Method and apparatus for transferring material into a fluid stream

Abstract

Method and apparatus for transfer of material such as liquids or fluid like solids into a high-pressure fluid stream to establish a desired flow rate by using a metering device, a reservoir for mixing fluids and solids, a first conduit connected to a top of the reservoir for flowing fluids and controlling atmosphere pressure, a second conduit connected to a top of the reservoir for supplying solids, the metering device connected to the bottom of the reservoir and controlled by a metering controller for controlling pressure of a mixture of fluids and solids, and a cross conduit mounted to the metering device for injecting the mixture of fluids and solids into the fluid stream.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority of U.S. Provisional Patent Application No. 60/665,117 filed Mar. 24, 2005, which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to a method and apparatus for transferring material into a fluid stream. More particularly, the present invention relates to a method and apparatus for transferring sieved solids into a high-pressure gas stream for hydraulically fracturing a subsurface reservoir or to deliver specialized chemical treatments before, during, or after hydraulic fracturing.

BACKGROUND OF THE INVENTION

In general, during hydrocarbon production from subsurface reservoirs, a fluid stream is often injected into wells to alter the effective permeability in the formation and assist in the mobilization of the gas or oil towards the wellbore for subsequent production to the surface, for example by hydraulically fracturing the subsurface reservoir.

During hydraulic fracturing, a high-pressure fluid is directed into the reservoir causing the reservoir to fracture. While the fractures are held open by the high-pressure fluid, it is desirable to place a proppant in the fractures to hold them open after hydraulic fracturing.

In coal bed methane (CBM) reservoirs, a gaseous fracturing fluid, preferably nitrogen is often used. However, due to the viscosity and other properties of nitrogen, it is not particularly good at carrying or supporting a proppant down the wellbore and into the reservoir.

Accordingly, in view of the above-mentioned deficiencies in the art, it is desirable to provide an improved method and apparatus for transferring materials into a fluid stream for hydraulic fracturing. More specifically, there is a need for transferring proppant into a high-pressure fluid stream for hydraulic fracturing of a subsurface reservoir.

SUMMARY OF THE INVENTION

It is an object of the present invention to obviate or mitigate at least one disadvantage of the previous systems.

In one aspect, the invention provides an apparatus for transferring material into a fluid stream comprising: a reservoir for storing material; a first conduit connected to a top portion of the reservoir for flowing fluids and controlling pressure; a metering device connected with the reservoir and controlled by a metering controller for controlling the pressure of a fluid stream; and a mixing chamber connected with the metering device for contacting the material with the fluid stream.

Preferably, the fluids are liquids, fluid like solids or nitrogen. Preferably, the material comprises sieved sand, resin-coated sand, resin coated ceramic proppant, glass spheres, plastic spheres, synthetic particles or a mix thereof. Preferably, the reservoir can subsist in high-pressure, 10,000 psi. Preferably, the reservoir has a working volume between about 0.001 m³ and 20 m³. Preferably, the first conduit includes a valve for controlling a volume of fluids and a valve for controlling atmosphere pressure. Preferably, the second conduit includes a valve for controlling a volume of material. Preferably, the metering device includes a seat and a dart for controlling pressure of the fluid stream. Preferably, the seat is cylindrically shaped and tapered both top and bottom toward the central portion. Preferably, the dart is cone shape and is movable toward and away from the seat. Preferably, the dart includes a linear actuator which is connected to a metering controller. Preferably, the mixing chamber includes an entering gate for controlling pressure and an exit gate for injecting the fluid stream. Preferably, the first conduit includes an adjustable choke between the first conduit and the entering gate for creating a pressure differential.

In another aspect, the invention provides a method for transferring fluids into a gas stream comprising the steps of adding material in a reservoir; flowing a fluid stream to the material in a reservoir; controlling pressure of the material and a fluid stream using a metering device; creating pressure differential using an adjustable choke; and injecting the fluid stream by desired injection rate and pressure continuously.

Preferably, the material comprises sieved sand, resin-coated sand, resin coated ceramic proppant, glass spheres, plastic spheres, synthetic particles or a mix thereof. Preferably, the fluid is nitrogen. Preferably, the material is a proppant.

Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described, by way of example only, with reference to the attached Figures, wherein:

FIG. 1 is a schematic representation of a system of the present invention for transferring a material into a fluid stream;

FIG. 2 is a partial detail view of a metering device of the present invention; and

FIG. 3 is a partial detail view of the metering controller of the present invention.

DETAILED DESCRIPTION

Generally, the present invention provides a method and apparatus to transfer a material into a high-pressure fluid stream.

Referring generally to FIG. 1, there is illustrated a transferring apparatus 100 to transfer fluids into a high-pressure fluid stream 7 using gravity and/or pressure differential.

Fluid Stream

A fluid stream 7 provides a fluid to the transferring apparatus 100. Preferably, the fluid stream 7 is a nitrogen stream. Preferably the fluid stream 7 flows at a rate between about 1 to about 30 m³/minute (liquid rate equivalent). The fluid stream 7 is preferably at about 10,000 psi. Preferably the fluid stream 7 is at a temperature in the range of about 0° C. to 60° C. More preferably, the temperature is about 40° C.

Other suitable fluids for the fluid stream 7 include liquid CO₂, water (as liquid or steam), liquid hydrocarbons, methane, liquid propane, etc., or other fluids used for hydraulic fracturing or otherwise injected or forced into a subsurface reservoir/formation.

Reservoir

A transferring apparatus 100 includes a reservoir 10 such as a cylindrical pressure vessel to hold the material 15 to be added. The reservoir 10 is designed for a volume and working pressure suitable for the particular operation. Preferably, the reservoir 10 is suitable for about 10,000 psi and with a working volume between about 0.001 m³ to 20 m³. A first conduit 21 is used to provide a positive blanket pressure to the reservoir 10 from the fluid stream 7. A second conduit 22 transfers fluids from a transport truck or other supply (not shown) to the reservoir 10. The first conduit 21 includes a valve 21a to control blanket pressure or isolate the reservoir 10 from the first conduit 21. A vent 21b may be used to vent the reservoir 10 to atmosphere and may be located on the first conduit 21 or directly on the reservoir 10.

Material Added

The material 15 may be a sieved solid. The sieved solid may be any material used for propping open (e.g. a proppant) a fracture created by the fluid, delivering a chemical to the fracture system (e.g. encapsulated chemicals, powders, etc.), or scouring or eroding a fracture system. Solids may include sieved sand, resin coated sand, resin coated ceramic proppant, glass spheres, plastic spheres or synthetic particles. Preferably, the material 15 is a ceramic round synthetic polishing type proppant. The material 15 may be an abrasive or scaling type proppant, but may cause increased mechanical wear when the fluid stream 7 containing the material 15 is directed into the subsurface reservoir (not shown) through regular or coiled tubing (not shown) down a wellbore (not shown).

The material 15 may also be a specialized chemical for treatment before, during, or after hydraulic fracturing.

Metering Device

Referring to FIGS. 1 and 2, a metering device 30 including a seat 31 and a dart 32 is mounted between the reservoir 10 and the mixing chamber 40. The seat 31 is preferably cylindrically shaped tapered both top and bottom toward a central portion. The dart 32 is preferably cone shaped and is movable between a seated position and an open position by a linear actuator 32a for controlling flow of material 15 from the reservoir 10. The dart 32 has a linear actuator 32a operable by a metering controller 50. The seat 31 and dart 32 are replaceable. The taper on the seat 31 and dart 32 may range from 100 to 800 to adjust for solid or liquid materials or to adjust flow control characteristics. Preferably the linear actuator 32a is a standard hydraulically operated blow out preventor (BOP) known in the art. Preferably the linear actuator 32a includes an indicator to show the position of the dart 32.

Mixing Chamber

Referring to FIG. 3, a mixing chamber 40 provides a connection between the fluid stream 7 and the material 15. Upstream of the mixing chamber 40, an adjustable choke 21c may be used to provide a pressure differential between the mixing chamber 40 and the reservoir 10. The choke 21c preferably is adjustable to create a pressure differential of between about 0 to about 1000 psi. A guide bushing 51 directs the linear actuator 32a, and sealing means in the form of a packing seal 52 allows the linear actuator 32a to be movable while retaining pressure within the mixing chamber 40.

Preferably, the pressure of the fluid stream 7 is about from 30 to 70 MPa, and more preferably is from 35 to 55 MPa. Preferably, volume flow rate is from about 100 to 5000 SCM/min. (standard cubic meters per minute) and more preferably is from about 500 to 2000 SCM/min. Most preferably, the volume rate is 1500 SCM/min. Preferably, the velocity of the fluid stream 7 is about 125 m/sec in at least a portion of the mixing chamber 40. Depending upon pressures and specific gravity of the material being added, velocity ranges from about 50 m/sec to over 300 m/sec.

Operation

In operation, in order to fill the reservoir 10, the dart 32 is seated in the seat 31 to isolate reservoir 10 from the mixing chamber 40. The valve 21a is closed and the valve 21b opened to vent the reservoir 10 to atmosphere, and the valve 22a opened to allow material 15 to transfer through the second conduit 22 from the transport truck or other source (not shown) into the reservoir 10. Once the reservoir 10 is filled with material 15 to a desired level, the valve 21b and the valve 22a are closed, and the valve 21a opened to allow pressure from the fluid stream 7 to pressurize the reservoir 10.

When the fluids such as liquids, fluid like solids or nitrogen (N₂) are flowing through the fluid stream 7, the adjustable choke 21c may be used to create a pressure differential between the mixing chamber 40 and the reservoir 10. This differential pressure will push material 15 towards the metering device 30. The flow of the material 15 into the fluid stream 7 may be controlled by moving the dart 32 towards or away from the seat 31 to vary the flow area available for the material 15 through the metering device 30. Different seat 31 and dart 32 pairs can be used to further refine the control the flow of materials, e.g. by using different taper on the seat 31 or on the dart 32.

The amount of the material 15 in an outlet fluid stream 8 may be monitored by means known in the art, such as a measurement of density using a radioactive or ultrasonic densometer (not shown), and adjustment made by moving the dart 32 in response.

In a hydraulic fracturing operation or chemical treatment operation, the outlet fluid stream 8 may be directed into the reservoir/formation as is known in the industry.

Multi-Batch

In a normal hydraulic fracturing operation a large quantity of fracturing fluid (e.g. nitrogen) may be used requiring a corresponding relatively large quantity of material (e.g. sieved solids). This relatively large quantity of material can be supplied in a single reservoir similar to the reservoir 10, sized to suit the quantity of material. As outlined above, a batch of material is loaded into the reservoir 10 and then mixed into the fracturing fluid (e.g. nitrogen) until it is all gone.

Alternatively, a plurality of reservoirs similar to the reservoir 10 may be used together to provide a suitable size (e.g. at least two reservoirs to provide at least two times the volume, etc.), or to provide for different materials (e.g. different reservoirs may contain different materials).

In such a multi-reservoir, or multi-batch configuration, a plurality of sets (or trains) having a reservoir 10, a metering device 30, and a mixing chamber 40 and additional conduits (e.g. piping) may be used to allow the isolation or sequencing of trains to operate the mixing of material in a semi-continuous batch mode. In operation, at least one train could be operating, while at least a second train is isolated from the fluid stream 7 and being filled from the transport truck or other source (not shown). When the reservoir 10 of the first train is empty or near empty, the second train may be brought into operation by opening and closing appropriate valving. Thus, allowing substantially continuous flow of the fluid stream 7.

The above-described embodiments of the present invention are intended to be examples only. Alterations, modifications and variations may be effected to the particular embodiments by those of skill in the art without departing from the scope of the invention, which is defined solely by the claims appended hereto.

Claims

1. An apparatus for transferring material into a fluid stream comprising:

(a) a reservoir adapted to store the material;

(b) a first conduit connected to a top portion of the reservoir for flowing fluids and controlling pressure;

(c) a metering device connected with the reservoir and controlled by a metering controller for controlling the pressure of a fluid stream; and

(d) a mixing chamber connected with the metering device, said mixing chamber adapted to contact the material with the fluid stream.

2. The apparatus according to claim 1, wherein the fluids are liquids, fluid like solids or nitrogen.

3. The apparatus according to claim 1, wherein the material comprises sieved sand, resin coated sand, resin coated ceramic proppant, glass spheres, plastic spheres, synthetic particles or a mix thereof.

4. The apparatus according to claim 1, wherein the reservoir is adapted to withstand high-pressure, of at least about 10,000 psi.

5. The apparatus according to claim 1, wherein the reservoir has a working volume between about 0.001 m3 and 20 m3.

6. The apparatus according to claim 1, wherein the first conduit includes a valve for controlling a volume of fluids and a valve for controlling an atmospheric vent.

7. The apparatus according to claim 1, wherein the second conduit includes a valve for controlling a volume of material.

8. The apparatus according to claim 1, wherein the metering device includes a seat and a dart for controlling pressure of the fluid stream.

9. The apparatus according to claim 8, wherein the seat is cylindrically shaped and tapered both top and bottom toward the central portion.

10. The apparatus according to claim 8, wherein the dart is cone shape and is movable toward and away from the seat.

11. The apparatus according to claim 8, wherein the dart includes a linear actuator which is connected to a metering controller.

12. The apparatus according to claim 1, wherein the mixing chamber includes an entering gate for controlling pressure and an exit gate for injecting the fluid stream.

13. The apparatus according to claim 6, wherein the first conduit includes an adjustable choke between the first conduit and the entering gate for creating a pressure differential.

14. A method for transferring material into a fluid stream comprising the steps of:

(a) adding material into a reservoir;

(b) flowing a fluid stream to the material;

(c) controlling pressure of the material and a fluid stream using a metering device;

(d) creating a pressure differential across the material using an adjustable choke; and

(e) allowing gravity and the pressure differential to add the material into the fluid stream,

wherein the metering device may be used to control the rate at which the material is added.

15. The method of claim 14, wherein the material comprises sieved sand, resin coated sand, resin coated ceramic proppant, glass spheres, plastic spheres, synthetic particles or a mix thereof.

16. The method of claim 14, wherein the fluid is nitrogen.

17. The method of claim 14, wherein the material is a proppant.