RU2673895C1 - Methods and systems for discharging aggressive fluid media - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: group of inventions relates to the systems for pumping fluid from the surface of the well into the wellbore at high pressure and, specifically, to the pressure exchanger, using which pressure energy is taken from the high-pressure fluid system and transferred to the low-pressure fluid system. Method provides for a source of low pressure of aggressive fluid. At least one high pressure pump is driven to inject clean fluid. Piston unit is used, which is in contact with the clean fluid in the direction of movement, by means which the clean fluid is pushed, using pressure from at least one high pressure pump, into the wellbore. To do this, the system having at least two tubular elements, each of which contains a corresponding piston unit, is used. Operation of piston blocks in the opposite phases is ensured. Aggressive fluid is continuously injected into the wellbore so that in the first half of the cycle the first of the respective piston blocks causes the aggressive fluid to be pushed out of the first of the two tubular elements under high pressure, while the second of the tubular elements is filled with an aggressive low pressure fluid. In the second half of the cycle, the second of the respective piston units provides for the ejection of aggressive fluid from the second of the two tubular elements under high pressure, while the first of the tubular elements is filled with aggressive fluid under low pressure.

EFFECT: improved efficiency of the mentioned pressure exchanger.

24 cl, 17 dwg, 1 tbl

Description

[0001] This application claims priority according to provisional application for US patent No. 62/119392, filed February 23, 2015, the contents of which are incorporated herein by reference.

FIELD OF TECHNOLOGY

[0002] This invention generally relates to methods and systems for pumping fluid from a well surface into a well bore at high pressure. More specifically, the present invention relates to a pressure exchanger that draws pressure energy from a fluid system flowing under high pressure and transfers it to a fluid system flowing at a relatively low pressure.

BACKGROUND

[0003] In special applications for oil fields, pumping units are used to pump fluid from the surface of the well into the wellbore under very high pressure. Such applications include, but are not limited to, fracturing, cementing, and pumping through flexible tubing. In the example of a fracturing operation, in order to direct a fluid containing an abrasive or fracturing fluid through the wellbore to the designated areas of the well to create lateral fractures in the wellbore, a multi-unit pump unit is often used. To create such fractures, fracturing fluid is pumped at very high pressures, sometimes in the range of 10,000 to 15,000 psi. inch (68.95-103.4 MPa) or more. In addition, fracturing fluids contain an abrasive proppant, which helps to start creating a fracture, and also serves to keep the fracture “wedged” after creating the fracture. These gaps provide additional pathways for the flow of underground oil and gas deposits from underground formations to the surface of the well. These additional paths serve to increase well productivity.

[0004] Plunger pumps are typically used for applications in the oil field during injection under high pressure, for example, fracturing operations. Such plunger pumps are sometimes also referred to as positive displacement pumps, intermittent pumps, three-cylinder pumps or five-cylinder pumps. Plunger pumps typically contain one or more plungers driven from the crankshaft in the direction of the chamber and away from it in a pressurized casing (commonly referred to as the “pressure part”) to create pressure fluctuations with alternating high and low pressures in the chamber. These pressure fluctuations allow the pump to receive fluid at low pressure and discharge it under high pressure through single-acting valves (also called check valves).

[0005] Pumps with multiple plungers are often used simultaneously in large scale fracturing operations. These pumps can be connected to each other through a common collector that mechanically collects and distributes the combined outlet from the individual pumps. For example, fracturing operations are often performed in this manner, with as many pumps as possible from twenty or more connected to each other by a common collector. A centralized computerized system can be used to control the entire pump system during operation.

[0006] However, the abrasive nature of the fracturing fluids is not only effective in destroying underground rocks to create a fracture therein, but also causes wear on the internal components of the plunger pumps that are used for pumping. Thus, when plunger pumps are used for pumping the fracturing fluids , the repair, replacement and / or maintenance costs of the internal components of the pumps are extremely high, and the overall pump life is short.

[0007] For example, when a plunger pump is used to pump fracturing fluid, the pressure portion, valves, valve seats, seals, and pump plungers require frequent maintenance and / or replacement. Such a replacement of the pressure part is very expensive, not only due to the fact that the pressure part itself is expensive, but also because of the complexity and complexity of the necessary replacement. A large percentage of the cost of servicing a plunger pump can be spent on valve replacement. In addition, when the valve fails, the valve seat is also often damaged, and replacing the seat is much more difficult than replacing the valve, due to the need to exert a very large force to expel it from the pressure part.

SUMMARY OF THE INVENTION

[0008] This description section is provided to represent a selection of principles that are further disclosed in the following detailed description. This summary is not intended to identify the main (XE "Narrowing designation: essential") or significant (XE "Narrowing designation: essential") differences of the claimed invention, nor is it intended to be used as a means of limiting the scope of the claimed invention.

[0009] In one embodiment, a method for pumping an oilfield fluid from a surface of a well into a wellbore is disclosed. The method includes the action of at least one low pressure pump for pumping aggressive fluid; the action of at least one high pressure pump for pumping clean fluid; using a piston that is in contact with a clean fluid and that pumps clean fluid in the direction of travel using pressure from the high pressure pump to provide pressure on the aggressive fluid, thereby pumping the aggressive fluid into the wellbore. In one aspect, when the aggressive fluid is pumped by the high pressure pump, it is not in contact with the piston unit.

[0010] In one embodiment, the aggressive fluid is not in contact with either side of the piston.

[0011] In another embodiment, a system for pumping oilfield fluid from a surface of a well into a wellbore is disclosed. The system comprises at least one low pressure pump in communication with an aggressive fluid supply device; at least one high pressure pump in communication with a source of clean fluid; and a tubular element comprising a piston block, wherein the piston block is in contact with the clean fluid in the direction of travel, and the piston block pumps clean fluid using pressure from the high pressure pump to provide pressure on the aggressive fluid, thereby by pumping aggressive fluid into the wellbore. In one aspect, with the apparatus described, aggressive high pressure fluid does not come into contact with the piston.

[0012] In one embodiment, a system for continuously pumping high-pressure oilfield fluid from a surface of a well into a wellbore comprises at least one pair of tubular elements, each of which contains a piston unit, wherein one tubular element of the pair is in a cycle phase high pressure, while the other tubular element of the pair is in the phase of the low pressure cycle.

[0013] Further features and advantages of the present invention will be more apparent from the following detailed description, taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF GRAPHIC MATERIALS

[0014] The present invention is further described in detail with reference to the plurality of drawings as an example, not limiting to the subject matter, in which the same reference numbers indicate similar parts in several types of drawings, and in which:

[0015] FIG. 1-5 are diagrams depicting an embodiment of the present invention at several stages of a half cycle;

[0016] FIG. 6-10 are diagrams depicting another embodiment of the invention at several stages of the cycle, in which the embodiment includes an “stop” element near the end of the tubular element and a check valve in the piston;

[0017] FIG. 11 depicts one piston diagram for embodiments of the present invention; and

[0018] FIG. 12a through 12f depict several steps of a flowchart in an embodiment of the present invention using check valves.

DETAILED DESCRIPTION OF THE INVENTION

[0019] The features shown herein are exemplary and for purposes only (XE "Narrowing designation: only") of an illustrative description of examples of disclosure of an object of the invention and given to represent what is considered the most useful and easily understood description of the principles and conceptual aspects of the object inventions. In this regard, no attempt is made to show the structural details more fully than necessary (XE "Narrowing designation: necessary"), the description together with the drawings makes obvious to experts in this field how several forms of the object of the invention can be implemented. In addition, the same reference characters and symbols in the various drawings show the same elements.

[0020] Injecting a suspension containing erosive, corrosive, or abrasive fluids (also called "aggressive" fluids) leads to high costs for the manufacture and maintenance of pumps. Embodiments of the present invention generally relate to a pump system for pumping fluid from a well surface into a well bore under high pressure, and more particularly, to a system that includes the use of clean fluids to transfer pressure to aggressive fluids. This provides a low cost of operation for these systems.

[0021] FIG. 1-5 depict an embodiment of the present invention at several points in a half cycle. The system 10 comprises two storage tanks 20, 30, three pumps 42, 44, 46, two (additional) tubular elements 50, 60 with corresponding first ends 50a, 60a and second ends 50b, 60b, having respective pistons 55, 65, ten electromagnetic valves SV-1 to SV-10, and a series of pipes 71-78 containing clean fluid 95, for example water, and a series of pipes 81-85, often containing aggressive fluids 96. Pure fluid 95 is shown in figures lighter color and the aggressive fluid 96 is shown in a darker color. The storage tank 20 is designed for clean fluid, while the storage tank 30 is designed for aggressive fluid. Pump 42 is a high pressure clean fluid pump. For the purposes of this invention, “high” pressure should be considered a relative term compared to “low” pressure, and in various embodiments, pressures of 5,000 psi may be generated. inch, or 10,000 psi inch, or 15,000 psi inch (33.47 or 68.95 or 103.4 MPa), or more, or pressure in this range. In non-limiting examples, high pressure pumps may be three-plunger or five-plunger pumps. Pumps 44 and 46 are low pressure pumps for clean and aggressive fluids, respectively. For the purposes of this invention, “low” pressure should be considered a relative term compared to “high” pressure, and in various embodiments, an absolute pressure of 20, or 60, or 100 psi may be created. inch ,, (0.1379, or 0.4137, or 0.6895 MPa), or pressures between them, or other, smaller or larger pressures that are less than the pressure of the high pressure pump. In a non-limiting example, low pressure pumps may be C. pumps.

[0022] As shown in FIG. 1-5, the storage tank 20 is connected to the low pressure pump 44 via a pipe 71. The low pressure pump 44 is connected to the second end 50b of the tubular member 50 via the pipe 72 and valve SV-5, and to the second end 60b of the tubular member 60 through the pipe 73 and valve SV-6. The storage tank 20 is also connected to the high-pressure pump 42 via a pipe 74. The outlet of the high-pressure pump 42 is connected to the first end 50a of the tubular element 50 via the pipe 75 and valve SV-1, and to the first end 60a of the tubular element 60 through the pipe 76 and valve SV -2. The storage tank 20 is furthermore connected to the first end 60a of the tubular member 60 via a pipe 77 and an SV-4 valve, and to the first end 50a of the tubular member 50 through a pipe 78 and an SV-3 valve.

[0023] The storage tank 30 is connected to the low pressure pump 46 via a pipe 81. The low pressure pump 46 pumps aggressive fluid from the storage tank 30 into the second end 50b of the tubular member 50 through the pipe 82 and the valve SV-7, and into the second end 60b of the tubular element 60 through pipe 83 and valve SV-8. The second ends of the tubular elements 50 and 60 are also connected to a high pressure manifold (not shown) via valves SV-9 and SV-10, respectively.

[0024] To start the system 10, the high-pressure pump 42 and the low-pressure pump 44 are turned on, and the valves SV-2 and SV-10 are opened to fill the tubular element 60 with clean fluid (thus pushing the piston 65 to the second end 60b of the tubular item 60). Similarly, to fill the tubular member 50 with clean fluid, the valves SV-1 and SV9 are opened (thus pushing the piston 55 toward the second end 50b of the tubular member 50). After the tubular elements 50, 60 are filled with clean fluid, valves SV-1 and SV-9 are closed. Then, to introduce a predetermined amount of clean fluid 95a into the second rear side of the piston 55, valves SV-6 and SV-3 are opened. Embodiments for selecting a predetermined amount of clean fluid (also called a buffer) to be administered are described below. In any case, the SV-5 valve then closes. With the SV-5 valve closed, pump 46 starts and the SV-7 and SV-3 valves open. Valve SV-7 allows the introduction of aggressive fluid into the second end of piston 55 into the tubular member 50, and valve SV-3 allows the introduction of clean fluid pushed from the front end 50a of the tubular member 50 to direct it back to the storage tank 20. Aggressive fluid is introduced into the tubular member 50 until the piston 55 moves to the first end 50a of the tubular member 50.

[0025] After the system 10 is started, it is possible to start pumping the aggressive fluid under high pressure. At the beginning of the cycle, as shown in figure 1, the valves SV-1, SV-4, SV-6 and SV-9 are open, and the valves SV-2, SV-3, SV-5, SV-7, SV-8 and SV-10 are closed. In this configuration, clean fluid from tank 20 can be pumped at high pressure through pump 42 and valve SV-1 to the first end of tubular member 50 to push forward piston 55. Piston 55, in turn, displaces clean fluid buffer 95a directly in front of and aggressive fluid 96 in front of the clean fluid buffer to the second end 50b of the tubular member 50 and out through the valve SV-9 and pipe 85 to a high pressure manifold that is connected to the wellhead. At the same time, clean fluid 95 from the tank 20, pipe 71, low pressure pump 44, pipe 73 and pump SV-6 is introduced into the second end face of the piston 65 in the tubular member 60. Thus, when the cycle begins, under the influence of high pressure the piston 55 starts to move to the right (towards the second end of the tubular element 50), while under the influence of low pressure the piston 65 starts to move to the left (towards the first end of the tubular element 60), while the pure fluid 95 leaves the tubular element 60 and is directed through the pipe 77 and valve sv-4 back to nako feed tank 20. As will be further understood, with this arrangement, both pistons 55, 65 contain clean fluid 95, 95a on both sides of the pistons. An arrangement with open valves SV-1, SV-4, SV-6 and SV-9, and closed with the rest of the valves lasts until, as shown in FIG. 2, a predetermined amount of clean fluid medium. At this point, the SV-6 valve closes and the SV-8 valve opens, so that aggressive fluid can be pumped from the tank 30, through the low pressure pump 46, pipe 83 and the SV-8 valve into the second end of the tubular member 60b, as shown in figure 3.

[0026] With the valves SV-1, SV-4, SV-8, and SV-9 open and the remaining valves closed, the aggressive fluid 96 continues to be pumped from the tubular member 50 under high pressure through pipe 85 and valve SV-9 into the wellbore while the pure fluid 95 is pushed out of the tubular member 60 at low pressure through the pipe 77 and the valve SV-4 into the storage tank until the pistons 55 and 65 almost reach the respective first and second ends 50b, 60a of the respective tubular elements 50, 60, as shown in FIG. 4, and all aggressive fluid the medium will be pushed out of the tubular element 50. At this point, if necessary, and in one embodiment, the valves SV-1, SV-4 SV-8 and SV-9 are closed, and the valves SV-7, SV-3, SV -2 and SV-10 open to reverse the direction of movement of the pistons 55, 65, and begin the second half of the cycle. With this arrangement, clean high-pressure fluid is pumped into the tubular member 60 through an SV-2 valve to cause aggressive fluid 96 to be expelled from the tubular member 60 into the high-pressure manifold through an SV-10 valve. At the same time, aggressive fluid 96 from the storage tank 30 is pumped through the low pressure valve SV-7 to the second end 50b of the tubular member 50, and the clean fluid 95 is pumped from the first end 50a of the tubular member 50 back to the clean fluid storage tank 20 through the valve SV-3. This arrangement can continue until the piston 55 is pushed back almost to the first end 50a of the tubular member 50 and the piston 65 is pushed back almost to the second end 60b of the tubular member 60. At this point, the fluids from the tubular elements will acquire positional relationship shown in Figure 2, and the complete cycle can be completed. In addition, at this moment, the valves SV-1, SV-4, SV-8 and SV-9 will open again, and the valves SV-2, SV-3, SV-5, SV-6, SV-7 and SV- 10 will close and a new cycle will begin.

[0027] In another embodiment, the valves SV-1, SV-4, SV-8 and SV-9 can remain open until the pistons reach the ends of the respective tubular elements, as shown in FIG. 5, so that all the contents of the tubular elements are released. The amount of clean fluid 95a ejected from the second end 50b of the tubular member 50 may be sufficient to flush the aggressive fluid from the pipe segment 85 from the second end 50b of the tubular member 50 and the valve SV-9, thereby prolonging the life of this valve.

[0028] If the corresponding valves are held in position to reach the arrangement of FIG. 5, at that moment the valves SV-1, SV-4, SV-8 and SV-9 will close and the valves SV2, SV-10, SV -5 and SV-3 will open to change the direction of movement of the pistons 55, 65, and begin the second half of the cycle. At the beginning of the second half of the cycle, high pressure clean fluid is pumped into the first end 60a of the tubular member 60 to force aggressive fluid to expel from the second end 60b of the tubular member 60 through the valve SV-10 in the direction of the wellbore. At the same time, the clean fluid is pumped at low pressure through the valve SV-5 at the second end of the piston 55, and the clean fluid is directed from the first end 50a of the tubular element 50 through the valve SV-3 back to the storage tank 20. After in advance a certain amount of clean fluid 95a fills the second end 50b of the tubular member 50, the valve SV-5 closes, and the valve SV-7 opens to allow aggressive fluid 96 to fill the tubular member 50 “behind” the clean fluid buffer 95a adjacent to the piston. As in the previously described embodiment, this arrangement will last as long as the pistons 55 and 65 are pushed back to the location of figure 2, or to the location of figure 1, so that (in any case), a full cycle will be performed . If the pistons are pushed back to the arrangement of FIG. 1, with the piston 55 at the first end 50a of the tubular member 50 and the piston 65 pushed back to the second end 60b of the tubular member 60, clean fluid 95a from the tubular member 60 will clean the pipe segment 84 and valve SV-10. At this point, the valves SV-1, SV-4, SV-6 and SV-9 will open again, and the valves SV-2, SV-3, SV-5, SV-7, SV-8 and SV-10 will close , and a new cycle will begin. If the pistons are pushed back to the arrangement of FIG. 2, with the piston 55 located near the first end 50a of the tubular member 50 and the piston 65 located near the second end 60b of the tubular member 60, valves SV-1, SV-9, SV-8 and SV -4 opens again, and the remaining valves close, and a new cycle begins.

[0029] In one aspect, the cycles of the above described embodiments are repeated between two tubular elements in order to maintain a constant flow rate of aggressive high pressure fluid. The cycles may alternate between the arrangement shown in FIG. 1, to the arrangement shown in FIG. 4, or the arrangement shown in FIG. 1, to the arrangement shown in FIG. 5, to the arrangement shown in FIG. 2, to the arrangement shown in figure 4, or the location shown in figure 2, to the location shown in figure 5. If it is necessary to "flush" the valves SV-9 and SV-10 only periodically, the cycles can be changed so that the constant cycle is shown in figure 1 - figure 4, and periodically the cycle can continue until the location of figure 5.

[0030] In the above embodiments of the present invention, two tubular elements are used, but this method is applicable to any number of tubular elements.

[0031] In the embodiments of the present invention described above, a low pressure pump and a storage tank for aggressive fluid are provided, but this method is applicable when the aggressive fluid is supplied through upstream operations without a storage tank for aggressive fluid or a pressure pump for aggressive fluid.

[0032] In one embodiment, the tubular members have a diameter between two and six inches (50.8-152.4 mm) and a length between ten and forty feet (3.048-12.19 m). In other embodiments, tubular elements have smaller or larger diameters and smaller or larger lengths.

[0033] In one embodiment, some or all of the valves are check valves.

[0034] In one embodiment, the inner diameters of the tubular elements and / or pipes 84 and 85 are coated with a hard, abrasion resistant coating to withstand the injection of aggressive suspensions at high pressures.

[0035] In one embodiment, the valves are electrically actuated and are controlled by a processor. Optionally, sensors may be provided to detect the position of one or both of the pistons 55, 65, and the sensors may be connected to the processor so that the processor can open and close the valves accordingly.

[0036] In one embodiment, the tubular elements are arranged horizontally (ie, perpendicular to gravity).

[0037] In one aspect, the service life of the piston blocks 55, 65 (and the exhaust valves SV-9 and SV-10) is increased by injecting a small amount of clean fluid as a protective layer (buffer front) between the piston blocks and the aggressive fluid.

[0038]The amount of clean fluid used as the backing layer can be determined in advance, and in one embodiment selected to exceed the dispersion lengthl _D aggressive fluid. The propagation length can be calculated as follows.

[0039] Consider a pipe of diameter d and length l, and the flow velocity is fixed at q. A fluid of monitored concentration C, when introduced into a pipe of length l , undergoes dispersion. The initial step profile with concentration C is “washed away” over distances of the order of length l _D , and for a sufficiently large l the profile becomes Gaussian. For a sufficiently large Reynolds number, Re , the calculation is based on friction of the turbulent flow, which provides an estimate of the velocity profile. For a laminar flow, propagation is caused by a shift and is non-Gaussian. It becomes Gaussian when 2 (D t ) ^1/2 >> d , where D is the diffusion coefficient. In the following calculations, only Gaussian propagation is considered, and when this is not applicable, the pipe length required for acceptable propagation is so large that the concept of the buffer front becomes inappropriate. It is also assumed that clean and aggressive fluids have similar viscosities, and therefore, friction instability does not occur during displacement. The similarity of viscosities can be justified, since it is assumed that a clean fluid is similar to an aggressive fluid, but without a proppant. The following are calculations along with a dispersion length table.

[0040]Density givenρ,viscosityμ,consumptionq, and diffusion coefficient D.The goal is to estimate the dispersion length.l _D or its functions. The results are presented for two different pipe diameters, approximately 10 cm and 7.5 cm, corresponding to nominal sizes of 4 inches and 3 inches, respectively. The average speed is

(1)

(one)

with the corresponding Reynolds number equal

. (2)

. (2)

This makes it possible to distinguish the flow regime into laminar, transitional and turbulent categories so that the corresponding propagation length can be calculated. The transition part is neglected, and it is assumed that the cutoff between the turbulent and laminar regimes is at Reynolds number Re = 2400, since most applications of the rupture have sufficient noise with a finite amplitude to cause turbulence.

[0041] For a turbulent flow, the friction coefficient f is calculated either from the diagrams or from one of the known functions. For simplicity, it is assumed that the pipe is smooth, and thus, the Nikuradze form gives:

. (3)

. (3)

[0042] For Taylor propagation, the friction velocity can be obtained from f, which, in turn, can be used to determine the dispersion coefficient D according to the formula

. (4)

. (four)

The propagation length l _D can be obtained from the distribution coefficient D according to the formula

(5)

(5)

where L is the length of the tubular element. The length of the buffer l _b can be chosen so that it is a multiple of the propagation length l _D. As an example, for the sake of definiteness, three sigma (i.e., 99.7%), at which the buffer length will be sufficient to prevent the piston from reaching the aggressive fluid, the buffer length l _b can be chosen in accordance with l _b = 3 l _D. In other embodiments, the length of the buffer may be chosen to be equal to or greater than the propagation length. In another embodiment, the buffer length may be twice as long as the propagation length. In another embodiment, the buffer length is approximately equal (here defined as plus or minus 20%) to three propagation lengths. With the selected buffer length and the known inner diameter of the tubular element, a predetermined amount of clean fluid pumped into the tubular element onto the piston surface in front of the aggressive fluid can easily be calculated as equal to l _b π d / 4.

_[0043] For laminar flow, the calculations are different. The propagation is Gaussian for a very long pipe, i.e., for situations in which radial diffusion is calculated as the concentration, which is a function of the axial distance. For such cases, the dispersion coefficientDdefined by the Taylor-Aris theory in accordance with the formula

_/ D _{)2} (6)} D ₌ D _{1+

_/ D _{) 2} (6)}

, где время конвекции (convection time) равно длине трубчатого элемента, разделенной на среднюю скорость. Данная длина распространения зачастую намного больше, чем длина трубчатого элемента, что видно из приведенной ниже таблицы 1.It should also be noted that the propagation coefficient D according to equation (6) is the longitudinal propagation coefficient, which shows what is the amount of mixing that occurs between the two types of fluid in parallel with the direction of movement. From equation (6), as the longitudinal propagation coefficient for the laminar flow, the characteristic propagation length is

where convection time is equal to the length of the tubular element divided by the average speed. This propagation length is often much larger than the length of the tubular element, as can be seen from Table 1 below.

Table 1. Dispersion length for various conditions. The density is maintained at 1100 kg m^-3, and the Schmidt number Sc = 1000. The number of the schedule is 80. The inner diameter of the pipe is calculated accordingly. All units in the SI system:din mμin Pa sl _D d in mqin m³ from^-one

μ d q Sc l _D ^{0.1 0.09718 0.265 38189 1.08 1.0 0.09718 0.265 3819 1.25 0.1 0.07366 0.265 50383 0.92 1.0 0.07366 0.265 5038 1.07 0.1 0.09718 0.265 38139 1.08 0.1 0.09718 0.053 7638 1.19 1.0 0.09718 0.053 764 5 0.1 0.07366 0.053 10077 1.02 1.0 0.07366 0.053 1008 5 0.1 0.09718 0.053 7638 1.19 0.1 0.09718 0.265 38189 1.53 1.0 0.09718 0.265 3818 1.77 0.1 0.07366 0.265 50383 1.31 1.0 0.07366 0.265 5038 1.51 0.1 0.09718 0.265 38189 1.53 0.1 0.09718 0.053 7638 1.69 1.0 0.09718 0.053 764 10 0.1 0.07366 0.053 1007 1.44 1.0 0.07366 0.053 1078 10 0.1 0.09718 0.053 7638 1.69 0.01 0.07366 0.008 15115 1.40 0.001 0.07637 0.008 151148 1.23 0.001 0.07637 0.008 151148 1.23}

Thus, the obtained dispersion length becomes insignificant, and it can be neglected for cases where the radial diffusion length, defined as (D * convection time) ^.5 , is very small compared with the radius of the tubular element. In most cases, this condition is satisfied, and therefore, the length of the longitudinal propagation is limited by the length of the tubular element. In other words, when the radial diffusion length is very small compared to the radius of the tubular element, the propagation length is considered equal to the longitudinal propagation length, which will often be longer than the length of the tubular element (and therefore has little effect on buffering).

[0044] Based on an analysis of the laminar flow situations described above, according to one embodiment of the invention, the tubular flow used to pump aggressive high pressure fluid in the direction of the wellbore is intentionally supported as a turbulent flow to prevent the entry of aggressive fluid in contact with the front moving surfaces of the pistons in these tubular elements.

[0045] Referring to FIG. 6-10, another embodiment is shown. System 110 is similar to system 10 of FIGS. 1-5, and when the elements are the same or substantially the same, the same designation number is used. Thus, it is shown that the system 110 comprises two storage tanks 20, 30, two pumps 42, 46, two (additional) tubular elements 50, 60 with respective first ends 50a, 60a and second ends 50b, 60b having respective pistons 155, 165 with check valves and stop elements 158, 168, eight solenoid valves SV-1, SV-2, SV-3, SV-4, SV-7, SV-8, SV-9 and SV-10, and a number of pipes 74 -78, which contain clean fluid, such as water, and a series of pipes 81-85, often containing aggressive fluids. Pure fluid is shown in the figures by shading with dashed lines, and aggressive fluid is shown with darker shading. The storage tank 20 is designed for clean fluid, while the storage tank 30 is designed for aggressive fluid. Pump 42 is a high pressure pump for clean fluid, and pump 46 is a low pressure pump for aggressive fluid.

[0046] As shown in FIG. 6-10, the storage tank is connected to the high pressure pump 42 via a pipe 74. The outlet of the high pressure pump 42 is connected to the first end 50a of the tubular member 50 via the pipe 75 and valve SV-1, and to the first end 60a of the tubular member 60 through the pipe 76 and Valve SV-2. The storage tank 20 is furthermore connected to the first end 60a of the tubular member 60 via a pipe 77 and an SV-4 valve, and to the first end 50a of the tubular member 50 through a pipe 78 and an SV-3 valve.

[0047] The storage tank 30 is connected to the low pressure pump 46 via a pipe 81. The low pressure pump 46 pumps aggressive fluid from the storage tank 2 to the second end 50b of the tubular member 50 via the pipe 82 and the valve SV-7, and to the second end 60b of the tubular element 60 through pipe 83 and valve SV-8. The second ends of the tubular elements 50 and 60 are also connected to a high pressure manifold (not shown) via valves SV-9 and SV-10, respectively.

[0048] The tubular element 50 is provided with a piston 155 with a non-return valve and an abutment 158, and the tubular element 60 is provided with a piston 165 with a non-return valve and an abutment 168. The stops limit the movement of pistons with non-return valves in the tubular elements, as further described below, and can be made different ways. In non-limiting examples, the thrust elements can be inner rings, individual ring parts, filters, or any device that will prevent the piston from moving. Check valve pistons allow clean fluid to flow through the check valve at the end of the aggressive fluid discharge cycle and flush the check valve, tubular element, downstream piping and clean fluid valves, as further described below.

[0049] To start the system 110, the high pressure pump 42 is turned on, valves SV-1 and SV-2 (and SV-9 and SV-10) are opened to fill the tubular elements 50 and 60 with clean fluid 95 (thus pushing pistons 155 and 165 to the second ends 50b and 60b of the tubular elements 50 and 60). All other valves are in the closed position. When the pistons 155 and 165 with check valves reach the stops 158 and 168 inside the tubular elements, the check valves in the pistons open at a set pressure to allow the rest of the tubular elements to fill with clean fluid. The clean fluid supplied to the right of the stops acts as buffers 95a. Thus, the position of the stops can be chosen to provide the required buffer size. When the tubular elements are completely filled with clean fluid, valves SV-2, SV-9, and SV-10 close and valves SV-4 and SV-8 open and pump 46 starts. As a result, the aggressive fluid is directed to the end 60b of the tubular member 60 and pushes the piston 165 back toward the end 60a of the tubular member. When the piston 165 reaches the end 60a of the tubular element, aggressive fluid 96 fills the tubular element 60, with the exception of the buffer 95a, as shown in Fig.6.

[0050] After the system 10 is started, it is possible to start pumping the aggressive fluid 96 at high pressures into the wellbore. In particular, when both pumps 42 and 46 are operating, the valves SV-2, SV-10, SV-7 and SV-3 are open and all other valves are closed. The tubular member 60, which was previously filled with aggressive fluid 96 (excluding buffer 95a) now receives clean fluid 95 through valve SV-2, and aggressive fluid 96 is released under high pressure through valve SV-10, with pressure being applied to the fluid medium through the valve SV-2. The pressure difference between the clean fluid side and the aggressive fluid side in the tubular member 60 is less than the set pressure for the check valve in the piston 165, so that the check valve remains closed. Similarly, the tubular member 50, which was previously filled with clean fluid 95, now receives aggressive fluid 96 through the valve SV-7, and clean fluid 95 is discharged back into the storage tank 20 through the valve SV-3. Again, the pressure of the aggressive fluid 96 is higher than the pressure of the clean fluid 95, so that the check valve remains closed. The non-return valves in both pistons are designed to open when the pressure on the side of the clean fluid is higher than the pressure on the side of the aggressive fluid by a predetermined amount called the response pressure.

[0051] Fig. 7 shows the same valve arrangement as in Fig. 6, with the two pistons 155, 165 moving towards the middle of the tubular elements 50, 60 after a while. The piston 155 moves to the left (towards the end 50a of the tubular element 50) and the piston 165 moves to the right (towards the end 60b of the tubular member 60), and the check valves in both pistons are closed.

[0052] After some time, and as shown in Fig. 8, the piston 165 reaches the stop 168 along the inner diameter of the tubular element 60 earlier than the piston 155 reaches the first end 50a of the tubular element 50 (since in this embodiment it moves faster ) After the piston 165 reaches the stop 168, the piston 165 will be unable to move despite the pressure exerted by the clean high pressure fluid 95. Since the piston 165 is unable to move, the pressure on the side of the clean fluid builds up, and this opens the check valve in the piston 165, which allows clean high pressure fluid to move past the piston 165 and discharged into the pipe 84 and valve SV-10, thus cleaning this pipe and valve. In addition, moving pure fluid past the piston 165 effectively feeds the buffer 95a; i.e., removes aggressive fluid elements that can be dispersed in the buffer.

[0053] A little later, and as shown in FIG. 9, the piston 155 will extend to the end 50a of the tubular member, thus completing half the cycle. After half a cycle, valves SV-2, SV-3, SV-7 and SV-10 can be closed, and valves SV-1, SV-9, SV-8 and SV-4 can be opened. The clean high pressure fluid 95 will begin to move into the tubular member 50 through the valve SV-1, pushing the piston 155 and the clean fluid buffer 95a toward the end 50b of the tubular member, thereby pumping the aggressive fluid 96 that is discharged through the valve SV-9 towards the high pressure manifold. Similarly, aggressive fluid 96 will be supplied to the end 60b of the tubular member, thereby pushing the clean fluid buffer 95a, the piston 165, and the clean fluid 95 in the tubular member 60 toward the end 60a of the tubular member.

[0054] The system configuration is shown in FIG. 10 after a short time, with the piston 155 pushing the buffer 95a and the aggressive fluid 96 toward the end 50b of the tubular member and the piston 165 pushing the clean fluid 95 toward the end 60a of the tubular member. This configuration is essentially the same as that shown in Fig.7, except that the tubular elements are switched; that is, the tubular element 50 delivers the aggressive fluid 96 for release into the wellbore, and the tubular element 60 is filled with the aggressive fluid 96, while the clean fluid 95 is diverted back to the storage tank 20. This process continues, and to ensure a steady flow of high pressure aggressive fluid 96, the tubular element that supplies the aggressive fluid to the wellbore is switched at regular intervals.

[0055] According to another embodiment described in more detail with reference to FIG. 11 and 12a-12f, the system 110 shown in FIG. 6-10, except that it is changed in that the stops are not made in the tubular elements, and a check valve having a low pressure is used in each of the pistons, therefore, the piston will continuously release clean fluid to the side of the aggressive fluid during the cycle of release of aggressive fluid. In one embodiment, the flow rate of clean fluid through a non-return valve will be determined by the geometry of the treated surface through the piston and the friction on the piston rings. The non-return valve, the geometry of the downstream flow on the piston and the friction resistance on the piston are designed so that the volume of clean fluid at the rear of the piston increases at the required speed, so that the final volume is sufficient to “flush” the downstream check valves with clean fluid. In one embodiment of the invention, the release of fluid through the side of the aggressive fluid is tangential in nature, and may cause the piston to rotate in response to the impact.

[0056] The piston created for this embodiment (and the embodiment described in FIGS. 6-10) is shown in FIG. 11. The piston (block) 175 comprises a cylindrical block 1100 having at least one circular piston ring 1101 extending around block, and forming a channel 1103 of the fluid, which contains a spring-loaded check valve 1105. Downstream of the check valve 1103, the channel 1103 of the fluid is divided into many streams that flush the aggressive fluid from the piston rings 1101.

[0057] When using the piston 175 with a check valve shown in FIG. 11 in the system of FIGS. 6-10 and without stops in the tubular elements, the sequence of operations is shown in FIGS. 12a - 12f. The start of the cycle is shown in FIG. 12a, with the tubular element 50 being completely filled with aggressive fluid 96, and the tubular element 60 at the end of the exhaust cycle filled with clean fluid 95. Since the tubular element 50 is provided with clean high pressure fluid, the piston 175a is in the tubular element 50 begins to move to the right, so that aggressive fluid 96 is discharged from the end 50b of the tubular member under high pressure. At the same time, and immediately after the clean high pressure fluid is supplied to the tubular member 50, depending on the design of the piston, the check valve in the piston will open and a small amount of clean fluid will be released through the check valve to the aggressive side of the piston 175a, thereby creating a clean fluid layer 95a close to the surface of the piston unit 175. The fluid leakage rate is determined so that, despite the dispersion, a clean fluid layer is maintained near the piston assembly Reds. Thus, when the piston 175a provides high pressure to release aggressive fluid 96, a layer (or buffer) of clean fluid 95a is created in front of the piston in the direction of movement of the piston. As shown in FIGS. 12b, 12c, and 12d, the size of the clean fluid buffer 95a increases as the piston 175a moves toward the end 50b of the tubular member. Thus, before the piston 175a reaches the end 50b, a sufficient amount of clean fluid moves through the piston 175a to ensure that when the piston 175a reaches the end 50b of the tubular member (in FIG. 12e), the aggressive fluid 96 will be flushed out tube and valve outlet (SV-9).

[0058] Since the tubular member 50 pushes the aggressive fluid 96 into the high pressure manifold, the tubular member 60 is filled with the aggressive fluid 96 at low pressure, and the clean fluid 95 contained in the tubular member 60 is discharged through the end 60a of the low pressure tubular member back to the storage tank. This process continues, as shown in FIGS. 12b, 12c, 12d and 12e. It should be noted that in FIGS. 12a-12e, the aggressive fluid 96 is in contact with the piston 175b, although not during the high pressure release cycle, but only under low pressure conditions. However, since the piston 175b has a check valve 1105, aggressive fluid 96 will not move toward the clean fluid of the check valve and tubular member. In addition, since the tubular member 60 is not under high pressure in this part of the cycle, aggressive fluid is unlikely to damage the piston. Pistons 175a and 175b push clean fluid, and therefore damage by aggressive fluid is avoided.

[0059] After all the clean fluid 95 has been pushed out of the tubular member 50 and the tubular member 60 is completely filled with aggressive fluid (as shown in FIG. 12e), the corresponding valves open and close, and the cycle continues by switching the action of the tubular member, as shown in FIG. 12f. Aggressive fluid 96 is now pushed out of the tubular member 60 as a layer of clean fluid 96a is pushed through the valve and protects the piston block 175b. At the same time, aggressive fluid is pumped into the end 50b of the tubular member 50 under high pressure.

[0060] In one embodiment, a high viscosity backing layer between the piston and the aggressive fluid will help extend the life of the piston unit.

[0061] In one embodiment, the low pressure pump 46 and / or the storage tank 30 may be undesirable if there is a continuous supply of aggressive fluid at low pressure available from the upstream operations.

[0062] In one aspect, various types of high pressure generating devices can be used, including but not limited to reciprocating pumps, centrifugal pumps, rotary screw compressors, and vane pumps.

[0063] In one embodiment, the clean fluid may include gas.

[0064] In one aspect, embodiments of the invention efficiently provide pressure exchangers that collect pressure energy from relatively high pressure clean fluid systems and transmit it to relatively low pressure aggressive fluid systems for use in pumping aggressive fluids and directing them into the wellbore, as aggressive high-pressure fluids, without contact of aggressive fluids with certain parts of pressure exchangers.

[0065] Some of the methods, processes, and systems described above may be performed by a processor and / or using a processor. The term "processor" should not be construed as limiting the embodiments disclosed herein to any particular type of device or system. The processor may include a computer system. A computer system may also include a computer processor (e.g., a microprocessor, microcontroller, digital signal processor, or general purpose computer) to perform any of the methods and processes described above.

[0066] The computer system may further comprise a storage device, such as a semiconductor storage device (eg, RAM, ROM, ROM, EEPROM, or flash RAM), a magnetic storage device (eg, a floppy disk or non-removable disk), optical storage device (e.g., CD), personal computer card (e.g., PCMCIA card), or other storage device.

[0067] Some of the methods and processes described above can be implemented as computer program logic devices for use with a computer processor. A computer program logic device may be embodied in various forms, including source code or an executable file. The source code may include a number of computer control commands in various programming languages (for example, object code, assembly language, or a high-level language such as C, C ++, or JAVA). Such computer instructions may be stored on a non-volatile computer-readable medium (for example, in memory) and executed by a computer processor. Computer commands can be distributed in any form as a removable storage medium with accompanying printed or electronic documentation (for example, boxed software), pre-installed in a computer system (for example, ROM or a non-removable system disk), or distributed from a server or electronic bulletin board a communication system (for example, the Internet as a whole or through a web interface).

[0068] Alternatively or additionally, the processor may comprise discrete electronic components connected to a printed circuit board, integrated circuits (eg, special purpose integrated circuits, ASICs and / or programmable logic devices (eg, user-programmable logic arrays). Any of the methods and processes described above can be implemented using these logical devices.

[0069] Although only a few examples are described in detail above (XE "Narrowing designation: only"), those skilled in the art will understand that many modifications are possible in the examples without substantially deviating from the subject matter of the invention (XE "Narrowing designation: invention"). Accordingly, all (XE "Narrowing designation: all") such modifications are intended to be included within the scope of this invention, as indicated in the following claims. In the claims, the paragraphs setting forth both the means and the function are intended to cover the structures disclosed herein as performing the specified function, and not only structural equivalents, but also equivalent structures. Thus, although a nail and a screw may not be structural equivalents in the sense that the nail uses a cylindrical surface to bond the wooden parts together, and the screw uses a screw surface, when the wooden parts are fastened, the nail and the screw can be equivalent structures. It is not the applicant’s explicit intention to apply Section 35 of the Code of the United States, 112, paragraph 6, for any restrictions on any claims in this document except those that specifically use the words “intended for” in conjunction with the associated function.

Claims (37)

1. The method of pumping oil field fluid from the surface of the well into the wellbore, in which: provide a source of low pressure aggressive fluid; at least one high pressure pump is driven to pump clean fluid; and using a piston unit that is in contact with the clean fluid in the direction of travel and which pushes the clean fluid, using pressure from at least one high pressure pump to provide high pressure to the aggressive fluid, thereby pushing the aggressive fluid under high pressure into the wellbore, moreover the use of a piston block includes the use of a system having at least two tubular elements, each of which contains a corresponding piston block, while the piston blocks operate in opposite phases to continuously pump aggressive fluid into the wellbore, so that in the first half of the cycle the first of the respective piston blocks forces aggressive fluid out of the first of the two tubular elements under high pressure, while the second of the tubular elements fills it is absorbed by aggressive fluid at low pressure, and in the second half of the cycle, the second of the corresponding piston blocks causes the aggressive fluid to be expelled from the second of the two tubular elements at high pressure, while the first of the tubular elements is filled with aggressive fluid at low pressure. 2. The method of claim 1, wherein a predetermined amount of clean fluid is used to create a buffer separating the piston unit from the aggressive fluid. 3. The method of claim 2, wherein the predetermined amount is a function of the dispersion length of the aggressive fluid in the clean fluid, when the piston unit moves the clean fluid and the aggressive fluid under high pressure. 4. The method of claim 3, wherein the dispersion length function is approximately three dispersion lengths. 5. The method of claim 1, wherein the respective piston blocks are surrounded by clean fluid in both the first half of the cycle and the second half of the cycle. 6. The method according to p. 5, in which a predetermined amount of clean fluid is used to create a buffer that separates each of the respective piston blocks from the aggressive fluid, both in the first half of the cycle and in the second half of the cycle. 7. The method of claim 1, wherein an increasing amount of clean fluid is used in the first half of the cycle to create a buffer separating the first of the respective piston blocks when the first of the respective piston blocks moves at high pressure from the first end to the second end of the first of two tubular elements. 8. The method according to p. 7, in which in the first half of the cycle, the aggressive fluid is in contact at low pressure with the second corresponding piston on the side opposite to the direction of movement of the piston block. 9. The method of claim 1, wherein the clean fluid is water. 10. The method of claim 1, wherein the piston unit comprises a check valve. 11. The method according to p. 1, which further prevent moving the piston block using a thrust element. 12. The method according to p. 1, in which the aggressive fluid is a fluid for hydraulic fracturing. 13. A system for pumping oil field fluid from the surface of the well into the wellbore, comprising: low pressure aggressive fluid supply device; a high pressure pump in communication with clean fluid, and at least two tubular elements, each of which contains a piston block, each piston block being in contact with a clean fluid in the direction of movement of the piston block and pushing the clean fluid using pressure from a high pressure pump to provide pressure and push aggressive fluid, thereby pushing the aggressive fluid under pressure into the wellbore, wherein piston blocks operate in opposite phases to continuously pump aggressive fluid into the wellbore, so that in the first half of the cycle, the first of the respective piston blocks expels the aggressive fluid from the first of the two tubular elements under high pressure, while the second of the tubular elements is filled aggressive fluid at low pressure, and in the second half of the cycle, the second of the respective piston blocks forces the aggressive fluid out of the second of two tubular elements under high pressure, while the first of the tubular elements is filled with aggressive fluid at low pressure. 14. The system of claim 13, further comprising: a plurality of valves, the high pressure pump being in fluid communication with the at least two tubular elements at respective first ends of the tubular elements by means of corresponding first and second valves of the plurality of valves, and the aggressive low-pressure fluid is in fluid communication with the tubular elements on respective the second ends of the tubular elements through the corresponding third and fourth valves of the plurality of valves. 15. The system of claim 14, further comprising: a first storage tank for clean fluid, the respective first ends of the tubular elements being in fluid communication with the first storage tank through fifth and sixth valves of the plurality of valves, and the plurality of valves includes a seventh and an eighth valve, respectively, connected between the respective second ends of the tubular elements and the wellbore. 16. The system of claim 15, further comprising a low pressure pump for aggressive fluid and a second storage tank for aggressive fluid. 17. The system of claim 13, wherein each piston block is in contact with a predetermined amount of clean fluid in the direction of movement of the piston block. 18. The system of claim 17, wherein the predetermined amount is a function of the dispersion length of the aggressive fluid in the clean fluid when the piston unit displaces the clean fluid and the aggressive fluid under high pressure. 19. The system of claim 18, wherein the dispersion length function is three dispersion lengths. 20. The system of claim 13, wherein the respective piston blocks comprise check valves. 21. The system of claim 20, wherein the check valves allow fluid to flow through the check valves at a predetermined response pressure. 22. The system of claim 21, further comprising: a stop element located in each of at least two tubular elements, wherein the stop elements are located in the direction of the respective second ends of the at least two tubular elements, the stop elements are arranged so as to stop the movement of the piston blocks outside the stop elements in the direction of the corresponding second ends . 23. The system of claim 13, wherein in the first half of the cycle, clean fluid is continuously pushed through a check valve, so that an increasing amount of clean fluid is used to create a buffer separating the first of the respective piston blocks when the first of the corresponding piston blocks moves under high pressure from the first end to the second end of the first of the two tubular elements. 24. The system of claim 18, wherein in the first half of the cycle, the aggressive fluid is in contact at low pressure with a second corresponding piston on the side opposite to the direction of movement of the piston block.

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