WO2013014434A2

WO2013014434A2 - Particulate material delivery method and system

Info

Publication number: WO2013014434A2
Application number: PCT/GB2012/051757
Authority: WO
Inventors: William Harden
Original assignee: Clyde Union Limited
Priority date: 2011-07-25
Filing date: 2012-07-23
Publication date: 2013-01-31
Also published as: WO2013014434A3; GB201112754D0

Abstract

A method for delivering a particulate material into a wellbore comprises pumping a carrier fluid into a delivery conduit which is in communication with a wellbore, loading particulate material into a vessel, and driving the particulate material from the vessel and into the delivery conduit at a location which is downstream of the pumping system.

Description

PARTICULATE MATERIAL DELIVERY METHOD AND SYSTEM

FIELD OF THE INVENTION

The present invention relates to a method and system for use in delivering a particulate material into a wellbore within a fluid carrier.

BACKGROUND TO THE INVENTION

Natural resources, such as oil, gas, water and the like contained in subterranean formations are typically accessed by drilling a wellbore to intercept the formation and provide a production conduit to surface via appropriate completion and production equipment. It is also known in the art to utilise a drilled wellbore to inject fluids into a subterranean formation, such as a targeted formation with desired geology, or a formation which has been depleted of natural resources through previous production operations. Such injection of fluids may be used in the sequestration of carbon dioxide, disposal of previously produced water or the like.

In many wellbore operations there is a requirement to deliver particulate or granular material into the wellbore and/or formation. Such particulate material may be used in the treatment of a wellbore and/or formation or to form part of wellbore architecture. For example, granular material, which may include sand, gravel, ceramic beads, glass beads, drill cuttings, nut shells and the like, may be used (among others) in hydraulic fracturing of a formation, as lost-circulation material during drilling and to create gravel packs. Such exemplary uses are described in further detail below.

Hydraulic fracturing, or tracing, of a formation is a well known technique used to increased production into the wellbore, or permit increased injection rates from the wellbore. Fracturing may be used in formations with a naturally low permeability or where permeability has reduced over time, for example due to formation compression following extraction of oil, gas, water or the like. Of particular interest is the hydraulic fracturing of shale formations, which typically contain hydrocarbon gas. Shale formations are extremely impermeable and without treatment the extraction of contained resources is difficult and often deemed not viable.

Hydraulic fracturing involves creating or enhancing fractures in the formation which propagate outwardly from the wellbore in order to increase the effective production/injection surface area. Fracturing is achieved by a high pressure fluid which is delivered from surface via the wellbore and which carries a particulate material called a proppant which is accumulated within the fractures to hold or prop these open after hydraulic pressure is relieved.

Lost-circulation material is typically used during drilling operations to seal regions of the surrounding rock which are extremely permeable or which have a local pressure which can cause expensive drilling fluids, generally known as drilling mud, to be lost into the formation, rather then being recirculated back to surface for treatment and re-use. The lost-circulation material is delivered into the wellbore suspended within the drilling mud.

Gravel packing is used to establish an effective filter region at the formation/wellbore interface to prevent the production of sand. Typically, screens are located within the wellbore as part of a completion and gravel is delivered and packed behind or within these screens to define, effectively, a media filter.

In the examples provided above it is necessary to deliver the particulate material into the well, and in some cases also into the formation. Also, delivery may be required at extremely high pressures, such as in the case of hydraulic fracturing where the fracture gradient of the formation rock must be exceeded, perhaps requiring pressures in excess of 690 bar (10,000 psi). However, the abrasive nature of the particulate material, and any requirement to establish these high pressures makes handling extremely challenging. Typically, particulate material is mixed with a carrier fluid, such as water, and the mixture or slurry is then delivered into the well at the required pressure via a pumping system. This arrangement exposes the pumping system to the particulate material such that damage, for example erosion, is inevitable.

Due to a lack of alternative solutions, damage to pumping systems has become accepted in the art, particularly in fracturing operations. For example, known fracturing methods involve the use of frac pumps, typically positive displacement pump units such as reciprocating pumps, which are accepted in the art as expendable or sacrificial. This sacrificial use continues to be accepted due in part to the fact that reciprocating pumps are widely available and are quite traditional in the oil and gas industry as high pressure fluid service pumps. However, such reciprocating pumps are, by their nature, low volume displacement machines which necessitates parallel operation of multiple units to meet overall fluid flow rate requirements. Such use of multiple units may be extremely undesirable due to the footprint requirement at the production facility where space is usually at a premium.

Furthermore, many operations may require very specific dimensions or grade of particulate material, such as in the case of gravel packing, for example. However, the process of pumping such particulate material, for example as part of a slurry, may result in modification to the particulate dimensions which could adversely effect end use. SUMMARY OF THE INVENTION

Aspects of the present invention, generally, may permit a particulate material to be delivered into a wellbore without or with minimised exposure to pumping equipment, thus limiting or eliminating damage to such equipment. Furthermore, aspects of the invention may permit appropriate delivery volumes and flow rates to be achieved within a reduced equipment footprint.

According to a first aspect of the present invention there is provided a method for delivering a particulate material into a wellbore, comprising:

delivering a carrier fluid which is substantially free from particulate material to an inlet of a pumping system;

delivering the carrier fluid at an increased pressure from an outlet of the pumping system into a delivery conduit which is in communication with a wellbore; loading particulate material into a vessel; and

driving the particulate material from the vessel and into the delivery conduit at a location which is downstream of the pumping system.

As the particulate material is driven or injected into the delivery conduit downstream of the pumping system which is used to pressurise the carrier fluid, said pumping system may be isolated from any exposure and thus potential damage from the particulate material. Accordingly, the problems associated with pumping particulate material directly with the carrier fluid are eliminated, which may eliminate the requirement to utilise pumps and associated equipment in a sacrificial manner.

In some embodiments the particulate material may be driven from the vessel using a drive fluid.

Using a drive fluid to drive the particulate material from the vessel and into the delivery conduit may further remove or minimise the requirement to pump the particulate material.

The drive fluid may eject the particulate material from the vessel. That is, the drive fluid may be communicated into the vessel to eject the particulate material therefrom. The drive fluid may define a motive fluid for an eductor which entrains the particulate material from the vessel. In such an arrangement the drive fluid may not be communicated into the vessel.

In some embodiments the particulate material may be assisted in being driven from the vessel, for example by a mechanical arrangement, such as an auger device, slurry pump or the like. Such an arrangement may be utilised to deliver the particulate material into a stream of drive fluid, such as into an eductor which is operated by the drive fluid.

The method may comprise elevating the drive fluid pressure above the carrier fluid pressure. Such an arrangement may ensure that the particulate material may be communicated or injected into the delivery conduit. The method may comprise establishing a pressure differential between the drive fluid and carrier fluid to permit the drive fluid to drive the particulate material from the vessel and into the delivery conduit.

The method may comprise isolating the vessel from the delivery conduit while communicating the drive fluid into said vessel and establishing a desired pressure within the vessel with the drive fluid. Such a pressure may be defined as a static pressure. The desired pressure is preferably greater than the pressure of the carrier fluid within the delivery conduit. The method may comprise subsequently establishing communication between the pressurised vessel and the delivery conduit to cause the particulate material to be ejected from said vessel and into the delivery conduit.

The method may comprise establishing communication between the vessel and the delivery conduit while communicating the drive fluid into said vessel. In such an arrangement the drive fluid may flow through the vessel to eject or flush the particulate material from the vessel and into the delivery conduit. Also in such an arrangement the drive fluid may be communicated into the vessel at a desired pressure. The desired pressure may be greater than the carrier fluid pressure within the delivery conduit. The desired pressure of the drive fluid may be selected to account for any pressure loss by the flow of the drive fluid through the vessel.

The drive fluid may be driven via a pressurising apparatus, such as a compressor, pump or the like. The pressurising apparatus may comprise a rotodynamic pump, such as a centrifugal pump. The pressurising apparatus may comprise a positive displacement pump, such as a reciprocating pump. In some embodiments a centrifugal pump may be preferred to a reciprocating pump due to the greater flow rate capabilities of a centrifugal pump. The carrier fluid may comprise any fluid. The carrier fluid may comprise a gas, such as nitrogen, carbon dioxide or the like. In such an arrangement the pumping system may define a compressor system.

The carrier fluid may comprise a liquid. The carrier fluid may comprise water.

The carrier fluid may comprise a foam.

The carrier fluid may comprise a gel.

A drive fluid used to drive particulate material from the vessel may comprise any suitable fluid. The drive fluid may comprise a gas. In such an arrangement the gas may be compressed to define a desired drive fluid pressure. The drive fluid may comprise a liquid. The drive fluid may comprise water.

The carrier fluid and a drive fluid may comprise different fluids.

The carrier fluid and a drive fluid may comprise a common fluid. The carrier fluid and a drive fluid may be provided from a common source.

In some embodiments the carrier fluid and a drive fluid may be communicated through or along separate flow paths.

The carrier fluid may define the drive fluid.

The vessel may be provided in-line with the delivery conduit at a location downstream of the pumping system. In such an arrangement the carrier fluid may be communicated through the vessel to eject particulate material therefrom and thus function as or define a drive fluid.

In some embodiments the particulate material may be driven from the vessel and into the delivery conduit using a mechanical arrangement or means. For example, the particular material may be pumped from the vessel, for example via a solids pumping arrangement, such as a solids slurry pump. The particulate material may be positively displaced from the vessel by a mechanical component, such as via a piston, auger, or the like.

Although in some embodiments, as defined above, mechanical means may be utilised to drive the particulate material from the vessel, the pumping system used to pressurise the carrier fluid is still protected from exposure to this particulate material. This may permit a more specialised pumping system to be used to pressurise the carrier fluid, such as a compact pumping system, high pressure pumping system or the like, without having to take account of the effect of particulate material on such a pumping system.

In some embodiments the particulate material may be driven from the vessel by a combination of a drive fluid and a mechanical arrangement or means. The method may comprise isolating the vessel from the delivery conduit while loading particulate material into the vessel. The method may comprise subsequently establishing communication between the vessel and delivery conduit to permit the drive fluid to drive the particulate material into the delivery conduit.

The method may comprise cyclically:

isolating the vessel from the delivery conduit;

loading the particulate material into the vessel; and

establishing communication once again between the vessel and the delivery conduit to permit the particulate material to be driven or injected into said delivery conduit.

The pumping system may comprise one or more positive displacement pumps, such as reciprocating pumps. The pumping system may comprise one or more rotodynamic pumps, such as centrifugal pumps. Although in some embodiments reciprocating pumps may be of utility, in other embodiments centrifugal pumps may be preferred due to their higher flow rate capabilities. That is, for a given flow rate requirement it is understood that a greater number of reciprocating pumps would be required than centrifugal pumps. Accordingly, using one or more centrifugal pumps in the present invention permits equipment footprint to be minimised, which can be extremely desirable in wellbore applications.

In some embodiments a single vessel may be provided.

The vessel may define a fixed internal volume.

The vessel may define a pressure vessel.

A plurality of vessels may be provided. In such an arrangement the method may comprise loading particulate material into a plurality of vessels, and driving the particulate material from each vessel and into the delivery conduit.

The method may comprise driving particulate material from different vessels simultaneously.

The method may comprise driving particulate material from different vessels in a temporal sequence. Such a temporal sequence may permit a substantially continuous delivery of particulate material to be achieved. For example, one vessel may be loaded with particulate material while particulate material is being driven from another vessel and into the delivery conduit. The method may comprise cyclically driving particulate material from different vessels. The step of driving particulate material from one vessel may proceed the step of driving particulate material from another vessel. That is, there may be no temporal overlap between ejection from different vessels. The step of driving particulate material from one vessel may partially coincide or occur simultaneously with the step of driving particulate material from another vessel. That is, there may be a temporal overlap between ejection from different vessels.

The method may comprise loading the particulate material from a solids handling system. The solids handling system may comprise a particulate material storage arrangement, such as a tank, hopper and/or the like. The solids handling system may comprise a conveying system for delivering the particulate material from the storage system to the vessel.

The method may comprise driving the particulate material from the vessel and into the delivery conduit at a location which is above a wellhead.

The method may comprise driving the particulate material from the vessel and into the delivery conduit at a location which is below a wellhead.

The method may comprise driving the particulate material from the vessel and into the delivery conduit at the location of a wellhead.

The particulate material may comprise or define a proppant. In such an arrangement the method may be for use in fracturing a subterranean formation. Also in such an arrangement the carrier fluid may define a hydraulic fracturing fluid.

The method may comprise fracturing a subterranean formation with the carrier fluid and propping the fractured formation with the particulate material. The subterranean formation may comprise a shale formation.

The particulate material may define a lost circulation material. In such an arrangement the carrier fluid may comprise or define a drilling fluid.

The particulate material may define a filtering or gravel media. In such an arrangement the method may be for use in establishing one or more gravel packs within a wellbore.

The method may comprise mixing one or more chemicals with the carrier fluid. Such mixing may be achieved by injecting a chemical into the carrier fluid. Chemical injection may occur downstream of the pumping system. Chemical injection may occur upstream of the pumping system. Chemicals such as stabilisers, acids and the like may be used.

The particulate material may comprise a trace component permitting the location of the particulate material to be identified, for example after delivery into a wellbore. Such a trace component may comprise a radioactive trace component. The particulate material may be of any desired form. For example, the particulate material may comprise any one or combination of sand, gravel, ceramic beads, glass beads, drill cuttings, nut shells and the like.

The pumping system may comprise one or more pumps such as described in GB 2379718, the disclosure of which is incorporated herein by reference.

According to a second aspect of the present invention there is provided an apparatus for use in delivering a particulate material into a wellbore, comprising:

a pumping system configured to pump a carrier fluid through a delivery conduit; and

a vessel for receiving a particulate material and being in communication with the delivery conduit downstream of the pumping system;

wherein in use particulate material is driven from the vessel and into the delivery conduit.

The apparatus according to the second aspect may be configured for use in carrying out the method according to the first aspect.

According to a third aspect of the present invention there is provided a method for delivering a particulate material into a wellbore, comprising:

delivering the carrier fluid at an increased pressure from an outlet of the pumping system into a delivery conduit which is in communication with a wellbore; and injecting a particulate material into the delivery conduit at a location which is downstream of the pumping system without exposing the particulate material to a working component of the pumping system.

The step of injecting the particulate material may be achieved without exposing the particulate material to a working component of any pump.

According to a fourth aspect of the present invention there is provided a method for fracturing a subterranean formation, comprising:

delivering a hydraulic fracturing fluid which is substantially free from particulate material to an inlet of a pumping system;

delivering the fracturing fluid at an increased pressure from an outlet of the pumping system into a delivery conduit which is in communication with a wellbore; loading proppant material into a vessel;

driving the proppant material from the vessel and into the delivery conduit at a location which is downstream of the pumping system; and delivering the fracturing fluid and proppant into a wellbore to fracture a formation.

According to a fifth aspect of the present invention there is provided a method for delivering a particulate material into a wellbore, comprising:

Other aspects of the present invention may relate to drilling a wellbore, for example using lost circulation material within drilling mud.

Other aspects of the present invention may relate to installing or forming a gravel pack within a wellbore.

It should be understood that one or more features defined in relation to one aspect may be applied to any other aspect.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a diagrammatic illustration of a particulate delivery system and method in accordance with an embodiment of the present invention;

Figure 2 is a diagrammatic illustration of a particulate delivery system and method in accordance with an alternative embodiment of the present invention;

Figure 3 is a diagrammatic illustration of a particulate delivery system and method in accordance with a further alternative embodiment of the present invention; and

Figure 4 is a diagrammatic illustration of a portion of a particulate delivery system in accordance with a further alternative embodiment of the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

The present invention generally relates to methods and systems for delivering particulate material into a wellbore, and may thus be used in numerous applications, such as in drilling applications, completion applications, workover applications, stimulation applications and the like. However, in the following embodiments the exemplary application of fracturing a subterranean formation, such as a shale formation, is illustrated.

Reference is initially made to Figure 1 in which there is shown diagrammatic illustration of a system or apparatus, generally identified by reference numeral 10, for delivering a particulate material, specifically a proppant, into a well bore 12 within a carrier fluid, specifically a hydraulic fracturing fluid, to be used in fracturing a subterranean formation (not illustrated). Generally, the apparatus 10 includes a pumping system 14 for pumping the carrier fluid along a delivery conduit 16 which is in communication with the well bore 12, a solids handling system 18 for handling and appropriately treating particulate material, and a particulate material injection system 20 for injecting the particulate material into the delivery conduit 16 at a location which is downstream of the pumping system 14. As such, the pumping system 14 is not exposed to the particulate material.

The pumping system 14 comprises a plurality of centrifugal pump units 22 (only two shown, but more or less are possible) which receive the carrier or fracturing fluid, for example water, from a storage tank 24 and a suitable transfer pump 26. The use of centrifugal pumps 22 within the pumping system 14 is particularly advantageous as high pressures, for example in excess of 690 bar (10,000psi) may be achieved while providing suitably high flow rates, for example around 540 m³/h (1 bbl/min). Such a combination of high pressures and flow rates can be provided by a minimal number of centrifugal pumping units 22, as opposed to, for example, more conventional pumps used in the art, such as reciprocating pumps. Accordingly, equipment footprint can be minimised, which is extremely desirable in a typical production environment. The pumping system 14 may comprise one or more pumps such as described in GB 2379718, the disclosure of which is incorporated herein by reference.

A chemical injection system 27 may be provided for injecting appropriate chemicals, such as stabilisers, acids and the like, into the carrier fluid. Although the injection system is shown located downstream of the pumping system 14 this need not always be the case.

The particulate material handling system 18 includes a storage facility 28 which feeds particulate material, or proppant, to a conveying device 30 which delivers the particulate material to the particulate injection system 20.

The particulate material injection system 20 includes a plurality of vessels 32a, 32b arranged in parallel and which are capable of being filled with particulate material, or proppant, from the handling system 18, via respective valves 34a, 34b. Although two vessels 32a, 32b are illustrated, more or less may be provided. Each vessel 32a, 32b is in communication with a feed line 36 and ultimately the delivery conduit 16 via respective valves 38a, 38b. A source 40 of pressurised fluid is in selective communication with each vessel 32a, 32b and in use delivers high pressure fluid into the vessels 32a, 32b which thus become pressurised. Although separate sources 40 of pressurised fluid are illustrated, a single source may be provided. The source 40 of fluid may comprise a gas, such as nitrogen, carbon dioxide or the like, or a liquid, such as water. As will be described below, the pressurised fluid functions as a drive fluid and ejects the particulate material from each vessel 32a, 32b. More specifically, the vessels 32a, 32b are pressurised to a higher pressure than the delivery conduit 16 such that the driving force for the particulate material is provided by a pressure differential.

In use, one vessel 32a is filled with particulate material via valve 34a, while associated valve 38a remains closed. Once the vessel 32a is appropriately filled valve 34a is closed and the vessel 32a is pressured by fluid source 40. As noted above, the vessel 32a is pressured to a higher pressure than the delivery conduit 16. Valve 38a is then opened and the effect of the pressure differential ejects the particulate material into the feed line 36 and the delivery conduit 16 to thus be mixed with the carrier fluid and carried into the wellbore 12. While particulate material is being ejected from vessel 32a, vessel 32b is being filled and pressurised. Cyclically operating the vessels 32a, 32b in this manner may permit particulate material to be continuously injected into the delivery conduit 16. In this respect, the particulate material injection system 20 may be configured to inject material at a rate of, for example, between 500 to 1 ,500 kg/min. Such a rate may be suitable for fracturing a shale formation.

Accordingly, in the embodiment described above the particulate material is ejected from the vessels 32a, 32b using a drive fluid. As such, the particulate material is not passed through a pump and thus the problems associated with pumping particulate material are eliminated, which may eliminate the requirement to utilise pumps and associated equipment in a sacrificial manner as is known and accepted in the art.

In the embodiment described above each vessel is closed following filling with particulate material and then pressurised, with the process of venting pressure resulting in injection of the stored particulate material into the delivery conduit. However, in other embodiments the particulate material may be flushed from each vessel using a flowing stream of drive fluid. Such an embodiment is illustrated in Figure 2, reference to which is now made. It should be understood that the arrangement shown in Figure 2 is similar to that shown in Figure 1 and as such like components share like reference numerals, incremented by 100.

In Figure 2 the apparatus, generally identified by reference numeral 1 10, includes a pumping system 1 14, a particulate material handling system 1 18 and a particulate material injection system 120. Pumping system 1 14 and handling system 1 18 are similar to the corresponding systems of Figure 1 and as such no further description will be provided.

Particulate material injection system 120 includes a plurality of vessels 132a,

132b (only two shown) arranged in parallel. Each vessel 132a, 132b receives particulate material from the handling system 1 18 via respective valves 134a, 134b. Further, each vessel 132a, 132b is in communication with a drive fluid supplied from a storage tank 50 and a pump 52 (more than one pump may be used) and delivered via respective valves 54a, 54b. Although a separate storage tank 50 is illustrated, the drive fluid may be supplied from tank 124 which feeds the pumping system 1 14. Each vessel 132a, 132b is in communication with a feed line 136 and delivery conduit 1 16 via respective valves 138a, 138b.

In use, one vessel 132a is filled with particulate material via valve 134a, while associated valves 54a, 138a remain closed. Once the vessel 132a is appropriately filled valve 134a is closed and valves 54a, 138a are opened to permit the drive fluid to flow through the vessel 132a and flush the particulate material into the feed line 136 and the delivery conduit 1 16 to be mixed with the carrier fluid from the upstream pumping system 1 14. While particulate material is being ejected from vessel 132a, vessel 132b is being filled, and cyclically operating the vessels 132a, 132b may permit particulate material to be continuously injected into the delivery conduit 1 16. It should be noted that the drive fluid is delivered at a pressure above that of the carrier fluid within the delivery conduit 1 16, taking into account of any pressure drop as the drive fluid flows through the vessels 132a, 132b.

In the embodiment illustrated in Figure 2 the drive fluid and carrier fluids are delivered through separate flow paths and mixed at some pint along the delivery conduit 1 16 downstream of the pumping system 1 14. However, in other embodiments it is possible to utilise the carrier fluid from the pumping system as a drive fluid to drive particulate material from a particulate material injection system. Such an embodiment is illustrated in Figure 3, reference to which is now made. It should be understood that the arrangement shown in Figure 3 is similar to that shown in Figure 2 and as such like components share like reference numerals, incremented by 100.

In Figure 3 the apparatus, generally identified by reference numeral 210, includes a pumping system 214, a particulate material handling system 218 and a particulate material injection system 220. Pumping system 214 and handling system 218 are similar to the corresponding systems of Figures 1 and 2 and as such no further description will be provided.

As will become apparent from the following description, particulate material injection system 220 is substantially identical to the injection system 120 of Figure 2, with the exception that in Figure 3 the injection system 220 is installed in-line with the delivery conduit 216 such that pressurised carrier fluid from the pumping system 214 also functions as the drive fluid.

Particulate material injection system 220 includes a plurality of vessels 232a, 232b (only two shown) arranged in parallel. Each vessel 232a, 232b receives particulate material from the handling system 218 via respective valves 234a, 234b. Further, each vessel 232a, 232b is in communication with the delivery conduit 216 upstream of the injection system 220 via respective valves 154a, 154b, and with the delivery conduit downstream of the injection system 220 via respective valves 238a, 238b.

In use, one vessel 232a is filled with particulate material via valve 234a, while associated valves 154a, 238a remain closed. Once the vessel 232a is appropriately filled valve 234a is closed and valves 154a, 238a are opened to permit the carrier/drive fluid to flow through the vessel 232a and flush the particulate material into the delivery conduit 216 to be delivered into well bore 212. While particulate material is being flushed from vessel 232a, vessel 232b is being filled, and cyclically operating the vessels 232a, 232b may permit particulate material to be continuously injected into the delivery conduit 1 16. Although not illustrated, in some embodiments some level of bypass facility may be provided to permit at least a proportion of the carrier fluid to bypass the injection system 220.

Reference is now made to Figure 4 in which there is shown a diagrammatic illustration of an apparatus or system, generally identified by reference numeral 310, in accordance with an embodiment of the present invention. The apparatus 310 of Figure 4 is largely similar to apparatus 10 shown in Figure 1 , and as such like features share like reference numerals, incremented by 300. Accordingly, apparatus 310 includes a pumping system 314, a particulate material handling system 318 and a particulate material injection system 320. Pumping system 314 and handling system 318 are similar to the corresponding systems of Figure 1 and as such no further description will be provided.

The injection system 320 includes a vessel 332 (only one vessel is illustrated, although a number may be provided, for example in a parallel configuration) which receives particulate material from the handling system 318 via inlet valve 334. The injection system 320 further includes an eductor 60 having a motive fluid port 62, a suction port 64 and an outlet port 66. The motive fluid port is in communication with a source 340 of drive fluid, such as water. The suction port 64 is in communication with an outlet of the vessel 332, via outlet valve 338. The outlet port 66 is in communication with the delivery conduit 316 via feed line 336. Further, the vessel 332 is configured to receive a fluid 68 which functions to fluidise the particulate material contained therein.

In use, valve 334 is opened and valve 338 is closed to permit the vessel 332 to be filled with particulate material from the handling system 318. Once the vessel 332 is filled valve 338 is opened to establish communication with the suction port 64 of the eductor. Drive fluid 340 is communicated to the motive port 62 of the eductor 60 resulting in particulate material being drawn or sucked through the eductor 60 and a mix of particulate material and drive fluid being delivered into the feed line 336 via outlet port 66. Fluid from the fluid source 68 is fed into the vessel 332 to fluidise the particulate material and assist entrainment from the vessel and through the eductor.

In some embodiments particulate material may be continuously fed into the vessel.

In some embodiments some form of mechanical assistance may be provided to drive particulate material from a vessel, such as an auger type device or the like. Such an arrangement could be provided in combination with any of the exemplary embodiments described above. For example, and auger type device could be provided within the vessel 332 of Figure 4 and assist to deliver the particulate material to the suction port 64 of the eductor 60.

It should be understood that the embodiments described above are merely exemplary and that various modifications may be made thereto without departing from the scope of the invention. For example, although the systems and methods described above are intended for use in a fracturing operation, other applications are possible, such as delivering a lost circulation material into a drilling mud, delivering gravel into a well bore for gravel packing and the like. Further, a combination of the different embodiments may be possible. For example, one vessel or group of vessels may be operated in the manner disclosed in, for example Figurel , and another vessel or group of vessels may be operated in the manner disclosed in, for example, Figure 2, 3 and/or 4. Also, in certain embodiments the particulate material may be ejected from the vessel or vessels using mechanical means, such as a solids slurry pump.

Claims

CLAIMS:

1 . A method for delivering a particulate material into a wellbore, comprising:

2. The method according to claim 1 , wherein the particulate material is driven from the vessel using a drive fluid.

3. The method according to claim 1 or 2, comprising communicating a drive fluid into the vessel to eject the particulate material therefrom.

4. The method according to claim 1 , 2 or 3, comprising educting the particulate material from the vessel.

5. The method according to any preceding claim, wherein a drive fluid defines a motive fluid for an eductor which entrains the particulate material from the vessel.

6. The method according to any preceding claim, comprising isolating the vessel from the delivery conduit while loading particulate material into the vessel.

7. The method according to claim 6, comprising subsequently establishing communication between the vessel and delivery conduit to permit the drive fluid to drive the particulate material into the delivery conduit.

8. The method according to any preceding claim, comprising cyclically:

isolating the vessel from the delivery conduit;

loading the particulate material into the vessel; and establishing communication once again between the vessel and the delivery conduit to permit the particulate material to be driven or injected into said delivery conduit.

9. The method according to any preceding claim, comprising elevating the pressure of a drive fluid used to drive the particulate material from the vessel above the carrier fluid pressure.

10. The method according to any preceding claim, comprising establishing a pressure differential between a drive fluid used to drive the particulate material from the vessel and carrier fluid to permit the drive fluid to drive the particulate material from the vessel and into the delivery conduit.

1 1 . The method according to any preceding claim, comprising isolating the vessel from the delivery conduit while communicating a drive fluid used to drive the particulate material from the vessel into said vessel and establishing a desired pressure within the vessel with the drive fluid.

12. The method according to claim 1 1 , comprising subsequently establishing communication between the pressurised vessel and the delivery conduit to cause the particulate material to be ejected from said vessel and into the delivery conduit.

13. The method according to any preceding claim, comprising establishing communication between the vessel and the delivery conduit while communicating a drive fluid into said vessel.

14. The method according to claim 13, wherein the drive fluid flows through the vessel to eject or flush the particulate material from the vessel and into the delivery conduit.

15. The method according to any preceding claim, wherein the pumping system comprises one or more centrifugal pumps.

16. The method according to any preceding claim, comprising driving a drive fluid used to drive the particulate material from the vessel via a pressurising apparatus.

17. The method according to any preceding claim, comprising providing the carrier fluid and a drive fluid used to drive the particulate material from the vessel from a common source.

18. The method according to any preceding claim, wherein the carrier fluid and a drive fluid used to drive the particulate material from the vessel are communicated through or along separate flow paths.

19. The method according to any preceding claim, wherein the carrier fluid defines a drive fluid used to drive the particulate material from the vessel.

20. The method according to any preceding claim, wherein the vessel is provided in-line with the delivery conduit at a location downstream of the pumping system and the carrier fluid is communicated through the vessel to eject particulate material therefrom.

21 . The method according to any preceding claim, wherein one vessel is provided.

22. The method according to any preceding claim, wherein a plurality of vessels are provided.

23. The method according to claim 22, comprising loading particulate material into a plurality of vessels, and driving the particulate material from each vessel and into the delivery conduit.

24. The method according to claim 22 or 23, comprising driving particulate material from different vessels simultaneously.

25. The method according to claim 22, 23 or 24, comprising driving particulate material from different vessels in a temporal sequence.

26. The method according to any one of claims 22 to 25, comprising cyclically driving particulate material from different vessels.

27. The method according to claim 26, comprising loading the particulate material from a solids handling system.

28. The method according to any preceding claim, comprising driving the particulate material from the vessel using a mechanical arrangement.

29. The method according to any preceding claim, comprising driving the particulate material from the vessel and into the delivery conduit at a location which is above, below or at a wellhead.

30. The method according to any preceding claim, wherein the particulate material comprises or defines a proppant.

31 . The method according to claim 30, wherein the carrier fluid comprises or defines a hydraulic fracturing fluid.

32. The method according to claim 31 , comprising fracturing a subterranean formation with the carrier fluid and propping the fractured formation with the particulate material.

33. The method according to claim 32, comprising fracturing a shale formation.

34. The method according to any preceding claim, wherein the particulate material comprises or defines a lost circulation material.

35. The method according to any preceding claim, wherein the particulate material comprises or defines a filtering or gravel media.

36. The method according to claim 35, comprising establishing a gravel pack within a wellbore.

37. An apparatus for use in delivering a particulate material into a wellbore, comprising:

a pumping system configured to pump a carrier fluid through a delivery conduit; and a vessel for receiving a particulate material and being in communication with the delivery conduit downstream of the pumping system;

38. A method for delivering a particulate material into a wellbore, comprising:

39. A method for fracturing a subterranean formation, comprising:

driving the proppant material from the vessel and into the delivery conduit at a location which is downstream of the pumping system; and

delivering the fracturing fluid and proppant into a wellbore to fracture a formation.