for this soft of material, the bit stilllooked new after being retrieved. There was no damage to theinserts or cones, even though some small stringers of chert mayhave been encountered during the drilling. The center bit, thoughhaving been run twice before in basalt, did not show any addi-tional wear after drilling/washing another 119.3 m (391 ft). Thebit was redeployed a third time and drilled another 13.72 m (45.65ft) where the BHA was finally backed off. However, due to aproblem with the C-ring on the back-off sub, the BHA did notlatch-in but continued downward approximately 26 m (85 ft)deeper than it was supposed to land. This necessitated a fishingtrip to retrieve the BHA. Upon recovery to the rig floor, it wasobserved that the bit was totally destroyed after falling onto thehard chert layer with 50,000 lb of BHA behind it. The weld onone arm had broken and allowed it to be pulled from its originalsocket. The other three arms were broken at the bit body. Theimpact was so severe that even the throat of the bit was deformedand slightly flattened on one side. What was surprising was thatthe center bit again came out without any appreciable additionalwear over the previous run. It is speculated that due to its positionwithin the larger bit (1.5 in. behind the larger cones), the majorityof the impact was taken by the four cones/arms. A record of bitperformance while using the PDCM is provided in Table 7.

Runno.

123456789

101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354

55

565758596061626364

WOB(1000 1b)

2-52-52-52-52-52-52-52-52-52-55-85-85-85-85-85-88-108-108-105-10

—

—0-50-50-50-20-20-20-20-20-20-22-52-52-50-50-50-50-50-50-50-5

Flowratea

(gpm)

225225225225300300350350350350350350350400450450350350350350500

—365350350350400400400400450450460550450470475475500500530500

10-15pull 4500-52-84-84-80-50-52-42-42-8

4-10

4-104-104-104-104-104-104-104-104-8

535620620610595590585580

575-600

575-600

575-600575-600575-600575-600575-600

600585585450

Operatingpressure

(psi)

—200-250200-250375-400

300400

400-525450-500400-475425-475475-550525-600475-550525-700

800-1000600-675675-750700-750700-800

1000-1200625-850

800-10001000-1100

500-600650-750650-700600-650700-800650-750650-750700-850850-950850-900

800-1000

800-900800-900800-900

1000900-1000900-1000

10001400

1300-140014001400

1300-14001400

1300-14001300-1550

1300-1550

1300-15001300-15501200-15001350-15501350-15501350-15501300-14001300-1400

900-950

Stallingpressure

(psi)

——————

1000—

b

—

700c

de

———

1000f

—g

—h1

—

750950——

900—

J

—

k1500

—1200

1m

—

—1200

no

—

1600p

q

goodrotationrotation

ok1600

——

16001600

r

——

1050

Pene-tration

(m)

0.000.501.001.502.002.503.003.504.004.505.005.006.006.507.00

—7.508.008.508.758.758.758.758.753.002.5-32.5-32.5-32.002.001.502.002.753.003.003.503.504.004.254.504.005.005.505.505.505.506.006.006.507.007.107.207.257.30

7.40

7.507.707.707.757.807.857.908.008.00

Time(hr)

064406450646064806500651065306550657070107060712071307180748

—0827084509200921

—100610141026112011231130114011411147115311551200121212151230124513001301131513201332133413401410142014251435145515251545155017001730

1743

180018201830184519001915193019452030

Comments: Penetration rate decreased to almost nothing, decision made to pullout BHA and check bits.a Gallons per minute divided by 5 equals strokes per minute.b 10 bbl high viscosity mud pumped down.c 10 bbl high viscosity mud pumped down.d 15 bbl high viscosity mud pumped down.e Penetration rate decreased significantly.f Problems with stalling out and drag (over pull).g 15 bbl high viscosity mud pumped down.h Pulling back to keep motor running.1 Pulling back to keep motor running.j Motor stalls out with very little WOB.k Reestablish rotation.

Stall out at 5 gpm, pull back to restore rotation.Im Reestablish rotation.n 50 kip overpull to free BHA.0 Good rotation.p Motor stalling out.q 10 bbl high viscosity mud pumped down.r Motor stalling out, pick up BHA 0.2 m.

218


Table 6. Coring motor runs, Hole 809F. Table 7. Coring motor runs, Hole 810D.

Runno.

WOB(1000 lb)

Flowratea

(gpm)

Operatingpressure

(psi)

Stalling Pene-pressure tration

(psi) (m)Time(hr)

123456789

1011121314

2-52-52-52-52-52-52-52-52-52-50-52-50-50-5

225225225300300300350350350350350350350350

200-300250-325300-450450-575400-525375-475475-600400-500425-500450-650450-600475-550450-525

300

500

700

700700

—

0.000.501.001.502.002.503.003.504.004.505.005.505.905.90

22222223222622282229223522382239224022432245224722502252

Comments: Pressure spikes not real obvious, but dropped off to 300 psiafter back off.a Gallons per minute divided by 5 equals strokes per minute.

RECOMMENDATIONS/CONCLUSIONS

Performance of the roller cone bits, center bits, and latchassemblies illustrated that the concept of a removable center bitwas a viable alternative when an additional tubing string was tobe deployed through the initial drilled-in BHA. Though possiblynot as demanding as some young fractured basalt formations, theBonin site did provide several instances where total rotating hoursexceeded that accomplished during Legs 106 and 109. It wasreported not uncommon for bit failure to occur within 6 hr inunsupported bare rock spud-in on Leg 106 and up to 12 hr for thebits used on Leg 109. Designs incorporated from those bits wereused as the basis for the bits manufactured for Leg 132. Better bitlife could also possibly be attributed to overall bit and bearingassembly design, better control of the PDCM, less weight on thebit, better stabilization/centralization, and/or manufacturer/ven-dor quality control.

It was felt that the reduced hole diameter and annulus with the9-7/8 in. bit improved hole stability and hole cleaning charac-teristics over that of the larger 11-5/8 in. bit. However, with onlytwo tests for comparison, definitive answers can not be claimedat this time. It is recommended that additional testing of the bitsin a similar material be performed so that conclusive evidence cansupport this premise.

The two-cone center bits provided a prototype design whichmay be improved after further studying their performance. Sincethese small bearing bits are more apt to wear out sooner than thelarger cone bearings, a more robust design should be investigatedalong with a possible wireline replaceable version, when the holeis not initially drilled with the PDCM. Using the center bit as apilot for bare rock spud-in appeared to prevent the bit fromwalking on the seafloor and may possibly have reduced the wearon the larger cones by removing the initial core. However, pro-longed use in this mode could result in the complete failure andpossible loss of the smaller cones.

The fact that the BHA was somewhat supported and central-ized by the hard rock guide base on Leg 109 was cited as reasonfor longer bit life and performance over what was experienced onLeg 106. This concept was taken a step further using the techniqueof continual centralization and stabilization of the bit until bore-

Runno.

WOB(1000 lb)

Flowratea

(gpm)

Operatingpressure

(psi)

Stallingpressure

(psi)

Pene-tration

(m)Time(hr)

123456789

10111213141516171819202122232425262728293031323334353637383940414243444546

0-20-20-2

75-10075-10075-100

— 0.003.006.00

from 0427 to 0431 made up pipe connection ?0-20-20-50-50-5

75100-125

125100-125100-125

150-250150-200100-200100-200150-250

9.0012.0015.0018.0020.00

from 0414 to 0448 made up pipe connection0-50-50-50-50-50-5

7125125125125

140-150

—200-225

150-225300

250-300

24.0027.0030.0033.0036.0039.00

from 0457 to 0503 made up pipe connection2-62-62-6

165170170

250-300250-300215-425

42.0045.0049.00

from 0511 to 0524 made up pipe connection6-106-106-106-106-106-106-10

150150165210210200200

225-300300-400300-350400-450300-400300-375300-400

51.0054.0057.0060.0063.0067.0069.00

from 0540 to 0545 made up pipe connection6-106-106-10

200200-210

215

300-400275-400300-400

73.0076.0079.00

from 0553 to 0610 made up pipe connection6-106-100-60-62-86-86-8

210230220225225225225

300-350300-400300-400300-400300-400300-450325-450

82.0085.0088.0091.0094.0097.0099.00

from 0623 to 0632 made up pipe connectionfrom 0632 to 0635 made up pipe connection6-106-106-10

—

235225225—

325-450300-400500-550

shut down

103.00106.00107.00107.50

04100411041504270431043304350436043704380450045104520454045504570503050605080511052405270530

0532/053405360538054005450549055105530610061306140616061806200622062306320635063806400641

—


hole termination depth was reached on the hard rock sites. Therestrained bit movement due to the tight diameter of the landingseat inside the casing hanger, coupled with the centralization fromthe spiral-bladed stabilizers, is felt to have added significantly tothe bit life and performance. A schematic of the spudding tech-nique is illustrated in Figure 9. Annular clearance through the 12in. landing seat between it and the BHA was typically less than1/2 in. throughout the drilling process. Annular clearances for theHRB used on Leg 109 were much larger due to the 31 in. diameteropening in the guide base despite the fact that a 24 in. diameterguide bushing was run when spudding the hole.

Another possible reason for better bit performance was thedifferent design philosophy used to establish the hole. Leg 109attempted to use the more conventional oilfield approach ofdrilling a larger hole and setting surface casing strings, whereasa drill-in type BHA was used on Leg 132. This concept of the

219

G. L. HOLLOWAY

Table 8. Summary of bit performance.

Bit no.a

1.01.12.03.04.05.06.07.08.09.0

10.011.011.112.013.013.113.214.015.016.017.0

Manu-facturer

SecuritySecuritySecuritySecuritySecuritySecuritySecuritySecuritySecuritySecuritySecuritySecuritySecuritySecuritySecuritySecuritySecuritySecuritySecuritySecuritySecurity

Type

M84FM84FM84FM84FH87FH87FH87FH87FM84FH87FH87FM100FM100FM100FM100FM100FM100FM100FM100FM100FM100F

Numberof

cones

444444444442222222222

Size(in.)

H 5 / 8

115/8

11%l lYsWAI VA11 VsIP/897/89%97s4444444444

Serialno.

489656489656489657489658489659489660489661489662489663489664489665489713489713489712489711489711489711489709489710489714489715

Hole

809A809E809C809DNewNewNew809F809BNew810D809A809E809B809C809F810D809DNewNewNew

Depthdrilled

(m)

8.394.16.2

613.4

119.38.39

13.44.16

119.36.2

Cumulativedepth

drilled (m)

8.317.34.16.2

613.4

119.38.3

17.313.44.1

10.1129.4

6.2

Hours

7141.750.58

0.59

2.57

1491.750.52.50.58

Cumulativehours

7211.750.58

0.59

2.57

219

7/l6

2.254.75

7/l6

Jet size(in.)

4-144-144-144-14

4-144-14

4-167/l67/l67/l6

Basalt7/l67/l6

Basalt7/l67/l67/l6

Remarks

BasaltBasaltBasaltBasaltNot runNot runNot runBasaltBasaltNot runSoft chalkWithout spacers-1.75 in. stick outWashed outWithout spacers-1.75 in. stick out

BasaltSoft chalk

Not runNot runNot run

a Bits 1 and 8 were bare-rock spud-ins, Bits 1.1 and 2.0 were drilled at reduced torque due to contact with the hanger; all center bits run after Hole 809B were spaced1.5 in. behind large roller cones.

drill-in BHA allowed the hole to be drilled down only oncewithout retracting the drill string. This lead not only to a morestable hole but also did not require the bits to drill out rubblecreated when the drill string and bit were removed.

It is recommended that ODP continue a dialogue with Securityin order to upgrade and/or modify the bits once Security has

reviewed the dull bits. Additional information and insight as tothe bit's performance and failure mode might be gained fromSecurity which could allow all bits designed in the future tobenefit from the information learned on this leg.

Ms 132A-108

220


Top view

Discharge manifold

Conductor

Casing hanger

16 in. casing

Figure 8. Reentry cone base.

221

G. L. HOLLOWAY

0.00 penetration

Figure 9. DCS borehole spudding techniques.

18 in. penetration

222

r

\ \

i r~

I /i /

54 in. penetration

/ 7

/

1 1

Figure 9 (continued).


r

\\

V.

i r~

[ I

_ J

I /I /U

108 in. penetration

π 1

VJ

t ry

223

G. L. HOLLOWAY

,_ ^

\\

w

I r~

IZZ

-/ 7/ /

r==t

I /I /

180 in. penetration

I Z l

Figure 9 (continued).

\ -/ 7

/ /

\

\

\ \ \ i/>,

216 in. penetration

π 1

U L _

VJ

224

8. diamond coring system—roller cone bits ......diamond coring system—roller cone bits 9.875...

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