Directional drilling method and apparatus

A directional or horizontal hole may be drilled into a formation by first positioning or orienting a window turning shoe in an original well bore. Once the window turning shoe has been positioned, a window is milled through the casing with a window mill. The window mill is then removed and a guide tool is then latched to the window turning shoe. Once in position, the guide tool enables a mechanical motor driven curve drilling assembly to create a curved hole. Following the completion of the curved hole, the directional or horizontal hole is extended with a conventional drilling assembly.

FIELD
 The present invention pertains to well drilling methods and equipment; more
 particularly, the present invention pertains to a method and equipment
 used for drilling directional or horizontal holes away from a vertical
 well bore.
 BACKGROUND
 There are many oil and gas fields that have a significant percentage of
 their reserves still remaining in the underground formation. Yet wells in
 these oil and gas fields are only producing at rates which render these
 wells only marginally profitable. This marginal profitability is due to
 the characteristic rapid production decline of many reservoirs. This rapid
 production decline has resulted in the majority of the proven reserves
 being produced at low rates over many years. Production declines can be
 attributed to a variety of causes including: water and/or gas coning,
 compartmentalization of the reservoir, poor horizontal permeability, well
 bore skin damage and reservoir pressure depletion.
 In recent years it has been found that directional or horizontal well
 drilling technology can make a direct positive impact on all of these
 reservoir problems, thereby increasing well production rates and ultimate
 reserve recovery. Unfortunately, directional or horizontal well drilling
 requires the use of expensive steering tools and complex monitoring
 equipment. For many well operators, the complexity and associated cost of
 directional or horizontal drilling into previously untapped reserves is
 prohibitive and not economically justifiable. There remains, therefore, a
 need in the art for a method and apparatus that can reliably drill
 directional and horizontal wells at a relatively low cost.
 SUMMARY
 The method and apparatus of the present invention provides a low cost,
 reliable method and apparatus to drill one or more short radii directional
 or horizontal holes from an existing substantially vertical well bore.
 Utilized in the disclosed method and apparatus are three components, as
 follows:
 1. Window turning shoe with an on-off guide tool: This tool combination
 facilitates the milling of an opening in the production casing of the
 original well bore and then provides for the mechanical orientation and
 guidance of the mechanical curve building assembly.
 2. Mechanical curve building assembly: This mechanical tool assembly drills
 an arcuate well bore outwardly from the original well bore.
 3. Mud motor driven drilling tool assembly: The mud motor driven curve
 drilling tool assembly drills an arcuate well bore outwardly from the
 original well bore.

DESCRIPTION OF THE EMBODIMENTS
 A better understanding of the directional drilling method and apparatus of
 the present invention may be had by understanding the steps taken to drill
 first an arcuate hole then a directional or horizontal hole away from an
 original well bore.
 ESTABLISHING THE DEPTH AND THE ORIENTATION FOR THE DIRECTIONAL OR
 HORIZONTAL HOLE
 1. As may be seen by reference to FIG. 1, a directional or horizontal hole
 into the formation surrounding the casing begins with cutting or milling a
 window through the casing 102 in an original well bore 100 to gain access
 to the surrounding formation 104.
 2. A conventional whipstock type packer 106 with an integral latch profile
 (not shown) is set and tied into the production casing 102 at the desired
 depth with an electric line unit.
 3. Once the packer 106 has been set and tied into the casing 102, the
 directional heading of the integral latch profile's orientation key (not
 shown) is determined.
 MILLING A WINDOW THROUGH THE CASING
 4. A packer anchor 108 is attached to the bottom of a window turning shoe
 110. The packer anchor assembly 108 orients the window turning shoe 110 in
 the proper direction by contact with the integral latch profile's
 orientation key. The window mill 112 (FIG. 2) is stabbed into the window
 turning shoe 110 and pinned in place.
 5. The window turning shoe 110 with a properly oriented packer anchor
 assembly 108 together with the window assembly 112 is run into the hole on
 the workstring 114.
 6. The packer anchor assembly 108 is inserted into the whipstock type
 packer 106 where it is secured in place.
 7. The necessary force is applied to the workstring 114 to disengage the
 shear pins (not shown) which hold the window assembly 112 to the window
 turning shoe 110.
 8. A window 116 (FIGS. 3 and 3A) is cut through the casing 102 as shown in
 FIG. 7 by rotating the workstring 114 with a designated WOB (weight on
 bit) and RPM (revolution per minute). The conforming wedge face 111 within
 the window turning shoe 110 turns the window mill 112 into the casing 102.
 Once the window 116 has been cut through the casing 102 a pilot hole (not
 shown) is drilled into the formation 104 beyond the casing wall 102. This
 pilot hole assists in beginning the drilling of a curved hole 150
 described in the following steps. Rotation of the workstring 114 causes
 rotation of the window mill 112 shown in FIG. 2. Because of the vertical
 directional change imparted in the window milling tool 112 by the
 conforming wedge face 111 in the window turning shoe 110, the turning of
 the window milling shoe 112 causes the teeth 120 on the window milling
 shoe 112 to cut through the casing 102.
 9. Once a window 116 has been milled through the casing 102 the window
 assembly 112 is pulled out of the hole 100. The window turning shoe 110,
 packer anchor assembly 108 and packer 106 all remain in place in the hole
 100.
 DRILLING THE CURVED HOLE
 10. The curve building assembly 122 is made up by stabbing the mechanical
 curve drilling tool assembly 140 or mud motor assembly 144 through the
 on-off guide tool 124(FIGS. 6 and 7).
 11. The on-off guide tool 124 together with the curve building assembly 122
 are run into the well bore 100 on the workstring 114.
 12. The on-off guide tool 124 is inserted into the window turning shoe 110
 and "J" latched into place within the window turning shoe 110. While a "J"
 latch mechanism is shown in the preferred embodiment, those of ordinary
 skill in the art will understand that equivalent latching may be used. As
 shown in FIGS. 4A and 4B, the on-off guide tool 124 includes a pin 126,
 127 on either side. These pins 126,127 slide into the top 129 of a "J"
 slot 128 (see FIGS. 4C and 4D) within the window turning shoe 110. As
 shown in FIG. 4C the opening to the tope of the "J" slots 128 on either
 side of the inside of the window turning shoe 110 are of different sizes
 to assure the orientation of the curve building assembly 122 in the proper
 direction.
 13. The force necessary to disengage the shear pins (not shown) which hold
 the curve building assembly 122 to the on-off-guide tool 124 is applied to
 the workstring 114.
 14. An arcuate or curved hole 150 is drilled by passing the bit 123 (FIG.
 10) on the end of the curve drilling tool assembly 122 through the casing
 window 116 (FIG. 5) using procedures specific to the curve drilling tool
 assembly 122 (FIGS. 6 and 7) being utilized. Progress in drilling the
 arcuate hole 150 is surveyed as necessary. As shown in FIG. 6 a torque
 tube 132 within a non-rotating sleeve 134 (FIG. 8) is used to transmit
 torque from the workstring 114 to the curve drilling tool assembly 122
 shown in FIG. 10. Shown in FIG. 9A is a cross-section of the non-rotating
 sleeve 134 within the on-off guide tool 124. This cross-sectional view is
 taken between the stabilizers 138 on the non-rotating sleeve 134 as shown
 in FIG. 8. FIG. 9B is a cross-section of the stabilizers 138 as shown in
 FIG. 8. Proper orientation of the mechanical drilling tool assembly 140
 driven by a mud motor (not shown) and contained within curve building
 assembly 122 is controlled by the on-off guide tool 124. As may be seen in
 FIGS. 6, 9C and 9D the on-off guide tool 124 guides and maintains the
 proper orientation of the non-rotating sleeve 134 and torque tube 132.
 This is done in a similar fashion for the stabilized tube 135. Water
 courses 133 are provided as needed.
 15. Once the curved hole 150 has been drilled, the curve building assembly
 122 is removed from the well bore 100 along with the on-off guide tool 124
 by unlatching the on-off guide tool 124 from the window turning shoe 110.
 The window turning shoe 110, packer anchor assembly 108, and packer 106
 all remain in place within the well bore 100.
 CREATING A DIRECTIONAL OR HORIZONTAL HOLE
 16. A conventional drilling assembly 152 is run into the well bore 100
 through the curved hole 150 to extend the hole 154 laterally as desired
 (FIG. 11). When complete, the drilling assembly 152 is removed from the
 well bore 100.
 17. To remove the window turning shoe 110 a pulling tool (not shown) with
 the on-off latch profile is run into the well bore 100. The pulling tool
 is latched into window turning shoe 110. The force necessary to disengage
 the anchor assembly 108 from packer 106 is applied to the worksting 114 to
 remove the window turning shoe 110 and the anchor assembly 108. The packer
 106 remains in place.
 Multiple directional or horizontal holes may be drilled by repeating the
 foregoing procedures at various depths and orientations within the well
 bore 100.
 FEATURES AND ADVANTAGES OF THE WINDOW TURNING SHOE WITH ON-OFF GUIDE TOOL
 The following features and advantages of using the window turning shoe 110
 with the on-off guide tool 124 are listed below:
 A. Use of the disclosed method and apparatus allows for a one trip
 operation to execute the following:
 1. run the window turning shoe 110 with the packer anchor assembly 108 and
 milling assembly 112 into the hole 100;
 2. latch into a packer 106;
 3. mill a window 116 in the production casing 102 (at a pre-set directional
 orientation);
 4. leave the window turning shoe 110 in place while retrieving the window
 milling assembly 112 from the hole 100.
 B. Use of the disclosed apparatus and method allows for milling of the
 casing window 116 in one trip, building a curved hole 150 in a second trip
 and drilling a directional or horizontal hole 154 on a third trip.
 C. Multiple trips may be conducted through the window turning shoe 110 for
 window milling, curve building and lateral drilling operations. Upon the
 completion of the lateral drilling operations, the window turning shoe 110
 and packer anchor assembly 108 can be retrieved from the hole 100.
 D. Use of the disclosed apparatus and method allows the window milling
 assembly 112 to cut through the casing wall 102 at a constant desired
 angle. This angle is maintained by providing a conforming wedge face 111
 in the window turning shoe 110 to both guide and support the window
 milling assembly 112 through its cutting of a window 116 in the casing
 wall 102.
 E. Use of the disclosed apparatus and method results in a milled window 116
 through the casing wall 102 having known dimensions and oriented in a
 known direction.
 F. The window milling assembly 112 allows the entire window 116 to be cut
 in the casing wall 102 with one run of the window milling assembly 112
 into the bore hole 100.
 G. The connection on the bottom of the window turning shoe 110 can be
 readily made up with conventional downhole accessories.
 H. Use of the disclosed apparatus and method allows the workstring 114 to
 bend at a desired normal curve as it passes through the window turning
 shoe 110.
 I. The "J" slot latch 128 within the window turning shoe 110 receives and
 positions the on-off guide tool 124.
 J. The on-off guide tool 124 serves as a positive orientation guide for the
 curve drilling tool assembly 122.
 K. The on-off guide tool 124 fixes the orientation of the curve building
 assembly 122, thereby eliminating the need for a gyro when drilling of the
 curved hole 150 into the formation 104 outside the milled window 116 in
 the casing 102.
 L. Eliminating the need of a gyro allows for the use of smaller tubulars,
 (2-1/16" tubing and less). Smaller tubulars allow for shorter turning
 radii.
 M. The utilization of extensions of various lengths (not shown), between
 the window turning shoe 110 and the packer anchor assembly 108, allows for
 multiple lateral holes to be drilled outwardly from one well bore, and
 then ultimately produced simultaneously. These multi-lateral well bores
 can be at various predetermined depths and in various directional
 orientations, as desired.
 FEATURES AND ADVANTAGES OF THE MECHANICAL CURVE DRILLING ASSEMBLY
 A. The non-rotating sleeve 134 body both retains the torque tube 132 and
 serves as a directional guide to the mechanical curve drilling tool
 assembly 140.
 B. Compression and tensile loads are transferred through the torque tube
 132, not the non-rotating sleeve 134.
 C. The non-rotating sleeve 134 engages the torque tube 132 to maintain
 relative vertical positioning.
 D. The torque tube 132 provides a conduit for fluid circulation.
 E. A plurality of stabilizers or orientation keys 138 are spaced along the
 length of the non-rotating sleeve 134 so that a set of stabilizers 138 is
 always engaged with the keyed profile through the on-off guide tool 124,
 thereby maintaining the orientation of the mechanical curve drilling tool
 assembly 140 as the curved hole 150 is made.
 F. The mechanical curve drilling tool assembly 140 (FIG. 10) provides the
 proper geometry bend angle and length in relation to bit tool diameter to
 create a predictable rate of build or arcuate turn in the curved hole 150
 being drilled. A predictable rate of build coupled with a mechanically
 fixed angular orientation eliminates the need for surveying while drilling
 the curved section of the hole 150. In the mechanical curve drilling tool
 assembly shown n FIG. 10, this mechanically fixed angular orientation is
 11/2.degree..
 G. The non-rotating sleeve 134 may incorporate articulated joints to
 transmit torque through the bend in the on-off guide tool 124 without
 putting excessive axial or bending loads on the non-rotating sleeve 134
 body.
 H. A plurality of stabilizers 138 on the non-rotating sleeve body
 facilitates the directional alignment of the mechanical curve drilling
 tool assembly 140 while at the same time providing structural support.
 I. The plurality of stabilizers 138 facilitate the normal bending of
 non-rotating sleeve 134 and the torque tube 132 through the on-off guide
 tool 124 and the window turning shoe 110 and the curved section of well
 bore 150. The stabilizers 160 and 162 (FIG. 10) on the mechanical curve
 drilling assembly 140 also assist in guiding the bit 123 in a curved path.
 J. The on-off guide tool 124 serves as an orientation guide for
 non-rotating sleeve 134.
 K. The on-off guide tool 124 is unlatched from the window turning shoe 110
 and lifted out of the hole 100 by the mating surface (not shown) on the
 mechanical curve drilling tool assembly 140.
 FEATURES AND ADVANTAGES OF THE MUD MOTOR DRIVEN CURVE DRILLING TOOL
 ASSEMBLY
 A. A stabilized tube 135 serves as a directional guide to the mud motor
 driven drilling tool assembly 144.
 B. A stabilized tube 135 provides a conduit for fluid circulation.
 C. A plurality of stabilizers or orientation keys 136 are spaced out along
 the length of the stabilized tube 135 so that a set of stabilizers is
 always engaged with the inside of the on-off guide tool 124, thereby
 maintaining the orientation of the mud motor driven drilling tool 144 as
 it passes through the on-off guide tool 124 as the arcuate hole 150 is
 being drilled.
 D. The mud motor driven drilling tool assembly 144 provides the proper
 geometry to create a predictable rate of build or turn in the arcuate hole
 150 being drilled. A predictable rate of build coupled with a mechanically
 fixed orientation eliminates the need for surveying while drilling the
 curved or arcuate section 150 away from the original hole 100.
 E. A plurality of stabilizers 136 facilitates the normal bending of the
 stabilized tube 135 through the window turning shoe 110 and the curved
 section of well bore 150. This will reduce drag and increase fatigue life.
 F. The on-off guide tool 124 serves as an orientation guide for the
 stabilized tube 135.
 G. The on-off guide tool 124 is unlatched from the window turning shoe 110
 and lifted out of the hole 100 by the mating surface (not shown) on the
 mud motor driven drilling tool assembly 144.
 It will be apparent to those skilled in the art that various changes may be
 made to the disclosed apparatus and method without departing from the
 spirit and scope thereof and therefore the invention is not limited by
 that which is disclosed in the drawings and specification but only as
 indicated in the appended claims.