GlobalSantaFe
DRILLING & WELL CONTROL TRAINING LESSON Issue No:
20
Content(s):
DRILLING LINE AND TON-MILE TRAINING MODULE
Distribution:
To Zone Managers, Training Coordinators and STO’s To be distributed within the zone to Rig Superintendents and to each rig. One set should be maintained at rig-site and copies made for relevant crews or individuals.
November 1998 Compiled by R.C. Schwenker and Rex Cramer Date:
Reviewed by G.L. Bauer
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KUWAIT GLOBALSANTAFE COMPANY
DRILLING LINE
AND
TON-MILE TRAINING MODULE
FOR THE MAN IN THE FIELD AND HIS BOSS REVISION 2
Distribution:
G.W. McCullough C.M. Sheldon G.L. Bauer R.C. Schwenker H.S. Beshay J.A. Wilson C.W. Wilmeth J. Lopez J.E. Hutchison S.K. Abassi D.L. Ruhlin R.M. Cramer M. Lodge
COMPILED BY R.C. SCHWENKER AND REX CRAMER
Date: November 1998
REVIEWED BY G.L. BAUER
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CONTENTS
I.
INTRODUCTION
II.
GENERAL
Wire Rope Construction
Wear : Line Speed Fleet Angle Deadline Sheaves & Drum Grooves Fastline Wear at the Drum Wire Rope Inspection Breaking Strength & Design Factors
III.
TON-MILE PROGRAMME
IV.
TON-MILE CALCULATIONS
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INTRODUCTION
The contents of this module have been assembled from a wide range of information and field experience. References can be obtained from the I.A.D.C. Drilling Manual, Eleventh Edition, Chapter M, Union Wire Rope and GlobalSantaFe Drilling Formula Book. The purpose is to encourage proper operations, maintenance and repair of equipment and training and safety aspects of personnel. As technology continues to develop it is important that we continue to update our knowledge through research and study.
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GENERAL The drilling line is arguably the most important piece of equipment on a drilling rig and possibly the least understood. Drilling lines are expensive and over a period of time the rig will spend more money for drilling line than for drill pipe or mud tanks or drawworks parts - it is only the labour and perhaps the cost of mud pump parts that are more expensive. To keep the drilling line costs at a minimum the rig crews and all levels of management should know how to obtain maximum safe life from drilling line. The following is basic to that objective:
A)
Select the proper size and type of line to meet the requirements
B)
Care for the line to prevent damage
C)
Choose a cut-off programme which best suits the conditions and follow it carefully. This will greatly increase the service obtained from the line.
D)
Compute the service obtained from the line in Ton-Miles
When a new line is received the reel number, make and description of the line should be recorded and the certificate archived. The Ton-Mile service should be computed daily and a record kept so cut-offs can be made at predetermined intervals to achieve the individual Rig Ton-Mile goal.
Wire Rope Construction Wire rope is composed of three parts: the CORE, the STRAND and the WIRE: (see Fig. 1)
Fig. 1
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The following is an example description of a rotary drilling line; the identifying terms are translated and explained individually. 1” x 5000' 6 x 19 S PRF RRL IPS IWRC 1” 5000' 6 19 S PRF RRL IPS IWRC
= = = = = = = = =
Diameter of Line Length of Line Number of Strands per Line Number of Wires per Strand Seale Pattern Preformed Strands Right Regular Lay Improved Plow Steel Independent Wire Rope Core
This translates to a 1" diameter, 5000 foot length of 6-strand rope with 19 wires in each strand laid in a Seale Pattern (S). The strands are preformed (PRF) in a helical shape before being laid in a Right Regular Lay (RRL) pattern. The grade of the rope is Improved Plow Steel (IPS) and it has an Independent Wire Rope Core (IWRC). Diameter measurements are correct only when made across the "crowns" of the rope strands so that the true diameter is the widest diameter of the rope. Always rotate the calliper on the rope - or rotate the rope inside the calliper to take the measurement (see Fig. 2). Most ropes are manufactured larger than the nominal diameter. When first placed in operation strands of new unused rope will "seat in" and "pull down" from its original diameter. Therefore, measurements recorded for future reference and comparison should be taken after the rope has been in service for a short period of time. Whenever possible a new drilling line should have a break-in period. It should be run under a light load for a short period after it has been installed. This will help to adjust the rope to working conditions. It is suggested that 15 cycles with 3 joints of pipe would be a sufficient break-in. A cycle consisting of the blocks at their highest point, to their lowest. Fig.2
Wear due to Line Speed Excessive speeds when blocks are running up light may injure wire rope. For most drums a maximum rope speed of 4000 feet travel per minute for hoisting or lowering is recommended. Since the movement of drilling line, being wound or unwound on the drum is greater than the movement of the travelling block, the speed with which it moves is also greater. Thus, if the travelling block is being lowered at the rate of 10 ft per second in a 6-line system, the fastline is paying off the drum at 60 ft per second or 3600 feet per minute. Remember the maximum recommended speed for movement of wire rope through the sheaves is 4000 feet per minute. Therefore if the blocks were an 8-line system that was moving at 10 feet per second the line speed would exceed the recommended rate and accelerate fastline fatigue.
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Line whip and natural vibrations also cause fast line fatigue. If these are excessive a wire line stabiliser may need to be employed
Wear due to Fleet Angle All sheaves should be in proper alignment. The last sheave should line up with the centre of the hoisting drum. It is parallel to the sheave groove only when at this point on the drum. As the rope departs from this point either way, an angle is created which starts wear on the side of the rope. This angle is called the fleet angle (see Fig. 3). The fleet angle, although necessary, should be held to a minimum. Experience indicates that it should be held to less than 1-1/2 degrees for smooth faced drums and to less than 2 degrees for grooved drums. Any greater angle creates needless wear on the sides of the rope. This holds true for either grooved or smooth drums. Poor fleet angles not only cause excessive abrasive wear, but also build up excessive torque in a rope. To check the fleet angle, refer to Figure 4. The fleet angle is the included angle between a line representing travel of the rope across the drum and a line drawn through the centre line of the lead sheave perpendicular to the axis of the drum. Fleet angles for several ratios of "A" and "B" are shown in Table 1. The figure shows the relationship between the two critical dimensions used in calculating the fleet angle.
Fig. 4
Fig. 3
Table 1
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Wear at the Deadline Reverse bending at the dead line sheave (crown block) may produce a set in the line which will cause excessive wear when a cut-off procedure is utilised. The line should go around the dead line anchor in the same direction as it comes from the storage reel to prevent reverse bending.
Wear at Sheaves & Drum Grooves Just as your drilling line wears with usage, so do the sheaves. If rope is operated for a long period of time under heavy loads scouring or corrugation of drum and sheaves will occur. This causes a filing action during every stop and start. When new rope is installed after such corrugation forms, its lay will not fit the imprints left by previous ropes and very rapid wear takes place. When these danger signs are found the grooves should be turned smooth or sheaves replaced. If corrugations reoccur in a short space of time, chances are that the rope diameter is too small. Sheave grooves should be checked periodically with a sheave gauge to ensure correct size.
Fig. 5
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In conjunction with proper groove maintenance, the leebus grooving on the drum and the wear pads should be checked periodically. Plus, a sufficient number of wraps should be maintained on the drum at all times. When the travelling block is at the lower pick-up point a minimum of 10 wraps should be on the drum (if grooved). Plain-faced drums must have a full layer of line plus 4-6 wraps on the second layer. Grooved drums are recommended in preference to smooth drums as the grooves furnish better support for the rope than the flat surfaces of plain faced drums, and the more uniform winding results in less abrasive wear on the rope. Grooves in drums should be deep enough to create an angle of 150° with the wire rope (see Fig. 6 below). This is approximately equal to 1/3rd of a rope diameter. Grooves should be smooth. Those, which have taken the imprint of the outer wires of previous ropes, exert a grinding action on new ropes. Proper measurement for grooved drums may be taken using the appropriate sized feeler gauge, as illustrated in Figure 6. Please reference Table 2 for appropriate clearance. ‘C’
‘C’ Groove Dia .
150 0
Groove Dia .
Appro x. 1 /3 Ro pe Dia.
Fig.6
Rope Diameter Inches
Clearance “C” in Inches
1/2 - 1-1/4 1-3/8 - 1-3/4 1-7/8 - 2/1/2
1/16 3/32 1/8 Table 2
The most excessive wear on grooving always occurs closest to the wear pads. Wear pads should be visually checked for excessive wear. Always maintain proper adjustment on turn back rollers. This will help relieve shock at the crossover point on the drum and prevent line piling up at the drum flanges.
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Fastline Wear at the Drum The heaviest wear to a drilling line occurs when spooling on the drum. Each succeeding layer causes crossover points. At these crossover points where the rope climbs from one layer to the next, wear is severe. Wear due to crossover points cannot be completely avoided. It can only be reduced by controlled spooling. In any type of spooling there must necessarily be two crossover points with each wrap. As a lower layer proceeds in one direction across the spool, the next layer must proceed in the other direction. Along most of the turn the upper wrap rides in a groove between two wraps of the lower layer. The rope must leave this groove in order to cross to the next groove and in doing so crosses over a wrap of the line in the lower layer. Two ropes are crossed over in each drum revolution. In the portion of the line that spools last when the blocks are raised and loaded, terrific cribbing and wear occur when the load of the drill string is suddenly lifted. In the portion of the line that lies next to the drum, which must withstand the loading of all the other layers, crushing is considerable. Slack line causes severe wear because of cutting and scrubbing of one layer of line against the next. This condition is most likely to occur when going in the hole, where the travelling block is brought up fast with no load other than the weight of the block and hook to hold the line in tension. When the full load of the drill string is picked up from this position, the top layer from the drum may cut into the loosely spooled layers. To keep this line tight and to minimise the spooling damage to the line, it is important to use a heavy travelling block and hook, see Table 3. Approximate Travelling Block Assembly Weights (Hook, Block, Elevator and Links) Capacity - Tons
Weight - Pounds
100 150 250 350 500 650 750
6,300 7,400 12,900 16,700 26,500 34,000 46,000
Table 3
Where wire line slipping is employed, new rope is spooled onto worn rope. The worn rope has a smaller diameter and when it is wound tight, the new line will not track. The new line instead will jump a wrap and leave a gap into which the line of the next layer will cut. Therefore it is suggested that slipping is only helping to temporarily relieve a wearing condition in the drilling line between blocks, and perhaps, may even be detrimental to the line on the drum.
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Taking the aforementioned into consideration, a ton-mile programme should not incorporate a slipping procedure, as this will not move these heavy wear crossover points. It is best to set up a cut-off programme with a maximum ton-mile figure never to be exceeded and then bounce around your programme, cutting with a low ton-mile accumulation sometimes and alternating with medium or higher ton-mile accumulation. This will move the crossover points and other critical wear points more rapidly and keep wear to a minimum (see Fig.7).
Fig.7
DAILY VISUAL INSPECTION OF OUR DRILLING LINE IS T HE KEY T O PREVENTING FAILURE, AND MUST T AKE PRECEDENCE OVER ANY OTHER PROGRAMME, SUCH AS A T ON-MILE PROGRAMME! Wire Rope Inspection Carefully conducted inspections are necessary to ascertain the condition of drilling line and all wire rope at various stages of its useful life. The object of wire rope inspection is to allow for removal of the rope from service before the rope’s condition, as a result of usage, could pose a hazard to continued normal operations. The inspection frequency should be determined by a qualified person and should be based on such factors as: expected rope life as determined by experience on the particular installation or similar installations, severity of environment, percentage of capacity lifts, frequency rates of operation, and exposure to shock loads. This inspection should cover, as much as possible, the entire length of rope being used. The individual wires in the strands of the rope should be visible to this person during the inspection. Any deterioration resulting in appreciable loss of original strength, such as described below, should be noted and determination made as to whether further use of the rope would constitute a hazard.
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The individual making the inspection should be familiar with the product and the operation, as his judgement is a most critical factor. The following should aid in making these critical judgements:
Distortion of the rope such as kinking, birdcaging, crushing, unstranding, main strand displacement, or core protrusion.
Reduction of rope diameter below normal diameter due to loss of core support, internal or external corrosion, or wear of outside wires.
Lack of Lubrication
Severely corroded or broken wires at end connections.
Severely corroded, cracked, bent, worn, or improperly applied end connections.
No precise rules can be given for determination of the exact time for replacement of rope, since many variable factors are involved. Continued use in this respect depends largely upon good judgement by the inspector evaluating remaining strength in a used rope, after allowance for deterioration disclosed by inspection. Continued rope operation depends upon this remaining strength. Conditions such as the following should be sufficient reason for questioning continued use of the rope or increasing the frequency of inspection:
In running ropes, six randomly distributed broken wires in one lay, or three broken wires in one strand in one lay (see Fig.8).
Fig.8
One outer wire broken at the contact point with the core of the rope which has worked its way out of the rope structure and protrudes or loops out from the rope structure.
Wear of one-third the original diameter of outside individual wires.
Kinking, crushing, birdcaging, or any other damage resulting in distortion of the rope structure.
Evidence of any heat damage from any cause.
Valley breaks.
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Reductions from nominal rope diameter of more than:
Reduction of
Nominal Rope Diameters
1/64"
Up to & inc. 5/16"
1/32"
over 5/16" through 1/2"
3/64"
over 1/2" through 3/4"
1/16"
over 3/4" through 1-1/8"
3/32"
over 1-1/8"
Table 4
In standing ropes, more than two broken wires in one lay in section beyond end connections or more than one broken wire at an end connection.
WIRE ROPE INSPECTION TOOLS CAN BE USED TO INSPECT FOR DAMAGE INSIDE THE DRILLING LINE (FIG.9) Fig.9 FIG.9
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Wire Rope Maintenance Checklist Problem
Probable Cause
Rope broken square-off
Overload, kink, damage or localized wear weakening one or more strands.
One or more strands breaking
Overload or localized wear. If overload is sudden, it will cause a square-off break. In some cases, it will show a necked-down condition of wires.
Undue corrosion
Lack of proper lubrication; exposure to salt or alkaline water. Idle periods.
Ropes damaged by careless hauling to location
Rolling reel over obstruction or dropping from truck onto any hard material. Results in distortion or damage to rope. The use of chains for lashing or use of lever against rope.
Ropes showing kinks, dog legs, and other distorted places
The result of improper handling, installation or operative abuse.
Ropes showing excessive wear in spots
Kinks or bends in rope due to improper handling during installation or service. Repetitive contact point causing severe localized wear.
Ropes damaged by irregular or improper winding on drums
Excessive fleet angle or lack of attention when rope is installed. Worn grooves, worn flanges, lack of level wind system.
Unequal pressure and distortion of wires and rope
Damage due to scraping of rope over sharp surface or because of improperly fitted clamps or clips.
Side wear on rope
Ropes operated over damaged sheaves or drums or improperly aligned equipment.
Fatigue breaks in wire
Severe bending. Possibly due to excessive vibration, due to poor operating conditions.
Spiraling or curling
Allowing rope to drag or rub over any small radius bend.
Ropes showing excessive flattening or crushing
Overloading or poor spooling.
Table 5
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The preceding few pages on wire line inspections by no means covers all scenarios. When in doubt, it is better to cut the appropriate length of drilling line to remove the bad spot or severely worn line. Otherwise, it may severely affect the nominal breaking strength of the line.
Breaking Strength & Design Factors ALL drilling lines have a nominal breaking strength. It will be listed on the certificate. In order to lift heavy loads and stay below the breaking strength of the wire rope, a reeving system is utilised. This simple pulley system allows for the lifting of heavy loads with lighter fast (lead) line pulling loads by stringing through the blocks, giving you a mechanical lifting advantage. This mechanical advantage is equal to the number of lines strung between the crown and the travelling block, taking into consideration accumulated friction. Thus for a 6-line system, without friction, you could lift a weight by a pulling force of only 1/6 th of the weight. With an 8-line system the pull would only be 1/8 th of the weight, with 10 lines, 1/10 th and so forth. The reason for this mechanical advantage is that the lines emerging from the travelling block divide the load equally among themselves. Therefore the load on the fast line is the total weight of the load divided by the number of lines strung. But the load is increased by the friction of the sheave bearings and the bending of the line around the sheaves. Starting at the dead line sheave, each successive line has, during hoisting, an extra load on it caused by the "sum" of the frictional loads from all previous rotating sheaves. Since the fast line experiences the accumulation of frictional forces from all the rotating sheaves, its load is the greatest and should be used when calculating design factors. Design factor is defined as the ratio of nominal wire rope breaking strength to the wire rope tension. The maximum rope tension occurs in the fast line or "lead line" because of friction losses due to rope stiffness and bearing inefficiencies throughout the system. Consequently, the lead line tension is greater than the weight of the load divided by the number of parts of line. To calculate design factor it is necessary to calculate the lead line tension using the following equations and Table 6 of fast (lead) line constants. Design Factor
=
Nominal Rope Strength Lead Line Tension
Lead Line Tension
=
Weight of Load X Constant
FAST (LEAD) LINE CONSTANTS No. of Parts of Line
Constant
4 6 8 10 12 14
.2710 .1882 .1469 .1224 .1062 .0948 Table 6
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TABLE 7:- NOMINAL ROPE STRENGTH 6 x 19 Classification, Bright (Uncoated), Independent Wire Rope Core Nominal Diameter
Improved Plow Steel
1” 1-1/8” 1-1/4" 1-3/8" 1-1/2" 1-5/8"
Extra Improved Plow Steel
89,800lbs 113,000lbs. 138,800lbs. 167,000lbs. 197,800lbs. 230,000lbs.
103,400lbs. 130,000lbs. 159,800lbs. 192,000lbs. 228,000lbs. 264,000lbs.
For example, if the weight indicator reads 304,000lbs. With ten parts of 1-3/8" Improved Plow drilling line, the design factor may be calculated as follows: Lead Line Tension Lead Line Tension Lead Line Tension
= = =
Weight of Load X Constant 304,000lbs. X .1224 37,210lbs.
Design Factor
=
Nominal Rope Strength Lead Line Tension
= =
167,000lbs. ÷ 37,210 lbs. 4.5
Using Data from Table 7 Design Factor Design Factor
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API Recommended Practice 9B and most wire rope manufacturers suggest a minimum design factor of 3.0 for drilling and tripping. If heavier loads are used so that the design factor drops below 3.0, the ton-mile service falls off sharply. Below a design factor of about 2.0 wire rope is permanently and irreversibly damaged. Consequently 3.0 would seem to be the minimum for safe operation, giving some margin for stuck pipe and similar emergencies. However, a more realistic figure to use whenever possible would be 5.0. a.
When a wire rope is operated close to its minimum design factor, care should be taken that the rope and related equipment are in good operating condition. At all times, the operating personnel should use diligent care to minimise shock, impact, and acceleration or deceleration of loads.
b.
Successful field operations indicate that the following design factors should be regarded as minimum. Minimum Design Factor Cable-tool line Sand line Rotary drilling line Rotary drilling line when setting casing Pulling on stuck pipe and similar infrequent operations Mast raising and lowering line
c.
3 3 3 2 2 2.5
Wire rope life varies with the design factor. Therefore longer rope life can generally be expected when relatively high design factors are maintained
Rigs running with loads so light that their design factor is above 7.0 for extended periods of time will not be able to get expected ton-mile service. Laboratory tests and actual field experience confirm that with light loads, the ton-miles add up so slowly that the wire rope will wear out in fatigue due to the higher number of bending cycles required to accumulate each ton-mile. These high design factors are especially common on workover rigs. When this is the case, it is a good idea to make cuts more frequently than normal, perhaps every few round trips. Another problem is that a high design factor means that too many parts of line are strung. An excessive number of parts of string-up puts extra rope on the drum where crossover and wear take their toll on the life of the rope. The excessive length in the string-up takes more cuts to work through the reeving system, and consequently any section of rope is in the system longer than necessary before it is finally cut off. An example of using the fewest possible parts of string-up while still maintaining a safe rig operation and reasonable design factors is illustrated on the next page (Fig.10).
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Fig.10 CARE OF DRILLING LINE IS VITAL Proper care of drilling line will go a long way towards extending its life and the following guidelines should be adhered to: 1. Sharp objects coming into contact with the drilling line should be avoided. 2. Keep drilling line free of mud, dirt or corrosive materials. Corrosion reduces a wire rope's strength, resistance to fatigue and service life. 3. Never use your wire rope in an arc welding circuit. If using a torch near the wire rope, always protect the rope from the flare and sparks.
AND ABOVE ALL ELSE, REMEMBER THAT IN ALL CASES, VISUAL INSPECTION OF THE WIRE ROPE MUST TAKE PRECEDENCE OVER ANY PREDETERMINED CALCULATIONS.
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TON-MILE PROGRAMME The whole objective of a ton-mile programme is to obtain maximum rope service without jeopardising the safety of the rig operation. This is achieved by shifting the rope through the previously discussed critical wear areas and distributing the wear more uniformly along the length of the rope. If too much wire rope is cut off too frequently, there will be an obvious waste of usable drilling line, which will result in higher than necessary rig operating costs. However if the rope is moved through the reeving system too slowly, sooner or later some section of the drilling line will become worn and damaged to such an extent that there will be a danger of failure, injury to personnel, damage to equipment and expensive downtime. At the very least it will be necessary to make a "long cut" to eliminate some broken wires, such as has happened quite frequently over the past couple of years on several rigs in Kuwait. For these reasons it is important that the drilling line be cut off at the proper rate. The purpose of a ton-mile programme is to provide a method for keeping track of the amount of work done by the drilling line, and a systematic procedure for making cuts of the appropriate length at the appropriate time. In conjunction with the record keeping required for the cut-off procedure, daily visual inspection of the drilling line should be made for broken wires and any other rope damage. It should be reiterated here that in all cases visual inspection of the wire rope must take precedence over any predetermined calculations. Once a ton-mile programme has been decided upon, the next step is the determination of how much work has been done by the drilling line. The various operations performed such as drilling, coring, fishing, setting casing, etc., subject the line to different amounts of wear. For an accurate record of the amount of work done by a drilling line, it is necessary to calculate the weight lifted and the distance it is raised and lowered. In engineering terms, work is measured in foot-pounds. On a drilling rig the loads and distances are so great that we use "ton-miles”. One ton-mile equals 10,560,000 foot-pounds, and is equivalent to lifting 2000 pounds a distance of 5,280 feet. The purpose of calculating the amount of work done by the drilling line is to give an accurate method for determining when and how much drilling line to slip through and cut off. The objective of spreading the rope wear along the length of the line can be accomplished best by cutting lengths proportional to the ton-miles of work accumulated. All that is necessary is to maintain a consistent number of ton-mile per foot of rope cut. For a given rope size, any particular rig can get only so many ton-miles of service. The key to a successful cut-off procedure is to spread these ton-miles uniformly by using the optimum ton-mile per foot cut goal. The ton-mile goal for any rig with good past performance records can be calculated using the following formula: A rig which has been able to get 66,000 ton-miles out of a 1-3/8" X 5000' drilling line, may have a string-up of 1700' for ten parts. The remaining 3300' available to be cut off should be cut at a rate of one foot for every 20 ton-miles. (66000 TM ÷ 3300 ft = 20 TM / ft) The ton-mile goal would be 20. If the rig is new, or if the records are unavailable, a ton-mile goal can be selected from Table 8 overleaf. You will note that only the drilling line size and the drum diameter are needed to determine a ton-mile goal. These are by far the most important factors that influence ton-mile service on a drilling rig.
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TABLE 8: - TON-MILE PER FOOT CUT GOAL For rigs having no past performance records Drum Diameter
1”
1-1/8”
18” 19” 20” 21” 22”
6.0 6.0 7.0 7.0 7.0
9.0 9.0 9.0 10.0 10.0
23” 24” 25” 26” 27”
8.0 8.0 8.0 9.0 9.0
10.0 11.0 11.0 11.0 12.0
13.0 13.0 14.0 14.0 15.0
17.0 17.0 17.0 18.0
12.0 12.0 13.0
15.0 15.0 16.0 16.0 17.0
18.0 18.0 19.0 19.0 20.0
17.0 18.0
20.0 21.0 21.0 22.0
28” 29” 30” 31” 32”
Rope Diameter 1-1/4"
33” 34” 35” 36”
1-3/8"
1-1/2"
1-5/8"
24.0 25.0 25.0
28.0
Once the ton-mile goal is decided upon, the cut-off programme can be summarised by the statement Length To Cut = TM Since Last Cut ÷ Ton-Mile Goal Experience has indicated that the maximum ton-mile accumulation to be allowed on the drilling line before a cut is made is equal to approximately 120'. In other words, if your ton-mile goal were 19, the maximum allowable ton-miles would be approximately 2280. An example of a cut-off programme would be as follows: Assuming that 1-3/8" drilling line is used on a National 130 (30" drum) rig with no past performance records: a suggested ton-mile goal of 19 is given. So long as the maximum ton-mile accumulation shown on the programme is not exceeded, a cut may be made whenever it is convenient. It is only necessary to total the ton-miles accumulated since the last cut and divide by 19 to determine the length to cut. This way the ton-miles per foot cut will always be exactly 19 and the wear on the drilling line will be uniformly spread along its length. An example of a Ton-Mile Cut-Off Programme is shown in Table 9 below: TABLE 9: - UNION WIRE ROPE CUT-OFF PROGRAMME FOR 1-3/8” ROTARY DRILLING LINE Goal is 19.0 Ton-Miles per Foot Cut Length to Cut = Ton-Miles Since Last Cut ÷ 19.0 T-M Since Last Cut
Length to Cut
T-M Since Last Cut
Length to Cut
1150 1200 1250 1300 1350 1400
61 63 66 68 71 74
1450 1500 1550 1600 1650 1700
76 79 82 84 87 89
T-M Since Last Cut 1750 1800 1850 1900 1950 2000
Length to Cut 92 95 97 100 103 105
T-M Since Last Cut 2050 2100 2150 2200 2250 2300
Length to Cut 108 111 113 116 118 121
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Whatever programme is being used, it should be followed throughout the life of one entire drilling line. If no long cuts were required, and if it is believed that more service can be had from the next line, the goal can be raised one ton-mile per foot cut. This procedure should be followed until the optimum goal is found. Avoid accumulating more ton-miles between cuts than the maximum shown on the programme for your rig even on the first cut on a new line. It is best not to run up to the maximum permitted ton-miles before making a cut, as some problem on the rig could prevent a cut being made at the proper time and lead to a ton-mile overrun. As mentioned earlier, a better approach is to bounce around on your programme, cutting with a low tonmile accumulation sometimes, and alternating with medium or higher ton-mile accumulations. This practice does not waste rope because you are always cutting lengths in proportion to the work accumulated. Accurate measurement of the length to cut is very important. A steel tape should be used when making this measurement. When stringing back from 12 to 10 lines or from 10 to 8 lines, make a cut of the appropriate length based upon the ton-mile accumulation at that time. This procedure will shift the critical wear points on the rope following heavy operations such as setting casing. Keep your wire rope Record Book current, accurate and complete. Calculate ton-miles for drilling after each round trip. Failure to record drilling ton-miles is probably the MOST COMMON mistake made in cut-off practice. The best cut-off practice is the one with the most consistent ton-mile per foot values. By staying as close as possible to the ton-mile goal you will avoid long cuts and maintain the safest, most economical use of your rotary drilling line. DAILY VISUAL INSPECTION OF THE DRILLING LINE SHOULD BE MADE FOR BROKEN WIRES AND ANY OTHER ROPE DAMAGE. IT MUST BE REMEMBERED THAT IN ALL CASES, VISUAL INSPECTION OF THE WIRE ROPE BY THE DRILLING CONTRACTOR MUST TAKE PRECEDENCE OVER ANY PREDETERMINED CALCULATIONS.
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TON-MILE CALCULATIONS Ton-Mile Tables for calculating ton-miles can be found in most wire line books and the I.A.D.C. Manual. Also, most all wire line manufacturers have some sort of slide rule or handbook for calculating ton-miles. No matter which you use, the answers are generally close to the same. But the input data must be correct to get an accurate ton-mile per foot figure. Most times when problems occur with drilling lines it is because in reality we are running an unrealistically high tonmile per foot figure. Our goal may only be 19.0 ton-miles per foot, but actual ton-miles on line may be 25. A typical example is drilling ton-miles. Everyone knows that drilling ton-miles is calculated by the difference between the two trips, times three. The reason it is multiplied by three is because we drill down the length, ream it once and make a connection. But what if we have a tight hole and ream it three or four times? What if we have to do this through a 1000' shale section? A lot of unrecorded ton-miles will accumulate on the line, giving us a false ton-mile per foot reading. The same holds true for drilling cement, cleaning out casing and reaming after a trip. Accuracy in recording ton-miles must be paramount for a safe, successful operation. One should become familiar not only with the following formulas, but also what makes them work. Therefore each operation is explained with the corresponding formula. And remember one ton-mile equals 10,560,000 foot-pounds and is equivalent to lifting 2000 pounds a distance of 5280 feet. Ton-Mile Formulas 1. Round Trip Operations: Most of the work done by a drilling line is that performed in making round trips (or half-trips) involving running the string of drill pipe into the hole and pulling the string out of the hole. The amount of work performed per round trip can be determined by use of the following formula: Tr =
W x D x ( D + L ) D x ( M + .5C ) + 10,560,000 2,640,000
Wherein: Tr = D = L = W = M = C =
ton-miles (weight in tons times distance moved in miles) bit depth, ft. average length of drill pipe stand, ft. buoyed weight per foot of drill pipe, lb. total weight of travelling block-elevator assembly, lb. buoyed weight of drill collar assembly minus the buoyed weight of the same length of drill pipe, lb.
22
2.
Drilling Operations: The ton-miles of work performed in drilling operations is expressed in terms of work performed in making round trips, since there is a direct relationship as illustrated in the following cycle of drilling operation:
1. 2. 3 4. 5. 6.
Drill ahead length of the Kelly. Pull up length of the Kelly. Ream ahead length of the Kelly. Pull up length of the Kelly to add single or double. Make up single and add to drill stem. Lower drill stem in hole.
Analysis of the cycle of operations shows that for any one hole, the sum of all operations 1 and 2 is equal to one round trip, the sum of all operations 3 and 4 is equal to another round trip. The sum of all operations 5 and 6 is equal to another round trip; thereby making the work of drilling the hole equivalent to three round trips to bottom, which relationship can be expressed as follows: Td
=
Wherein: Td = T1 T2
=
3 (T2 - T1) ton-miles drilling ton-miles for one round trip at depth D1 (depth where drilling started after going in hole, ft.) ton-miles for one round trip at depth D 2 (depth where drilling stopped before coming out of the hole, ft.)
If operations 3 and 4 are omitted, then the formula becomes: - T d= 2 (T2 - T1) Conversely, if the Kelly is reamed down more than once, the variable in the formula will increase. 3.
Coring Operations: The ton-miles of work performed in coring operations, as for drilling operations, is expressed in terms of work performed in making round trips, since there is a direct relationship that is illustrated in the following cycle of coring operations.
1. 2. 3. 4.
Core ahead length of core barrel. Pull up length of Kelly. Make up single and add to drill stem. Pick up Kelly.
Analysis of the cycle of operation shows that for any one hole the sum of all operations 1 and 2 is equal to one round trip and the sum of all operations 3 and 4 is equal to another round trip; thereby making the work of drilling the hole equivalent to two round trips to bottom, which relationship can be expressed as follows: Tc
=
Wherein: Tc = T3 = T4 NOTE:
=
2 (T4 - T3) ton-miles coring ton-miles for one round trip at depth D 3 (depth where coring started after going in hole, ft.) ton-miles for one round trip at depth D 4 (depth where coring stopped before coming out of hole, ft.) Extended coring operations are ordinarily not encountered.
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4.
Setting Casing Operations: The calculation of the ton-miles for the operation of setting casing should be determined as in Para. 1. As for drill pipe, but with the effective weight of the casing being used, and with the result being multiplied by one-half, since setting casing is a one-way (1/2 round-trip) operation. Ton-miles for setting casing can be determined from the following formula:
Wcb x D x ( D + Lcs ) D x ( M + .5C ) TS = + x .5 10,560,000 2,640,000
Since no excess weight for drill collars need be considered, this formula becomes: DM x .5 Wcb x D x ( D + Lcs ) TS = + x .5 10,560,000 2,640,000
Wherein: TS = Lcs = W cb = W ct =
ton-miles setting casing length of joint casing, ft. buoyed weight per foot of casing, lb. total buoyed weight of casing at Shoe Depth, lb.
W cb
W ca (1 - 0.015B)
=
Wherein: W ca = B =
weight per foot of casing in air, lb. weight of drilling fluid, Ib./gal.
Perhaps a simpler formula is the one found in the GlobalSantaFe Drilling Formula Book: Wct Shoe Depth, ft. M TS = + x 5280 1000 4000 5.
Short Trip Operations: The ton-miles of work performed in short trip operations, as for drilling and coring operations, is also expressed in terms of round trips. Analysis shows that the tonmiles of work done in making a short trip is equal to the difference in round trip ton-miles for the two depths in question. This can be expressed as follows:
Tst
=
Wherein: Tst = T5 = T6 =
T6 - T5 ton-miles for short trip ton-miles for one round trip at depth D5 (shallower depth) ton-miles for one round trip at depth D6 (deeper depth)
This can also be expressed by the following formula:
Tst =
(S x N ) 56774
Wherein: S = N =
+
( M x N) 28387
string weight after half the stands pulled, lb. number of stands of drill pipe pulled on short trip
24
6.
Tapered Or Mixed Strings: Use the same formula as in Para. 1, but replace W with W avg
Wherein: W avg = E.g.
average buoyed weight of drill pipe, ft.
3.5" DP 5" DP
= =
2187 ft. x 15.5 lb./ft. 6766 ft. x 19.5 lb./ft.
= =
33,898 lb. 131,937 lb.
Total for 8953 ft. 165,835 ÷ 8953
= =
165,835 lb. 18.52 lb./ft.
Avg. Wt. = If 10 ppg mud is being used: W avg
=
18.52 x .847 =
15.69 lbs./ft.
7.
Drilling Ton-Miles for Top Drive (Drilling with Stands): Ton-mile calculations for other operations tend to be unaffected by the addition of the top drive, with the exception of the additional travelling equipment weight as illustrated in the following cycle of drilling operations:
1. 2. 3. 4. 5.
Drill down length of stand (Ls) Raise stand and ream back down full length Set slips and break out at pipe handler Raise travelling equipment; pick up next stand and make up Pick up off slips and begin again
Ton-Miles Generated Per Cycle Segment: 1. 2. 3. 4. 5.
((W ds + M) x Ls) ÷ (2000 x 5280) (2 x (W ds + M) x Ls) ÷ (2000 x 5280) N/A (M x Ls) ÷ (2000 x 5280) N/A
If one combines steps 1 through 5, the following will apply: Ton-Miles Per Stand Drilled = Wherein: W ds = M = Ls =
(Ls x (3 W ds + 4 M) ÷ (2000 x 5280)
Buoyant weight of drill string for stand being calculated (drill pipe & BHA) Weight of travelling equipment Length of a stand
Ton-miles are also accumulated when jarring down, when jarring up and when working stuck pipe. These can be figured from the following charts:
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TON-MILES FOR PULLING ON STUCK PIPE Chart is for One Pull * (Pull is from 85% of pipe weight to 100,000 lb. over pipe weight and back) Drill Pipe Size (in.) and Weight (lb./ft.) Clear Length 2-3/8” (Feet) 6.650
2-7/8” 3-1/2” 3-1/2’ 4” 10.400 13.300 15.000 14.000
4-1/2” 16.600
4-1/2" 20.000
5” 19.500
5-1/2” 21.900
5-1/2” 24.700
6-5/8” 25.200
1,000 2,000 3,000 4,000 5,000
0.031 0.065 0.104 0.148 0.196
0.020 0.045 0.075 0.109 0.148
0.017 0.038 0.063 0.094 0.129
0.014 0.033 0.056 0.084 0.118
0.016 0.036 0.061 0.091 0.126
0.014 0.033 0.056 0.085 0.119
0.012 0.028 0.049 0.075 0.106
0.012 0.029 0.050 0.077 0.109
0.011 0.027 0.048 0.074 0.106
0.010 0.025 0.045 0.070 0.101
0.010 0.025 0.046 0.072 0.104
6,000 7,000 8,000 9,000 10,000
0.249 0.307 0.369 0.437 0.509
0.192 0.241 0.295 0.355 0.420
0.170 0.216 0.268 0.326 0.389
0.156 0.200 0.250 0.305 0.367
0.167 0.213 0.264 0.321 0.385
0.159 0.204 0.255 0.313 0.378
0.143 0.186 0.235 0.291 0.354
0.147 0.191 0.241 0.298 0.361
0.144 0.188 0.239 0.296 0.361
0.138 0.182 0.232 0.290 0.355
0.142 0.188 0.240 0.300 0.368
11,000 12,000 13,000 14,000 15,000
0.587 0.670 0.758 0.852 0.951
0.491 0.568 0.651 0.740 0.835
0.459 0.535 0.618 0.708 0.804
0.435 0.510 0.592 0.680 0.776
0.455 0.531 0.614 0.704 0.801
0.449 0.527 0.613 0.706 0.807
0.432 0.500 0.585 0.677 0.778
0.432 0.510 0.595 0.689 0.791
0.434 0.514 0.603 0.700 0.806
0.428 0.510 0.600 0.699 0.808
0.444 0.528 0.622 0.725 0.839
16,000 17,000 18,000 19,000 20,000
1.060 1.170 1.280 1.400 1.530
0.937 1.050 1.160 1.280 1.410
0.908 1.020 1.140 1.260 1.400
0.880 0.991 1.110 1.240 1.370
0.905 1.020 1.140 1.260 1.400
0.916 1.030 1.160 1.290 1.440
0.887 1.010 1.130 1.270 1.410
0.902 1.020 1.150 1.290 1.430
0.922 1.050 1.180 1.330 1.480
0.926 1.050 1.190 1.340 1.500
0.962 1.100 1.240 1.400 1.560
21,000 22,000 23,000 24,000 25,000
1.670 1.810 1.950 2.110 2.270
1.550 1.690 1.840 2.000 2.170
1.540 1.690 1.850 2.020 2.190
1.520 1.670 1.830 2.000 2.180
1.540 1.700 1.860 2.030 2.210
1.590 1.750 1.930 2.110 2.300
1.570 1.740 1.910 2.100 2.300
1.590 1.760 1.940 2.130 2.330
1.650 1.830 2.010 2.210 2.430
1.680 1.860 2.060 2.270 2.490
1.740 1.940 2.140 2.360 2.590
26,000 27,000 28,000 29,000 30,000
2.430 2.600 2.780 2-970 3.160
2.340 2.530 2.720 2.920 3.130
2.380 2.570 2.780 2.990 3.210
2.370 2.570 2.780 3.000 3.230
2.400 2.590 2.800 3.020 3.250
2.500 2.720 2.940 3.180 3.430
2.510 2.730 2.970 3.210 3.470
2.540 2.760 3.000 3.240 3.500
2.650 2.890 3.140 3.410 3.680
2.720 2.970 3.240 3.520 3.810
2.840 3.100 3.380 3.670 3.970
*Example Number 1: If approximately 25 pulls are made on 12,000’ of clear 5” (19.5lbs.) pipe, the ton-miles accumulated are: .510 x 25 = 13 ton-miles. Example Number 2: If approximately 100 pulls are made on 20,000’ of clear 4-1/2” (16.6lbs.) pipe, the ton-miles accumulated are: 1.44 x 100 = 144 ton-miles.
26
TON-MILES FOR JARRING UP (OIL JARS) Chart is for One Pull (Pull is from 20,000 lb. under pipe weight to 70,000 lb. over pipe weight and back) Drill Pipe Size (in.) and Weight (lb./ft.) Clear Length 2-3/8” (Feet) 6.650
2-7/8” 3-1/2” 3-1/2” 4” 4-1/2” 4-1/2” 10.400 13.300 15.500 14.000 16.600 20.000
5” 19.500
5-1/2” 21.900
5-1/2” 24.700
6-5/8” 25.200
1,000 2,000 3,000 4,000 5,000
0.034 0.074 0.121 0.174 0.233
0.023 0.052 0.088 0.130 0.179
0.019 0.044 0.076 0.144 0.158
0.016 0.039 0.068 0.103 0.145
0.018 0.043 0.074 0.111 0.155
0.016 0.039 0.068 0.104 0.146
0.013 0.033 0.059 0.092 0.131
0.014 0.034 0.061 0.095 0.135
0-013 0.033 0.059 0.091 0.131
0.012 0.030 0.055 0.086 0.124
0.012 0.031 0.056 0.089 0.128
6,000 7,000 8,000 9,000 10,000
0.298 0.370 0.448 0.533 0.623
0.234 0.295 0.363 0.437 0.518
0.209 0.267 0.331 0.401 0.478
0.192 0.247 0.307 0.374 0.447
0.205 0.262 0.325 0.395 0.471
0.195 0.251 0.313 0.382 0.457
0.176 0.228 0.286 0.350 0.421
0.181 0.234 0.293 0.359 0.431
0.176 0.229 0.288 0.353 0.425
0.168 0.219 0.277 0.341 0.411
0.173 0.226 0.285 0.351 0.424
11,000 12,000 13,000 14,000 15,000
0.721 0.824 0.934 1.050 1.170
0.604 0.698 0.797 0.903 1.020
0.561 0.650 0.746 0.848 0.957
0.526 0.612 0.704 0.802 0.906
0.554 0.642 0.738 0.840 0.948
0.539 0.628 0.723 0.825 0.933
0.498 0.581 0.671 0.767 0.870
0.510 0.595 0.686 0.784 0.889
0.504 0.589 0.681 0.780 0.885
0.488 0.571 0.661 0.758 0.861
0.504 0.590 0.683 0.783 0.889
16,000 17,000 18,000 19,000 20,000
1.300 1.440 1.580 1.720 1.880
1.130 1.260 1.390 1.530 1.670
1.070 1.190 1.320 1.460 1.600
1.020 1.130 1.260 1.390 1.520
1.060 1.180 1.310 1.450 1.590
1.050 1.170 1.300 1.430 1.570
0.978 1.090 1.220 1.340 1.480
1.000 1.120 1.240 1.370 1.510
0.996 1.110 1.240 1.370 1.510
0.970 1.090 1.210 1.340 1.470
1.000 1.120 1.250 1.380 1.520
21,000 22,000 23,000 24,000 25,000
2.040 2.210 2.380 2.560 2.740
1.820 1.980 2.140 2.310 2.490
1.740 1.900 2.060 2.230 2.400
1.670 1.810 1.970 2.130 2.300
1.730 1.890 2.050 2.210 2.390
1.720 1.880 2.040 2.200 2.380
1.620 1.770 1.920 2.080 2.240
1.650 1.800 1.960 2.120 2.290
1.650 1.800 1.960 2.120 2.300
1.620 1.760 1.920 2.080 2.250
1.670 1.820 1.980 2.150 2.330
26,000 27,000 28,000 29,000 30,000
2.940 3.130 3.340 3.550 3.770
2.670 2.860 3.060 3.260 3.470
2.580 2.760 2.960 3.150 3.360
2.470 2.650 2.840 3.030 3.230
2.560 2.750 2.940 3.140 3.350
2.560 2.750 2.940 3.140 3.350
2.420 2.600 2.780 2.970 3.170
2.470 2.650 2.840 3.030 3.320
2.470 2.660 2.850 3.040 3.250
2.420 2.600 2.790 2.990 3.190
2.510 2.690 2.890 3.090 3.300
*Example Number 1: if approximately 25 pulls are made on 12,000’ of clear 5” (19.5lbs.) pipe, the ton-miles accumulated are: .595 x 25 = 15 ton-miles. Example Number 2: if approximately 100 pulls are made on 20,000’ of clear 4-1/2” (16.6lbs.) pipe, the ton-miles accumulated are: 1.57 x 100 = 157 ton-miles.
27
TON-MILES FOR JARRING DOWN (BUMPER JARS) Chart is for One Pull (Pull is from zero load to pipe weight plus 5’ stroke and back) Drill Pipe Size (in.) and Weight (lb./ft.) Clear Length 2-3/8” (Feet) 6.650
2-7/8” 3-1/2” 3-1/2’ 4” 10.400 13.300 15.000 14.000
4-1/2” 16.600
4-1/2" 20.000
5” 19.500
5-1/2” 21.900
5-1/2” 24.700
6-5/8” 25.200
1,000 2:000 3,000 4,000 5:000
0.032 0.037 0.043 0.052 0.064
0.033 0.040 0.049 0.061 0.076
0.034 0.042 0.053 0.067 0.085
0.035 0.044 0.056 0.071 0.091
0.035 0.043 0.054 0.069 0.087
0.036 0.045 0.058 0.075 0.096
0.037 0.048 0.063 0.081 0.105
0.037 0.048 0.062 0.081 0.104
0.038 0.050 0.066 0.086 0.112
0.039 0.053 0.070 0.092 0.121
0.039 0.053 0.071 0.094 0.124
6,000 7,000 8,000 9,000 10,000
0.078 0.096 0-117 0.143 0.172
0.095 0.118 0.147 0.181 0.221
0.107 0.135 0.169 0.210 0.258
0.116 0.147 0.184 0.229 0.283
0.111 0.140 0.175 0.218 0.268
0.123 0.156 0.197 0.247 0.305
0.136 0.173 O.Z19 0.275 0.341
0.134 0.172 0.218 0.273 0.339
0.146 0.187 0.238 0.300 0.373
0.157 0.203 0.259 0.326 0.407
0.162 0.210 0.268 0.339 0.424
11,000 12,000 13,000 14,000 15,000
0.206 0.245 0.289 0.339 0.395
0.267 0.321 0.382 0.452 0.530
0.315 0.380 0.455 0.540 0.635
0.345 0.417 0.501 0.595 0.702
0.327 0.395 0.473 0.561 0.662
0.374 0.454 0.545 0.649 0.767
0.419 0.509 0.612 0.731 0.864
0.416 0.505 0.609 0.726 0.859
0.459 0.560 0.675 0.807 0.956
0.502 0.612 0.739 0.885 1.050
0.523 0.639 0.773 0.926 1.100
16,000 17,000 18,000 19,000 20,000
0.458 0.526 0.602 0.685 0.776
0,618 0,715 0,823 0,941 1.070
0.743 0.863 0.995 1.140 1.300
0.822 0.956 1.100 1.270 1.450
0.774 0.898 1.040 1.190 1.360
0.900 1.050 1.211 1.390 1.590
1.020 1.180 1.370 1.580 1.800
1.010 1.180 1.360 1.570 1.790
1.120 1.310 1.520 1.750 2.010
1.240 1.440 1.670 1.930 2.210
1.290 1.510 1.760 2.030 2.320
21,000 22,000 23,000 24,000 025,000
0.875 0.982 1.100 1.270 1.360
1.210 1.370 1.540 1.720 1.910
1.480 1.670 1.880 2.100 2.350
1.640 1.860 2.090 2.350 2.620
1.540 1.750 1.960 2.200 2.450
1.810 2.050 2.310 2.590 2.890
2.050 2.330 2.620 2.940 3.290
2.040 2.310 2.610 2.920 3.270
2.290 2.590 2.920 3.280 3.670
2.520 2.860 3.230 3.630 4.060
2.650 3.010 3.390 3.810 4.220
26,000 27,000 28,000 29,000 30,000
1.500 1.660 1.820 2.000 2.180
2.120 2.350 2.590 2.840 3.120
2.610 2.890 3.190 3.510 3.850
2.910 3.230 3.570 3.930 4.310
2.730 3.020 3.340 3.680 4.040
3.220 3.570 3.940 4.340 4.770
3.660 4.060 4.500 4.960 5.450
3.640 4.040 4.470 4.930 5.410
4.090 4.540 5.030 5.540 6.100
4.520 5.020 5.560 6.130 6.750
4.760 5.290 5.850 6.460 7.110
*Example Number 1: If approximately 25 pulls are made on 12,000’ of clear 5” (19.5lbs.) pipe, the ton-miles accumulated are: .505 x 25 = 13 ton-miles. Example Number 2: If approximately 100 pulls are made on 20,000’ of clear 4-1/2” (16.6lbs.) pipe, the ton-miles accumulated are: 1.59 x 100 = 159 ton-miles.
28
