WO2014160581A1

WO2014160581A1 - Shale fracture flow simulation apparatus

Info

Publication number: WO2014160581A1
Application number: PCT/US2014/031286
Authority: WO
Inventors: James B. Crews; Robert Samuel HURT
Original assignee: Baker Hughes Incorporated
Priority date: 2013-03-27
Filing date: 2014-03-20
Publication date: 2014-10-02
Also published as: US20140290937A1; AR095914A1

Abstract

An apparatus having conduits, flattened tubing or pipes of varying widths, heights and/or lengths may simulate a network of fractures that may be used to experimentally evaluate the flow of treatment fluids (e.g. fracturing fluids) within narrow, shale-type fractures. The tubing or pipes each have an interior space with a height and a width, and in one non-limiting embodiment the ratio of height/width is at least 10. The conduits may be constructed of flattened tubing or constructed from components designed and engineered to have the correct height/width ratio. The apparatus may be used to empirically develop diversion principles, more precise numeric models and the parameter relationships that control fluid diversion, secondary fracture initiation and the development of complex fracture networks.

Description

SHALE FRACTURE FLOW SIMULATION APPARATUS

TECHNICAL FI ELD

[0001] The present invention relates in one non-limiting embodiment to methods and apparatus to model and obtain data on the flow of fluids and proppants in subterranean formations, and more particularly relates, in another non-restrictive version, to methods and apparatus to model and obtain data on the flow of fluids and proppants in subterranean formations that can be employed in a laboratory.

TECHNICAL BACKGROUND

[0002] Hydraulic fracturing of subterranean formations to extract hydrocarbons such as oil and gas is well known. Hydraulic fracturing (or "tracking") involves a stimulation treatment performed on oil and gas wells in low-permeability reservoirs. Specially engineered fracturing fluids are pumped at high pressures and rates into the reservoir interval to be treated, causing a vertical fracture to open. The two wings of the fracture extend away from the wellbore in opposing directions according to the natural stresses within the formation. Proppant, which in one non-limiting embodiment may be grains of sand of a particular size, is mixed with the treatment fluid to keep the fracture open when the treatment is complete. Hydraulic fracturing creates high-conductivity communication with a large area of formation and bypasses damage that may exist in the near-wellbore area.

[0003] The recent surge in oil and gas production in North America has resulted from a combination of directional drilling and hydraulic fracturing of shale formations. Oil and gas in shale is tightly held and difficult to release. Indeed, it has been realized that conventional hydraulic fracturing needs to be reinvented to work optimally in shale formations.

[0004] Most work currently being done to understand and improve shale fracturing has been through numerical modeling and field treatment evaluations. To date, marginal laboratory empirical data has been generated related to fluid and proppant flow in narrow fracture networks. It is possible lack of experimental laboratory data has slowed the industry's learning curve in how to divert fluids and distribute proppants in complex fracture networks. Numeric computer modeling depends on a number of assumptions about what is happening in rock thousands of feet below ground that is difficult to directly observe, thus at best computer modeling of tracking, diversion and distribution is a rough approximation.

[0005] There remains a need to find a way to improve the knowledge of hydraulic fracturing in general and in particular to improve the computer modeling of hydraulic fracturing.

SUMMARY

[0006] There is provided in one non-limiting embodiment an apparatus for modeling flow in subterranean fractures comprising at least one primary conduit having an interior space with a height at least ten times its width, where the conduit comprises a first end, a second end, a first side, and a second side. The apparatus additionally comprises an entry pipe in fluid communication with the first end of the at least one conduit; an exit pipe in fluid communication with the second end of the at least one conduit, a pump in fluid communication with the entry pipe and/or the exit pipe; and at least one data collection sensor in communication with the at least one primary conduit. The data collection sensor may be on or within the primary conduit, but in any event is placed so that it collects data of some type about what is happening within the primary conduit.

[0007] There is additionally provided in one non-restrictive version, a method for modeling the behavior of materials injected into a subterranean fracture, where the method uses the apparatus previously described. The method comprises pumping a fluid through the apparatus and receiving and analyzing data from the at least one data collection sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] FIG. 1 a is a schematic illustration of flattening pipe or tubing between two rollers to form flattened tubing to serve as simulated fractures;

[0009] FIG. 1 b is a schematic illustration of a simple transition from a round pipe to a flattened pipe;

[0010] FIG. 2 is a schematic illustration of the various types of tubing fracture widths that could be simulated with the apparatus and method described herein;

[001 1] FIG. 3 is a three-quarters schematic illustration of the flattened tubing fracture apparatus for modeling flow in subterranean fractures;

[0012] FIG. 4 is an alternative, top, plan view of a fracture apparatus for modeling flow in subterranean fractures described herein;

[0013] FIG. 5 is an alternative side view of another non-limiting embodiment of a fracture apparatus for modeling flow in subterranean fractures described herein;

[0014] FIG. 6 is a cross-sectional view of a fracture-like conduit constructed using spacer fracture widths;

[0015] FIG. 7 is a cross-sectional view of a fracture-like conduit constructed using machined fracture widths;

[0016] FIG. 8 is a cross-sectional view of a fracture-like conduit constructed using a combination of machined and spacer fracture widths;

[0017] FIG. 9 is a side view of a sealing gasket; and

[0018] FIG. 10 is a side view of a fracture width spacer.

[0019] It will be appreciated that the various Figures are not necessarily to scale and that certain features have been exaggerated for clarity and do not necessarily limit the features of the invention.

DETAILED DESCRI PTION

[0020] A method and apparatus have been discovered that may be used to experimentally evaluate the flow of treatment fluids within narrow shale-type fractures. The method is based on artificially creating varying width, height and length "fractures" by flattening tubing (or pipes), or otherwise constructing conduits with relative large height/width ratios, and connecting them to resemble fractures.

[0021] Several material and manufacturing methods may be employed to produce flatten tubing with different gauged internal widths, as described and shown in the Figures. Alternatively, fracture-like conduits may be constructed from multiple parts. A wide range of equipment may be configured to build a shale fracture flow apparatus contemplated herein including, but not necessarily limited to, flow system pumps, accumulators, connections, pressure transducers, pressure discs, gauged cross-intersections, fluid collection chambers, thermocouples, automation hardware and software, and the like. The apparatus may be used inter alia to empirically develop diversion principles, more precise numeric models, and the parameter-relationships that control fluid diversion, secondary fracture initiation, the transport of proppants in narrow fractures and fracture junctions, developing methods and materials for suspending proppant, and development of complex fracture networks. A wide range of empirical data may be generated based on variations of treatment parameters such as fluid viscosity, flow rate, treatment fluid volumes and sequences, fluid cleanup, pressure-controlled diversions, process-control diversions, diversion materials, diversion by a wide range of high-viscosity ratio fluid types, proppant sizes, proppant shapes, proppant aggregation properties, and the like.

[0022] A goal of the apparatus and method described herein would be to properly design and build a shale fracture flow simulation apparatus with the capacity to generate secondary "fractures". The process of constructing fracture-like conduits or flattening tubing through roller dies could be used to create artificial fractures with narrow widths. Additional components would include, but not necessarily be limited to, pumps, pressure transducers, flow meters, software and hardware computer interface, discharge sampling collectors, and the like. Similar to the use of specialized equipment for other treatment designs (e.g. consistometers, ultrasonic compressive strength analyzers (UCAs), Fann 50 viscometers, Fann 70 viscometers, high tempera- ture-high pressure (HTHP) and dynamic fluid loss devices, core permeameters, proppant conductivity cells, etc.) this apparatus could serve to improve fluid designs, and proppant and pump schedules for controlling diversion and distribution of material placements. A sequential project could then be open to utilize the apparatus. Various data collection sensors including, but not necessarily limited to, pressure transducers, flow meters, thermometers, thermocouples, viscosity sensors, sampling collectors, and the like can transmit the data to a computer with appropriate hardware and software configured to analyze the data. It is possible the data generated using this apparatus could allow better understanding of how to induce pressure diversion through fluid and modifying pump parameters, and develop a complex fracture network of proppants of optimized size and density. This work could provide treatment guidelines for reducing "choke points" of restricted conductivity in complex fracture networks, where conductivity is transitionally optimized from nano to micro to millidarcy to macrodarcy or darcies in the direction from fracture tips to wellbore perforations.

[0023] In further detail shown in FIG. 1 a is a schematic illustration of the manufacture of flattened tubing by passing tubing 10 through a pair of pressure rollers 12 that compress and flatten the tubing to give flattened tubing 14. In the particular embodiment shown in FIG. 1 a, the tubing 10 moves from left to right. Due to its greater malleability, tubing may prove to be more suitable than pipe. In one non-limiting embodiment the tubing may be that used as coiled tubing in the oilfield which is well known. Such tubing diameters may range from about 1 inch (2.5 cm) to about 4.5 inches (1 1.4 cm). Regardless whether metal tubing, pipe or casings are used, the diameters may be very small or very large to represent a wide range in height to width size of fractures when flattened. For example, the tubing or pipe diameters may range from 0.25" to 3' (0.64 to 91 cm) or more. The compression by rollers 12 should be such that a very narrow space is present inside the flattened tubing as shown by the cross-sections 20, 22, 24 and 26 of FIG. 2. The metal used should be strong enough to withstand the high pressures (such as 100 psi to 10,000 psi (6.9 MPa to 69 MPa)) expected during testing and not suffer from stress cracking. Suitable metals may include, but are not necessarily limited to, steel, copper, stainless steel and other alloys and the like. It may be necessary for the tubing to pass through the same or different pressure rollers 12 two or three or more times until a suitable final shape is obtained.

[0024] The various sizes schematically illustrated in FIG. 2 represent the various size ranges of narrow fracture widths that could be evaluated using the apparatus and methods described herein. For instance, the inner gap of flattened tubing 20 may represent a fracture width of 6 mm or less; alternatively 1 mm or less, the inner gap of flattened tubing 22 may represent a fracture width of 0.8 mm, the inner gap of flattened tubing 24 may represent a fracture width of 0.6 mm, and the inner gap of flattened tubing 26 may represent a fracture width of 0.4 mm. It will be appreciated that when the same initial tubing is flattened and the inner gap decreases the height will increase slightly as shown in the progression from 20 to 22 to 24 to 26 in FIG 2, since the circumference must generally stay the same. To give a sense of scale, when hydraulically fracturing shale rock formations the planar (main or primary) fracture typically is about 6 to 7 mm wide at the wellbore. The numerous complex fractures generated during shale fracturing are much narrower than the planar fracture width. It is the creation of and flow within narrow complex fractures that designs of the apparatus is to simulate.

[0025] Shown in FIG. 3 is schematic representation of a complex fracture network apparatus 30, where flattened tubing represents a primary conduit or fracture 32 having a primary fracture height of Hn and a primary inner fracture width of W_f1. Generally, the primary fracture width W_f1 is the inner width distance between the first side 34 and second, opposite side 36 of primary conduit 32. Primary conduit 32 has a first end 38 and a second, opposite end 40 and the distance between first end 38 and second end 40 is the primary fracture length L_fi . In one non-limiting embodiment and to give a sense of scale, L_fi may be 10 feet or longer. [0026] In one non-limiting embodiment, the inner-wall (or gap) distance of primary conduit 32 may have "fracture width" of about 6 mm or less, alternatively about 2 mm or less, whereas the secondary conduits or "secondary fractures" may have relative fracture widths smaller as visually represented by flattened tubing 20, 22, 24 or 28.

[0027] In another non-limiting embodiment, the primary conduit 32 may have fracture width comparable to very narrow complex fracture, such as 0.5 mm, and the secondary fractures shown as 20, 22, 24 and 28 will have less than 0.5 mm fracture widths.

[0028] In one non-limiting embodiment fracture height Hn is at least ten times the fracture width Wn ; in a different non-restrictive version at least 20 times, and in another alternate embodiment at least 40 times. The interior dimensions of the open, interior spaces modeling the fractures may also have height/width ratios of these ratios. The size ratio of Hn to W_fi in some cases may be limited to the diameter and thickness of the tubing or conduit selected. Versatility in design is of importance in order to be able to evaluate a wide range of fracture width to height flow conditions.

[0029] First end 38 is in fluid communication with an entry pipe 42, which in turn is in fluid connection with a pump 44. Second end 40 is in fluid communication with an exit pipe 46. It is possible that a pump 44 could alternatively or in addition be in fluid communication with exit pipe 46 if desired, but such a configuration is not as representative of a subterranean formation fracture network. Such a configuration could be helpful in evacuating or draining the network apparatus 30 after use. Primary conduit 32 is provided with at least one data collection sensor 48 for measuring a parameter within the primary conduit, including but not necessarily limited to, pressure, temperature, flow rate, viscosity and the like. Thus data collection sensors 48 may be pressure transducers. It will be appreciated that hydraulically induced fractures in subterranean formations commonly occur as bi-wings on opposite sides of a well bore. Thus, the fracture flow apparatus can be configured where there would be another primary conduit or fracture 32 extending from entry pipe 42 to the left in FIG. 3 toward the viewer. However, for most testing purposes only one primary conduit or fracture 32 from entry pipe may be utilized.

[0030] Optionally, as a non-limiting embodiment, the entry and exit of fracture 32 is the original tubing or pipe or conduit. In FIG. 1 b the entry pipe 42 may be tubing 10, and the fracture 32 may be flattened tubing 14. The first end 38 could be from 1 " to 4" (2.5 cm to 10.2 cm) from the beginning of tubing or pipe item 10. The exit of the fracture item 40 could be manufactured where the original pipe diameter is the exit; thus one tubing or pipe could be used and the fracture width does not include the entry or exit sections of the tubing or pipe.

[0031] Further shown in FIG. 3 are a plurality of secondary conduits 50 extending from and in fluid communication with the at least one primary conduit 32, extending from the first side thereof. An optional configuration is secondary fractures wings 50" shown to the right and extending from the second side 36 of primary conduit 32. Secondary conduits 50 have a height H_f2, a width W_f2 and a length L_f2. Secondary conduits or fractures 50 and 50" are also provided with one or more data collection sensors 48 along their lengths.

[0032] Generally the width of secondary conduits 50 is less than that of primary conduit 32, or W_f2 < Wn , to more accurately simulate fracture structure. In one embodiment, all of secondary conduits 50 and 50" all have the same dimension, that is W_f2, H_f2 and L_f2 are all the same for each secondary conduits 50 and 50". In another non-limiting embodiment, these dimensions may vary, for instance, the fracture widths W_f2 may become smaller as the secondary conduits 50 and 50" progress from the entry pipe 42 to the exit pipe 46. Similarly, the other dimensions, height and length, may optionally become smaller or diminish as the secondary conduits 50 and 50" progress from the entry pipe 42 to the exit pipe 46.

[0033] There may also be present a pressure rupture device, such as a rupture diaphragm, burst disc or burst sheet (not shown) at or adjacent where the at least one secondary conduit 50 or 50" extends from the at least one primary conduit 32, where the pressure rupture device is configured so that for fluid to flow from the at least one primary conduit 32 into the at least one secondary conduit 50 or 50" the pressure rupture device must rupture. There may be more than one pressure rupture device along the juncture where at least one secondary conduit 50 or 50" branches off from the at least one primary conduit 32. Suitable pressure rupture device may be pressure disks, diaphragms, burst discs or burst sheets. By using pressure rupture devices, the creation and filling of secondary fractures under pressure may be simulated by secondary conduits 50 or 50". As a non-limiting example, the pressure rupture devices may be designed to rupture at a pressure of 50 psi (0.34 MPa) or higher; alternatively at a pressure of 500 psi (3.4 MPa) or higher. An important aspect in understanding pressure controlled fluid diversion is use of rupture discs that have a range of pressure required to rupture, such as 100 psi (0.69 MPa), 150 psi (1.0 MPa), 200 psi (1.4 MPa), 300 psi (2.1 MPa), 400 psi (2.8 MPa) and the like. In different studies, no pressure rupture devices are adjacent these junctures (i.e. simulate presence of natural fractures in subterranean formation, such as in coal formations and many shales and carbonates due to regional tectonic stresses and the like).

[0034] Optionally, and for manufacturing simplicity, either wings 50 (or when wings 50' are also optionally configured in the apparatus design), wings 50 are tubing or pipes with end sections like FIG. 1 b tubing or pipe 10 (original tubing or pipe diameter). Connection of wing 50 to fracture 32 would then use conventional pipe and tubing connections commonly used in laboratory equipment, such as Swagelok fittings. This configuration would allow more point entry into fracture 50 and easier placement and use of conventional rupture disc components between fracture 32 and wing 50. The same can be for wings 50' if optionally utilized.

[0035] It should be appreciated that many configurations and orientations of the apparatus 30 may be envisaged. The secondary conduits 50 or 50' and primary conduit 32 are shown in FIG. 1 as oriented at right angles to each other, which is expected to be suitable from the point of view of being convenient to manufacture. However, while it is imagined that in an actual subterranean formation fracture, secondary fractures can be at a right angle or 90° to the primary fracture, it is unlikely that the angle is precisely 90°. Thus, secondary conduits 50 or 50" may optionally be attached to primary fracture 32 at an angle different from 90°. Further, it may be readily understood that tertiary conduits (not shown) may extend from secondary conduits 50 or 50" in a similar manner to the way that the secondary conduits 50 or 50" extend from primary conduit 32, and in most cases the tertiary conduits may have an even smaller fracture width than the secondary conduits 50 or 50". Again, pressure rupture devices may be present adjacent where the at least one tertiary conduit extends from the at least one secondary conduit, where the pressure rupture devices in this location is configured so that for fluid to flow from the at least one secondary conduit into the at least one tertiary conduit the pressure rupture devices must rupture.

[0036] It will also be appreciated that the various components of the apparatus 30 may be designed to be modular so that the primary conduits, secondary conduits, tertiary conduits may be rearranged and reconfigured to conduct various studies. For instance, two or more primary conduits may be configured in series or end-to-end to extend the length of the "fracture" being studied.

[0037] Although it is expected that in most cases exit pipe 46 will be open to let fluid exit apparatus 30, it will be appreciated that in some embodiments and methods, the exit pressure will be adjustable (i.e. like use of a back pressure regulator) or will be blocked or closed by a valve so that fluid pressure within apparatus 30 builds more quickly.

[0038] It will also be appreciated that the apparatus 30 and its various components may be assembled and constructed using methods and materials well known to those skilled in the art of such assembly, including but not necessarily limited to, welding, brazing, bolts and nuts, rivets, pins, screws, valves, threaded pressure connections, unions, quick connections, braided hoses, regulators, aluminum or steal frame components, brackets, wheels and the like. [0039] The apparatus 30 in the configurations discussed as well as those which can be further imagined may be used in a method for modeling the behavior of materials injected into a subterranean fracture. The method includes pumping a fluid through apparatus 30 via fluid injection pump 44 into entry pipe 42 which then enters primary conduit 32 at first end 38. In one non- limiting embodiment the fluid is pumped through apparatus 30 at a pressure of 50 psi or greater, or alternatively below 10,000 psi (69 MPa), in another non- limiting embodiment below 1000 psi (6.9 MPa). Expected pressures may be higher for different kinds of research; as previously noted these could range as high as from 1000 to 10,000 psi (6.9 MPa to 69 MPa). As the fluid travels from first end 38 to second end 40, some of which exits via exit pipe 46 via second end 40, other of the fluid will enter and travel through secondary conduits 50 and 50". As the fluid passes and engages data collection sensors 48, data will be collected, in one non-limiting embodiment pressure data such as through pressure transducers. If pressure rupture diaphragms or pressure disks are present adjacent where the at least one secondary conduit 50 or 50" extends from the at least one primary conduit 32, then when the pressure builds to the yield point of the pressure rupture devices only then will the fluid flow from the primary conduit 32 into the secondary conduits 50 or 50". The point in time and the effective pressures will be noted. It will be appreciated that all of the data collection sensors 48, pressure rupture devices and other sensors will all be configured (e.g. wired or wireless) to send data to an appropriate data collection and analysis system (not shown), such as a computer, which operation is known in the art.

[0040] Shown in FIG. 4 is a top, plan view of an alternative fracture apparatus 60 for modeling flow in subterranean fractures described herein, having a primary fracture conduit 62 with an entrance component 64 and an exit component 66 where flow travels in the direction of arrow 68 from entrance component 64 to exit component 66. Right-angled junction 70 joins primary fracture conduit 62 with secondary fracture conduit 72 extending from primary fracture conduit 62 at 90° in fluid communication with primary fracture conduit 62. However, as noted, in actuality secondary fractures do not necessarily propagate from primary fractures at exactly 90°, thus it may be desirable for primary fracture conduit 62 to also have angled junction 74 to extend angled secondary fracture conduit 76 at angle X from primary fracture conduit 62. In one non-limiting embodiment, angle X may range from about 5° to about 175°; alternatively from about 20° to about 160°. The entrance component 64 and exit component 66 can vary in design, composition, seals, isolation valves, methods of attachment, and the like. In one non-limiting embodiment the flow channels or conduits of components 64 and 66 may be machined into one or both fracture plates 90 and 92, where fluid entrance and/or exit is machined passageway within either fracture plates 90 and 92 as options in methods of sealing and attaching piping and other flow equipment. For example, if machined into plate 92 then plate 92 would possibly be thicker than plate 90 to allow clearance and strength integrity to plate 92 after machining the entrance and/or exit conduits that lead to and from the variable inner gap width (fracture width) of gaps 84 and 102 in FIGS 6-8.

[0041] Shown in FIG. 5 is an alternative side view of another non-limiting embodiment of a fracture apparatus 60 for modeling flow in subterranean fractures similar to that depicted in FIG. 4, where the same reference numerals refer to the same part types, illustrating an end-on view of exit component 66 at the end of secondary fracture conduit 72.

[0042] The conduits forming a fracture network apparatus as described herein may also be fabricated from component parts as schematically illustrated in FIGS. 6-10, in contrast to the process of flattening tubing as schematically illustrated in FIG. 1. In one non-limiting embodiment, FIG. 6 illustrates a cross- sectional view of a fracture-like conduit assembly 80 constructed using a fracture width spacer 82, shown in schematic side profile in FIG. 10, where the vacant space of the fracture is illustrated at 84. As previously mentioned, this vacant or open interior space may have a ratio of height to width of at least ten. Again, it will be appreciated that the relative proportions of the elements presented in the Figures may not be to scale. These vacant or interior spaces 84 may vary in relative sizes and ratios depending on whether they simulate a primary fracture, secondary fracture or tertiary fracture, as previously described. Fracture-like conduit 80 contains fracture width spacer 82 between two sealing gaskets 86. A sealing gasket 86 is shown in schematic side profile in FIG. 9, where the vacant space of the fracture is illustrated at 88. Plates 90 and 92 are secured on either side of the fracture-like conduit 80 using any appropriate fastener, including, but not necessarily limited to nuts 94 and bolts 96, screws, rivets, clamps, locks, and the like and combinations thereof. In one non-limiting embodiment where the conduits are modular, it would be advantageous for the fasteners to be easy to assemble and disassemble.

[0043] Shown in FIG. 7 is a cross-sectional view of a fracture-like conduit assembly 100 constructed using machined fracture widths, where plate 92" has an open, interior space 102 machined, cast, or otherwise provided within its interior-facing surface. The interior space 102 thus defines the height and width of the simulated fracture. Sealing gasket 104 may be provided between plates 90 and 92" to provide a secure, leak-proof seal when fracture-like conduit 100 is assembled with nuts 94 and bolts 96.

[0044] Shown in FIG. 8 is a cross-sectional view of a fracture-like conduit assembly 110 constructed using a combination of machined and spacer fracture widths used in FIGS. 6 and 7, where machined plate 92"with an interior space 102 provided within by machining, casting or other provision, is held against sealing gasket 82, fracture width spacer 112 and another sealing gasket 82 against which plate 90 is held with nuts 94 and bolts 96.

[0045] It will be appreciated that assembling the conduits (such as 62, 72, 80, 100 and 110) from component parts that are modular to a large extent will make the fracture network modeling apparatus more versatile to design, assemble, disassemble and operate, and provide considerably more accuracy, be easier to manufacture, and have much higher pressure ratings that would be possible using the flattened tubing. More specifically, the interior spaces simulating fractures of a particular conduit may be changed by changing the fracture width spacers and/or the plates having different interior spaces. [0046] Besides the materials noted above with respect to the flattened tubing embodiment, the plates may be made from a variety of materials including, but not necessarily limited to, stainless steel, aluminum, aluminum alloys, titanium, titanium alloys, polycarbonate, and other types of clear, strong plastics, and combinations thereof. The fracture width spacers may be made of materials including, but not necessarily limited to, stainless steel, aluminum, aluminum alloys, titanium, titanium alloys, copper, copper alloys, paper, nitrile rubber, polytetrafluoroethylene (PTFE, also known by the trademark TEFLON^® polymers), polychlorotrifluoroethylene, and other plastic polymers and combinations thereof. Suitable materials for the sealing gaskets are flat materials which are sheet-like in structure including, but not necessarily limited to, aluminum alloys, titanium, titanium alloys, copper, copper alloys, asbestos, paper, rubbers (such as butadiene and nitrile rubbers), polytetrafluoroethylene (PTFE, also known by the trademark TEFLON^® polymers), polychlorotrifluoroethylene, and other plastic polymers, O-rings composed of Buna-N (nitrile rubber), silicon, VITON^® (synthetic rubber and fluoropolymer elastomer), EPDM, KALREZ^® perfluoroelastomer, nitrile, urethane, zinc, brass, aluminum, stainless steel, and the like, and combinations thereof. The non-limiting expected range of thicknesses for the sealing gaskets is from about 0.5 independently to about 8 mm for rubber or metal O-rings, and from about 0.005 independently to about 3 mm for flat sheet materials; alternatively from about 1.5 independently to about 6 mm for rubber or metal O-rings, and from about 0.01 independently to about 2 mm for flat sheet materials; As previously discussed, the inner gap or "fracture" width may be 6 mm and smaller.

[0047] The entrance components, exit components and junctions may be custom fabricated and designed to be modular so that fracture simulation apparatus may be readily reconfigured without wasting previously made or procured components. The entrance components, exit components and junctions should be designed for isolation, to control fluid displacement, to limit excess volume, and of course to prevent leaks. Additionally, in a non-limiting example, the entrance and exit components can be designed to mate and seal with flow conduits machined in either plates 90 or 92. For the design example of conduits machined within either plates 90 or 92, this would allow sealing gasket 86 and fracture width spacer 82 to not be double open-ended (at entrance and exit positions), as shown in FIGS. 9-10, but will allow them to be made and used as closed-ended, a design that could simplify fracture pressure containment and simplify apparatus maintenance and use.

[0048] The apparatus and methods described herein will be suitable to conduct experimental flow tests in narrow fractures. Factors that may be evaluated may include, but not necessarily be limited to, fracture widths, lengths and heights, flow rates, fluid viscosities, fluid sequences, fluid cleanups and combinations of these. It will be appreciated that all of these variables except one may be held constant while the effects of changes in the one variable may be measured and analyzed. The method and apparatus will thus provide greater understanding of pressure diversion, diversion processes, diversion materials, proppant sizes, proppant shapes, and/or proppant aggregation. For instance, it is usual that conventional commercial proppants are of a size of 100 mesh (0.149 mm). However, it would be useful to know whether the proppant in fractures having narrower fracture widths should be smaller than conventional proppants. The fluids pumped into and/or through the apparatus may have their viscosities increased by the addition of a gelling agent which may include, but not be limited to, at least one polymer (e.g. a polysaccharide such as xanthan gum), at least one crosslinked polymer, at least one viscoelas- tic surfactant (VES), and a combination thereof.

[0049] Suitable studies include but are not necessarily limited to:

• Evaluating how different sizes, shapes and/or densities of proppants will travel through narrow fractures, enter and flow in offset (i. e. perpendicular, etc.) secondary and tertiary fractures widths and directions, settle out (sedimentation), or congregate in fractures of different widths.

• Studying the behavior of opening and diverting flow into the secondary and tertiary fractures, such as use of rate, difference in fracture widths, a relatively high viscosity fluid followed by a relatively low viscosity fluid, influence of friction pressure, fracture geometry, and the like.

• Studying anisotropic effects, where low anisotropy indicates that the pressures to fracture in one direction (i.e. the direction of the primary conduit) is similar to the pressures necessary to fracture in a generally perpendicular direction (i. e. the direction of the secondary conduit).

• Studying the effects of using a different pressures, flow rates and/or different fluid viscosities in different fracture geometries (width, height, length) in different configuration of primary, secondary and tertiary conduits.

• Evaluating diversion principles to determine the effects of using too much pressure, flow rate and/or viscosity too soon or too small of a flow rate, and/or too little of viscosity for given fracture size or geometry.

• Determining effective pumping strategies to increase conductivity particularly as flow nears the wellbore.

• Evaluating how to minimize or eliminate choke points of restricted conductivity in complex fracture networks.

[0050] It will be appreciated that by collecting all of the above-noted data and more that including this data into existing computer models for shale fracturing will improve those models by increasing their accuracy in many respects.

[0051] In the foregoing specification, the invention has been described with reference to specific embodiments thereof, and has been demonstrated as effective in providing methods and apparatus for modeling flow and fracture behavior in subterranean formations, particularly shale formations. However, it will be evident that various modifications and changes can be made thereto without departing from the broader scope of the invention as set forth in the appended claims. Accordingly, the specification is to be regarded in an illustrative rather than a restrictive sense. For example, specific combinations of primary conduits, secondary conduits, tertiary conduits, entry pipes and exit pipes, fluid pumps, data collection sensors, pressure rupture devices and other components such as gauged cross-intersections, fluid collection chambers, thermocouples, automated hardware, data collection and analysis software are expected to be within the scope of this invention. Further, it is expected that the components and proportions of the various conduits and components may change somewhat from one application to another and still accomplish the stated purposes and goals of the methods described herein. For example, the methods may use different components, component combinations, different component proportions and additional or different steps than those described and exemplified herein.

[0052] The words "comprising" and "comprises" as used throughout the claims is to be interpreted as "including but not limited to".

[0053] The present invention may suitably comprise, consist of or consist essentially of the elements disclosed and may be practiced in the absence of an element not disclosed. For instance, an apparatus for modeling flow in subterranean fractures may consist of or consist essentially of at least one primary conduit having an interior space with a height at least ten times its width, where the conduit has a first end, a second end, a first side and a second side; where the apparatus additionally consists of or consists essentially of an entry pipe in fluid communication with the first end of the at least one conduit; an exit pipe in fluid communication with the second end of the at least one conduit, a pump in fluid communication with the entry pipe (and/or the exit pipe); and at least one data collection sensor within the at least one primary conduit, and at least one secondary conduit extending from and in fluid communication with the at least one primary conduit.

[0054] Alternatively, a method for modeling the behavior of materials injected into a subterranean fracture may consist of or consist essentially of pumping a fluid through an apparatus, where the apparatus is any of those described in the previous paragraph, or those further above, where the method additionally consists of or consists essentially of receiving and analyzing data from the at least one data collection sensor.

Claims

CLAIMS What is claimed is:

1. An apparatus for modeling flow in subterranean fractures comprising: at least one primary conduit having an interior space with a height at least ten times its width, the at least one primary conduit comprising:

a first end,

a second end,

a first side, and

a second side;

an entry pipe in fluid communication with the first end of the at least one primary conduit;

an exit pipe in fluid communication with the second end of the at least one primary conduit,

a pump in fluid communication with a pipe selected from the group

consisting of the entry pipe, the exit pipe and combinations thereof; and

at least one data collection sensor in communication with the at least one primary conduit.

2. The apparatus of claim 1 where the at least one data collection sensor is a pressure transducer.

3. The apparatus of claim 1 further comprising at least one secondary conduit extending from and in fluid communication with the at least one primary conduit.

4. The apparatus of claim 3 where the inner widths of the at least one primary conduit and the at least one secondary conduit are less than 6 mm.

5. The apparatus of claim 3 comprising a pressure rupture device adjacent where the at least one secondary conduit extends from the at least one primary conduit, where the pressure rupture device is configured so that for fluid to flow from the at least one primary conduit into the at least one secondary conduit the pressure rupture device must rupture.

6. The apparatus of claim 3 further comprising at least two secondary conduits extending from and in fluid communication with the at least one primary conduit, and where each secondary conduit comprises at least one data collection sensor therein.

7. The apparatus of claim 1 or 3 where the at least one primary conduit is constructed from an assembly selected from the group consisting of:

an assembly of at least one fracture width spacer between two sealing gaskets, all of which define the interior space, and all assembled between two plates;

an assembly of at least one plate comprising the interior space, a sealing gasket covering and enclosing the interior space, and a plate on a side of the sealing gasket away from the at least one plate; and combinations thereof.

8. The apparatus of claim 1 or 3 where the at least one primary conduit is flattened tubing.

9. A method for modeling the behavior of materials injected into a subterranean fracture comprising:

pumping a fluid through an apparatus, where the apparatus comprises: at least one primary conduit having an interior space with a height at least ten times its width, the at least one primary conduit comprising: a first end,

a second end,

a first side, and

a second side;

an entry pipe in fluid communication with the first end of the at least one conduit;

an exit pipe in fluid communication with the second end of the at least one conduit,

a pump in fluid communication with a pipe selected from the

group consisting of the entry pipe, the exit pipe and combinations thereof; and

at least one data collection sensor in communication with the at least one primary conduit;

receiving data from the at least one data collection sensor.

10. The method of claim 9 where the at least one data collection sensor is a pressure transducer and the data received is pressure data and where the method further comprises pumping the fluid through the apparatus at a pressure below 10,000 psi (69 MPa).

1 1. The method of claim 9 or 10 where the apparatus further comprises at least one secondary conduit extending from and in fluid communication with the at least one primary conduit, where the secondary conduit comprises at least one data collection sensor, where the method comprises receiving data from the at least two data collection sensors.

12. The method of claim 1 1 where the apparatus further comprises a pressure rupture device adjacent where the at least one secondary conduit extends from the at least one primary conduit, configured so that for fluid to flow from the at least one primary conduit into the at least one secondary conduit the pressure rupture device must rupture.

13. The method of claim 9 or 10 where the apparatus further comprises at least two secondary conduits extending from and in fluid communication with the at least one primary conduit, and where each secondary conduit comprises at least one data collection sensor therein, where the method further comprises collecting data from the at least one data collection sensor in the at least one primary conduit and from each of the at least one data collection sensors in each of the secondary conduits.

14. The method of claim 9 or 10 where the fluid further comprises a gelling agent selected from the group consisting of at least one polymer, at least one crosslinked polymer, at least one viscoelastic surfactant, and a combination thereof, where the gelling agent is present in an amount effective to increase the viscosity of the fluid.

15. The method of claim 14 where the fluid comprises a proppant.