GB2545914A

GB2545914A - Adjustable roller centralizer

Info

Publication number: GB2545914A
Application number: GB1523067.5A
Authority: GB
Inventors: Huyton Stuart; Wheater Guy
Original assignee: Individual
Current assignee: Individual
Priority date: 2015-12-30
Filing date: 2015-12-30
Publication date: 2017-07-05
Also published as: GB201523067D0

Abstract

An adjustable centraliser for a logging tool string within a wellbore having a coil spring 22 that applies pressure onto contact wheels 15 on the inner face of the wellbore via an array of radial arm mechanisms. Each arm mechanism comprises a tension arm 17 pivotally joined to a rocker arm 28; the rocker arm is pivotally mounted to the body of the centraliser, and the tension arm is pivotally mounted to a sliding sleeve 21. The coil spring 22 is positioned between the rocker and tension arm mountings, and pushes sliding sleeve away from the rocker arm mounting, and is restricted by an adjustable locking ring 29. The movement of the sliding sleeve affects the radial extension of the contact wheels. Changing the spring rating, dimensions of the rocker and tension arms and wheel, and the profile and material of the wheel, allows the centralising force, rolling resistance and road noise of the centralising tool to be adjusted, to assist the acquisition of data. The centralising tool may have radial guide wheels 13, and be pre-set via gauge rings (fig 5a) that has an array of strain gauges to measure the pressure applied to the wellbore.

Description

Adjustable Roller Centralizer

This invention relates to a device that provides positive centralization of a logging tool-string inside the casing, liner, or tubing of a wellbore, whilst reducing conveyance drag and road noise.

Cased-hole logging is a common operation in the oil industry whereby down-hole electrical tools, powered from surface or by internal batteries, are conveyed via wireline (“e-line”) or slickline to acquire measurements from inside the casing, liner, or tubular of a wellbore (referred to singularly as ‘Casing’ in this text from now on). Certain services, such as cement bond logging or Casing inspection, require the logging tool-string to be positively centralized inside the Casing in order to obtain good data. Inadequate tool-string centralisation may compromise the data acquisition and lead to an erroneous log or an invalid evaluation.

Currently, tool-string centralisation is generated by three methods: A) Steel “Gemcos’ that are bolted onto the exterior of the logging tool-string; B) Spring centralizers, which are integral to logging tool-string or bolted onto the exterior; C) Multi-arm callipers, which are integral to logging tool-string, providing centralising force at some distance from the tool-string sensors.

Under certain conditions each of these centralizer types (A, B, C) can compromise the data quality by not providing adequate tool-string centralisation inside the Casing, or by inducing too much drag to reach the target depth as planned, or by inducing too much road noise that upsets the data acquisition. A Gemco comprises an array of radial hoops, made from mild steel strip, that are welded onto end rings that create a cage over a short section of the logging tool-string. They can provide a reliable means of centralisation in vertical or near-vertical wellbores but in general they are not a precise centralising mechanism due to the possibility of a non-concentric fit on the tool-string body, plus the external diameters created by opposing hoops may vary due the manufacturing tolerance or wear and tear. Additionally, for non-vertical wellbores, the Gemcos may induce too much drag, compromising the descent to target depth, or the road noise generated could be high, potentially contaminating the sonic logging data. In short, Gemcos are a low technology solution which carry risk in terms of conveyance and data quality.

Spring centralisers typically have a radial array of expandable arms which contract to the size of the Casing being logged. They do not always provide effective or consistent centralising force since the springs that support the arms not be strong enough in large or deviated wellbores. Under certain circumstances the tool-string may suffer from lateral oscillations during data acquisition or the centralizers may simply collapse sideways under the weight of tool-string. A tool-string which has erratic dynamic behaviour and not consistently centralised may render the logging data unusable.

Multi-arm callipers are generally located a distance either side of the measurement sensors in the logging tool-string and may not provide sufficient centralisation force where it is actually needed, leading to tool-string oscillations during data acquisition or sonde sag to the low side of the wellbore in deviated hole. Again, the logging data may be unusable because the centralising force is insufficient, or applied at a distance too far from the important sensors in the tool-string.

Currently, for all centralizer options (A-C) the magnitude and distribution of centralising forces along the tool-string is not computed nor configured prior to a job. At best the Gemcos are selected for the nominal Casing size being logged, but no precise adjustment of the geometry or centralising force is possible. Spring centralisers are similarly non-configurable and Multi-arm callipers are simply not designed as cased hole centralisers.

In contrast, the Adjustable Roller Centralizer allows precise configuration of centraliser geometry, centralising force and rolling resistance, according to the specific job requirements. The configuration is based upon the tool-string weight and dimensions, the Casing type, size and deviation, the fluid in the wellbore, and the requirement to minimise road noise. By deploying multiple Adjustable Roller Centralizers along the length of the tool-string the centralising & drag forces may be fully optimised for successful conveyance whilst minimizing road noise, resulting in a successful descent and the acquisition of excellent logging data.

The Adjustable Roller Centralizer features several key innovations over existing centralisers: a) The radial contact wheels, between centraliser and Casing inner face, are selected for the toolstring and Casing being logged, in terms of diameter, profile and material. The material influences the contact mechanics and the road noise generated when moving inside the Casing. b) A single coil spring, aligned axially to the tool-string, applies equal centralising force to radial arm mechanisms and contact wheels. The coil spring is selected according to the wellbore environment and the centralising force required. c) The radial arm mechanisms, which push the contact wheels against the Casing inner face, comprise pairs of tension and rocker arms. The tension and rocker arm dimensions are governed by the contact wheel diameter, the tool-string and Casing dimensions, and the centralising force required. d) Prior to installation on the tool-string, the coil spring compression in each centraliser is adjusted using an array of strain gauges from a calibration ring that matches the geometry of Casing being logged; thus the centralsing force can be accurately adjusted as per job requirements. e) The tension and rocker arm mechanisms have a configurable upper limit to control the radial extension of the contact wheels, which minimises the risk of the tool-string hanging up or getting stuck in the wellbore during the job.

The invention will now be described in detail with the aid of Figures 1-5, as summarized below.

Figure 1a is view of the Adjustable Roller Centralizer in relation to the drilling rig, logging tools, and cased hole wellbore.

Figure 1 b is an end view of the Adjustable Roller Centralizer showing the radial contact wheels inside the Casing.

Figure 2 is view of the Adjustable Roller Centralizer in its entirety.

Figure 3 shows how the Adjustable Roller Centralizer transfers axial coil spring force (SF) to centralising force (CF) via tension & rocker arms and contact wheels.

Figure 4a is a pictorial view of the Adjustable Roller Centralizer inside the vice jig and gauge ring which determines the upper limit of the tension and rocker arm movement, such that the contact wheels will not exceed a certain rolling circumference (in this example 8.8”).

Figure 4b is a side view of the Adjustable Roller Centralizer inside the vice jig and gauge ring which shows the wheels sitting inside the inner surface of the gauge ring.

Figure 4c is a side view of the Adjustable Roller Centralizer, vice jig and gauge ring assembly, clamped in a vice.

Figue 5a is a pictorial view of the Adjustable Roller Centralizer situated in the vice jig and calibration ring with in-situ strain gauge array.

Figue 5b is a side view of the Adjustable Roller Centralizer situated in the vice jig showing the contact wheels applying pressure to the inner face of the calibration ring and generating radial and hoop stresses that are detected by the radial array of strain gauges for centralising force adjustment,

Figure 1a shows a generic cased hole logging operation with multiple Adjustable Roller Centralizers [1] deployed on a logging tool-string [2] in a cased hole wellbore [3], The drilling rig, ship, barge, or platform [10] is located above the borehole [3] and has a wireline or slickline unit [9] containing data acquisition equipment and associated devices mounted securely to the drilling structure. Wireline or slickline cable [5] is spooled off the drum [8] around the lower sheave [7] and upper sheave [6] into the wellbore [3], At the end of the cable is a tool-string [2] to deliver a wellbore service or acquire logging data. Attached to the tool-string [2] are multiple Adjustable Roller Centralizers [1] which position the tool-string [2] in the centre of the Casing [3] whilst permitting a smooth rolling action in up-hole and down-hole directions. A close up of the upper Adjustable Roller Centralizer [1] shows the positive alignment of the tool-string [2] inside the Casing [3] with respect to the Casing centreline [4],

Figure 1b shows the end on view of Adjustable Roller Centralizer [1] attached to the tool-string [2] which is positively centralised in the Casing [3],

Figure 2 is view of the Adjustable Roller Centralizer [1] in its entirety. The main body [11] is a tubular sleeve with tapered fins at the lower end that house the radial guide wheels [13] via axle assemblies [14] and with a central bore which is slightly larger than the tool-string onto which it is fitted. Attachment to the tool-string body is achieved by an array radial array of grub screws [12] located inside the tapered fins. The coil spring [22] provides the centralising force for the Adjustable Roller Centralizer [1], The coil spring rating, pitch and length is selected according to the job requirements prior to deployment. The coil spring [22] slides over the stub acme thread [23] on the main body [11] and fits between the upper sliding mount [21] and the lock rings [25] and [26], which control the compressive preload force. The purpose of the radial guide wheels [13] is two-fold: A) To facilitate smooth passage of the tool-string when moving in the downhole direction of the wellbore, past any debris or contractions that may exist; B) to ensure that that contact wheels [15] have a smooth transition through any wellbore restrictions, such as when moving from 9 5/8” casing to 7” liner for example. The radial guide wheels [13] control the direction of the impact force on the radial contact wheels [15] when entering such a restriction, ensuring that the tool-string movement is not impeded. Without the radial guide wheels [13] and tapered fins of the lower end of the main body [11] the tool-string could hang up in such restrictions, compromising the data acquisition objectives. The radial contact wheels [15] are supported by axle assemblies [16] and rocker arms [28] and tension arms [17]. The fixed ends of the rocker arms [28] allow rotational movement relative to the main body [11] via axle assemblies [27]. The tension arms [17] are connected to the sliding sleeve [21] by axle assemblies [18] which abut the upper end of the coil spring [22], The sliding sleeve [21] is permitted to move in an axial direction on a mounting sleeve [20] concentric to the main body [11] with its position adjusted via the stub acme thread [23]. The mounting sleeve [20] has a flange that limits the upper movement of the sliding sleeve [21] which in turn affects the positions of the tension arms [17], rocker arms [28] and radial contact wheels [15], and is locked in place by an upper tapered lock ring [19], The coil spring [22] is compressed by the two lock rings [25] & [26] via their radial spanner holes [24] and transfers compressive force to the sliding sleeve [21] and tension arms [17] which pull over the rocker arms [28] and extend the contact wheels [15] in an outwards and upwards direction, applying a positive centralising force to the tool-string inside the Casing. The upper limit for movement of the sliding sleeve [21] and radial contact wheels [15] is determined by the position of the mounting sleeve [20] in the main body [11],

Figure 3 demonstrates how the Adjustable Roller Centralizer [1] creates a positive centralising force for the tool-string [2] inside the Casing [3], For reasons of diagrammatic simplification the Casing [3] is only illustrated with one radial contact wheel [15] touching the inner face of the Casing [29] whereas in reality all the radial contact wheels are acting in unison. The net force applied by the radial contact wheels ensures the tool-string [2] is firmly aligned with the Casing centreline [4], The coil spring [22] provides a compressive force acting against the sliding sleeve [21] which pulls on the tension arms [17] and causes the rocker arms [28] to apply pressure to the radial contact wheels [15] against the inner Casing surface [29], The sliding sleeve movement [21] is limited by the flange on the mounting sleeve [20], held in place by the tapered lock ring [19],

It can be shown that:

Centralising force [CF] ©c SF *Tan(a)

Where: a = angle between rocker arm axis and the centreline of the tool-string [2] (the larger a the greater the CF)

And: SF = the applied compressive spring force which is selected and adjusted for a job in terms of rating, pitch, length, and preload level. a depends on the tool-string [2] and Casing [3] dimensions, the diameter of the radial contact wheel [15] and the combination of rocker arm [28] and tension arm [17] dimensions.

In summary, there are an infinite number of permutations for controlling CF based on the components selected and the preload compression of the coil spring in the Adjustable Roller Centralizer [1].

Figure 4a is a pictorial view of the Adjustable Roller Centralizer [1] sitting inside the vice jig [31] with the gauge ring [30] in situ. Note that it is intended that the Adjustable Roller Centralizers [1] are fully configured in a workshop area before being installed on the tool-string. The gauge ring [30] is selected according to the Casing being logged and its purpose is to limit the maximum opening diameter of the radial contact wheels [15], In this example the inner face of the gauge ring is shown to be 8.8” but it could be any size, according to the job requirements and Casing size. The Adjustable Roller Centralizer [1] sits concentrically in the vice rig [31] and the gauge ring [30] is vertically aligned with the contact wheels [15], The mounting sleeve [20] is then screwed down, pushing down the tension arms [17] and rotating the rocker arms until the radial wheels are just lifting off the inner face of the gauge ring [30], at which point the upper limit is set. The tapered lock ring [19] is then tightened against the mounting sleeve [20] to maintain the setting for the job.

Figure 4b is a side view of figure 4a, included for the sake of clarity

Figure 4c shows the vice jig [31] secured in a benchtop vice [32] for the configuration of the Adjustable Roller Centralizer [1],

Figure 5a is a pictorial view of the Adjustable Roller Centralizer [1] sitting concentrically inside the vice jig [31] with the calibration ring [33] in situ and its inner face vertically aligned with the radial contact wheels [15], The purpose of the calibration ring [33] is to allow the setting of the centralising force applied by the coil spring [22] to the radial arm mechanisms via the radial contact wheels [15], The calibration ring [33] matches the i.d. of the Casing being logged, in this example the wheels apply pressure at a contact diameter of 8.535” but the calibration ring could be any size. Note the sliding sleeve [21] has have moved down slightly from the maximum opening position governed by the mounting sleeve [20] which was previously adjusted using the gauge ring, illustrated in figures 4a, 4b, and 4c. The upper lock ring [25] is rotated to compress the main spring [22] which transfers force via the tension arms [17] to the rocker arms [28] and radial contact wheels [15], The force applied by the radial contact wheels results in radial and hoop stresses in the calibration ring which are measured using an array of calibrated strain gauges [34], Thus the centralisation force can be accurately set according to the requirements of the job. Once the correct centralising force has been achieved the lower lock ring [26] is tightened against the upper lock ring [25], thus maintaining the coil spring preload at the required contact diameter for the duration of the job.

Figure 5b is a side view of figure 5a, included for the sake of clarity.

Claims

Claims:

1. The Adjustable Roller Centralizer is a highly configurable device which, when deployed in plurality, positively centralises a logging tool-string inside a cased hole wellbore using a coil spring that transfers it’s compressive force via an array of radial arm mechanisms to contact wheels that apply equal pressure to the inner face of the wellbore, whereby all components of the device are selected and adjusted according to the specific wellbore environment, including the spring rating and preload, the radial arm component geometries, and the contact wheel size, profile and material, which in combination control the centralising force, rolling resistance and road noise, in accordance with the conveyance requirements and service objectives.

2. The Adjustable Roller Centralizer according to claim 1 possesses an array of radial guide wheels which support smooth conveyance in the cased hole wellbore and act as a guide for the radial contact wheels through wellbore restrictions or contractions.

3. The main body of the Adjustable Roller Centralizer, according to claim 1, suspends the radial guide wheels in tapered fins to aid smooth conveyance in the down-hole direction, past any wellbore restrictions or contractions.

4. The array of radial guide wheels, according to claim 2, are installed in the main body fins according to the conveyance requirements whereby the wheel diameters, the wheel profile, and wheel material may be selected to minimise rolling resistance and road noise.

5. The main body of the Adjustable Roller Centralizer, according to claim 1, has a stub acme thread onto which are threaded various components such as the sliding mount and multiple lock rings which adjust the limit of the radial contact wheel extension and the coil spring preload compression.

6. The Adjustable Roller Centralizer, according to claim 1, possesses a coil spring, which has a rating, length, coil pitch and diameter that is selected according to the job requirements and which slides over the stub acme thread on the main body, held in place by two threaded lock rings on the lower end and a sliding sleeve connected to the radial arm mechanisms and contact wheels on the upper end.

7. The sliding sleeve, according to claim 6, is held in place by a mounting sleeve which screws onto the upper end of the main body of the Adjustable Roller Centralizer and which transmits the coil spring compressive force to the tension arms that are connected to the rocker arms and radial contact wheels.

8. The mounting sleeve of the Adjustable Roller Centralizer, according to claim 7, controls the movement of the sliding sleeve and the subsequent extension of the radial contact wheels, and is held in place on the main body of the by a stub acme thread and a tapered lock ring.

9. The Adjustable Roller Centralizer, according to claim 1, possesses an array of radial arm mechanisms that comprise tension arms that connect the sliding sleeve to the rocker arms and radial contact wheels.

10. The radial arm mechanisms of the Adjustable Roller Centralizer according to claims 1 and 9, transfer the compressive force from the coil spring equally to the tension arms, rocker arms, and radial contact wheels thereby forcing positive centralisation of the tool-string onto which a plurality of Adjustable Roller Centralizers are attached, thus aligning the tool-string with the centreline of the Casing and wellbore.

11. The radial arm mechanisms, according to claims 1, 9, 10 have geometry and dimensions which are selected according to the tool-string and Casing, whereby the centralisation force applied is proportional to the coil spring force and the tangent of the rocker arm angle to the tool-string central axis.

12. The Adjustable Roller Centralizer, according to claims 1 possesses an array of radial contact wheels which freely rotate in axles that are attached to the radial arm mechanisms, comprising tension and rocker arms.

13. The radial contact wheels, according to claim 12, may be selected according to diameter, profile, and material for the specific conveyance requirements of a tool-string in a wellbore, and considering the centralising force, rolling resistance and road noise generated.

14. The Adjustable Roller Centralizer, according to claim 1, possesses a series of workshop gauge rings used in combination with a vice jig to set the maximum extension of the radial contact wheels by adjusting the mounting sleeve position on the main body, according to the Casing size in the wellbore.

15. The Adjustable Roller Centralizer, according to claim 1, possesses a series of workshop calibration rings that are used in combination with a vice jig to adjust the coil spring compressive preload force which then controls the resulting centralising force for any given radial arm mechanism and contact wheel configuration and which is measured by an array of calibrated strain gauges that measure the hoop and radial stresses generated in the ring by the device.