WO2011113096A1

WO2011113096A1 - Surface casing unit

Info

Publication number: WO2011113096A1
Application number: PCT/AU2011/000292
Authority: WO
Inventors: Arthur Charles Nommensen; David C. Nommensen
Original assignee: Viking Energy Pty Ltd
Priority date: 2010-03-15
Filing date: 2011-03-15
Publication date: 2011-09-22

Abstract

A surface casing unit for forming a surface casing for a well, the surface casing unit comprises: a mix bowl capable of containing a slurry; at least one high pressure pump associated with the mix bowl to pump at least part of the slurry into a surface casing; and at least one high pressure pump capable of pumping a fluid into a surface casing.

Description

SURFACE CASING UNIT

FIELD OF THE INVENTION

The present invention relates to a surface casing unit. In some embodiments, the invention is directed to a mobile surface casing unit that is able to safely and easily cement in the surface casing of oil and gas wells, although the scope of the invention is not necessarily limited thereto.

BACKGROUND

When an oil or gas well is drilled, initially a large drilling bit (approximately 12inch.es in diameter), is used to drill to a depth of approximately 100 meters (varies with geology). It is then normal practice to lower into the well, a large diameter pipe (surface casing pipes for coal seam gas wells are often 9 5/8 inches in diameter) to the bottom of the hole. This casing is then cemented into the well bore-hole by pump- filling the annular space between the pipe and the rock with a specialised oil-field cement. When the cement has set, this strong and secured-in-place surface casing allows the blow out preventer (or well-head valves) to be attached to the top of the steel casing. Then the well is again drilled with a smaller diameter bit which extends through the surface casing pipe, and the production steel casing pipe is then lowered down the hole to the full drilled depth and it is also then cemented into the well bore.

Due to the volume of cement required for deep wells (up to 30 tonnes or more), such deep production casing cementing operations always requires the use of large specialised oil/gas well cementing units. Such units continuously and on-the-spot bulk blend cement powders and water and additives, and at the same time also pump the cement slurry down the well at high pressures. At least two, and typically three or more personnel are usually required to operate such a unit. Additionally, a bulk cement powder tanker is also required to provide the cement powders. Further additional tankers and equipment is also required to deliver the water and additives to the large cementer units. The large eementer units are also commonly used to do the more benign surface casing jobs. However, it is not economical to use large cementer units for this initial job. The large pumps used on the larger cementer units cannot easily 'creep' i.e. work at low speeds, with the required precision needed to pressure test the well head fittings and also pressure-test the well after the cement is set to ensure that the well is leak-free and thus safe.

A common concrete mixer truck cannot deliver the large quantities of cement slurry required for the production casing stages of oil or gas wells. Common truck-mounted concrete pumps also do not have sufficient pressure to deliver the slurry down the well for this deeper production casing operation. They are not therefore appropriate technology for deep cementing work.

Nevertheless, the cement job for the first surface casing (particularly on the shallow coal seam gas wells) uses only a modest amount of cement (normally around 6 tonnes). It is within the capability of one common concrete mixer truck to deliver such quantity to the well-site from a cement batch plant. This alternative has been used to surface case oil and gas wells.

However there are some significant disadvantages to using a common concrete mixer truck to surface case oil and gas wells. These disadvantages include: When a mixer truck delivers the cement slurry, the rig crews must conduct the cementing operation using separate rig pumps or a separate pumper truck to do so, adding significant costs ' to the operation. Down-hole progress of the cement slurry is not monitored when using a common concrete mixer truck, this can result in ruined wells adding significant costs to the operation. If separate rig pumps or a separate pumper truck are not used, blow outs can occur due to the standard concrete pumps that a common concrete mixer truck utilises not being able to handle such high pressures and not including blow out preventers, such blowouts can result in ruined wells adding significant costs to the operation and can create very dangerous conditions for the operators. Additionally, the standard concrete pumps are not capable of producing enough pressure for most surface casing operations resulting in ruined wells.

Concrete pumps used in civil construction do not give sufficient pressure to pressure test the integrity of the oil wells, and are not equipped to work safely in the vicinity of gas wells, nor record for mines regulations the conduct (pressures and flow) of the cement pumping job. Common concrete mixer trucks also do not conform to gas and oil well safety requirements. Another disadvantage with large specialised oil/gas well cementing units and common concrete mixer trucks is that out at well sites the fluid used to test the well before and after the surface casing is drawn from creeks and bores, such 'dirty' water can contain gravel and the like which can block safety valves and pressure sensors. The large specialised oil/gas well cementing units also use this 'dirty' water to bulk blend cement powders resulting in variable cement properties.

It is an aim of the invention to provide a surface casing unit which overcomes or ameliorates one or more of the disadvantages or problems described above, or which at least provides the consumer with a useful choice.

It will be clearly understood that any reference herein to background material or information, or to a prior publication, does not constitute an admission that any material, information or publication forms part of the common general knowledge in the art, or is otherwise admissible prior art, whether in Australia or in any other country.

DESCRIPTION OF THE INVENTION

In one aspect, the present invention provides a surface casing unit for forming a surface casing for a well, the well initially including a drill hole, a casing in the drill hole to define a space between the drill hole and an outer surface of the casing and a cementing head, the surface casing unit comprising a mix bowl containing a settable slurry, at least one high pressure pump associated with the mix bowl to pump at least part of the settable slurry into a surface casing, and at least. one high pressure pump capable of pumping a fluid into a surface casing, wherein the settable slurry is pumped by the at_. least one high pressure pump through the. cementing head and into the casing, when the settable slurry has been pumped through the cementing head, the fluid is pumped by the at least one high pressure pump capable of pumping a fluid into the cementing head pushing on an interface on the settable slurry, the settable slurry is forced down the casing and up towards the top of the well, from the bottom of the casing, between a wall of the drill hole and the casing, forming the surface casing of the well. In another aspect .the -present invention provides a surface casing unit for forming a surface casing for a well, the well initially including a drill hole, a casing in the drill hole and a cementing head, the surface casing unit comprises: a mix bowl capable of containing a slurry; at least one high pressure pump associated with the mix bowl to pump at least part of the slurry into a surface casing; at least one high pressure pump capable of pumping a fluid at a pressure of at least 100 bar into a surface casing; and a non-return valve or a blow out preventer on the outlet side of at least one of the high pressure pumps capable of withstanding at least 100 bar of pressure; wherein the slurry is pumped by the at least one high pressure pump through the cementing head and into the casing, when. the slurry has been pumped through the cementing head, the fluid is pumped by the at least one high pressure pump capable of pumping a fluid into the cementing head pushing on an interface, such as a rubber plug, on the slurry, the slurry is forced down the casing and up towards the top of the well, from the bottom of the casing, between a wall of the drill hole and the casing, forming the surface casing of the well .

In one aspect, the present invention provides a surface casing unit for forming a surface casing for a well. Where the well normally has a drill hole that has been drilled by a larger drill bit, for example a 30cm drill bit is often used, although larger, and smaller drill bits can also be used. The hole is drilled to a suitable depth, such a depth could be between 100 and 200 meters for example, although the depth can also be more or less than this. A casing is normally lowered_. into the drill hole. Usually if a drill bit around 30cm in diameter is used, a casing with a 20cm diameter would be used. Such a casing can be fitted with a non-return valve such as a cement shoe which is made of softer material, such as concrete or plastics or the like, to enable subsequent drilling through the cement shoe.

A fitting is normally attached to the top of the casing to allow slurry and other liquids to be pumped into the casing, such a fitting can be a cementing head which has at least one inlet, or can have multiple inlets for the slurry or other liquids. The fitting such as the cementing head, may also include a rubber plug or the like to provide an interface between the slurry and the liquid or liquids. Such an interface is normally made of a softer material to enable subsequent drilling through the interface. Slurry such as cement, concrete, resins or the like is normally pumped or otherwise forced down through the casing, out a bottom end through the non-return cement shoe (if present) and up towards the top of the well, between a wall of the drill hole and the casing. Once the slurry has been pumped or otherwise inserted into the casing, a fluid can be pumped or otherwise inserted into the casing to force the slurry down the casing, normally with an interface such as a rubber plug between the slurry and the fluid. Normally enough slurry is provided to fill the volume between the wall of the drill hole and the casing. Once the slurry has cured and created a surface casing, the surface casing is ready to receive a smaller drill bit through the casing and drill down to production depth.

In one embodiment, the surface casing unit is part of a vehicle. Such an arrangement can be similar in size to a standard cement mixer, or can be a larger truck and trailer type setup or the like, or a smaller setup that can fit into a van or such. However, such a smaller setup would limit the amount of slurry that can be carried in a mixing bowl. The surface casing unit can also be a platform-type unit that can be lifted onto and off a trailer or the like. The surface casing unit can also be a trailerable unit that can be towed by a vehicle.

In another embodiment the surface casing unit has at least one high pressure pump which pumps the slurry and one high pressure pump that pumps the fluid. Typically, the at least one high pressure pump that pumps the slurry and the high pressure pump that pumps the fluid are one and the same and can be capable of switching between slurry and fluid. Additionally, the surface casing unit has one pump for slurry and a separate pump for fluid.

Another possible configuration is for the surface casing unit to have one low pressure pump which can initially pump the slurry and another high pressure pump which can pump the slurry when a higher pressure is required. In this case, the high pressure pump may also be the high pressure pump for the fluid or an additional high pressure pump may be used for the fluid. The pump or pumps of the surface casing unit can also be electronically controlled to vary such parameters as speed, pressure and volume. The pum or pumps can also be run hydraulieally, pneumatically, electrically and/or directly by an engine. In one embodiment, the well may be tested by fluid such as water being pumped by the high pressure fluid pump. This can test for leaks prior to beginning the process of forming the surface casing and ensure that the well is capable of receiving slurry. Additional an air-powered pump could also be used to conduct this testing and/or to test the fitting for leaks or the like. An advantage of using an air-powered fluid pump is that the pump will stall at a maximum set pressure depending on the air supply set pressure, so over-pressuring of the well is prevented. The fluid can also be used to force the slurry down the casing. Additionally, the fluid can be used to test the surface casing once the slurry has cured. During the testing stages, a drop in pressure of the fluid can indicate that there is a leak or some other type of problem. The fluid can be supplied externally via a hose or pipe or some other means or the surface casing unit can include a fluid tank capable of containing a required amount of fluid. The fluid pumped by the high pressure fluid pump may also be used to clean equipment.

In another embodiment, the surface casing unit can contain at least one blow out preventer and/or at least one non return valve. The at least one blow out preventer and/or at least one non return valve is preferably positioned after the outlet for the at least one high pressure pump which pumps the slurry and the outlet for the high pressure pump that pumps the fluid.

Alternatively the at least one blow out preventer and/or at least one non return valve can be located between the outlets of the at least one high pressure pump which pumps the slurry and the outlet for the high pressure pump that pumps the fluid. If the pump for the slurry and the fluid is one and the same, the at least one blow out preventer and/or at least one non return valve can be positioned after the outlet of the pump. The at least one blow out preventer and/or at least one non return valve can be used to protect the pump or pumps from blow out or fracturing pressures or other pressure variations. Other fittings on the surface casing unit and/or between the surface casing unit and the well can also be rated to higher pressures, such higher pressures can be above 100 bar, and typically up to 330 bar for surface casing leak tests. In one embodiment, the. flow and/or pressure of the pump and/or pumps can be monitored by a computer by flow and/or pressure sensors. The computer can also control the pump and/or pumps depending on the values of the flow and/or pressure sensors. For example if the pressure spikes due to plug stopping, the computer can determine if the plug is at the bottom of the casing and not stuck somewhere else, the computer can then control the pump and/or pumps accordingly either stopping the pump and/or pumps or continuing or altering the pump and/or pumps. The computer may also report and/or graph the values for the flow and/or pressure sensors for a job.

In another embodiment, the mix bowl can be the size and configuration of a standard cement truck mixer bowl. It is also envisaged that the mix bowl can be larger than a standard cement truck mixer bowl to allow for larger surface casing jobs. The mix bowl can also be smaller than a standard cement truck mixer bowl such that the surface casing unit can be optimised for smaller surface casing jobs. The mix bowl can also have different configurations to allow for different types of slurries to be mixed.

In one embodiment, one or more temperature sensors may be used to check the temperature of the slurry in the mix bowl and/or in other locations. Normally a temperature sensor such as an infra-red sensor would be used to measure the slurry in the mix bowl from outside the mix bowl to ensure that the sensor stays clean. Alarms can also be triggered when certain pre-set temperatures are encountered, for example if a certain temperature is sensed, an operator could be alerted to use the slurry immediately or to dump the slurry before the slurry is able to cause damage to the surface casing unit by setting solid. The temperature sensor may also be protected from the elements by fitting a protective cover through which the temperature sensor can operate. The protective cover may be air-purged by a flow of air to prevent being obscured by cement dust and/or spray or the like. The computer may also be able to report and/or graph the values for the temperatures for a job. For remote locations, additives can be added to the slurry to control the onset of curing.

The pumping pressures, test-pressures, pressure leak-off rate and/or flow rates may be recorded graphically by the Surface Casing unit to provide a record of the satisfactory and safe conduct of the job. The temperature of the cement slurry within the mixer bowl may be monitored to ensure that premature set-off of the pre-mixed slurry within the Surface Casing Unit mixer bowl does not commence before the mixture is pumped down the well, otherwise well damage and equipment damage could occur.

In another embodiment, the surface casing unit can include safety features such as spark arrestors fitted to the exhaust and the like, an air start system for engines instead of an electric start system, lights, signage and remote stop buttons and the like. The pump and/or pumps may also be configured to stall at a safe pressure to avoid dangerous over-pressure situations or the like. The pump and/or pumps may also be modified to conform with transport or other safety regulations and the like. Additional blow out preventers and/or non return valves may also be used in other equipment and/or locations that are prone to high pressure. The surface casing process may also be computer monitored and/or controlled for additional safety.

In one embodiment, some parts of the surface casing unit such as the control and work areas and the like may be fitted with canvas shelter clip-ons or the like to provide protection from the elements amongst others. The surface casing unit may also include work area lighting to enable night work and work in low light conditions. An operators "overview" platform may be provided at the rear of the truck to allow an operator to overlook the pump, to see if it is correctly filling, and to control aspects of the operation from there. Typically, if an operators platform is provided, it will be installed on one side of the truck, overlooking the pump hopper and the fill chute. Preferably if an operators platform is provided, it will be installed on right hand rear side of the truck. Such an operators platform may require an outlet chute between the mix bowl discharge and the slurry pump to be fixed in position. Alternatively the outlet chute may be fixed in position if an operators platform is not present. An advantage of fixing the outlet chute is that the outlet chute can be shielded against spillage.

In another aspect, the invention provides a method for forming a surface casing for a well including a drill hole, a casing in the drill hole to define a space between the drill hole and a outer surface of the casing and a cementing head, the method including the steps of providing a surface casing unit comprising a settable slurry container, at least one high pressure pump associated with the settable slurry container to pump at least part of a settable slurry into the casing, and at least one high pressure pump capable of pumping, a fluid into the casing, pumping the settable slurry using the at least one high pressure pump through the cementing head and into the casing, providing an interface on an upper portion of the settable slurry in the casing, pumping the fluid using the at least one high pressure pump capable of pumping a fluid into the cementing head to apply a force onto the interface to force the settable slurry downwardly through the casing and back upwardly through the space between the drill hole and an outer surface of the casing,, and allowing the settable slurry to set to form the surface casing of the well.

Some benefits of the surface casing unit of the present invention may include the following:

1. Reduced costs;

2. No need for separate rig pumps or pumping trailers;

3. Greater control over the properties of the cement;

4. Safer and easier operation;

5. Monitoring of process to avoid ruined wells;

6. Ability to operate under most conditions;

7. Ability to operate at remote locations; and

8. Testing of the well before and after surface casing.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:

Figure 1 shows a prior art common concrete mixer truck using separate rig pumps.

Figure 2 shows a prior art specialised oil/gas well cementing unit.

Figure 3 shows a prior art bulk cement powder tanker.

Figure 4 shows a drill hole of a well.

Figure 5 shows a casing in the drill hole.

Figure 6 shows a cementing head.

Figure 7 shows the slurry being pumped into the well.

Figure 8 shows liquid being pumped into the well. Figure 9 shows a conception of a surface casing unit.

Figures 10-12 show a high pressure slurry pump.

Figures 13-16 show a surface casing unit mounted on a vehicle.

BEST MODE

With reference to Figure 1, there is shown prior art, a common concrete mixer truck 10 adding slurry to a separate rig pump 12 which pumps the slurry into a cementing head 14, a pumping trailer 18 includes a water tank 16 for water that will be pumped into the cementing head 14.

Figure 2 shows a prior art specialised oil/gas well cementing unit 20, which blends cement powder with water and additives before pumping the slurry into a well, the specialised oil/gas well cementing unit 20 also needs to be supported by a bulk cement powder tanker 22 as shown in figure 3.

Figure 4 shows a well 24 and a drill hole 26 drilled by a drill bit 28.

Figure 5 shows a casing 30 in the drill hole 26, a cement shoe 32 is fitted to the bottom of the casing 30, the cement shoe 32 is a none return valve to prevent slurry from coming back through the cement shoe 32, made of plastic or cement so that the well 24 can be drilled later with a smaller bit down to production depths.

Figure 6 shows a cementing head 34 fitted to the top of the casing 30, the cementing head 34 has a slurry valve 36 to allow slurry to enter the cementing head 34, a fluid valve 38 to allow a fluid to enter the cementing head 34, a rubber plug 40 is pre-fitted in the. Cementing head 34 between the slurry valve 36 and the fluid valve 38 and held in position by a retainer bar 42.

Figure 7 shows slurry 44 being pumped under pressure through the slurry valve 36, into the cementing head 34, down the casing 30, through the non-return cement shoe 32 and up towards the top of the well 24, between a wall 46 of the drill hole 26 and the casing. Once the required amount of slurry 44 has been pumped into the cementing head 34, the slurry valve 38 is closed and the retainer bar 42 is removed so that a fluid can be pumped into the cementing head 34. Figure 8 shows the fluid 48 forcing the rubber plug 40 and the slurry 44 down the casing and through the non-return cement shoe 32. Once the rubber plug 40 has reached the bottom of the casing 30, the volume between- the drill hole 26 and the casing 30 is filled with slurry 44, and the casing 30 is filled with fluid 48. Once the slurry 44 has cured and created a surface casing 50, the fluid 48 is pressurised to test the surface casing 50. A smaller drill bit (not shown) can now be lowered down the casing 30 and drill down to production depth.

Figure 9 shows a surface casing unit 52 mounted on a vehicle 54, the mixing bowl 56 contains the slurry for a surface casing, the slurry is discharged from the mixing bowl 56 via a discharge chute 58 into the hopper 60 of the high pressure slurry pump 62, once the slurry has been pumped into a cementing head (not shown), a liquid, in this case water from the water tank 64 is pumped into the cementing head by a high pressure pump (not shown), which is used to test the well (not shown) before the slurry is pumped into it, to force the slurry down a casing (not shown) and to test the surface casing (not shown) once the slurry has cured. A Non-return valve or blow back preventer (not shown) is located on the outlet side of the high pressure slurry pump 62 to prevent a kick-back pressure from reaching back into the high pressure slurry pump 62.

Figures 10 to 12 show a high pressure slurry pump 66 that has been modified to satisfy transport regulations such as overhang and width when mounted to the rear of a vehicle. A non return valve (not shown) is fixed to the outlet pipe 68.

Figures 13-16 show a surface casing unit 52 mounted on a vehicle 54. An operators platform 72 is mounted above the high pressure slurry pump 62 to give an operator 80 (as seen in figures 15 and 16) a view into the hopper 60, Control panels 70 are mounted to the operators platform 72 such that the operator 80 can control certain aspects of the process. Lights 74 are provide such that the process can be conducted in low light conditions, such as during the night.

The foregoing embodiments are illustrative only of the principles of the invention, and various modifications and changes will readily occur to those skilled in the art. The invention is capable of being practiced and carried out in various ways and in other embodiments. It is also to be understood that the terminology employed herein is for the purpose of description and should not be regarded as limiting.

In the present specification and claims, the word "comprising" and its derivatives including "comprises" and "comprise" include each of the stated integers but does not exclude the inclusion of one or more further integers.

Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearance of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more combinations.

Claims

CLAIMS:

1. A surface casing unit for forming a surface casing for a well, the well initially including a drill hole, a casing in the drill hole to define a space between the drill hole and an outer surface of the casing and a cementing head, the surface casing unit comprising:

a. a mix bowl containing a settable slurry;

b. at least one high pressure pump associated with the mix bowl to pump at least part of the settable slurry into a surface casing; and c. at least one high pressure pump capable of pumping a fluid into a surface casing;

wherein the settable slurry is pumped by the at least one high pressure pump through the cementing head and into the casing, when the settable slurry has been pumped through the cementing head, the fluid is pumped by the at least one high pressure pump capable of pumping a fluid into the cementing head pushing on an interface on the settable slurry, the settable slurry is forced down the casing and up towards the top of the well, from the bottom of the casing, between a wall of the drill hole and the casing, forming the surface casing of the well.

2. A surface, casing unit as claimed in claim 1 further comprising a non-return valve or a blow out preventer on the outlet side of at least one of the high

. pressure pumps.

3. A surface casing unit as claimed in any one of the preceding claims wherein the at least one high pressure pump capable of pumping a fluid and the at least one high pressure pump associated with the mix bowl to pump at least part of the settable slurry is the same.

4. A surface casing unit as claimed in any one of the preceding claims wherein the at least one high pressure pump capable of pumping a fluid and the at least one high pressure pump associated with the mix bowl to

. pump at least part of the settable slurry are separate.

5. A surface casing unit as claimed in any one of the preceding claims wherein at least one low pressure pump is used to pump the settable slurry initially and the at least One high pressure pump associated with the mix bowl to pump at least part of the settable slurry is used when high pressure is required to pump the settable slurry.

6. A surface casing unit as claimed in any one of the preceding claims wherein the pressure and/or flow rate of the fluid and/or the settable slurry is monitored.

7. A surface casing unit as claimed in any one of the preceding claims wherein the surface casing unit is part of a vehicle.

8. A surface casing unit as claimed in claim 7, wherein the vehicle is a cement truck.

9. A surface casing unit as claimed in any one of the preceding claims further comprising a test pump to test fittings and/or the well for leaks or the like.

10. A surface casing unit as claimed in claim 9, wherein the test pump is an air-powered pump.

1 1. A surface casing unit as claimed in any one of the preceding claims further comprising an operators platform, from which an operator can oversee and/or control the surface casing unit.

12. _, A method for forming a surface casing for a well including a drill hole, a casing in the drill hole to define a space between the drill hole and an outer surface of the casing and a cementing head, the method including the steps of:

providing a surface casing unit comprising a settable slurry container, at least one high pressure pump associated with the settable slurry container to pump at least part of a settable slurry into the casing, and at least one high.pressure pump capable of pumping a fluid into the casing, pumping the settable slurry using the at least one high pressure pump through the cementing head and into the casing,

providing an interface on an upper portion of the settable slurry in the casing.

pumping the fluid using the at least one high pressure pump capable of pumping a fluid into the cementing head to apply a force onto the interface to force the settable slurry downwardly through the casing and back upwardly through the space between the drill hole and an outer surface of the casing, and

allowing the settable slurry to set to form the surface casing of the well.

13. A method as claimed in claim 12, further including the step of providing a non-return valve or a blow out preventer on the outlet side of at least one of the high pressure pumps.

14. A method as claimed in claim 12 or 13, further including the step of monitoring the pressure and/or flow rate of the fluid and/or the settable slurry.

15. A method as claimed in claim 12, 13 or 14, wherein the step of pumping the settable slurry and the step of pumping the fluid is performed by the same high pressure pump.

16. A method as claimed in claim 12, 13, 14 or 15, further including trie step of providing a test pump to test fittings and/or the well for leaks or the like.

17. A method as claimed in claim 12, 13, 14, 15 or 16 further including the ste of providing a low pressure pump to pump at least part of the settable slurry into the casing.

18. A surface casing unit substantially as described herein with reference to figures 4 to 16.