PRECISION-CUT TUBULAR LINING FOR CENTRALIZER ASSEMBLY

Abstract

A downhole method and tool set, the method comprising measuring the thickness and location of an outside diameter surface of the tubular on a plurality of tubular cross-sectional planes, simulating a cutting process to determine a position for the outside diameter surface of the tubular on a lathe, such that, after the simulated cutting process is performed, the thickness of the tubular is greater than a minimum thickness and an outside diameter defined by the tubular outside diameter surface is less than or equal to a maximum diameter, positioning the tubular on the lathe based on the simulation of the cutting process, cutting the tubular outside diameter surface to reduce the outside diameter thereof to the maximum diameter and thereby form a downward-bent region, and positioning the downhole tool on the tubular in the downward-bent region.

Description

PRECISION-CUT TUBULAR LINING FOR CENTRALIZER ASSEMBLY CROSS REFERENCES TO RELATED APPLICATIONS This application claims priority over U.S. Provisional Patent Application No. 63 / 107,568, filed on October 30, 2020, and is incorporated herein by reference in its entirety. BACKGROUND Oilfield tubulars, such as pipes, drill strings, casing, production tubing, etc., can be used to transport fluids or to produce water, oil, and / or gas from geological formations through wells. At various stages of well drilling and completion, such tubulars may be positioned within (i.e., run into) the well. During run-in, the oilfield tubulars may be held in a generally concentric position within the well, so that an annular space is formed between the oilfield tubular and the wellbore (and / or other surrounding tubulars positioned in the well). Tools known as centralizers are used to maintain the concentricity of the tubular in the wellbore. A variety of centralizers are used, including rigid centralizers, semi-rigid centralizers, and flexible arc-spring centralizers. Arc-spring centralizers, in particular, typically consist of two end collars and flexible ribs that extend between the collars. The ribs expand outward and can be elastic, so arc-spring centralizers are able to centralize the tubular in the wellbore across a range of wellbore sizes. There may be restrictions in the wellbore into which the oilfield tubular is run. These restrictions can be areas where the wellbore's internal diameter decreases, which, in turn, reduces the clearance between the oilfield tubular and the wellbore. Examples of restrictions include casing hangers, the internal diameter of another previously run casing string, and the internal diameter of the wellhead. When restrictions exist, arc spring centralizers can be used. These can be configured to collapse radially into the oilfield tubular, allowing the centralizer to pass through the restrictions while still providing annular clearance. However, arc spring centralizers typically have an operating clearance.When the clearance is too small, the arc spring centralizers can be damaged as they pass through the restriction, which can reduce the centralizers' ability to provide clearance below the restriction. Additionally, oilfield tubulars typically include a tolerance for the outside diameter (e.g., 1%), which can make determining the precise clearance size difficult. SUMMARY The described methods provide a way to position a downhole tool in a tubular. The method includes measuring the thickness and location of an outside diameter surface of the tubular on a plurality of cross-sectional planes of the tubular; simulating a cutting process to determine a position for the outside diameter surface of the tubular on a lathe, such that, after the simulated cutting process, the thickness of the tubular is greater than a minimum thickness and an outside diameter defined by the tubular's outside diameter surface is less than or equal to a maximum diameter; positioning the tubular on the lathe based on the simulated cutting process; cutting the outside diameter surface of the tubular to reduce the outside diameter to the maximum diameter and thus form a downward-bent region; and positioning the downhole tool in the tubular in the downward-bent region. The modalities of the description also include a downhole tool assembly, comprising a tubular having a downward-bent region and a raised region extending axially away from the downward-bent region. An inner diameter surface of the tubular in the downward-bent region has a higher ellipticity than an outer diameter surface in the downward-bent region, and wherein the outer diameter surface in the downward-bent region defines a first center that is offset from a second center defined by the outer diameter surface of the tubular away from the downward-bent region. The assembly also includes a cylindrical tool disposed at least partially in the downward-bent region. The modalities of the description further include a method for positioning a downhole tool in a tubular. The method includes measuring the thickness and location of an external diameter surface of the tubular in a plurality of transverse planes of the tubular, simulating a cutting process to determine a first radial position for the tubular in a first transverse plane of the plurality of transverse planes, and a second radial position for the tubular in a second transverse plane of the plurality of transverse planes. The first and second radial positions are then displaced radially. The first and second radial positions are selected such that, after performing the simulated cutting process, the thickness of the tubular in the first and second transverse planes is greater than a predetermined minimum thickness, and an external diameter defined by the external diameter surface of the tubular is less than or equal to a certain maximum diameter.The method also includes positioning the tubular on a lathe in the first radial position, based on the simulation of the cutting process, cutting the surface of the outer diameter of the tubular to reduce the outer diameter of the tubular to the maximum determined and thus form a region bent downwards, adjusting the position of the tubular, after reaching the first transverse plane, to the second radial location, cutting the surface of the outer diameter of the tubular after adjusting the position, and positioning the downhole tool on the tubular in the region bent downwards. BRIEF DESCRIPTION OF THE FIGURES The present description can be better understood by referring to the following description and the accompanying drawings used to illustrate some of the modalities. In the figures: Figure 1 illustrates a perspective side view of a centralizing assembly, according to one modality. Figure 2 illustrates a cross-sectional, side view of a portion of the centralizing assembly according to one modality. Figure 3 illustrates a cross-sectional, side view of a portion of another centralizing assembly according to a modality. Figure 4 illustrates a schematic view of a tubular positioned on an adjustable lathe to machine a downward-bent region configured to accept the centering tool (or other cylindrical tool), according to a modality. Figure 5 illustrates a schematic view of a cross-section of the tubular before a cutting process, according to a modality. Figures 6A and 6B illustrate two cross-sectional planes of the tubular, with a graph of a target or maximum external diameter and minimum thickness superimposed on it, according to a modality. Figure 7 illustrates a flow diagram of a method for positioning a tool in a tubular (e.g., casing pipe joint), according to a modality. Figure 8 illustrates a schematic view of the tubular positioned on the adjustable lathe such that the axis of rotation of the tubular is offset and parallel to the central axis of its internal diameter, according to a modality. Figure 9 illustrates a schematic view of the tubular positioned on the adjustable lathe such that the axis of rotation is not parallel to the central axis of the internal diameter, according to one modality. Figure 10 illustrates a schematic view of the tube having an axial bend (elbow) and positioned on the adjustable lathe, according to a modality. DETAILED DESCRIPTION The following description outlines several ways to implement different elements, structures, or functions of the invention. The component embodiments, arrangements, and configurations are described below for the sake of simplicity; however, these embodiments are provided merely as examples and are not intended to limit the scope of the invention. Additionally, this description may repeat reference characters (e.g., numbers) and / or letters in the various embodiments and in the Figures provided herein. This repetition is for the sake of simplicity and clarity and is not intended to dictate any relationship between the various embodiments and / or configurations discussed in the Figures.Furthermore, the formation of a first element on or within a second element in the description that follows may include modalities in which the first and second elements are formed in direct contact, and may also include modalities in which additional elements may be formed by interposing the first and second elements, such that the first and second elements may not be in direct contact. Finally, the modalities presented below may be combined in any combination of ways; for example, any element of one illustrative modality may be used in any other illustrative modality, without departing from the scope of the description. Additionally, certain terms are used throughout the following description and claims to refer to particular components. As one skilled in the art will appreciate, various entities may refer to the same component by different names, and as such, the naming convention for the elements described herein is not intended to limit the scope of the invention unless specifically defined otherwise herein. Furthermore, the naming convention used herein is not intended to distinguish between components that differ in name but not in function. Additionally, in the following discussion and in the claims, the terms "includes" and "comprises" are used broadly and should therefore be construed to mean "includes, but is not limited to."All numerical values ​​in this description may be exact or approximate unless specifically stated otherwise. Accordingly, various modalities of the description may deviate from the numbers, values, and ranges described herein without departing from the intended scope. Furthermore, unless otherwise provided, in this description, statements of “or” are intended to be non-exclusive; for example, the statement “A or B” should be understood to mean A, B, or both A and B. Figure 1 illustrates a side perspective view of the centralizer assembly 100, according to one embodiment. The centralizer assembly 100 can be used, for example, to maintain an annular clearance between a casing string (or any other type of oilfield tubular) and a surrounding tubular (for example, another casing string or casing, or the wellbore wall in open-hole situations). The centralizer assembly 100 can be attached to a tubular 102, which can be casing, drill pipe, or any other tubular that can be run into a well. In some embodiments, tubular 102 can be formed from the same casing (or tubular) as a remnant of a string to which centralizer assembly 100 can be attached. Furthermore, tubular 102 can be of a comparable length (e.g., the same, within tolerance, as) the adjacent casing. In one specific embodiment, the length of tubular 102 (and the other casing) can be approximately 40 feet. Additionally, tubular 102 can be made of the same or similar material as the remaining casing. In other embodiments, tubular 102 can be formed from a different type, material, etc., of tubing, production tubing, or the like, and can be longer or shorter than the joints of the adjacent casing. Furthermore, the tube 102 may include a first end 104, a second end 106, and a downward-bent region 108 disposed between the first and second ends 104, 106. In one embodiment, the downward-bent region 108 may be axially separated (for example, along a longitudinal axis 107 of the centralizing assembly 100) from the ends 104, 106. In another embodiment, the downward-bent region 108 may extend to one of the ends 104, 106. The ends 104, 106 may be configured to join axially adjacent tubes. Accordingly, in one embodiment, the first end 104 includes a threaded external end connection, and the second end 106 may include a threaded internal end connection (not visible in Figure 1).Although the phrase bent down normally refers to parts manufactured by turning operations, it will be appreciated that other machining operations can be used to form at least some forms of the bent down region 108. The tubular 102 can define a radius R and a wall thickness T. The down-bend region 108 can define an area of ​​the tubular 102 where the radius R and wall thickness T are reduced. In some embodiments, the down-bend region 108 can have a substantially circular outer diameter surface and a less circular, more oval, inner diameter. Furthermore, the inner and outer diameters of the tubular 102 may not be precisely concentric away from the down-bend region 108, but they may be forced to be (at least more nearly) concentric within the down-bend region 108 as a result of the machining operation applied to it. For example, the tubular 102 may start as a conventional casing pipe, which is generally not precisely cylindrical, but has an oval cross-section and potentially eccentric inner and outer diameters.The present modalities can accommodate these deviations from the cylindrical shape, while cutting a minimal amount of the surface from the outside diameter of the tubular 102, to maintain structural strength and blast ratings for the casing or other tubular 102. Furthermore, the down-bent region 108 may be formed as a recess in the tubular 102 and, therefore, may be separated from the ends 104, 106, so that the tubular 102 may define two raised regions 110, 112 that have larger radii R and wall thickness T than the down-bent region 108. The shoulders 114, 116 may be defined where the raised regions 110, 112 meet or transition to the bent region 108. The two raised regions 110, 112 may have equal or different outside diameters, which may be larger than the outside diameter of the down-bent region 108 and / or may be larger than the oilfield pipes to which the tubular 102 is connected. In some embodiments, however, one or more of the raised regions 110, 112 may be omitted. For example, in some In these modalities, the downward-folded region 108 can extend to either end 104, 106, so that it rubs against the tubular 102. The centralizer assembly 100 may also include, for example, a centralizer 118 or another cylindrical tool, which may be at least partially disposed in the downward-bent region 108. The centralizer 118 may include at least one end collar. In the illustrated embodiment, the centralizer 118 includes two axially offset end collars 120, 122. The six surfaces of the end collars 120, 122 that face in opposite directions (i.e., the outer surfaces) may define the axial extensions of the centralizer 118. In one embodiment, the end collars 120, 122 may be disposed at opposite ends of the downward-bent region 108, for example, typically adjacent to the shoulders 114, 116, respectively. The centralizer 118 may also include a plurality of ribs 124 that can extend axially between and connect to (for example, integrally or by welding, fasteners, tabs, etc.) the end collars 120, 122. In some embodiments, the ribs 124 may be flexible and can curve radially outward from the end collars 120, 122. Such curved, flexible ribs 124 may be referred to as "arc springs." In other embodiments, however, the ribs 124 may have other shapes, designs, and / or elastic properties. In some embodiments, a coating may be applied to the ribs 124, the end collars 120, 122 and / or the tubular 102. The coating may be configured to reduce abrasion of the ribs 124, the end collars 120, 122, the tubular 102, the casing pipe (or other surrounding tubular in which the centralizer 118 may be deployed), or one of their combinations.The coating can also, for example, serve to reduce friction and, therefore, torsional and drag forces in the wellbore. In other configurations, the 118 centralizer can be a rigid centralizer. The centralizer 118 can be formed in any suitable shape from any suitable material. In one specific embodiment, the centralizer 118 can be formed by rolling a flat plate and then seam-welding the flat plate to form a cylindrical starting piece. The cylindrical starting piece can then be cut to define the ribs 124 and end collars 120, 122. One such manufacturing process is as described in U.S. Patent Publication No. 2014 / 0251595, which is incorporated herein by reference in its entirety. In an embodiment where the tube 102 is roughened (ground or machined to one of the ends 104, 106), the centralizer 118 can slide over the fully assembled tube 102. Alternatively, the centralizer 118 can be received laterally in the tube 102 in the downward-bent region 108 and held in place, or temporarily expanded so that it can slide over the unbent region and within the downward-bent region 108. The centralizer assembly 100 can also include a plurality of stop elements (e.g., segments) 200A, 200B. The top segments 200A, 200B can be arranged generally close to the shoulders 114, 116, respectively, and can be axially separated from the shoulders 114, 116 to define channels that extend circumferentially 202, 204 between the top segments 200A, 200B and the shoulders 114, 116, respectively.Furthermore, the 200A stop segments can be axially aligned and circumferentially separated to define axial channels 206 between them. Similarly, the 200B stop segments can be axially aligned and circumferentially separated to define axial channels 208 between them. The stop segments 200A, 200B can be positioned between the axial extensions of the centralizer 118. In other words, the centralizer 118 can be positioned on both axial sides (i.e., opposite first and second axial sides) of the stop segments 200A, 200B. For example, as shown, the stop segments 200A, 200B can be received at least partially through the windows 210A, 210B formed in the end collars 120, 122, respectively. End collars 120 and 122 may have a similar structure. With end collar 120 as an example, it may include two offset bands 212 and 214, with bridges 216 spanning between them. Adjacent pairs of bridges 216, in addition to the bands 212 and 214, may define windows 210A. The bridges 216 may be configured to slide between, in an axial direction, and support, in a circumferential direction, the stop segments 200A. The stop segments 200A and the windows 210A can therefore cooperate to allow, as well as limit, an axial and / or circumferential range of movement of the centralizer 118 with respect to the tubular 102. In particular, the bands 212, 214 can be configured to engage the stop segments 200A to limit an axial range of movement of the centralizer 118 with respect to the tubular 102. In some embodiments, the 210A windows may be larger, axially and / or circumferentially (for example, having a larger axial dimension and / or a larger circumferential dimension), than the 200A stop segments they receive. This relative size may provide a range of rotational and / or axial movement for the 118 centralizer; however, in other embodiments, the 210A windows may be sized to more tightly receive the 200A stop segments, thereby restricting or eliminating the movement of the 118 centralizer relative to the 102 tube. Furthermore, bands 212, 214 of the end collar 120 can be received in the circumferential channels 202. In some embodiments, the coupling between shoulders 114, 116 and band 214 may limit the axial movement range of the centralizer 118 with respect to the tube 8 102. For example, a range of axial movement required to allow axial expansion of the centralizer 118 during radial collapse of the ribs 124 can be determined, and the channel spacing 202 can be calculated, taking into account the thickness of the band 214. In addition, in some situations, the thickness of the bands 214 can be adjusted. Figure 2 illustrates an enlarged partial cross-sectional view of the centralizing assembly 100, according to one embodiment. As shown, the centralizing assembly 100 includes the tube 102, which defines the raised regions 110 and 112 and the downward-bent region 108. The shoulders 114 and 116, defined where the bent region 108 transitions to the raised regions 110 and 112, respectively, may be inclined (e.g., beveled), as shown, to form an angle with respect to the longitudinal axis 107. For example, moving away from the stop segments 200A and 200B and / or away from the downward-bent region 108, the outside diameter of the tube 102 at the shoulders 114 and 116 may increase. The shoulders 114 and 116 may be inclined to reduce stresses at the diameter transition.In one configuration, shoulders 114, 116 can be positioned at any angle between approximately 10° and approximately 90°, for example, at an angle in the range of approximately 10° to approximately 20°, approximately 25°, approximately 30°. In one specific example, shoulders 114, 116 can be tilted at an angle of approximately 15°. Furthermore, the shoulders 114, 116 can extend at least as radially as the end collars 120, 122 and / or the top segments 200A, 200B. That is, the first diameter of the tubular 102 in the raised regions 110, 112 can be at least as large as the second diameter of the tubular 102 in the downward-bent region 108 plus twice the thickness of the end collars 120, 122 (or the top segments 200A, 200B). Consequently, the raised regions 110, 112 can protect the edges and end faces of the bands 212, 214 and prevent the segments 200A, 200B from contact with foreign objects in the wellbore. Since the centralizer 118 may be made of a relatively thin material (e.g., in relation to the tubular 102), protection by the shoulders 114, 116 may help to prevent damage to the centralizer 118.The butt segments 200A and 200B may be formed from a material different from that forming the tube 102 and may be attached to the tube 102 in the downward-bent region 108 using any suitable process. For example, the butt segments 200A and 200B may be formed from one or more layers of a thermal spray, such as WEARSOX®, which is commercially available from Innovex Downhole Solutions, Inc. In one embodiment, the thermal spray forming the butt segments 200 may be as described in U.S. Patent 9. United States Patent No. 7,487,840 or United States Patent No. 9,920,412, which are incorporated herein by reference in their entirety, to the extent that they are not inconsistent with this description. In another embodiment, the end segments 200A and 200B may be formed from an epoxy injected into a composite cover, such as, for example, that described in U.S. Patent No. 9,376,871, which is incorporated herein by reference in its entirety, to the extent that it is not inconsistent with this description. For example, in some embodiments, the end segments 200A and 200B may be formed from an epoxy, a composite material, or other molded material attached to the tube 102. In yet another embodiment, the end segments 200A and 200B can be made of the same material as the tube 102 and, for example, can be integrally formed from it. For instance, the downward-bent region 108 can be formed by grinding around the areas designated for the end segments 200A, for example, leaving the channels 202 and 206 and forming the shoulder 114. The end segments 200B and the channels 204 and 208 can be formed in a similar manner. Figure 3 illustrates a side cross-sectional view of another embodiment of the centralizer assembly 100. In this embodiment, the downward-bent region 108 bifurcates into two downward-bent regions 302, 304, which are axially separated along the tube 102 by a medial stop element (e.g., a stop member) 306. The end collars 120, 122 are positioned in the respective downward-bent regions 302, 304, as shown, with the ribs 124 extending over the medial stop member 306 and connecting the end collars 120, 122 to each other. The centralizer 118 can move freely along a range of motion that is limited by the distance between shoulder 114 and an end face 308 of the medial stop member 306, and between shoulder 116 and an end face 310 of the medial stop member 306.This distance can be selected so that ribs 124 can flex inward to avoid damage in tight constraints, while flexing outward to mate with larger surrounding tubular surfaces. The distances between end face 308 and shoulder 114 can be the same as, or different from, the distance between end face 310 and shoulder 116. Furthermore, the distances can be selected so that end collar 120 is prevented from mating with shoulder 114 by mating end collar 122 with end face 310, and similarly, end collar 122 is prevented from mating with shoulder 116 by mating end collar 120 with end face 308.Therefore, in at least one embodiment, the provision of the medial stop member 306, as distinct from the stop segments 200A, 200B, may result in the centralizer 118 being at least partially pulled through a restriction, rather than being pushed. Furthermore, in some embodiments, the end faces 308, 310 may be squared to provide a generally axially oriented force coupling with the respective end collars 120, 122 when mated with them. This can prevent the end collars 120, 122 from wedging radially outward, as could occur with chamfered or angled end faces 308, 310. The medial butt member 306 can be formed as an integral part of the tubular 102, i.e., a part that is either not ground or ground less than the downward-bent regions 302, 304. In another embodiment, the medial butt member 306 can be formed after grinding the entire length between the shoulders 114, 116 and then depositing a material, such as a combination of thermally sprayed metal, epoxy and coating, a separate metal collar or composite, etc., at the desired location of the downward-bent region 108. In addition, in some embodiments, the butt member 306 can be partially created by grinding the adjacent downward-bent regions 302, 304.However, the grinding operation may be restricted to a depth that is insufficient to provide an adequate butt surface; as such, another material may be applied to increase the size of the butt surface, e.g., a thermal spray material (e.g., WEARSOX®) may be applied to increase the height of the 306 butt member. The downward-bent region 108 of the tube 102 can be formed using a lathe, at least in some embodiments. Figure 4 illustrates a schematic view of the tube 102 positioned on a lathe 400, for example. As shown, the lathe 400 includes a fixed headstock 402 and a movable headstock 406. The fixed headstock 402 may include a plurality of jaws 404 that are configured to move toward one another and thereby grip the outer diameter surface of the tube 102. In some embodiments, the jaws 404 could grip the inner diameter surface of the tube 102 in addition to, or instead of, the outer diameter surface. In one specific embodiment, four jaws 404 may be employed. The use of four jaws 404 may allow adjustment of the center location of the tube 102 on the fixed headstock 402.The rotation axis 408 for the fixed head 402 cannot be changed, and therefore the movement of the four jaws 404 (for example, on one or two axes) can allow the tube 102 to move relative to the center of rotation. The movable head 406 can also be adjustable, for example, independently of the fixed head 402. Consequently, the angle of the tube 102, for example, the angle at which it extends with respect to the horizontal between the fixed head 402 and the movable head 406, can be adjusted. This allows the tube 102 to be positioned so that its central axis coincides with the rotation axis 408, at least in the downward-bent region 108, for example, by tilting, adjusting the elevation or lateral position, or otherwise adjusting the tube 102. The thickness of at least a portion of the tube 102 can be measured. For example, a downward-bent or rubbing region 410 can be defined along at least a portion of the tube 102. The thickness of the tube 102 in one or more cross-sections (planes normal to view) can be taken around the circumference of the tube 102. For example, five such measuring planes 412-420 are shown, although it will be appreciated that any number of planes can be used. A greater number of measuring planes can allow for a smaller axial distance between them over the same length of the rubbing region 410 and thus a more accurate representation of the tube 102 in the rubbing region 410; however, this may occur at the expense of the time required to prepare the tube 102, and therefore a reasonable offset in the number of measuring planes used may be selected.A measuring device 422, which includes one or more sensors, can be used to take the measurements, as will be described in more detail below. Figure 5 illustrates a conceptual view of a cross-section (e.g., an axial cross-section) of the tubular 102, according to one embodiment. The tubular 102 may have an outer diameter surface 500 and an inner diameter surface 502. The distance between the outer and inner diameter surfaces 500, 502 at any given angle is the wall thickness 504, which, in some embodiments, may be kept above a minimum value to maintain a burst or other strength index. These inner and outer diameter surfaces 500, 502 may not be precisely circular but have some degree of ellipticity and, therefore, a major axis 506 and a minor axis 508 may be defined. In some embodiments, the major and minor axes 506, 508 may be the same or different for the inner and outer diameter surfaces 500, 502.Furthermore, the surface of the outer diameter 500 may have a center (or center line) 510 that is different from the center 512 of the surface of the inner diameter 502. As noted above, the jaws 404 of the lathe 400 can clamp the outer diameter surface 500 (or the inner diameter surface 502) to perform a machining operation to reduce the outer diameter of the tube 102. The position of the tube 102 can therefore be adjusted (e.g., on two axes and tilted along a third axis) so that the axis of rotation 408 extends through the center 512 of the inner diameter surface 502. The cutting element of the lathe 400 can thus machine the outer diameter surface 500 into the more circular (lower ellipticity) outer diameter surface 514 in the downward-bent region 108. The outer diameter surface 514 has a generally constant radius extending from its center 512 at any angle. Furthermore, the surface of the outer diameter 514 has its center at the location of the center 512 of the surface of the inner diameter 502.This allows the cylindrical tool (e.g., the centralizer 518) to fit in the downward-bent region 108 without cutting the tubular 102 along the minor axis 508 more than is necessary for the centralizer 118 to fit around the surface of the outside diameter 514. Therefore, the ellipticity of the surface of the outer diameter 514 is reduced in the downward-folded region 108; that is, the radii along the minor axis 508 and the major axis 506 approach (if not exactly) equality. The term ellipticity is used herein qualitatively to refer to the inverse of how close a particular elliptic cross-section is to a circle. Ellipticity (e) can also be mathematically defined as: where a refers to the radius along the major axis 506, and c refers to the radius along the minor axis 508. Therefore, when the radii a and c converge, the ellipticity decreases towards zero. Figure 6A illustrates a schematic view of the tube 102 in one of the transverse measuring planes of the cross-section (e.g., plane 412), according to one modality. As shown, the measuring device 422 approaches an external diameter 600 of the tube 102 and is configured to measure its thickness T, for example, using an ultrasonic signal reflected from the interface formed by the internal diameter 602. The measuring device 422 may also include an optical sensor that measures the distance Do between the device 422 and the external diameter 600 of the tube 102. The position of the measuring device 422 may also be fixed at a known distance De from a centerline of rotation 606 of the lathe 400. The radius Ro of the external diameter 600 can therefore be calculated as the difference between the distance Do and the distance De.Furthermore, the radius Ri of the 602 internal diameter can be calculated as the distance De minus the distance Do and minus the thickness T. Because the cross-section of tubular 102 does not have a uniform thickness when moving circumferentially around tubular 102, tubular 102 may not meet the wall thickness specifications if tubular 102 is machined with the centerline of tubular 102 (specifically, as discussed above, the center of the outer diameter surface) 600) the same as the rotation axis 408 of the lathe 400. The graphs of the minimum wall thickness specification 610 as a function of position and target outside diameter 612 are shown superimposed on the transverse plane (axial cross-section) of the tube 102. It will be appreciated that the minimum wall thickness graph 610 is not necessarily representative of a location of the inside diameter 602; rather, the minimum wall thickness graph 610 represents, by means of the distance from the origin 614, which coincides with the axis of rotation 408, the minimum wall thickness at any position around the circumference of the tube 102. The minimum thickness may be constant around the circumference of the tube 102. Since the thickness T is measured, and not necessarily the location of the inside diameter surface, although the location of the inside diameter surface can be inferred, referencing the thickness T measurement may be more accurate.Furthermore, the surface of the 602 inner diameter may not be precisely circular, but, as discussed above, it may have a degree of ellipticity, unlike the 610 circular minimum thickness measurement chart. The target outside diameter 612 can be determined based on application specifications, for example, the maximum tolerable outside diameter to accommodate the centralizer. Therefore, it is clear that if the 102 tube or the 400 lathe is not adjusted, the machining operation will not achieve the required thickness, for example, in the upper left quadrant, where the target outside diameter 612 is radially inward of the inside diameter 602. Therefore, moving on to Figure 6B, the lathe 400 and / or the tube 102 can be adjusted to reposition the tube 102 with respect to the rotation axis 408. In particular, the tube 102 is moved radially with respect to the rotation axis 408, so that the original outside diameter 600 is now moved to a new position 600A. In this new position, the target outside diameter 612, for example, after the cutting operations have been completed, is within the cross-section of the tube wall 102, and furthermore, the minimum thickness is achieved around the tube 102. The centerline of the surface of the inside diameter 602 may or may not be collinear with the rotation axis 408. Figure 7 illustrates a flowchart of a Method 700 for positioning a tool in a tubular 102, according to one embodiment. Method 700 may include determining a maximum outside diameter for a tubular 102 to carry a cylindrical tool (e.g., the centralizer 118), as in 702. In some embodiments, this maximum outside diameter may be less than a nominal outside diameter of the tubular 102, and therefore it may be necessary to cut the tubular 102. In some embodiments, the maximum outside diameter may be received as input. Before cutting the tubular 102, a wall thickness 504 of the tubular 102, such as 704, can be measured using a measuring device 422, such as an ultrasonic measuring device. The measuring device 422 can be configured to detect the wall thickness 504 at any point along the tubular 102, for example, at 1-degree (or smaller) intervals. The tubular 102 can therefore be inspected or “mapped” at multiple points, for example, by forming a point cloud, to determine the dimensions of the tubular 102, for example, in many transverse planes 412–420. The measuring device 422 can start measurements at a null point, or angular position, and then move around the tube 102 to measure many points within a transverse or measuring plane 412. The surface position of the outer diameter of the tube 102 and the thickness T at each point can be stored and used in subsequent steps. Based on the measurements taken, a virtual cutting process can be performed, simulating the cutting of the outer diameter surface of tube 102, as in 706. The virtual cutting process can be based on the specified outer diameter for the application, as well as the minimum thickness specification. In at least some modes, the virtual cutting process can simulate machining the tube 102 in one or more axial positions to determine if, and where, the tube 102 can be positioned for bending operations to meet both the maximum outer diameter and minimum thickness specifications. In particular, the virtual cutting process can determine an offset between the centerline of the outer diameter surface of tube 102 and the rotation axis 408 of the lathe 400. For example, a certain minimum thickness may be required for the tubular 102 to meet blast classifications in specific applications. The virtual cutting process can be configured to determine a position for the tubular 102 on the lathe 400 at each individual measuring plane 412–420 in the friction region 410. This can be accomplished, for example, as explained with reference to Figures 6A and 6B, by comparing the target outside diameter with the cross-sectional position and the required minimum thickness. If the minimum thickness is not achieved, or if there is an offset that achieves a greater thickness, the virtual cutting process can determine to adjust the lathe 400 so that the center of the tubular 102 (particularly its inside diameter) is offset from the rotational axis 408. Such a determination can be made for each individual measuring plane 412–420.Restrictions can be imposed on the distance the tubular 102 can be moved between successive individual measuring planes 412-420, for example, to prevent large steps or shoulders from forming in the sliding region 410. In at least 15 some embodiments, the centerline 510 defined by the outer diameter of the tubular 102 can be aligned with the rotation axis 408 by removing a portion of the outer diameter surface in the rubbing region 410. In some configurations, the virtual shear process can generate a flat wall map. For example, the virtual shear process can receive, as input, the desired dimensions for the 410 friction region after shearing, such as the final (target) outside diameter (e.g., between approximately 9.875 inches and approximately 16 inches), the axial length (e.g., approximately 25 to approximately 30 inches), and the minimum allowable remaining body wall (e.g., approximately 87.5% to approximately 90%) for the 410 friction region. These target dimensions can be compared to the wall profile, for example, using a pipe coordinate system (e.g., polar coordinates, as discussed earlier, (x, r, theta)). Theta can be a null line at a predefined zero-degree point on the pipe, which can be drawn or plotted by an operator. In at least some modes, the virtual cutting process can define transverse plane wall maps corresponding to the individual measuring planes 412-420, which can include the outer diameter profile, the inner diameter profile, and the wall thickness. The virtual cutting process can also define longitudinal plane wall maps, which represent a longitudinal cross-section (parallel to the centerline 510) of the tube 102, and also include the inner diameter profile, the outer diameter profile, and the wall thickness in a certain angular orientation extending along the centerline 510 through, for example, the friction region 410. The virtual cutting process is also "virtually machined," i.e., it simulates a cutting process in one or more transverse planes and in one or more rotational positions for the tube 102.Reports such as measured minimum wall thickness, measured maximum wall thickness, measured average wall thickness, eccentricity, transverse plane visualization, longitudinal plane visualization (parallel to the longitudinal axis of the tubular 102), location of points in the pipe coordinate system, etc. With reference to Figure 8, in some embodiments, the virtual cutting process can prescribe displacement amounts and directions for the rotation axis 408 of the lathe 400 and the centerline 510 of the tube 102. The selected displacement amounts and directions can be chosen to ensure a minimum wall thickness. The rotation axis 408 can be offset from the centerline 510, which can induce an orbit of the centerline 510 around the rotation axis 408 when the tube 102 rotates on the lathe 400. In particular, the tube 102 can be offset so that the thickest areas are farther from the rotation axis 408.Furthermore, as shown in Figure 9, the centerline 510 of the tube 102 can also be angled with respect to the rotation axis 408, so that the depth of cut of a tool held at a constant distance from the rotation axis 408 would achieve a different depth of cut in the tube 102 depending on the axial position of the tool along the tube 102. This can be achieved by moving either the fixed head 402 or the movable head 406 relative to each other, to move one end of the tube 102 out of alignment with the rotation axis 408. The cutting tool of lathe 400 can be positioned at a stationary or fixed distance from the axis of rotation 408, and this orbit, at least initially, can result in uneven cutting of the outer diameter of the tube 102. Consequently, the thicker areas of the tube 102 can be machined first and to a greater extent, given the offset position. A small amount of material can be removed from the entire cross-section, for example, to maintain the circularity of the surface of the outer diameter of the tube 102. Furthermore, as discussed earlier, measurements can be taken at multiple cross-sectional positions (cross planes) 412-420. Consequently, the process in 706 can prescribe multiple adjustments to the lathe 400, for example, when achieving a desired depth of cut on each plane 412-420, to maintain the minimum thickness on the individual planes 412-420.As such, a stepped profile can be developed along the sliding region 410. In other embodiments, the process in 706 can be configured to generate a continuous movement of the cutting element or the jaws 404 / fixed head 402 to prescribe a smooth transition between the measuring planes 412-420. For example, interpolation could be performed between the position of the tube 102 with respect to the cutting tool between the measuring planes 412-420 to generate a continuous profile on the tube 102 that achieves the prescribed cutting profiles (referred to the position of the outer diameter surface 600 with respect to the inner diameter surface 602) on each of the measuring planes 412-420. Based on the prescribed positions derived from the virtual cutting process, method 700 can proceed to position the tubular 102 in the lathe 400, as in 708. With reference again to Figure 4, the jaws 404 can clamp the surface of the outer diameter 500 of the tubular 102, and a stroke indicator can be positioned on the surface of the outer diameter 500 before cutting. As described above, the lathe 400 can be adjusted to accommodate deviations from cylindrical geometry in the tube 102. In particular, the center 512 of the inner diameter surface 502 may not be the same as the center 510 of the outer diameter surface 500, and therefore the lathe 400 can position the tube 102 so that the center 512 of the inner diameter surface 502 is radially aligned with the rotation axis 408, for example, by moving the fixed headstock 402 and / or the movable headstock 406 of the lathe 400.In a configuration that uses a mill instead of a lathe, programming could be used to affect the mill's y-axis instead of adjusting the tube 102 on the lathe 400. As a result of this positioning and cutting, the center 512 of the outer diameter surface 514 may be radially displaced from the center 510 of the outer diameter surface 500 away from the downward-bent region 108. In other configurations, for example, such as those described above with reference to Figures 6A and 6B, the tube 102 may be positioned on the lathe 400 based on charts of the target outer diameter and minimum wall thickness. Method 700 can then proceed to cut at least a portion of the outside diameter surface 500 of the tube 102 on the lathe 400 (or a mill or other machining device) to form the downward-bent region 108, as in 710. The result is shown in Figure 5, for example, as an outside diameter surface 514, which has the same center 510 as the inside diameter surface 502 and therefore a different center from the outside diameter surface 500, far from the downward-bent region 108 (for example, at an axial location that is outside or adjacent to the downward-bent region 108).Furthermore, the ellipticity of the surface of the outer diameter 514 is reduced compared to the surface of the outer diameter 500 outside the downward-bent region 108, whereas the ellipticity of the surface of the inner diameter 502 does not change (since it is not cut) and is therefore greater than the ellipticity of the surface of the outer diameter 500 away from the downward-bent region 108. In some embodiments, an optional stop member 306 can be secured in the downward-bent region 108, as in 712. In addition, a centralizer 118 or other cylindrical tool can be positioned in the downward-bent region 108, as in 714. As previously stated, the 400 lathe may not maintain a single position throughout the cutting process, but may change the position of the 102 tube, for example, one or more times to achieve a desired cutting profile on each of the measuring planes 412–420. Furthermore, in some configurations, the 700 method may be set to account for non-straight sections in the 102 tube. As shown in Figure 10, the 102 tube may be arced or axially curved. The curved geometry may not be as severe as shown, as this illustration may reflect an exaggeration for illustrative purposes. Additionally, the geometry may be more complex than a single arc, curving two or more times as it progresses along its axis, potentially in any direction. To account for this curved geometry, the curvature can be measured, for example, using lasers or other measuring instruments positioned incrementally along the tubular 102. This can occur, for example, before, between, or simultaneously with other steps in method 700, before the cut in 710. The lasers can measure a lateral displacement of the tubular 102 along its length, providing a map of the curvature. If the curvature is beyond a certain threshold, the tubular 102 can be rejected for cutting, as it may not be machineable to a desired outside diameter while still being straight enough to accommodate a tight-tolerance centering tool and low clearance, depending on the application.If the curvature is not beyond the threshold, the thickness of the 102 tubular can be measured in multiple axial planes 412-420, as discussed above, and machined to meet the outside diameter and thickness requirements of the application. The foregoing has described elements of several modalities so that those skilled in the art may better understand the present description. Those skilled in the art should appreciate that they can readily use the present description as a basis for designing or modifying other processes and structures to accomplish the same purposes and / or achieve the same advantages as the modalities introduced herein. Those skilled in the art should also understand that such equivalent constructions do not depart from the spirit and scope of the present description, and that they may make various changes, substitutions, and alterations to the present description without departing from its spirit and scope.

Claims

1. A method for positioning a downhole tool on a tubular, comprising: measuring the thickness and location of an outside diameter surface of the tubular on a plurality of transverse planes of the tubular; simulating a cutting process to determine a position for the outside diameter surface of the tubular on a lathe, such that, after performing the simulated cutting process, the thickness of the tubular is greater than a minimum thickness and an outside diameter defined by the outside diameter surface of the tubular is less than or equal to a maximum diameter; positioning the tubular on the lathe based on the simulated cutting process; cutting the outside diameter surface of the tubular to reduce the outside diameter of the tubular to at most the maximum diameter and thereby form a downward-bent region; and positioning the downhole tool on the tubular in the downward-bent region.

2. The method according to claim 1, wherein cutting the surface of the outer diameter comprises reducing the ellipticity of the surface of the outer diameter of the tube in the downward-bent region.

3. The method according to claim 1, wherein, after cutting, a first center defined by the surface of the outer diameter of the tube in the downward-bent region is displaced radially from a second center defined by the surface of the outer diameter away from the downward-bent region.

4. The method according to claim 1, wherein a surface of the inner diameter of the tube is not cut as part of the cutting of the surface of the outer diameter.

5. The method according to claim 1, wherein, after cutting, the center of the surface of the inner diameter of the tube is the same as the center of the surface of the outer diameter in the downward-bent region.

6. The method according to claim 1, wherein simulating the cutting process comprises simulating the cutting process in each of the plurality of transverse planes, and wherein simulating the cutting process comprises determining a displacement between a center of the tubular in the respective transverse planes and a rotation axis of the lathe 7. The method according to claim 6, wherein the positioning comprises continuously adjusting the lathe while cutting between the transverse planes to form smooth transitions between them.

8. The method according to claim 1, further comprising adjusting the lathe to reposition the tube after reaching one of the transverse planes.

9. The method according to claim 1, further comprising displaying a visualization of the minimum thickness on a circular chart and the location of the outer diameter surface on a circular chart.

10. The method according to claim 1, further comprising determining an axial curvature of the tube before cutting, wherein the simulation comprises simulating the adjustment of the tube's position based at least in part on the axial curvature.

11. The method according to claim 1, further comprising: determining the maximum diameter for the tubular based on the size of the downhole tool; and determining whether the surface of the outer diameter of the tubular can be cut so that it is no larger than the maximum diameter while maintaining the minimum thickness.

12. The method according to claim 1, wherein measuring comprises using an ultrasonic measuring device to measure the thickness and an optical sensor to measure a surface position of the outer diameter of the tube.

13. A downhole tool assembly, comprising: a tubular comprising a downward-bent region and a raised region extending axially away from the downward-bent region, wherein an internal diameter surface of the tubular in the downward-bent region has a higher ellipticity than an external diameter surface in the downward-bent region, and wherein the external diameter surface in the downward-bent region defines a first center that is offset from a second center defined by the external diameter surface of the tubular away from the downward-bent region; and a cylindrical tool disposed at least partially in the downward-bent region.

14. The downhole tool assembly according to claim 13, wherein the tubular comprises a casing joint for a casing string.

15. The downhole tool assembly according to claim 13, wherein the first center is radially aligned with a third center defined by a surface of internal diameter of the tubular.

16. The downhole tool assembly according to claim 13, wherein the surface of the outside diameter along a portion of the tubular that is outside the downward-bent region has a greater ellipticity than the surface of the outside diameter of the tubular in the downward-bent region.

17. The downhole tool assembly according to claim 13, further comprising a stop element positioned in the downward-bent region, wherein the stop element is configured to engage the cylindrical tool to limit axial sliding movement thereof.

18. The downhole tool assembly according to claim 13, wherein the downward-bent region extends to an axial end of the tubular.

19. The downhole tool assembly according to claim 13, wherein the cylindrical tool comprises a centralizer.

20. A method for positioning a downhole tool in a tubular, comprising: measuring a thickness and location of an external diameter surface of the tubular in a plurality of transverse planes of the tubular; simulating a cutting process to determine a first radial position for the tubular in a first transverse plane of the plurality of transverse planes, and a second radial position for the tubular in a second transverse plane of the plurality of transverse planes, the first and second radial positions being radially offset, wherein the first and second radial positions are selected such that, after the simulated cutting process is carried out, the thickness of the tubular in the first and second transverse planes is greater than a certain minimum thickness and an external diameter defined by the external diameter surface of the tubular is less than or equal to a certain maximum diameter;Position the tubular on a lathe in the first radial position, based on the simulation of the cutting process; cut the surface of the tubular's outer diameter to reduce its outer diameter to the maximum determined, thus forming a downward-bent region; adjust the position of the tubular, after reaching the first transverse plane, to the second radial location; cut the surface of the tubular's outer diameter after adjusting the position; and position the downhole tool on the tubular in the downward-bent region.

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