Microfluidic devices and systems, and methods for operating microfluidic devices and systems

A microfluidic device includes a substrate having a first fluid inlet/outlet system, a second fluid inlet/outlet system, and a fluidic network between the first fluid inlet/outlet system and the second fluid inlet/outlet system and in fluid communication with the first fluid inlet/outlet system and the second fluid inlet/outlet system. The fluidic network includes a microfluidic channel network that is in fluid communication with the first fluid inlet/outlet system and spaced from the second fluid inlet/outlet system, a nanofluidic channel network fluidly connecting the microfluidic channel network and the second fluid inlet/outlet system, and a plurality of pores in fluid communication with the microfluidic channel network and the nanofluidic channel network.

FIELD

This document relates to microfluidics. More specifically, this document relates to microfluidic devices such as microfluidic chips, systems including microfluidic devices, and methods for operating microfluidic devices and systems.

BACKGROUND

U.S. Pat. No. 9,488,586 (He et al.) discloses a mini-reservoir device that may be used to screen or otherwise determine a composition of one or more treatment fluids, additives, and other fluids. Such fluids may be for use in a subterranean formation. Methods of determining a composition may include visual analysis of each of two or more fluids, each from a plurality of candidate fluids, flowed through a mini-reservoir device, and selection of one of the plurality of candidate fluids based at least in part upon that visual analysis. Certain methods may include determining an oil recovery factor for each of one or more fluids flowed through a mini-reservoir device. In particular methods, multiple treatment fluids and/or additives, such as surfactants, may be selected based at least in part upon visual analysis of the fluids' flow through a mini-reservoir device.

SUMMARY

The following summary is intended to introduce the reader to various aspects of the detailed description, but not to define or delimit any invention.

A microfluidic device is disclosed. According to some aspects, the microfluidic device includes a substrate having a first fluid inlet/outlet system, a second fluid inlet/outlet system, and a fluidic network between the first fluid inlet/outlet system and the second fluid inlet/outlet system and in fluid communication with the first fluid inlet/outlet system and the second fluid inlet/outlet system. The fluidic network includes a microfluidic channel network that is in fluid communication with the first fluid inlet/outlet system and spaced from the second fluid inlet/outlet system, a nanofluidic channel network fluidly connecting the microfluidic channel network and the second fluid inlet/outlet system, and a plurality of pores in fluid communication with the microfluidic channel network and the nanofluidic channel network.

In some examples, the microfluidic channel network has a first set of microfluidic inlet/outlets that are fluidly connected to the first fluid inlet/outlet system, and a second set of microfluidic inlet/outlets that are fluidly connected to the nanofluidic channel network. In some examples, the nanofluidic channel network has a first set of nanofluidic inlet/outlets that are fluidly connected to the microfluidic channel network, a second set of nanofluidic inlet/outlets that are fluidly connected to the first fluid inlet/outlet system, and a third set of nanofluidic inlet/outlets that are fluidly connected to the second fluid inlet/outlet system.

In some examples, the microfluidic channel network has a depth of between about 1 micron and about 500 microns. In some examples, the microfluidic channel network has a depth of between about 20 microns and about 150 microns.

In some examples, the nanofluidic channel network has a depth of between about 1 nm and about 999 nm. In some examples, the nanofluidic channel network has a depth of between about 50 nm and about 500 nm.

In some examples, the microfluidic channel network is triangle shaped and has a base adjacent the first fluid inlet/outlet system and a peak spaced from the first fluid inlet/outlet system. In some examples, the microfluidic channel network is arborescent and has a stem adjacent the first fluid inlet/outlet system and a plurality of branches spaced from the first fluid inlet/outlet system.

In some examples, the first fluid inlet/outlet system includes at least a first inlet/outlet port and at least a first inlet/outlet channel fluidly connecting the first inlet/outlet port and the fluidic network, and the second fluid inlet/outlet system comprises at least a second inlet/outlet port and at least a second inlet/outlet channel fluidly connecting the second inlet/outlet port and the fluidic network.

In some examples, the substrate includes i) a base panel in which the first fluid inlet/outlet system, the second fluid inlet/outlet system, and the fluidic network are etched, and ii) a cover panel secured to the base panel and covering the first fluid inlet/outlet system, the second fluid inlet/outlet system, and the fluidic network. At least one of the base panel and the cover panel is transparent.

A method for operating a microfluidic device is also disclosed. According to some aspects, the method includes a. flowing at least a first volume of fluid into a microfluidic channel network of the microfluidic device; b. flowing the first volume of fluid from the microfluidic channel network into a nanofluidic channel network of the microfluidic device; and c. conducting an optical investigation of the first volume of fluid as the first volume of fluid flows through the microfluidic channel network and/or the nanofluidic channel network.

In some examples, the method further includes, after step b.: d. flowing a second volume of fluid into the microfluidic channel network of the microfluidic device; e. flowing the second volume of fluid from the microfluidic channel network into the nanofluidic channel network; and f. conducting an optical investigation of the second volume of fluid as the second volume of fluid flows through the microfluidic channel network and/or the nanofluidic channel network.

In some examples, the method further includes, after step e.: g. flowing a third volume of fluid into the microfluidic channel network of the microfluidic device; h. flowing the third volume of fluid from the microfluidic channel network into the nanofluidic channel network; and i. conducting an optical investigation of the third volume of fluid as the third volume of fluid flows through the microfluidic channel network and/or the nanofluidic channel network.

In some examples, the method further includes, after step h.: j. reversing the flow of fluid by flowing a fourth volume of fluid into the nanofluidic channel network, and flowing the fourth volume of fluid from the nanofluidic channel network into the microfluidic channel network; and k. conducting an optical investigation of the fourth volume of fluid as the fourth volume of fluid flows through the nanofluidic channel network and/or the microfluidic channel network.

In some examples, the method further includes allowing at least one of the first volume of fluid, second volume of fluid, and third volume of fluid to soak in the microfluidic device for a period of at least 10 minutes.

In some examples, the first volume of fluid includes salt water, the second volume of fluid includes oil, the third volume of fluid includes a test fluid, and the fourth volume of fluid includes oil.

In some examples, the method further includes, after step b.: reversing the flow of fluid by flowing a subsequent fluid into the nanofluidic channel network and from the nanofluidic channel network back into the microfluidic channel network; and conducting an optical investigation of the subsequent fluid as the subsequent fluid flows through the nanofluidic channel network and/or the microfluidic channel network.

A microfluidic system is also disclosed. According to some aspects, the microfluidic system includes a microfluidic device having a substrate with at least a first fluid inlet/outlet system, at least a second fluid inlet/outlet system, and a fluidic network between the first fluid inlet/outlet system and the second fluid inlet/outlet system and in fluid communication with the first fluid inlet/outlet system and the second fluid inlet/outlet system. A fluid injection system is connected to the first fluid inlet/outlet system for forcing fluid in a forward direction through the microfluidic device from the first fluid inlet/outlet system to the second fluid inlet outlet system via the fluidic network, and connected to the second fluid inlet/outlet system for forcing fluid in a reverse direction through the microfluidic device from the second fluid inlet/outlet system to the first fluid inlet outlet system via the fluidic network. An optical investigation system is provided for conducting an optical investigation of the fluidic network (either in whole or in part).

In some examples, the fluidic network includes a microfluidic channel network that is in fluid communication with the first fluid inlet/outlet system and spaced from the second fluid inlet/outlet system, a nanofluidic channel network fluidly connecting the microfluidic channel network and the second fluid inlet/outlet system, and a plurality of pores in fluid communication with the microfluidic channel network and the nanofluidic channel network.

In some examples, the system further includes a first fluid collection system connected to the first fluid inlet/outlet system for collecting fluid from the first fluid inlet/outlet system when the fluid is forced in the reverse direction. In some examples, the system further includes a second fluid collection system connected to the second fluid inlet/outlet system for collecting fluid from the second fluid inlet/outlet system when the fluid is forced in the forward direction.

Another method for operating a microfluidic device is also disclosed. According to some aspects, the method includes a. flowing a least a first volume of fluid through a microfluidic device in a forward direction from a first fluid inlet/outlet system, through a fluidic network, and towards a second fluid inlet/outlet system; b. reversing the flow of fluid by flowing a subsequent volume of fluid in a reverse direction from second fluid inlet/outlet system, through the fluidic network, and towards the first fluid inlet/outlet system; and c. conducting an optical investigation of at least a portion of the fluidic network during step a. and/or step b.

In some examples, the method further includes, between steps a. and b.: i. flowing a second volume of fluid through the microfluidic device in the forward direction; and ii. conducting an optical investigation of at least a portion of the fluidic network during step i.

In some examples, the method further includes, after step i.: iii. flowing a third volume of fluid through the microfluidic device in the forward direction; and iv. conducting an optical investigation of at least a portion of the fluidic network during step iii.

In some examples, the method further includes, between steps a. and b., allowing at least one of the first volume of fluid, the second volume of fluid, and the third volume of fluid to soak in the fluidic network for a period of at least 10 minutes.

In some examples, the first volume of fluid includes salt water, the second volume of fluid comprises oil, the third volume of fluid comprises a test fluid, and/or the fourth volume of fluid comprises oil.

In some examples, step a. includes: flowing the first volume of fluid into a microfluidic channel network of the fluidic network, and then flowing the first volume of fluid from the microfluidic channel network into a nanofluidic channel network of the fluidic network.

In some examples, step b. includes flowing the subsequent fluid from the nanofluidic channel network back into the microfluidic channel network.

DETAILED DESCRIPTION

Various apparatuses or processes or compositions will be described below to provide an example of an embodiment of the claimed subject matter. No embodiment described below limits any claim and any claim may cover processes or apparatuses or compositions that differ from those described below. The claims are not limited to apparatuses or processes or compositions having all of the features of any one apparatus or process or composition described below or to features common to multiple or all of the apparatuses or processes or compositions described below. It is possible that an apparatus or process or composition described below is not an embodiment of any exclusive right granted by issuance of this patent application. Any subject matter described below and for which an exclusive right is not granted by issuance of this patent application may be the subject matter of another protective instrument, for example, a continuing patent application, and the applicants, inventors or owners do not intend to abandon, disclaim or dedicate to the public any such subject matter by its disclosure in this document.

Generally disclosed herein are microfluidic devices in the form of microfluidic chips, systems incorporating microfluidic devices, and related methods. The microfluidic devices, systems, and methods can be used in the oil and gas industry, in order to model shale and/or tight oil formations, as well as fracture zones (also known as “frac zones”) created in such formations during hydraulic fracturing (also known as “fracking”). More specifically, the microfluidic devices can include a nanoporous zone (i.e. a zone that includes channels having a depth on the nanometer scale, or that includes channels that cause fluid therein to behave as nano-confined fluid) that mimics the matrix of a shale and/or tight oil formation, a microporous zone (i.e. a zone that includes channels having a depth on the micron scale, or that includes channels that cause fluid therein to behave as micro-confined fluid) that mimics a fracture zone of a shale and/or tight oil formation, and pores that mimic pores in the matrix of the shale and/or tight oil formation. The inclusion of both a nanoporous zone and a microporous zone on a single device can allow for relatively accurate and realistic modeling of a fracking operation. Furthermore, the microfluidic system can operate in two directions—a forward direction in which fluid is injected into the microfluidic device and flows from the microporous zone to the nanoporous zone, and a reverse direction in which fluid is injected into the microfluidic device and flows from the nanoporous zone to the microporous zone. By operating in both directions, the system can allow for relatively accurate and realistic modelling of oil production in a fracking operation. That is, flow in the forward direction can model the injection of test fluids such as “frac fluids” (e.g. surfactants, friction reducers, gels, dilute acids, and/or corrosion inhibitors) into the shale and/or tight oil formation via the frac zone, and flow in the reverse direction can model the production of oil from the shale and/or tight oil formation via the frac zone. This can be beneficial, for example, to facilitate screening or performance of frac fluids.

Referring now toFIG. 1, an example microfluidic device100is shown. The device100is in the form of a microfluidic chip, and includes a substrate102that has fluid channels104(only some of which are labelled inFIG. 1) etched therein and that allows for optical investigation (e.g. imaging, with the use of an optical microscope and/or video recording equipment and/or a photographic camera) of at least some of the fluid channels104.

In the example shown, the substrate102includes a base panel106in which the fluid channels104are etched, and a cover panel108that is secured to the base panel106and that covers the fluid channels104. In the example shown, the base panel106is an opaque silicon panel, and the cover panel108is a transparent glass panel. In alternative examples, the substrate may be of another configuration. For example, both the base panel106and the cover panel108can be a transparent glass panel, or the base panel106can be a transparent glass panel while the cover panel108can be an opaque silicon panel.

Referring now toFIG. 2, in the example shown, the fluid channels104(again, only some of which are labelled) of the microfluidic device100are made up of a first fluid inlet/outlet system110, a second fluid inlet/outlet system112, and a fluidic network114between the first fluid inlet/outlet system110and the second fluid inlet/outlet system112.

In the example shown, the first fluid inlet/outlet system110includes a first116and a second118inlet/outlet port, into which fluid may be injected or out of which fluid may be ejected, and a set of channels. The channels are microfluidic channels—i.e. the channels have a depth that is in the micron scale, for example between about 1 micron and about 500 microns, or between about 20 microns and about 150 microns. The set of microfluidic channels includes a first120and a second122inlet/outlet line, each of which is connected to one of the inlet/outlet ports116,118, respectively; a third inlet/outlet line124that is connected to the first120and second122inlet/outlet lines; and a fluid distribution channel126, which distributes fluid to and/or collects fluid from the fluidic network114.

Similarly, in the example shown, the second fluid inlet/outlet system112includes a first128and a second130inlet/outlet port, into which fluid may be injected or out of which fluid may be ejected, and a set of microfluidic channels. The set of microfluidic channels includes a first132and a second134inlet/outlet line, each of which is connected to one of the inlet/outlet ports128,130, respectively; and a fluid distribution channel138that is connected to the first132and second134inlet/outlet lines, which distributes fluid to and/or collects fluid from the fluidic network114.

Referring still toFIG. 2, in the example shown, the fluidic network114includes both a microfluidic channel network140and a nanofluidic channel network142, as well as a plurality of pores144(only two of which are labelled inFIG. 2) that are in fluid communication with the microfluidic channel network140and the nanofluidic channel network142. The microfluidic channel network140has channels that have a depth on the micron scale, for example between about 1 micron and about 500 microns, or between about 20 microns and about 150 microns. The nanofluidic channel network142has channels that have a depth on the nanometer scale, for example between about 1 nm and about 999 nm, or between about 50 nm and about 500 nm. As mentioned above, the nanofluidic channel network142can mimic a matrix of a shale and/or tight oil formation, and the microfluidic channel network140can mimic a fracture zone of a shale and/or tight oil formation.

Referring still toFIG. 2, in the example shown, the microfluidic channel network140is in fluid communication with the first fluid inlet/outlet system110. Furthermore, the microfluidic channel network140is spaced from the second fluid inlet outlet system112. That is the microfluidic channel network140is not directly connected to the second fluid inlet/outlet system112. The nanofluidic channel network142is between the microfluidic channel network140and the second fluid inlet/outlet system112, and fluidly connects the microfluidic channel network140to the second fluid inlet outlet system112. In the example shown, the nanofluidic channel network142is also fluidly connected to the first fluid inlet/outlet system110. More specifically, in the example shown, the microfluidic channel network140has a first set of microfluidic inlet/outlets146(only one of which is labelled inFIG. 2) that are fluidly connected to the fluid distribution channel126of the first fluid inlet/outlet system110, and a second set of microfluidic inlet/outlets148(only one of which is labelled inFIG. 2) that are fluidly connected to the nanofluidic channel network142. The nanofluidic channel network142has a first set of nanofluidic inlet/outlets150(only one of which is labelled inFIG. 2) that are fluidly connected to the fluid distribution channel126of the first fluid inlet/outlet system110, a second set of nanofluidic inlet/outlets152(only one of which is labelled inFIG. 2) that are fluidly connected to the microfluidic channel network140, and a third set of nanofluidic inlet/outlets154(only one of which is labelled inFIG. 2) that are fluidly connected to the fluid distribution channel138of the second fluid inlet/outlet system112.

Accordingly, in the example shown, when operating in the forward direction, fluid flows into the first fluid inlet/outlet system110; from the first fluid inlet/outlet system110into the microfluidic channel network140and then into the nanofluidic channel network142, and also from the first fluid inlet/outlet system110into the nanofluidic channel network142directly; and finally, from the nanofluidic channel network142into the second fluid inlet/outlet system112. This flow pattern can mimic the flow of fluids—e.g. frac fluids and oil—in a fracking operation during frac fluid injection.

Similarly, when operating in the reverse direction, fluid flows into the second fluid inlet/outlet system112; from the second fluid inlet/outlet system112into the nanofluidic channel network142; from the nanofluidic channel network142into the microfluidic channel network140and then into the first inlet/outlet system110, and also from the nanofluidic channel network142into first inlet/outlet system110directly. This flow pattern can mimic the flow of fluids—e.g. frac fluids and oil—in a fracking operation during production.

In the example shown, the nanofluidic channel network142is generally rectangular shaped. In alternative examples, the nanofluidic channel network can be of another shape.

In the example shown, the microfluidic channel network140is triangle shaped, and has a base156adjacent the first fluid inlet/outlet system110and a peak158spaced from the first fluid inlet/outlet system110. In other examples, various other shapes are possible. For example, referring toFIG. 3, an example microfluidic device300is shown that includes a nanofluidic channel network342, a microfluidic channel network340, and pores344(only one of which is labelled). The nanofluidic channel network342is rectangular, and the microfluidic channel network340is arborescent. The microfluidic channel network340has a stem356adjacent the first fluid inlet/outlet system310and a plurality of branches358(only one of which is labelled inFIG. 3) spaced from the first fluid inlet/outlet system310. The arborescent microfluidic channel network340can, in appearance, closely mimic the shape of a frac zone in a shale and/or tight oil formation.

Furthermore, various arrangements of pores are possible. For example,FIG. 4shows an example microfluidic device400having a microfluidic channel network440and nanofluidic channel network442that are similar to those ofFIG. 3; however, the microfluidic device400has a density of pores444that is greater than the density of pores344ofFIG. 3.

Furthermore, various configurations of fluid inlet/outlet systems are possible. For example,FIG. 5shows a microfluidic device500that includes a microfluidic channel network540and a nanofluidic channel network542similar to those ofFIG. 2; however, the first fluid inlet/outlet system510and a second fluid inlet/outlet system512are of a different configuration from those ofFIGS. 2 to 4.

Furthermore, the relative area of the first fluid inlet/outlet system, second fluid inlet/outlet system, and fluidic network can vary depending on the magnification under which the microfluidic device is intended to be viewed. For example, the microfluidic device100ofFIG. 2may be suitable for viewing under a 1.25× objective lens. An alternative example is shown inFIG. 6, in which the microfluidic device600is suitable for viewing under a 5× objective lens.

The microfluidic devices described herein can be manufactured according to various methods, including methods known in the microfluidic industry for etching channels onto substrates. Briefly, the exact configuration of the fluidic network114can be determined using various algorithms, which are known in the art and are not described in detail herein. The nanofluidic channel network142can then be etched into the silicon base panel106, followed by etching of the microfluidic channel network140and the first110and second112fluid inlet/outlet systems. Optionally, the inlet/outlet ports116,118,120,122can be drilled into the base panel106with a laser. The cover panel108can then be secured over the base panel, for example by anodic bonding.

Referring now toFIG. 7, an example microfluidic system700is shown. Various microfluidic devices may be mounted in the microfluidic system, including those shown inFIGS. 1 to 6; however, for simplicity, the microfluidic system will be described with reference to the microfluidic device100described above.

In the example shown, the system700includes a holder702for the microfluidic device, which is schematically shown inFIG. 7. The holder702can be any suitable holder that allows for fluids to flow into and out of the first fluid inlet/outlet system110and second fluid inlet/outlet system112, and that allows for optical investigation of the fluids as they flow through fluidic network114. The holder702can optionally allow for temperature control of the microfluidic device100, and can optionally allow for operation of they system700under high pressure. An example of such a holder is described in our previous provisional patent application No. 62/721,719 (De Haas et al.), which is incorporated herein by reference in its entirety. Various other holders are known in the art and will not be described in detail herein.

Referring still toFIG. 7, in the example shown, the system700further includes a fluid injection system704, which is connected to the first fluid inlet/outlet system110of the microfluidic device100via the holder702, and which can force fluid in a forward direction through the microfluidic device100from the first fluid inlet/outlet system110to the second fluid inlet outlet112system via the fluidic network114. The fluid injection system704is also connected to the second fluid inlet/outlet system112of the microfluidic device100via the holder702, and can force fluid in a reverse direction through the microfluidic device100from the second fluid inlet/outlet system112to first fluid inlet/outlet system110via the fluidic network114.

In the example shown, the fluid injection system704includes a first injector706for injecting a first fluid, a second injector708for injecting a second fluid, and a third injector710for injecting a third fluid. The first706, second708, and third710injectors can be, for example syringe pumps. The first fluid can be, for example, salt water (e.g. brine) or water. The second fluid can be, for example, oil (e.g. an oil sample from the shale/tight oil reservoir that is modelled in the microfluidic device). The third fluid can be, for example, a test fluid (e.g. a frac fluid such as a surfactant). Alternatively, the first, second, and/or third fluids can be various other fluids.

The first706, second708, and third710injectors are connected to a header line712via valves714,716, and718, respectively. The header line712is in fluid communication with the first inlet/outlet port116of the first fluid inlet/outlet system110, via line720, valve722, and pressure gauge724, as well as the holder702. The header line712is in fluid communication with the first inlet/outlet port128of the second fluid inlet/outlet system112, via line726, valve728, and pressure gauge730, as well as the holder702.

In operation, in order to force fluid through the microfluidic device100in a forward direction, the first706, second708and/or third injector710can be engaged, with its corresponding valve open (i.e. valve714,716, and/or718), and with valve722open. In order to force fluid through the microfluidic device100in the reverse direction, the first,706, second708, and/or third injector710can be engaged, with its corresponding valve open (i.e. valve714,716, and/or718), and with valve728open.

Referring still toFIG. 7, the system700further includes a first fluid collection system732connected to the first fluid inlet/outlet system110for collecting fluid from the first fluid inlet/outlet system110when fluid is forced through the microfluidic device100in the reverse direction. The first fluid collection system includes a waste vessel734that is connected to the second inlet/outlet port118of the first fluid inlet/outlet system100, via the holder702, line736, valve738and relief valve740.

Similarly, referring still toFIG. 7, the system700further includes a second fluid collection system742connected to the second fluid inlet/outlet system112for collecting fluid from the second fluid inlet/outlet system112when fluid is forced through the microfluidic device100in the forward direction. The second fluid collection system742includes a waste vessel744that is connected to the second inlet/outlet port130of the second fluid inlet/outlet system112, via the holder702, line746, valve748, and relieve valve750.

The system700can further include an optical investigation system (not shown) for viewing at least a portion of the fluidic network114, e.g. the microfluidic channel network140and/or the nanofluidic channel network142, during operation. The optical investigation system can include, for example, an imaging system such as a microscope (e.g. an optical microscope), and/or a camera (e.g. a video camera or a photographic camera).

Referring now toFIG. 7as well asFIG. 8, a method800for operating the microfluidic system700and microfluidic device100will be described. Although the method800will be described with reference to the microfluidic system700and device100described above, the method800may be carried out with other systems and devices, and the systems and devices may be operated according to other methods. In the following description, unless a valve is specifically mentioned as being open, it is to be assumed that the valve is closed (e.g. if it is stated that valve714, valve728, and valve738are open, it can be assumed that valve716, valve718, valve722, and valve748are closed, even if not expressly stated).

As a first step802, various preparation procedures may be carried out, such as pressure testing of the system with nitrogen, and filtration of samples, etc. A vacuum may also be applied to the microfluidic device (e.g. via lines736and746, with valves738and748open).

As a next step, the microfluidic device100may be filled, at step804. This can be achieved by flowing a least a first volume of fluid through the microfluidic device100in a forward direction, from the first fluid inlet/outlet system110, through the fluidic network114, and towards the second fluid inlet/outlet system112. More specifically, valves714, and722may be opened, and the first injector706may be engaged, to force water or brine from the first injector706into the microfluidic device100. As described above, the water or brine may flow through the microfluidic device100from the first fluid inlet/outlet system100, through the fluidic network114(via the microfluidic channel network140and the nanofluidic channel network142), and towards the second fluid inlet/outlet system112. The water or brine can be forced into the microfluidic device100at a flow rate of, for example, between 10 microliters/min and 500 microliters/min. Optionally, the optical investigation system can be used during this step to visualize and/or record the water or brine flowing through the microfluidic device100(e.g. video of the water or brine flowing through the microfluidic device100can be recorded, or time-lapse images of the water or brine flowing through the microfluidic device100may be captured), or to assess various parameters (e.g. the velocity of the water or brine flowing through the microfluidic device100, by carrying out an imaging velocity investigation). Alternatively or in addition, the images and/or video can optionally be analyzed to assess various parameters. Optionally, the pressure can be monitored during filling of the microfluidic device100, to ensure that the maximum pressure rating of the microfluidic device100is not exceeded. Once the microfluidic device100is full of water or brine, valve748may be opened until the water or brine flows out of the microfluidic device100into the waste vessel744. Once the water or brine begins to flow out from valve744, flow can continue for an additional period of time, for example 10 minutes. All valves can then be closed.

As a next step, the water or brine may be allowed to soak in the fluidic network114, at step806, to achieve aging of the fluidic network114. The soaking step may be carried out for a period of, for example, 10 minutes or more.

As a next step, the first fluid (which in the present example is water or brine) can be displaced with a second fluid (which in the present example is oil), at step808. This can be achieved by flowing a least a second volume of fluid through the microfluidic device100in the forward direction, from the first fluid inlet/outlet system110, through the fluidic network114, and towards the second fluid inlet/outlet system112. More specifically, valves716,722and748may be opened, and the second injector708may be engaged, to force oil from the second injector708into the microfluidic device100. As described above, the oil may flow through the microfluidic device100from the first fluid inlet/outlet system110, through the fluidic network114(via the microfluidic channel network140and the nanofluidic channel network142), and towards the second fluid inlet/outlet system112. The oil can be forced into the microfluidic device100at a flow rate of, for example, between 10 microliters/min and 500 microliters/min. Optionally, the optical investigation system can be used during this step to visualize and/or record the oil flowing through the microfluidic device100(e.g. video of the oil flowing through the microfluidic device100can be recorded, or time-lapse images of the oil flowing through the microfluidic device100may be captured), or to assess various parameters (e.g. the velocity of the oil flowing through the microfluidic device100can be assessed, by carrying out an imaging velocity investigation). Alternatively or in addition, the images and/or video can optionally be analyzed to assess various parameters, e.g. to determine the oil saturation in the microfluidic device. Optionally, the pressure can be monitored during step808, to ensure that the maximum pressure rating of the microfluidic device100is not exceeded. Once the oil begins to flow out from valve748, flow can continue for an additional period of time, for example 10 minutes. All valves can then be closed. Upon completion of step808, when the microfluidic device100is filled with oil, the microfluidic device100can model a frac zone and matrix of a shale/tight oil formation.

As a next step, the oil may be allowed to soak in the fluidic network114, at step810, to achieve aging of the fluidic network114. The soaking step810may be carried out for a period of, for example, 10 minutes or more.

As a next step, the second fluid (which in the present example is oil) can be displaced with a third fluid (which in the present example is a surfactant), at step812. This can be achieved by flowing a least a third volume of fluid through the microfluidic device100in the forward direction, from the first fluid inlet/outlet system110, through the fluidic network114, and towards the second fluid inlet/outlet system112. More specifically, valves718,722and748may be opened, and the third injector710may be engaged, to force surfactant from the third injector710into the microfluidic device100. As described above, the surfactant may flow through the microfluidic device100from the first fluid inlet/outlet system110, through the fluidic network114(via the microfluidic channel network140and the nanofluidic channel network142), and towards the second fluid inlet/outlet system112. The surfactant can be forced into the microfluidic device100at a flow rate of, for example, between 10 nanoliters/min to 10 microliters/min. The optical investigation system can be used during this step to visualize and/or record the surfactant flowing through the microfluidic device100(e.g. video of the surfactant flowing through the microfluidic device100can be recorded, and/or time-lapse images of the surfactant flowing through the microfluidic device100can be captured), and/or to assess various parameters (e.g. the velocity of the surfactant flowing through the microfluidic device100can be assessed by carrying out an imaging velocity investigation). Alternatively or in addition, the images and/or video can optionally be analyzed to assess various parameters. This step—i.e. flowing surfactant through the microfluidic device100from a microporous channel network140to a nanoporous channel network142—can model the flow of surfactant into a frac zone of a shale/tight oil formation, and then into the matrix of the shale/tight oil formation, and analysis of the images and/or video can give an indication of the performance of the surfactant. Optionally, the pressure can be monitored during step812, to ensure that the maximum pressure rating of the microfluidic device100is not exceeded. Once the surfactant begins to flow out from valve748, flow can continue for an additional period of time, for example 10 minutes. All valves can then be closed.

As a next step, the surfactant may be allowed to soak in the fluidic network114, at step814, to achieve aging of the fluidic network. The soaking step may be carried out for a period of, for example, 10 minutes or more.

As a next step, at step816, the flow of fluid can be reversed, by flowing a subsequent volume of fluid (which in this example is a fourth volume of fluid) in a reverse direction from second fluid inlet/outlet system112, through the fluidic network114, and towards the first fluid inlet/outlet system110. In this example, the fourth volume of fluid includes oil (i.e. it is one and the same as the second fluid that was injected at step808), and forcing the oil through the microfluidic device100in the reverse direction, from the nanofluidic channel network142to the microfluidic channel network140, models the flow of oil from a matrix of a shale/tight oil formation through a frac zone of the shale/tight oil formation. That is, step816models the production of oil from a shale/tight oil formation. In this step, valves716,728and738may be opened, and the second injector708may be engaged, to force oil from the second injector708into the microfluidic device100. As described above, the oil may flow through the microfluidic device100from the second fluid inlet/outlet system112, through the fluidic network114(via the nanofluidic channel network142and the microfluidic channel network140), and towards the first fluid inlet/outlet system110. The oil can be forced into the microfluidic device100at a flow rate of, for example, between 10 nanoliters/min to 10 microliters/min. The optical investigation system can be used during this step (e.g. video of the oil flowing through the microfluidic device100can be recorded, and/or time lapse images of the oil flowing through the microfluidic device100can be captured) to visualize the oil flowing through the microfluidic device100, and/or to assess various parameters (e.g. the velocity of the surfactant flowing through the microfluidic device100can be assessed by carrying out an imaging velocity investigation). Visualizing the flow of oil can give a further indication of the performance of the surfactant (e.g. the images can be analyzed to allow for calculation of an oil recovery factor or oil saturation). Optionally, the pressure can be monitored during step814, to ensure that the maximum pressure rating of the microfluidic device100is not exceeded. Once the oil begins to flow out from valve738, flow can continue for an additional period of time, for example 10 minutes. All valves can then be closed.

As a next step, the oil may be allowed to soak in the fluidic network114, at step818, to achieve aging of the fluidic network. The soaking step may be carried out for a period of, for example, 10 minutes or more.

As mentioned above, video recordings and/or still images, particularly those of steps812to818, can be used to determine various parameters, which can be used to give an indication of surfactant performance. For example, the video recordings and/or still images can be used to calculate an oil recovery factor for the surfactant.

Referring now toFIG. 9, an alternative example of a microfluidic system900is shown. InFIG. 9, like features toFIG. 7will be referred to with like reference numerals, incremented by 200.

The microfluidic system900ofFIG. 9is similar to the microfluidic system700ofFIG. 7, and includes a holder902, and an injection system904with first906, second908, and third910injectors and corresponding valves and lines, and for simplicity these features are not described again in detail. However, the system900is configured for operation under extremely high pressures, for example up to 8000 psi, or between 1400 psi and 3000 psi, and instead of waste vessels, the system includes a back-pressure regulator954in fluid communication with first fluid inlet/outlet system110and the second fluid inlet/outlet system112of the microfluidic device100.

While the above description provides examples of one or more processes or apparatuses or compositions, it will be appreciated that other processes or apparatuses or compositions may be within the scope of the accompanying claims.

To the extent any amendments, characterizations, or other assertions previously made (in this or in any related patent applications or patents, including any parent, sibling, or child) with respect to any art, prior or otherwise, could be construed as a disclaimer of any subject matter supported by the present disclosure of this application, Applicant hereby rescinds and retracts such disclaimer. Applicant also respectfully submits that any prior art previously considered in any related patent applications or patents, including any parent, sibling, or child, may need to be re-visited.