CENTRALIZER, PROTECTOR AND STABILIZER FOR USE IN WELLBORE AND RELATED METHOD This invention relates to apparatus for use with a tubular member and, more particularly, but not exclusively, relates to protectors, stabilizers, centralizers and turbulating clamps. It also relates to a multi-component device for use with a string of tubular members and a method for rendering turbulent a flow of fluid or material in a wellbore. In various wellbore operations a tubular member used in a wellbore needs to be protected, stabilized, or centralized. For example, wellbores are often lined with a string of casing. The casing is held in place by cement which, prior to hardening, is pumped down the string of casing and then flows out from the bottom of the casing and thence upwardly in the annulus between the exterior of the casing and the interior of the wellbore. Centralizers are used to maintain the casing in the wellbore while the concrete is being pumped into place. It is also important for the upflowing cement to push ahead of it any drilling mud that may have remained in or on the wellbore. Prior art centralizers have tended to impede the removal of mud and one embodiment of the present invention is particularly intended to reduce this problem. The present invention may also be used for other purposes, for example as a protector, a stabilizer and a turbulating clamp.

GB-A-2 197 008 discloses an apparatus for use with a tubular member, which apparatus comprises: a generally cylindrical hollow body having an inner surface of substantially uniform diameter, an outer surface, a first end and a second end, and disposable on a tubular member, and a plurality of ribs extending from and spaced

apart on said body, each rib extending along said body.

This apparatus has the disadvantages discussed above.

The present invention is characterized in that the distance between at least one adjacent pair of ribs and/or the thickness of the generally cylindrical hollow body is not uniform throughout the length of the apparatus.

Preferably, the body has a wall thickness thicker at or near the first end than at or near the second end.

Advantageously, at least one of said first end and said second end is provided with one or more notches which protrude from the end, each notch fashioned for receiving a tongue protruding from an end of another adjacent well apparatus.

Preferably, the ribs extend obliquely along the outer surface of the body.

Preferably, the distance between adjacent ribs at a location between the first end and the second end is greater than the distance between said ribs to either side of said location.

Advantageously, the wall thickness at or adjacent the first end and second end of the body is less than the wall thickness at or adjacent the mid portion of the body.

The apparatus may be, for example, a casing centralizer, a pipe stabilizer, or a turbularizing clamp. A second aspect of the invention provides a multi-component device for use with a string of tubular members, which device comprises: two or more units (101, 102, 103), each unit having a generally cylindrical hollow body having an

inner surface and an outer surface, a first and a second end, the body disposable on a tubular member of the string of tubular members, a plurality of ribs extending from and spaced apart on the body, at least one of the ends of the body having one or more notches and one or more tongues for interengagement with corresponding notches and tongues on an adjacent unit. Preferably, each unit has a plurality of notches and tongues on each end thereof for interengagement with a corresponding adjacent unit.

Advantageously, the ribs of each unit extend from at or near the first end to at or near the second end of the body and wherein the ribs differ in width at one end of the body as compared to their width at the other end.

The multi-component device may be, for example, a casing centralizer or a drill pipe stabilizer.

The present invention also provides a method for rendering turbulent a flow of fluid or material in a wellbore, which method comprises the steps of: emplacing on a tubular member of a string of tubular members an apparatus according to the invention, and inserting the string of tubular members including the tubular member with the apparatus emplaced thereon into the wellbore.

For a better understanding of the present invention, reference will now be made, by way of example, to the accompanying drawings, in which:-

Fig. la is a perspective view of one embodiment of a centralizer according to the present invention;

Fig. lb is a top plan view of the centralizer shown in Fig. la;

Fig. lc is a bottom plan view of the centralizer shown in Fig. la;

Fig. 2 is a perspective view of a second embodiment of a centralizer according to the present invention;

Fig. 3 is a perspective view of a third embodiment of a centralizer according to the present invention;

Fig. 4 is a perspective view of a fourth embodiment of a centralizer according to the present invention; Fig. 5 is a perspective view of a fifth embodiment of a centralizer according to the present invention;

Fig. 6a is a perspective view of a sixth embodiment of a centralizer according to the present invention;

Fig. 6b is a longitudinal cross-sectional view of the centralizer taken along line VIb-VIb of Fig. 6a;

Fig. 7 is a perspective view of a turbulating clamp according to the present invention; and Fig. 8 is a perspective view of a seventh embodiment of a centralizer according to the present invention.

Referring to Figs, la, lb and lc, there is shown a centralizer which is generally identified by reference numeral 10. The centralizer 10 has a generally

cylindrical hollow body 11 with an upper body 12 which is thicker in wall thickness than a lower body 14. The difference in wall thickness is a gradual increase from the lower body 14 to the upper body 12 so that the outer surface of the body 11 is generally conical. When the centralizer 10 is placed within a wellbore of generally uniform diameter (or in a tubular of generally uniform diameter) a nozzle effect on fluids and materials flowing past the centralizer is created in the space between the outer surface of the body 11 and the interior wall of the wellbore due to the gradual change in thickness of the body 11.

The centralizer 10 has a plurality of protruding ribs 16 which are spaced apart on the outer surface of the body 11 and are inclined with respect to the longitudinal axis of the centralizer 10. The ribs 16 are wider at an upper rib area 18 than at a lower rib area 19 and the rib gradually increases in width from the bottom of the body 11 to its top. A valley 26 defines an area between each pair of consecutive ribs 16. A top area 28 of the valley 26 is narrower than a bottom area 29 of the valley 26 and the valley width (the distance between ribs 16 at a given point) gradually decreases from the bottom 14 of the body 11 to its top 12.

The configuration and disposition of the obliquely extending ribs 16 and the valleys 26 creates another nozzle effect on fluids and materials flowing past the outer surface of the centralizer since fluid flowing from the bottom of the centralizer 10 encounters an ever-decreasing space in which to move upwardly between the ribs 16.

Referring now to Fig. 2, a centralizer 40 has a generally cylindrical hollow body 41 with a body bottom 44, a body top 42, and a plurality of ribs 46

protruding from and spaced apart on the outer surface of the body 41 and inclined with respect to the longitudinal axis of the centralizer 40. Valleys 56 having top valley areas 58 and bottom valley areas 59 extend between pairs of consecutive ribs 46. Recesses 52 through a rib 16 and through the body 41 hold set screws 54 for attaching the centralizer 40 to a tubular member such as casing in a casing string.

A top area 48 of the ribs 46 is wider than a bottom area 49 of the ribs and a top area 58 of the valleys 56 is narrower than a bottom area 59 of the valleys so that the same nozzle effect is created by the centralizer 40 as by the ribs and valleys of the centralizer 10 (Fig. la). Referring now to Fig. 3, a centralizer 60 is similar to the centralizer 40, but one set screw 74 extends through a recess 72 in a rib 66 and through the body 61, while another set screw 73 extends through a recess 75 in a valley 76 through the body 61. The centralizer 60 has ribs 66 and rib top areas 68 and rib bottom areas 69, the rib width gradually increasing from a bottom 64 of the body 61 to a top 62 of the body 61. The width of the valleys 76 between consecutive ribs 66 gradually decreases from a valley bottom area 79 to a valley top area 78. The rib-valley configuration of the centralizer 60 creates a nozzle effect like that of the centralizers 10 and 40 previously discussed.

The wall thickness of the body 41 of the centralizer 40 and of the body 61 of the centralizer 60 is shown as uniform but can be varied to produce a nozzle effect like that of the centralizer 10.

Referring now to Fig. 4, a centralizer 80 has a body 81 which is generally cylindrical and is hollow with a bore therethrough (like the bodies 11, 41 and 61), and has a plurality of ribs 86 protruding from and

spaced apart on the outer surface of the body 81. Each rib 86 gradually increases in width from a bottom rib portion 89 to a top rib portion 88. Valleys 96 between consecutive ribs gradually decreases in width from a valley bottom area 99 to a valley top area 98. Thus, a nozzle effect is created with a centralizer 80 as with the previously described centralizers. The ribs 86 extend generally vertically on the body 81 rather than obliquely as do the ribs on the centralizers 10, 40 and 60.

A centralizer 100 shown in Fig. 5 is a multi-component centralizer made with a plurality (two or more) sub-units, in this case three substantially similar centralizers 101, 102 and 103. Only centralizer 101 will be described in detail here since centralizers 102 and 103 are similar.

The centralizer 101 has a body 110 which is generally cylindrical and hollow and which has a plurality of ribs 116 protruding from and spaced apart on its outer surface. Each rib 116 extends from a bottom 114 of the body 110 to a top 112 of the body 110 obliquely at an incline to the longitudinal axis of the centralizer.

A valley 126 extends between consecutive ribs 116. The width of the valley 126 decreases gradually upwardly from a bottom 129 of each valley 126 to a top 128 of each valley 126 so that a nozzle effect is created between the ribs 116, the valleys 126, and the wall of the wellbore in which the centralizer is situated (or the interior wall of the tubular in which the centralizer is disposed).

Around the upper part of the body 110 a plurality of tongues 132 and a plurality of notches 131 are disposed and spaced apart. Similarly such tongues and notches alternate around the lower part of the body

110. The centralizers 102 and 103 have corresponding tongues and notches so that adjacent centralizers (101, 102 and 102, 103) coact with the upper notches of centralizer 102 receive the lower tongues of centralizer 101; the upper notches of centralizer 103 receive the lower tongues of centralizer 102. Thus the proper combination of sub-units and their proper alignment can be assured. Using such sub-units also permits the construction of a centralizer of a desired length when using tubulars (e.g., casing) of different length.

The centralizer 100 can be constructed of sub-units with varying wall thickness to create a multi-component centralizer in which from the bottom of the lowest sub-unit (e.g., centralizer 103) to the top of the highest sub-unit (e.g., centralizer 101) the wall thickness gradually increases to create the previously described nozzle effect. By using appropriately and differently sized tongues and notches correct assembly of the multi-component centralizer could be made foolproof; e.g., the tongues on the centralizer 101 could be fashioned so that they fit only onto the notches at the upper portion of the centralizer 102. Also, although the ribs 116 are shown with uniform width from their bottoms 119 to their tops 118, they can be fashioned with increasing width to effect an overall nozzle effect as previously described herein.

As shown in Figs. 6a and 6b, a centralizer 140 has a generally cylindrical hollow body 141 with a bore therethrough and with a plurality of ribs 136 protruding from and spaced apart on the outer surface of the body 141.

As illustrated in Fig. 6b, the wall thickness of the body 141 varies from thinner at ends 133 and 134 to thicker at a mid portion 132. The width of the ribs 136 varies from wider near their ends 138 and 139 to

narrower in their mid portions 137 to form valleys 146 which are narrower at their upper portions 148 and lower portions 149 than at valley mid portions 147.

The configuration of varying wall thickness, varying rib width, and varying valley width serves to create multiple nozzle effects to enhance turbulence of a fluid or materials moving past the centralizer 140. By providing the relatively large mid portions 147 in the valleys 146, the amount of fluid or material flowing over the thick mid-portion 132 of the body is not materially impeded; i.e., no excessive pressure drop will occur. Although in the preferred embodiment illustrated in Fig. 6a the valley mid portions are located near the centre of the body 141, it is within the scope of this invention for the enlarged valley portions to be located nearer to either end of the body. Also, although the centralizer 140 combines both varying wall thickness and varying rib and valley widths, it is within the scope of this invention to provide a well apparatus (e.g., centralizer, protector, stabilizer) which has only the varying wall thickness or only the rib-valley configuration of the centralizer 140. Also a centralizer like the centralizer 100 can be constructed, in accordance with this invention, of sub-units that are the same so that ends of adjacent sub-units can have different wall thicknesses, and ribs (and valleys) at the ends of adjacent sub-units can have different widths; i.e., the smooth flowing overall surface of the centralizer 100 from top to bottom, edge-to-edge, end-to-end, rib-to-rib, would not be present.

Referring to Fig. 7, a turbulating clamp 150 has a body 151 which is generally cylindrical and hollow with a bore 152 therethrough and a plurality of ribs 156

(two shown) protruding from the spaced apart on the outer surface of the body 151. The distance 157 between

the ribs at one end of the clamp is greater than the distance 158 between the ribs at the other end of the clamp; thus coacting with a wellbore's interior wall or the interior wall of a tubular in which the clamp is disposed, the ribs serve to create a nozzle-effect area which serves to render turbulent or enhance the turbulence of fluid or fluid and material flowing around or past the exterior surface of the clamp. It is also within the scope of the present invention to vary the wall thickness of the body 151 to achieve the effects of a device, such as the centralizer 10 (Fig. la) whose wall thickness varies. Set screws 155 in bores 154 which extend through the body 151 may be used to secure the clamp 150 to a tubular member (not shown) about which the clamp 150 is disposed. It is also within the scope of the present invention to provide the clamp 150 with tongues and notches like the centralizer sub-unit 101 (Fig. 5).

Referring now to Fig. 8, a centralizer 170 has a generally cylindrical hollow body 171 with a bore 172 therethrough and a plurality of ribs (173, 174, 175 are shown) protruding from and spaced apart on the exterior surface of the body 171. Between adjacent pairs of ribs, e.g., ribs 173, 174, a valley 176 extends which grows progressively smaller from one end 177 of the body 171 to the other end 178 of the body 171; thus, coacting with the interior surface of a wellbore or a tubular member in which the centralizer 170 is disposed, the ribs 173, 174 create a nozzle-effect area which serves to render turbulent or enhance the turbulence of a fluid or a fluid and material flowing around or past the exterior surface of the centralizer. It is also within the scope of this invention to vary the wall thickness of the body 171 like the wall thickness of the body 11 of the centralizer 10 (Figs, la - lc) and/or to provide

the centralizer 170 with tongues and notches like those of centralizer sub-units 101 (Fig. 5).

Although in the preferred embodiments disclosed herein ribs which extend from one end of a device to the other, it is within the scope of this invention to utilize blades or ribs which do not extend from one end of a body to the other, but do extend sufficiently to create a nozzle effect.