CA1270378A - Rheometer bob mechanism - Google Patents
Rheometer bob mechanismInfo
- Publication number
- CA1270378A CA1270378A CA000567627A CA567627A CA1270378A CA 1270378 A CA1270378 A CA 1270378A CA 000567627 A CA000567627 A CA 000567627A CA 567627 A CA567627 A CA 567627A CA 1270378 A CA1270378 A CA 1270378A
- Authority
- CA
- Canada
- Prior art keywords
- bob
- stator
- rheometer
- rotor
- vessel
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N11/00—Investigating flow properties of materials, e.g. viscosity, plasticity; Analysing materials by determining flow properties
- G01N11/10—Investigating flow properties of materials, e.g. viscosity, plasticity; Analysing materials by determining flow properties by moving a body within the material
- G01N11/14—Investigating flow properties of materials, e.g. viscosity, plasticity; Analysing materials by determining flow properties by moving a body within the material by using rotary bodies, e.g. vane
Landscapes
- Physics & Mathematics (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Rotary Pumps (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
The bob of a rheometer has a concentric bore which co-operates with a stationary member disposed in the bore to form a stator-and-rotor pump mechanism utilizing the rotation of the bob to circulate the measured sample through a passage in the bob and through the measuring gap of the rheometer.
The bob of a rheometer has a concentric bore which co-operates with a stationary member disposed in the bore to form a stator-and-rotor pump mechanism utilizing the rotation of the bob to circulate the measured sample through a passage in the bob and through the measuring gap of the rheometer.
Description
~L2~37~3 This invention relates to rheometers and in particular to an improved bob design for a high temperature, high pressure rheometer of the Serle (rotating bob) type.
There are many problems a~ociated with high temperature, high pressure rheology measurements.
The first is the lengthy time required to establish temperature uniformity within the pressure cell.
~his is due to the thermal inertia of the large, heavy bob.
Also, when measuring rheology of high viscosity fluids at high shear rates, the di~sipation of frictional heat poses additional temperature distribution uncertainties.
An equally serious problem to particle settling and thermal effects is the tendency of slurries and certain polymer solutions to develop gel structures if not continuously sheared. While some rheological experiments are aimed at obtaining information on the development of these gel structures, in other cases their formation interferes with the desired measurement of the shear rate/æhear stress relationship o~ the fluids.
Another problem encountered with rotational rheometry of slurry is the weight of the bob and accompanying friction and wear on the supporting shaft.
The determination of bulk slurry rheology requires a relatively large gap, many times the particle diameters, to permit averaging. This in turn necessitates a large diameter bob in order to have uniform shear stresses and shear rates across the gap and to minimize turbulence at high shear rates.
Attempts have been made to alleviate the above problems by stirring ths test sample. For instance, US
Patent 4,524,611 issued June 15, 19~5 to Richon et al.
describes a rheometer wherein the test sample can be agitated prior to a measurement of rheological property, to maintain homogeneity. This was deemed particularly important in the measurement of the rheological properties of slurries, although, the same reasoning would apply to ~,.. ..
~7Q378 emulsions. From the standpoint of the present invention, it is noteworthy that in the Richon apparatus there is no displacement of the fluid in the measuring gap whils the measurements are being made. This necessitates short measurement time when rapidly settlin~ particlss are present.
It is an object of the present invention to improve on the ability of a rheometer to determine the rheological properties of drilling fluids, fracturing fluids, and cementing slurries at high temperatures and pressures, while minimizing the aomplexity, si~e, and associated expense of equipment re~uired to meet the desired objectives.
In general terms, the invention provides a rheometer bob mecha~ism for use in a stationary vessel of a high pressure rheometer with a rotatiny bob, including means for reactive torque measuring, the mechanism including a rotor-stator pump means disposed internally of the bob, wherein an internal part of the bob is a rotor portion of said pump means, said pump means furthe~
including a stator portion adapted to be held stationary relative to the vessel whereby, as the bob rotates, circulation of the test sample up or down an internal channel in the bob, and slow but positive displacement of the test sample in a bob/vessel wall gap is effected.
The invention will now be described by way of a preferred embodiment, with reference to the accompanying drawings, wherein;
Figure 1 depicts, in a simplified, diagrammatic fashion, a cross-sectional view of the general mechanical arrangement of a known rheometer;
Figure 2 depicts a similar cross-sectional view but showing, on an enlarged scale, the lower part of the device of Figure 1, incorporating an exemplary embodiment of the pre~ent invention.
The invention is described by way of describing the modification of the rotating bob of an existing ~t7~37~
rheometer to accommodate a stator attached to the stationary vessel or cell, so as to permit the construction of a pumping mechanism within the bob. As the bob turns, the pumping mechanism circulates the test sample up or down the internal bore and flow channels of the rotating ~ob and returns it via the gap between the rotating bob and the vessel wall, i.e. through the gap at which the actual measuring of shear rate takes place.
Two criteria must be met in the design o~ the pump: First, the shear rate in the gap due to circulation must be small compared to the shear rate due to the bob rotation. Simple vector analysis indicates that a circulation shear rate of 20% of the rotational shear rate gives a resulting shear rate only 2% higher than the shear rate due to rotation alone. The second criterion is that the torque required to provide circulation must be small compared to the torque provided by the shear of the test sample in the bob/vessel wall gap. It is also desirable for the shear rate in the pumping section to be similar to the shear rats in the gap.
In order to illustrate the application oE these design features, Figure 1 is provided to show a high pressure rheometer suitable for utilizing the improved bob arrangement. The rheometer contains the essential features of Delorey in Canadian Patent 1,223,458, along with some minor improvements.
A DC motor generator 16 provides means of applying and monitoring the torque to a rotational bob 28. Motor flange 8 is attached to the motor housing by screws 29, and screwed to a motor support 9. The motor shaft is fixe~ by means of a set screw 19 to an outer magnet assembly 5.
Non-magnetic housing equipped with oil filling port 27 provides a pressure barrier to an inner magnet shaft assembly 4. The inner magnet assembly is supported by bearings 17, 18 and attaches to a mechanical shaft coupling . High pressure seals 24 and a bearing support ring 7 complete the magnet assembly.
...... ;
~27~337~
A low pressure sealing ring 23 retained by bushing 15 and held at its lower limit of travel by a spring 13 provides means o-f keeping the magnetic drive section filled with hydraulic medium, such as low viscosity mineral oil.
The magnetic drive assembly attaches to a pres~ure vessel top 10 which contains a pressuring port 25 and air venting port 26. A retaining ring 1, a pressure vessel body 11, a base plug 12, a shaft supporting plug 2 and high pressure seals 21, 22 and 20 complete the high pressure vessel or cell.
As in other high pressure rotational rheometers, solid metal bob 28 rotates within the pressure vessel body 11 and is attached, via set screws, to the shaft 14 made from hardened metal. A small hole 30 in the shaft permits replacement of the metal bob by an alternate mixing paddle for determining consistenay. The test sample surrounds the bob within the pressuxe vessel body 11 and forms an interface with the pressurizing oil in the vicinity of the mechanical coupler 3 or fills the entire pressuring line to an external sample pressuring cylinder. The pressure vessel sits in a heating/cooling sleeve and a thermocouple is inserted in thermocouple well 31 for temperature monitoring and control purposes.
Referring now to Figure 2, the solid bob 32 has been partially bored out from the top and the internal surface so created machined with a shallow spiral groove 32a. Four large flow channels 32b to permit movement of the fluid to the bottom of the bob are also provided. On the hub of the bored out bob 32 sits a Teflon (TM) o-ring 37 which serves as a support for the stator portion of the pump which consists of a Teflon ~TM) cylinder 33, the outside surface of which also has a shallow spiral groove with the reversed thread to the thread of the groove 32a in internal surface of the rotary bob 32. The top surface of the stator portion contains grooves which are used to hold the stator in a stationary position by means of a ~ushing assembly 34, 36, 35. The metal bushing assembly consists ~ 3~
of two threaded part.s 34, 35 which, when screwed together, expand the elastomeric o-ring 36 against the bore of the pressure vessel top. Thus, in the embodiment just described, the reverse spiral grooves on the stator disposed internally of the bob and th0 internal part of the rotary bob form a progressive cavity pump means which, when the bob is rotated, causes up o~ down circulation of the test sample.
The invention permits the circulation of test fluid through the measuring gap and returning by means of the centre of the ~ob, while a rheological property is being measured.
An equally acceptable embodiment of this invention would have the stator sitting on the base of the pressure vessel and the bored out bob attached to the paadle shaft by the hub at the top of the bob. The stator could simply sit on pegs to hold it stationary. In both embodiments of this invention the test fluid would be sub;ected to shearing action similar to that in the bob wall gap. Also these two embodiments result in a design ~hich is easily machined and convenient to clean after use.
Similar embodiments utilizing stator blades and rotor bladee could be envisioned and may be desirable for fluids requiring greater agitation than that provided by the shallow grooved stator and rotor. The cleaning and machining difficulties, however, would be considerably increased.
Xt can be seen from the above that many embodiments of the present invention may exist which differ from the described embodiment without departing from the inventive concept. Accordingly, I wish to protect by Letters Patent which may issue on this application all embodiments which properly fall within the scope of my contribution to the art.
. , , . .
There are many problems a~ociated with high temperature, high pressure rheology measurements.
The first is the lengthy time required to establish temperature uniformity within the pressure cell.
~his is due to the thermal inertia of the large, heavy bob.
Also, when measuring rheology of high viscosity fluids at high shear rates, the di~sipation of frictional heat poses additional temperature distribution uncertainties.
An equally serious problem to particle settling and thermal effects is the tendency of slurries and certain polymer solutions to develop gel structures if not continuously sheared. While some rheological experiments are aimed at obtaining information on the development of these gel structures, in other cases their formation interferes with the desired measurement of the shear rate/æhear stress relationship o~ the fluids.
Another problem encountered with rotational rheometry of slurry is the weight of the bob and accompanying friction and wear on the supporting shaft.
The determination of bulk slurry rheology requires a relatively large gap, many times the particle diameters, to permit averaging. This in turn necessitates a large diameter bob in order to have uniform shear stresses and shear rates across the gap and to minimize turbulence at high shear rates.
Attempts have been made to alleviate the above problems by stirring ths test sample. For instance, US
Patent 4,524,611 issued June 15, 19~5 to Richon et al.
describes a rheometer wherein the test sample can be agitated prior to a measurement of rheological property, to maintain homogeneity. This was deemed particularly important in the measurement of the rheological properties of slurries, although, the same reasoning would apply to ~,.. ..
~7Q378 emulsions. From the standpoint of the present invention, it is noteworthy that in the Richon apparatus there is no displacement of the fluid in the measuring gap whils the measurements are being made. This necessitates short measurement time when rapidly settlin~ particlss are present.
It is an object of the present invention to improve on the ability of a rheometer to determine the rheological properties of drilling fluids, fracturing fluids, and cementing slurries at high temperatures and pressures, while minimizing the aomplexity, si~e, and associated expense of equipment re~uired to meet the desired objectives.
In general terms, the invention provides a rheometer bob mecha~ism for use in a stationary vessel of a high pressure rheometer with a rotatiny bob, including means for reactive torque measuring, the mechanism including a rotor-stator pump means disposed internally of the bob, wherein an internal part of the bob is a rotor portion of said pump means, said pump means furthe~
including a stator portion adapted to be held stationary relative to the vessel whereby, as the bob rotates, circulation of the test sample up or down an internal channel in the bob, and slow but positive displacement of the test sample in a bob/vessel wall gap is effected.
The invention will now be described by way of a preferred embodiment, with reference to the accompanying drawings, wherein;
Figure 1 depicts, in a simplified, diagrammatic fashion, a cross-sectional view of the general mechanical arrangement of a known rheometer;
Figure 2 depicts a similar cross-sectional view but showing, on an enlarged scale, the lower part of the device of Figure 1, incorporating an exemplary embodiment of the pre~ent invention.
The invention is described by way of describing the modification of the rotating bob of an existing ~t7~37~
rheometer to accommodate a stator attached to the stationary vessel or cell, so as to permit the construction of a pumping mechanism within the bob. As the bob turns, the pumping mechanism circulates the test sample up or down the internal bore and flow channels of the rotating ~ob and returns it via the gap between the rotating bob and the vessel wall, i.e. through the gap at which the actual measuring of shear rate takes place.
Two criteria must be met in the design o~ the pump: First, the shear rate in the gap due to circulation must be small compared to the shear rate due to the bob rotation. Simple vector analysis indicates that a circulation shear rate of 20% of the rotational shear rate gives a resulting shear rate only 2% higher than the shear rate due to rotation alone. The second criterion is that the torque required to provide circulation must be small compared to the torque provided by the shear of the test sample in the bob/vessel wall gap. It is also desirable for the shear rate in the pumping section to be similar to the shear rats in the gap.
In order to illustrate the application oE these design features, Figure 1 is provided to show a high pressure rheometer suitable for utilizing the improved bob arrangement. The rheometer contains the essential features of Delorey in Canadian Patent 1,223,458, along with some minor improvements.
A DC motor generator 16 provides means of applying and monitoring the torque to a rotational bob 28. Motor flange 8 is attached to the motor housing by screws 29, and screwed to a motor support 9. The motor shaft is fixe~ by means of a set screw 19 to an outer magnet assembly 5.
Non-magnetic housing equipped with oil filling port 27 provides a pressure barrier to an inner magnet shaft assembly 4. The inner magnet assembly is supported by bearings 17, 18 and attaches to a mechanical shaft coupling . High pressure seals 24 and a bearing support ring 7 complete the magnet assembly.
...... ;
~27~337~
A low pressure sealing ring 23 retained by bushing 15 and held at its lower limit of travel by a spring 13 provides means o-f keeping the magnetic drive section filled with hydraulic medium, such as low viscosity mineral oil.
The magnetic drive assembly attaches to a pres~ure vessel top 10 which contains a pressuring port 25 and air venting port 26. A retaining ring 1, a pressure vessel body 11, a base plug 12, a shaft supporting plug 2 and high pressure seals 21, 22 and 20 complete the high pressure vessel or cell.
As in other high pressure rotational rheometers, solid metal bob 28 rotates within the pressure vessel body 11 and is attached, via set screws, to the shaft 14 made from hardened metal. A small hole 30 in the shaft permits replacement of the metal bob by an alternate mixing paddle for determining consistenay. The test sample surrounds the bob within the pressuxe vessel body 11 and forms an interface with the pressurizing oil in the vicinity of the mechanical coupler 3 or fills the entire pressuring line to an external sample pressuring cylinder. The pressure vessel sits in a heating/cooling sleeve and a thermocouple is inserted in thermocouple well 31 for temperature monitoring and control purposes.
Referring now to Figure 2, the solid bob 32 has been partially bored out from the top and the internal surface so created machined with a shallow spiral groove 32a. Four large flow channels 32b to permit movement of the fluid to the bottom of the bob are also provided. On the hub of the bored out bob 32 sits a Teflon (TM) o-ring 37 which serves as a support for the stator portion of the pump which consists of a Teflon ~TM) cylinder 33, the outside surface of which also has a shallow spiral groove with the reversed thread to the thread of the groove 32a in internal surface of the rotary bob 32. The top surface of the stator portion contains grooves which are used to hold the stator in a stationary position by means of a ~ushing assembly 34, 36, 35. The metal bushing assembly consists ~ 3~
of two threaded part.s 34, 35 which, when screwed together, expand the elastomeric o-ring 36 against the bore of the pressure vessel top. Thus, in the embodiment just described, the reverse spiral grooves on the stator disposed internally of the bob and th0 internal part of the rotary bob form a progressive cavity pump means which, when the bob is rotated, causes up o~ down circulation of the test sample.
The invention permits the circulation of test fluid through the measuring gap and returning by means of the centre of the ~ob, while a rheological property is being measured.
An equally acceptable embodiment of this invention would have the stator sitting on the base of the pressure vessel and the bored out bob attached to the paadle shaft by the hub at the top of the bob. The stator could simply sit on pegs to hold it stationary. In both embodiments of this invention the test fluid would be sub;ected to shearing action similar to that in the bob wall gap. Also these two embodiments result in a design ~hich is easily machined and convenient to clean after use.
Similar embodiments utilizing stator blades and rotor bladee could be envisioned and may be desirable for fluids requiring greater agitation than that provided by the shallow grooved stator and rotor. The cleaning and machining difficulties, however, would be considerably increased.
Xt can be seen from the above that many embodiments of the present invention may exist which differ from the described embodiment without departing from the inventive concept. Accordingly, I wish to protect by Letters Patent which may issue on this application all embodiments which properly fall within the scope of my contribution to the art.
. , , . .
Claims (3)
1. A rheometer bob mechanism for use in a stationary vessel of a high pressure rheometer with a rotating bob, including means for reactive torque measuring, the mechanism including a rotor-stator pump means disposed internally of the bob, wherein an internal part of the bob is a rotor portion of said pump means, said pump means further including a stator portion adapted to be held stationary relative to the vessel whereby, as the bob rotates, circulation of the test sample up or down an internal channel in the bob, and slow but positive displacement of the test sample in a bob/vessel wall gap is effected.
2. The mechanism of Claim 1 in which said rotor portion of the pump means includes an opening in the bob, said opening being co-axial with the axis of rotation of the bob, a spiral groove forming a flow channel being provided in the surface of the opening, said stator portion being a cylindrical sleeve including a reverse shallow spiral groove on its external surface, said mechanism including mounting means holding said sleeve stationary relative to the pressure vessel whereby mating rotor and stator spiral grooves provide a progressive cavity pumping action when the bob is rotated.
3. The rheometer bob of Claim 1, in which said rotor and stator portions are fashioned with blades to provide a turbine pumping action.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000567627A CA1270378A (en) | 1988-05-25 | 1988-05-25 | Rheometer bob mechanism |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000567627A CA1270378A (en) | 1988-05-25 | 1988-05-25 | Rheometer bob mechanism |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1270378A true CA1270378A (en) | 1990-06-19 |
Family
ID=4138073
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000567627A Expired CA1270378A (en) | 1988-05-25 | 1988-05-25 | Rheometer bob mechanism |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1270378A (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1992010736A1 (en) * | 1990-12-04 | 1992-06-25 | Services Petroliers Schlumberger | Rheometer |
| WO2002010086A1 (en) * | 2000-07-28 | 2002-02-07 | Technische Universität Clausthal | Method for production of an expanding cement and corresponding test device |
| CN103234869A (en) * | 2013-04-26 | 2013-08-07 | 中国石油天然气股份有限公司 | Oil reservoir fluid on-line high-pressure rotary viscometer |
| JP2016529517A (en) * | 2013-08-28 | 2016-09-23 | ビクトリア リンク リミテッド | Rheology measuring device |
-
1988
- 1988-05-25 CA CA000567627A patent/CA1270378A/en not_active Expired
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1992010736A1 (en) * | 1990-12-04 | 1992-06-25 | Services Petroliers Schlumberger | Rheometer |
| US5546791A (en) * | 1990-12-04 | 1996-08-20 | Schlumberger Technology Corporation | Rheometer |
| WO2002010086A1 (en) * | 2000-07-28 | 2002-02-07 | Technische Universität Clausthal | Method for production of an expanding cement and corresponding test device |
| CN103234869A (en) * | 2013-04-26 | 2013-08-07 | 中国石油天然气股份有限公司 | Oil reservoir fluid on-line high-pressure rotary viscometer |
| JP2016529517A (en) * | 2013-08-28 | 2016-09-23 | ビクトリア リンク リミテッド | Rheology measuring device |
| EP3055667A4 (en) * | 2013-08-28 | 2017-08-09 | Victoria Link Limited | Rheological measurement devices |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |