PROPPANT CONTROL IN AN LPG FRAC SYSTEM
An apparatus for supplying proppant is disclosed, comprising a vessel and a level monitor. The vessel has an interior containing a mixture of proppant and liquid, an inlet for supplying proppant to the interior, and an outlet for supplying the mixture of proppant and liquid from the interior of the vessel. The level monitor is associated with the vessel for monitoring at least a level of liquid and has a discriminator for discriminating between the level of liquid and a level of proppant in the mixture of proppant and liquid. A method of supplying proppant is also disclosed. A vessel is provided at least partially filled with a mixture of proppant and liquid and having a level of liquid and a level of proppant. The level of liquid in the mixture of proppant and liquid is monitored. The mixture of proppant and liquid is supplied from the vessel through an outlet in the vessel.
This document relates to methods and apparatus for controlling proppant in a well treatment system.
BACKGROUNDIn hydraulic fracturing, frac fluids may be sent to a high pressure pump to be pumped down a well to fracture a formation. Typically, these frac fluids contain proppant supplied into the frac fluid for propping open fractures created in the formation by the pressure of the frac fluid. Proppant may be supplied into the frac fluid from a proppant supply source. Fluid may be added to the proppant supply source to assist in controlling gas break out. A method of monitoring fluid level in the proppant is required.
SUMMARYAn apparatus for supplying proppant is disclosed, comprising a vessel and a level monitor. The vessel has an interior containing a mixture of proppant and liquid, an inlet for supplying proppant to the interior, and an outlet for supplying the mixture of proppant and liquid from the interior of the vessel. The level monitor is associated with the vessel for monitoring at least a level of liquid and has a discriminator for discriminating between the level of liquid and a level of proppant in the mixture of proppant and liquid.
A method of supplying proppant is also disclosed. A vessel is provided at least partially filled with a mixture of proppant and liquid and having a level of liquid and a level of proppant. The level of liquid in the mixture of proppant and liquid is monitored. The mixture of proppant and liquid is supplied from the vessel through an outlet in the vessel.
An apparatus for supplying proppant is also disclosed, comprising a pressure vessel and a level monitor. The pressure vessel has an interior containing a mixture of proppant and liquid, an inlet for supplying proppant to the interior, and an outlet at or near a base of the interior for supplying the mixture of proppant and liquid from the interior of the pressure vessel. The level monitor is associated with the pressure vessel for monitoring at least a level of liquid of the mixture of proppant and liquid.
These and other aspects of the system and method are set out in the claims, which are incorporated here by reference.
Embodiments will now be described with reference to the figures, in which like reference characters denote like elements, by way of example, and in which:
Immaterial modifications may be made to the embodiments described here without departing from what is covered by the claims.
Proppant may be required to be supplied into a stream of fluid, for example a stream of frac fluid. In some cases it is desirable to supply the proppant as a mixture of proppant and liquid. This may wet the proppant, allowing it to be more easily transferred from the proppant supply source. In cases where the proppant supply source is under positive pressure, the liquid in the proppant can act as a liquid seal to prevent gas breakthrough into the stream of frac fluid from the proppant vessel.
Referring to
Referring to
In some embodiments, the mixture of proppant and liquid is a mixture of proppant wetted with liquid. In some embodiments, a suitable amount of liquid is maintained or supplied into interior 16 to provide at least one of a liquid seal and saturation of the pores of the proppant contained within. Because sand has around 30% porosity an exemplary load of 15 tonnes of sand would contain 3 m3 of propane.
Referring to
Sheath 34 may be a radar rod, for example of the type sold by Endress and Hauser. Sheath 34 may also have a flange 35 for coupling to a head 13 of level monitor 14 for example by bolting. Referring to
Referring to
Referring to
Level monitor 14 monitors the amount of liquid that is contained in the proppant supply source 12. This may allow a user to estimate the effective size of the liquid seal provided by the liquid in the mixture at the outlet of the proppant supply source. The amount of liquid may be monitored by taking at least one of direct and indirect measurements of a level of liquid. As further described below, the level of liquid may be the actual height of the liquid in the proppant supply source, or it may be other measurable levels for example the level liquid rises to in sheath 34. In order to accurately measure a level of liquid and infer the amount of liquid present, calibration of the measuring equipment may be required, to take into differences in for example proppant, liquid, container size, and outlet location. The discriminator 28 is configured to distinguish between the level of liquid and the level of proppant in the mixture, so that at least the level of the liquid can be measured.
This distinguishing may be accomplished at least in part by isolating at least one of the levels, for example by physically separating the liquid from the proppant using sheath 34. The distinguishing may also be done at least in part electronically, for example by analyzing measured data obtained from monitor 14 using a computing device. The analyzation part may be provided for example in at least one of head 13 and from a remote location for example in a control console. In this way, monitor 14 obtains measurements that are then interpreted by another part of the level monitor 14. The final information may be then conveyed to at least one of a user and a control algorithm, and may be used to make further decisions. For example, if the level of liquid, and hence the effectiveness of the liquid seal is low, a decision may be made to increase the amount of liquid in the mixture. Any software used is contained on a computer readable medium.
Referring to
Referring to
Referring to
Referring to
A further option is to use a camera such as a video camera and image analysis software. Image analysis software can detect edges in an image such as an edge caused by the levels 26 or 30. The camera can be inside the vessel 12 or directed towards a sight tube on the exterior of the vessel, though this complicates design of the vessel 12 and is not preferred. Other embodiments may detect level 26 using refractive index measurements for example with fibre optic cables, or using infra-red detectors. In other embodiments, a density meter may be used.
Referring to
Referring to
In stage 102 (shown in
In stage 104 (shown in
Referring to
Level of liquid 26 may not be the actual height of the liquid in the vessel. For example, when level 26 is below level 30, some liquid may be absorbed on to the proppant and may migrate to a higher level than in sheath 34. In this case, level 26 may be the level of liquid as discriminated by the discriminator 28. Referring to
Liquefied petroleum gas (LPG) includes a variety of petroleum and natural gases existing in a liquid state at ambient temperatures and moderate pressures. In some cases, LPG refers to a mixture of such fluids. These mixes are generally more affordable and easier to obtain than any one individual LPG, since they are hard to separate and purify individually. Unlike conventional hydrocarbon based fracturing fluids, common LPGs are tightly fractionated products resulting in a high degree of purity and very predictable performance. Exemplary LPGs used in this document include ethane, propane, butane, pentane, hexane, and various mixes thereof. Further examples include i-butane, i-pentane, n-pentane, and n-butane. The LPG mixture may be controlled to gain the desired hydraulic fracturing and clean-up performance.
LPGs tend to produce excellent fracturing fluids. LPG is readily available, cost effective and is easily and safely handled on surface as a liquid under moderate pressure. LPG is completely compatible with formations and formation fluids, is highly soluble in formation hydrocarbons and eliminates phase trapping—resulting in increased well production. LPG may be readily and predictably viscosified to generate a fluid capable of efficient fracture creation and excellent proppant transport. After fracturing, LPG may be recovered very rapidly, allowing savings on clean up costs.
Referring to
Nitrogen may be introduced into the system via lines 74, 76 from at least one N2 pumper (not shown). Nitrogen pass through a surge tank 78, and can be supplied to at least one of the proppant vessels 12A, 12B, the LPG tanks, and all the lines that carry LPG at any point in the process. Nitrogen is supplied through a pressure regulator R1 to proppant vessels 12A and 12B via lines 80, 82, respectively. Nitrogen can then be supplied, via a series of valves to vessels 12A, 12B via connections at the top (84A, 84B) or bottom (86A, 86B) of the vessels. Nitrogen pressure may be controlled to add a suitable amount of pressure on the proppant and liquid in the vessels 12A, 12B. Nitrogen may also be sent to the LPG tanks via pressure regulator R2 to control the balance of pressure in the LPG tanks.
Proppant, for example sand, may be supplied to vessels 12A, 12B from a sand loader through lines 88A, 88B through sand inlets SI1-SI2. LPG can be controllably supplied to vessels 12A, 12B through connections S1-S4 of the suction manifold 60, and connection 90, which feeds to lines 90A, 90B. LPG can be added to the vessels 12A, 12B through a series of valves and via connections at the top (84A, 84B) or bottom (86A, 86B) of the vessels, similar to nitrogen addition. The pressure may be balanced and equalized between the LPG tanks and vessels 12A, 12B, in order to prevent over or under pressuring vessels 12A, 12B. Once the system is ready to add proppant to the stream of frac fluid, valves HV1 and HV2, which may be electro-hydraulic valves, are opened, and augers 68A and 68B supply the mixture of proppant and liquid into the stream of frac fluid at region 66. During the process, level monitoring devices 14C and 14D monitor the levels of liquid in vessels 12A, 12B, sending feedback to a controller in charge of the entire operation. Based on the levels of liquid in each respective vessel, the controller may decide to add more liquid to each respective tank as required.
The system may use relief valves and mechanisms at any point in the system as mandated for safety by law, for example relief valves RV1-RV5. Upon completion of the frac, connections D1-D4 may be closed, and all lines bled, for example via bleed valves BV1-BV3, through line 92, hose reel 94, and to the flare stack.
In the claims, the word “comprising” is used in its inclusive sense and does not exclude other elements being present. The indefinite article “a” before a claim feature does not exclude more than one of the feature being present. Each one of the individual features described here may be used in one or more embodiments and is not, by virtue only of being described here, to be construed as essential to all embodiments as defined by the claims.
Claims
1. An apparatus for supplying proppant comprising:
- a vessel having an interior containing a mixture of proppant and liquid, an inlet for supplying proppant to the interior, and an outlet for supplying the mixture of proppant and liquid from the interior of the vessel; and
- a level monitor associated with the vessel for monitoring at least a level of liquid and having a discriminator for discriminating between the level of liquid and a level of proppant in the mixture of proppant and liquid.
2. The apparatus of claim 1 in which the discriminator comprises a sheath having an upper end, a lower end, at least an opening at or near the lower end for allowing liquid in the interior to flow into the sheath and at least restricting the flow of proppant into the sheath, and an equalization vent.
3. The apparatus of claim 2 in which the sheath is straight along a sheath length.
4. The apparatus of claim 2 in which the sheath spans an upper end of the interior to a lower end of the interior.
5. The apparatus of claim 2 in which the level monitor is configured to use time domain reflectometry to determine the level of liquid within the sheath.
6. The apparatus of claim 2 in which the opening comprises at least one slot.
7. The apparatus of claim 2 in which the opening comprises a proppant screen.
8. The apparatus of claim 1 in which the level monitor is located at least partially outside the interior of the vessel.
9. The apparatus of claim 1 in which the vessel further comprises a liquid inlet for supplying liquid to the interior of the vessel.
10. The apparatus of claim 1 in which the vessel comprises a positive-pressure vessel.
11. The apparatus of claim 10 in which the liquid comprises liquefied petroleum gas.
12. The apparatus of claim 1 in which the outlet is connected to supply proppant into a pressurized stream of fluid.
13. The apparatus of claim 1 in which the mixture of proppant and liquid is a mixture of proppant wetted with liquid.
14. The apparatus of claim 1 in which the level monitor is configured to monitor both the level of liquid and the level of proppant.
15. A method of supplying proppant comprising:
- providing a vessel at least partially filled with a mixture of proppant and liquid and having a level of liquid and a level of proppant;
- monitoring the level of liquid in the mixture of proppant and liquid; and
- supplying the mixture of proppant and liquid from the vessel through an outlet in the vessel.
16. The method of claim 15 in which monitoring further comprises monitoring the level of liquid within a sheath in the vessel, the sheath having at least an opening at or near a lower end of the sheath for allowing liquid to flow into the sheath and at least restricting the flow of proppant into the sheath, and an equalization vent.
17. The method of claim 16 in which the sheath spans from an upper end of the vessel to a lower end of the vessel.
18. The method of claim 16 in which the opening comprises a proppant screen.
19. The method of claim 16 in which monitoring further comprising monitoring using time domain reflectometry.
20. The method of claim 15 in which the vessel is pressurized.
21. The method of claim 20 in which the liquid comprises liquefied petroleum gas.
22. The method of claim 20 in which the mixture of proppant and liquid is supplied from the vessel to a pressurized stream of fluid.
23. The method of claim 15 in which liquid is supplied into the vessel from an inlet in the vessel.
24. The method of claim 23 further comprising controlling the supply of liquid into the vessel based on the level of liquid in the vessel.
25. The method of claim 15 in which the mixture of proppant and liquid is a mixture of proppant wetted with liquid.
26. The method of claim 15 further comprising monitoring a level of proppant in the vessel.
27. An apparatus for supplying proppant comprising:
- a pressure vessel having an interior containing a mixture of proppant and liquid, an inlet for supplying proppant to the interior, and an outlet at or near a base of the interior for supplying the mixture of proppant and liquid from the interior of the pressure vessel; and
- a level monitor associated with the pressure vessel for monitoring at least a level of liquid of the mixture of proppant and liquid.
28. The apparatus of claim 27 in which the liquid comprises liquefied gas.
Type: Application
Filed: Dec 29, 2008
Publication Date: Jun 24, 2010
Inventor: Victor Fordyce (Red Deer)
Application Number: 12/345,577
International Classification: E21B 43/267 (20060101); E21B 41/00 (20060101);