EP1389666A2 - Kraftmässig ausgeglichene Rollenmeissel, Systeme, Bohrverfahren und entsprechende Konstruktionsmethoden - Google Patents

Kraftmässig ausgeglichene Rollenmeissel, Systeme, Bohrverfahren und entsprechende Konstruktionsmethoden Download PDF

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Publication number
EP1389666A2
EP1389666A2 EP03021140A EP03021140A EP1389666A2 EP 1389666 A2 EP1389666 A2 EP 1389666A2 EP 03021140 A EP03021140 A EP 03021140A EP 03021140 A EP03021140 A EP 03021140A EP 1389666 A2 EP1389666 A2 EP 1389666A2
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European Patent Office
Prior art keywords
bit
simulating
formation
drill bit
volume
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Application number
EP03021140A
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English (en)
French (fr)
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EP1389666A3 (de
Inventor
Shilin Chen
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Halliburton Energy Services Inc
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Halliburton Energy Services Inc
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Priority to EP04025234A priority Critical patent/EP1498574A3/de
Priority to EP04025233A priority patent/EP1498573A3/de
Priority to EP04025235A priority patent/EP1498575A3/de
Priority claimed from EP99945375A external-priority patent/EP1112433B1/de
Publication of EP1389666A2 publication Critical patent/EP1389666A2/de
Publication of EP1389666A3 publication Critical patent/EP1389666A3/de
Withdrawn legal-status Critical Current

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    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B10/00—Drill bits
    • E21B10/08—Roller bits
    • E21B10/16—Roller bits characterised by tooth form or arrangement
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B10/00—Drill bits
    • E21B10/08—Roller bits

Definitions

  • the present invention relates to down-hole drilling, and especially to the optimization of drill bit parameters.
  • Oil wells and gas wells are drilled by a process of rotary drilling, using a drill rig such as is shown in Figure 10 .
  • a drill bit 10 is mounted on the end of a drill string 12 (drill pipe plus drill collars), which may be miles long, while at the surface a rotary drive (not shown) turns the drill string, including the bit at the bottom of the hole.
  • roller cone bit an example of which is seen in Figure 11 .
  • a set of cones 16 two are visible
  • teeth or cutting inserts 18 are arranged on rugged bearings on the arms of the bit.
  • the second type of drill bit is a drag bit, having no moving parts, seen in Figure 12 .
  • roller cone bits There are various types of roller cone bits: insert-type bits, which are normally used for drilling harder formations, will have teeth of tungsten carbide or some other hard material mounted on their cones. As the drill string rotates, and the cones roll along the bottom of the hole, the individual hard teeth will induce compressive failure in the formation. The bit's teeth must crush or cut rock, with the necessary forces supplied by the "weight on bit” (WOB) which presses the bit down into the rock, and by the torque applied at the rotary drive.
  • WOB weight on bit
  • the individual elements of a drill string appear heavy and rigid. However, in the complete drill string (which can be more than a mile long), the individual elements are quite flexible enough to allow oscillation at frequencies near the rotary speed. In fact, many different modes of oscillation are possible. (A simple demonstration of modes of oscillation can be done by twirling a piece of rope or chain: the rope can be twirled in a flat slow circle, or, at faster speeds, so that it appears to cross itself one or more times.)
  • the drill string is actually a much more complex system than a hanging rope, and can oscillate in many different ways; see WAVE PROPAGATION IN PETROLEUM ENGINEERING, Wilson C. Chin, (1994).
  • the oscillations are damped somewhat by the drilling mud, or by friction where the drill pipe rubs against the walls, or by the energy absorbed in fracturing the formation: but often these sources of damping are not enough to prevent oscillation. Since these oscillations occur down in the wellbore, they can be hard to detect, but they are generally undesirable. Drill string oscillations change the instantaneous force on the bit, and that means that the bit will not operate as designed. For example, the bit may drill oversize, or off-center, or may wear out much sooner than expected. Oscillations are hard to predict, since different mechanical forces can combine to produce "coupled modes"; the problems of gyration and whirl are an example of this.
  • Hard formations are drilled by applying high weights on the drill bits and crushing the formation in compressive failure. The rock will fail when the applied load exceeds the strength of the rock. Roller cone bits designed for drilling hard formations are designed to roll as close as possible to a true roll, with little gouging or scrapping action. Offset will be zero and journal angles will be higher. Teeth are short and closely spaced to prevent breakage under the high loads. Drilling in hard formations is characterized by high weight and low rotary speeds.
  • Medium formations are drilled by combining the features of soft and hard formation bits.
  • the rock is failed by combining compressive forces with limited shearing and gouging action that is achieved by designing drill bits with a moderate amount of offset. Tooth length is designed for medium extensions as well. Drilling in medium formations is most often done with weights and rotary speeds between that of the hard and soft formations.
  • the "cones" in a roller cone bit need not be perfectly conical (nor perfectly frustroconical), but often have a slightly swollen axial profile. Moreover, the axes of the cones do not have to intersect the centerline of the borehole. (The angular difference is referred to as the "offset" angle.) Another variable is the angle by which the centerline of the bearings intersects the horizontal plane of the bottom of the hole, and this angle is known as the journal angle. Thus as the drill bit is rotated, the cones typically do not roll true, and a certain amount of gouging and scraping takes place. The gouging and scraping action is complex in nature, and varies in magnitude and direction depending on a number of variables.
  • roller cone bits can be divided into two broad categories: Insert bits and steel-tooth bits. Steel tooth bits are utilized most frequently in softer formation drilling, whereas insert bits are utilized most frequently in medium and hard formation drilling.
  • Steel-tooth bits have steel teeth formed integral to the cone. (A hard facing is typically applied to the surface of the teeth to improve the wear resistance of the structure.) Insert bits have very hard inserts (e.g. specially selected grades of tungsten carbide) pressed into holes drilled into the cone surfaces. The inserts extend outwardly beyond the surface of the cones to form the "teeth" that comprise the cutting structures of the drill bit.
  • the design of the component elements in a rock bit are interrelated (together with the size limitations imposed by the overall diameter of the bit), and some of the design parameters are driven by the intended use of the product. For example, cone angle and offset can be modified to increase or decrease the amount of bottom hole scraping. Many other design parameters are limited in that an increase in one parameter may necessarily result in a decrease of another. For example, increases in tooth length may cause interference with the adjacent cones.
  • the teeth of steel tooth bits are predominantly of the inverted "V" shape.
  • the included angle i.e. the sharpness of the tip
  • the length of the tooth will vary with the design of the bit. In bits designed for harder formations the teeth will be shorter and the included angle will be greater.
  • Gage row teeth i.e. the teeth in the outermost row of the cone, next to the outer diameter of the borehole
  • inserts The most common shapes of inserts are spherical, conical, and chisel.
  • Spherical inserts have a very small protrusion and are used for drilling the hardest formations.
  • Conical inserts have a greater protrusion and a natural resistance to breakage, and are often used for drilling medium hard formations.
  • Chisel shaped inserts have opposing flats and a broad elongated crest, resembling the teeth of a steel tooth bit. Chisel shaped inserts are used for drilling soft to medium formations.
  • the elongated crest of the chisel insert is normally oriented in alignment with the axis of cone rotation.
  • the chisel insert may be directionally oriented about its center axis. (This is true of any tooth which is not axially symmetric.) The axial angle of orientation is measured from the plane intersecting the center of the cone and the center of the tooth.
  • roller cone bit designs remain the result of generations of modifications made to original designs. The modifications are based on years of experience in evaluating bit run records and dull bit conditions. Since drill bits are run under harsh conditions, far from view, and to destruction, it is often very difficult to determine the cause of the failure of a bit. Roller cone bits are often disassembled in manufacturers' laboratories, but most often this process is in response to a customer's complaint regarding the product, when a verification of the materials is required. Engineers will visit the lab and attempt to perform a forensic analysis of the remains of a rock bit, but with few exceptions there is generally little evidence to support their conclusions as to which component failed first and why.
  • roller cone bits should be run at low to moderate rotary speeds when drilling medium to hard formations to control bit vibrations and prolong life, and to use downhole vibration sensors. (Dykstra, et al, EXPERIMENTAL EVALUATIONS OF DRILL STRING DYNAMICS, Amoco Report Number F94-P-80, 1994).
  • roller cone bit designs should have equal mechanical downforce on each of the cones. This is not trivial: without special design consideration, the weight on bit will NOT automatically be equalized among the cones.
  • Roller-cone bits are normally NOT balanced, for several reasons:
  • Equalization of downforce per cone is a very important (and greatly underestimated) factor in roller cone performance.
  • Equalized downforce is believed to be a significant factor in reducing gyration, and has been demonstrated to provide substantial improvement in drilling efficiency.
  • the present application describes bit design procedures which provide optimization of downforce balancing as well as other parameters.
  • a roller-cone bit will always be a strong source of vibration, due to the sequential impacts of the bit teeth and the inhomogeneities of the formation. However, many results of this vibration are undesirable. It is believed that the improved performance of balanced-downforce cones is partly due to reduced vibration.
  • Any force imbalance at the cones corresponds to a bending torque, applied to the bottom of the drill string, which rotates with the drill string.
  • This rotating bending moment is a driving force, at the rotary frequency, which has the potential to couple to oscillations of the drill string.
  • this rotating bending moment may be a factor in biasing the drill string into a regime where vibration and instabilities are less heavily damped. It is believed that the improved performance of balanced-downforce cones may also be partly due to reduced oscillation of the drill string.
  • each tooth shown on the right side, can be thought of as composed of a collection of elements, such as are shown on the left side.
  • Each element used in the present invention has a square cross section with area S e (its cross-section on the x-y plane) and length L e (along the z axis).
  • F ze is the normal force and F xe
  • F ye are side forces, respectively
  • ⁇ is the compressive strength
  • S e the cutting depth
  • k e the cutting depth
  • ⁇ x and ⁇ y are coefficient associated with formation properties. These coefficients may be determined by lab test.
  • a tooth or an insert can always be divided into several elements. Therefore, the total force on a tooth can be obtained by integrating equation (1) to (3).
  • the single element force model used in the invention has significant advantage over the single tooth or single insert model used in most of the publications.
  • the next step is to determine the interaction between inserts and the formation drilled. This step involves the determination of the tooth kinematics (local) from the bit and cone kinematics (global) as described below.
  • the applied forces to bit are the weight on bit (WOB) and torque on bit (TOB). These forces will be taken by three cones. Due to the asymmetry of bit geometry, the loads on three cones are usually not equal. In other words, one of the three cones may do much more work than other two cones.
  • ⁇ i Fzi / ⁇ Fzi *100 % with Fzi being the i-th cone axial force.
  • ⁇ i Mzi / ⁇ Mzi *100 % with Mzi being the i-th cone moment in the direction perpendicular to i-th cone axis.
  • ⁇ is the bit imbalance force ratio with F r being the bit imbalance force.
  • a force balanced bit uses multiple objective optimization technology, which considers weight on bit, axial force, and cone moment as separate optimization objectives.
  • Energy balancing uses only single objective optimization, as defined in equation (11) below.
  • the first step in the optimization procedure is to choose the design variables.
  • a cone of a steel tooth bit as shown in Figure 3 .
  • the cone has three rows.
  • the journal angle, the offset and the cone profile will be fixed and will not be as design variables. Therefore the only design variables for a row are the crest length, Lc, the radial position of the center of the crest length, Rc, and the tooth angles, ⁇ and ⁇ . Therefore, the number of design variables is 4 times of the total number of rows on a bit.
  • the second step in the optimization procedure is to define the objectives and express mathematically the objectives as function of design variables.
  • equation (1) the force acting on an element is proportional to the rock volume removed by that element. This principle also applies to any tooth. Therefore, the objective is to let each cone remove the same amount of rock in one bit revolution. This is called volume balance or energy balance.
  • volume balance or energy balance The present inventor has found that an energy balanced bit will lead to force balanced in most cases.
  • Figure 4 which shows the patterns cut by each cone on the hole bottom. The first rows of all three cones have overlap and the inner rows remove the rock independently. Suppose the bit has a cutting depth ⁇ in one bit revolution.
  • V 32 is the element in the volume matrix representing the rock volume removed by the second row of the third cone.
  • the elements V ij of this matrix are all functions of the design variables.
  • K v V 3d0 (i,j) / V 2d0 (i,j)
  • V 3d0 is the volume matrix of the initial designed bit (before optimization).
  • V 3d0 is obtained from the rock bit computer program by simulate the bit drilling procedure at least 10 seconds.
  • V 2d0 is the volume matrix associated with the initial designed matrix and obtained using the 2D manner based on the bottom pattern shown in Figure 4 .
  • V 1 , V 2 and V 3 be the volume removed by cone 1,2 and 3, respectively.
  • the third step in the optimization procedure is to define the bounds of the design variables and the constraints.
  • the lower and upper bounds of design variables can be determined by requirements on element strength and structural limitation. For example, the lower bound of a tooth crest length is determined by the tooth strength.
  • the angle ⁇ and ⁇ may be limited to 0 ⁇ 45 degrees.
  • Figure 6 shows the flowchart of the optimization procedure.
  • the procedure begins by reading the bit geometry and other operational parameters. The forces on the teeth, cones, bearings, and bit are then calculated. Once the forces are known, they are compared, and if they are balanced, then the design is optimized. If the forces are not balanced, then the optimization must occur. Objectives, constraints, design variables and their bounds (maximum and minimum allowed values) are defined, and the variables are altered to conform to the new objectives. Once the new objectives are met, the new geometric parameters are used to re-design the bit, and the forces are again calculated and checked for balance. This process is repeated until the desired force balance is achieved.
  • Figures 7A-C show the row distributions on three cones of a 9" steel tooth bit before and after optimization.
  • Figures 8A and 8B compare the bottom hole patterns cut by the different cones before and after optimization.
  • Figures 9A and B compare the cone layouts before and after optimization.
  • a roller cone bit for which the volume of formation removed by each tooth in each row, of each cutting structure (cone), is calculated. This calculation is based on input data of bit geometry, rock properties, and operational parameters. The geometric parameters of the roller cone bit are then modified such that the volume of formation removed by each cutting structure is equalized. Since the amount of formation removed by any tooth on a cutting structure is a function of the force imparted on the formation by the tooth, the volume of formation removed by a cutting structure is a direct function of the force applied to the cutting structure. By balancing the volume of formation removed by all cutting structures, force balancing is also achieved.
  • a roller cone bit for which the width of the rings of formation remaining uncut is calculated, as it remains between the rows of the intermeshing teeth of the different cutting structures.
  • the geometric parameters of the roller cone bit are then modified such that the width of the uncut area for each row is substantially minimized and equalized within selected acceptable limits.
  • a roller cone drill bit comprising: a plurality of arms; rotatable cutting structures mounted on respective ones of said arms; and a plurality of teeth located on each of said cutting structures; wherein approximately the same axial force is acting on each of said cutting structure.
  • a roller cone drill bit comprising: a plurality of arms; rotatable cutting structures mounted on respective ones of said arms; and a plurality of teeth located on each of said cutting structures; wherein a substantially equal volume of formation is drilled by each said cutting structure.
  • a rotary drilling system comprising: a drill string which is connected to conduct drilling fluid from a surface location to a rotary drill bit; a rotary drive which rotates at least part of said drill string together with said bit said rotary drill bit comprising a plurality of arms; rotatable cutting structures mounted on respective ones of said arms; and a plurality of teeth located on each of said cutting structures; wherein approximately the same axial force is acting on each said cutting structure.
  • a method of designing a roller cone drill bit comprising the steps of: (a) calculating the volume of formation cut by each tooth on each cutting structure; (b) calculating the volume of formation cut by each cutting structure per revolution of the drill bit; (c) comparing the volume of formation cut by each of said cutting structures with the volume of formation cut by all others of said cutting structures of the bit; (d) adjusting at least one geometric parameter on the design of at least one cutting structure; and (e) repeating steps (a) through (d) until substantially the same volume of formation is cut by each of said cutting structures of said bit.
  • a method of designing a roller cone drill bit comprising: (a) calculating the axial force acting on each tooth on each cutting structure; (b) calculating the axial force acting on each cutting structure per revolution of the drill bit; (c) comparing the axial force acting on each of said cutting structures with the axial force on the other ones of said cutting structures of the bit; (d) adjusting at least one geometric parameter on the design of at least one cutting structure; (e) repeating steps (a) through (d) until approximately the same axial force is acting on each cutting structure.
  • a method of designing a roller cone drill bit comprising: (a) calculating the force balance conditions of a bit; (b) defining design variables; (c) determine lower and upper bounds for the design variables; (d) defining objective functions; (e) defining constraint functions; (f) performing an optimization means; and, (g) evaluating an optimized cutting structure by modeling.
  • a method of using a roller cone drill bit comprising the step of rotating said roller cone drill bit such that substantially the same volume of formation is cut by each roller cone of said bit.
  • a method of using a roller cone drill bit comprising the step of rotating said roller cone drill bit such that substantially the same axial force is acting on each roller cone of said bit.

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  • Engineering & Computer Science (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Geology (AREA)
  • Mining & Mineral Resources (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Environmental & Geological Engineering (AREA)
  • Fluid Mechanics (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Geochemistry & Mineralogy (AREA)
  • Earth Drilling (AREA)
EP03021140A 1998-08-31 1999-08-31 Kraftmässig ausgeglichene Rollenmeissel, Systeme, Bohrverfahren und entsprechende Konstruktionsmethoden Withdrawn EP1389666A3 (de)

Priority Applications (3)

Application Number Priority Date Filing Date Title
EP04025234A EP1498574A3 (de) 1998-08-31 1999-08-31 Verfahren zur Bestimmung eines Bohrparameters eines Rollenbohrmeissels
EP04025233A EP1498573A3 (de) 1998-08-31 1999-08-31 Entwurfsverfahren für einen Rollenbohrmeissel
EP04025235A EP1498575A3 (de) 1998-08-31 1999-08-31 Entwurfsverfahren für einen Rollenbohrmeissel

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
US9846698P 1998-08-31 1998-08-31
US98466P 1998-08-31
EP99945375A EP1112433B1 (de) 1998-08-31 1999-08-31 Rollenbohrmeissel, zugehöriges Entwurfsverfahren und Drehbohrsystem

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EP99945375A Division EP1112433B1 (de) 1998-08-31 1999-08-31 Rollenbohrmeissel, zugehöriges Entwurfsverfahren und Drehbohrsystem

Related Child Applications (3)

Application Number Title Priority Date Filing Date
EP04025233A Division EP1498573A3 (de) 1998-08-31 1999-08-31 Entwurfsverfahren für einen Rollenbohrmeissel
EP04025234A Division EP1498574A3 (de) 1998-08-31 1999-08-31 Verfahren zur Bestimmung eines Bohrparameters eines Rollenbohrmeissels
EP04025235A Division EP1498575A3 (de) 1998-08-31 1999-08-31 Entwurfsverfahren für einen Rollenbohrmeissel

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EP1389666A2 true EP1389666A2 (de) 2004-02-18
EP1389666A3 EP1389666A3 (de) 2004-03-24

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4056153A (en) * 1975-05-29 1977-11-01 Dresser Industries, Inc. Rotary rock bit with multiple row coverage for very hard formations
EP0384734A1 (de) * 1989-02-21 1990-08-29 Amoco Corporation Bohrkrone mit Kraftausgleich

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4056153A (en) * 1975-05-29 1977-11-01 Dresser Industries, Inc. Rotary rock bit with multiple row coverage for very hard formations
EP0384734A1 (de) * 1989-02-21 1990-08-29 Amoco Corporation Bohrkrone mit Kraftausgleich

Non-Patent Citations (4)

* Cited by examiner, † Cited by third party
Title
MA DEKUN ET AL: "Computer simulation of the interaction between roller bit and rock" PROCEEDINGS OF THE INTERNATIONAL MEETING ON PETROLEUM ENGINEERING. PART 1 (OF 2);BEIJING, CHINA NOV 14-17 1995, vol. 1, 1995, pages 309-317, XP002266077 Richardson, TX, USA *
SHEPPARD M C ET AL: "Forces at the teeth of a drilling rollercone bit: theory and experiment" PROCEEDINGS: 1988 SPE ANNUAL TECHNICAL CONFERENCE AND EXHIBITION;HOUSTON, TX, USA OCT 2-5 1988, vol. DELTA, 1988, pages 253-260 18042, XP002266080 Soc Pet Eng AIME Pap SPE 1988 Publ by Soc of Petroleum Engineers of AIME, Richardson, TX, USA *
WARREN T M: "FACTORS AFFECTING TORQUE FOR A ROLLER CONE BIT" JPT J PET TECHNOL SEP 1984, vol. 36, no. 10, September 1984 (1984-09), pages 1500-1508, XP002266078 *
WARREN TOMMY M ET AL: "Drag-bit performance modeling" SPE DRILL ENG JUN 1989, vol. 4, no. 2, June 1989 (1989-06), pages 119-127 15618, XP002266079 *

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