WO2023041949A1

WO2023041949A1 - Device for injecting a fluid in at least one core

Info

Publication number: WO2023041949A1
Application number: PCT/IB2021/000641
Authority: WO
Inventors: Magalie SARTHOU; Thomas DELHOSTE; Didier Bielawski
Original assignee: Totalenergies Onetech
Priority date: 2021-09-16
Filing date: 2021-09-16
Publication date: 2023-03-23

Abstract

The invention relates to a device (1) for injecting a fluid in at least one core comprising: a fluid chamber (2) extending along a fluid chamber axis and having a first fluid outlet (2d); a first core holder (3) configured to comprise a core and extending from the first fluid outlet (2d), along a core axis which is transversal to the fluid chamber axis; a first piston (8) and a second piston (9) slidably arranged in the fluid chamber (2), configured for displacing and compressing a fluid sample in the fluid chamber (2). The invention further relates to a method for determining at least one property of at least one core by using said device (1).

Description

Device for injecting a fluid in at least one core

Technical field

The present invention relates to a device for injecting a fluid in at least one core, for example for plugging the core or treating a cracked core. The present invention further relates to a method for measuring at least one property of at least one core.

Technical background

Hydrocarbons (such as crude oil) are extracted from a subterranean formation (or reservoir) by means of one or more production wells drilled in the reservoir. Before production begins, the formation, which is a porous medium, is saturated with hydrocarbons.

The initial recovery of hydrocarbons is generally carried out by techniques of “primary recovery", in which only the natural forces present in the reservoir are relied upon. In this primary recovery, only part of the hydrocarbons is ejected from the pores by the pressure of the formation. Typically, once the natural forces are exhausted and primary recovery is completed, there is still a large volume of hydrocarbons left in the reservoir.

This phenomenon has led to the development of enhanced oil recovery (EOR) techniques. Many of such EOR techniques rely on the injection of a fluid into the reservoir in order to produce an additional quantity of hydrocarbons.

The fluid used can in particular be a gas (“gas flooding process"), such as natural gas, methane, nitrogen or carbon dioxide.

Alternatively, the fluid used can be an aqueous solution (“waterflooding process"), such as brine, which is injected via one or more injection wells.

Large amounts of water can also be recovered from the production wells. This is called “produced water"’. The produced water can be e.g. discharged to the environment (after treatment) or reinjected into the subterranean formation via the injection wells.

A polymer can also be added to the water to increase its viscosity and increase its sweep efficiency in recovering hydrocarbons (“polymer flooding process’’). In this case, the produced water contains part of the polymer, which can thus be recovered.

In subterranean formations having layered systems comprising low permeability and high permeability layers, the existing methods have shown hydrocarbon recovery levels that need improvement. More specifically, when the subterranean formation comprises low permeability and high permeability zones, the gas or water (due to their high mobility) may by-pass sections of the subterranean formation comprising recoverable oil by entering and moving along other sections or channels (“thief zones") of the subterranean formation, which do not comprise recoverable oil. These thief zones are generally high-permeability zones. The low permeability zones comprising the recoverable oil may therefore remain un-swept. More particularly, as the viscosity of the gas or the water used for oil recovery is low relative to the viscosity of the targeted oil, this may cause viscous fingering and low oil recovery. Furthermore, the low density of gas or the high density of water results in gravity override where the gas rises to the top parts and water sinks to the bottom parts of the porous medium without contacting the targeted oil.

In order to optimize and facilitate hydrocarbon recovery, it is useful to be able to study and find solutions that allow, at the same time, to reduce the permeability of high permeability zones and increase the permeability of low permeability zones.

It is known to perform an acid diversion in order to increase the permeability of low permeability zones. More particularly, an acidic fluid can be injected into the well, wherein some of the particles and some of the rock in the formation are partially soluble in this acidic fluid. Thus, this method can cause these particles and rock to partially dissolve, and make the formation more porous thereby increasing the mobility of the oil in the formation and increasing well production.

Regarding the reduction of the permeability of a subterranean formation, among different methods, it is known to use a solution comprising particles in order to plug (block) high permeability zones. However, the use of such particles also risks plugging the equipment (notably any tubing) used to experiment and simulate the subterranean conditions.

Before injecting a fluid increasing or decreasing permeability in situ, it is useful to study the effect of the fluid injection on cores (for example cores from a subterranean formation).

Document CN 206339468 U relates to a dual-core acid diversion experiment device which makes it possible to simultaneously study two cores with different permeability under the same injection pressure, the same confining pressure, and the same temperature. The device of this document comprises a base and a core holder arranged on the base, a liquid inlet port and two liquid outlet ports. Two rubber sleeves are arranged in parallel in the cavity of the core holder so as to hold two different cores.

The article “Acid diversion from an undamaged to a damaged core using multiple foam slugs" of F.R. Behenna (paper presented at the SPE European Formation Damage Conference, The Hague, Netherlands, May 1995, Paper Number: SPE-30121-MS, https://doi.org/10.2118/30121 -MS) relates to studies conducted with two undamaged core plugs having different permeabilities regarding the injection of a foam slug in each core. This article also studies regarding the injection of a foam slug into a damaged and an undamaged sandstone core.

There is still a need for a device for injecting a fluid in at least one core preferably from a subterranean formation, advantageously in two cores, notably having different permeabilities, that makes it possible to study at least one property of the core(s), without the risk of plugging the equipment.

Summary of the invention

It is a first object of the invention to provide a device for injecting a fluid in at least one core comprising: a fluid chamber extending along a fluid chamber axis and having a first fluid outlet; a first core holder configured to comprise a core and extending from the first fluid outlet, along a core axis which is transversal to the fluid chamber axis; a first piston and a second piston slidably arranged in the fluid chamber, configured for displacing and compressing a fluid sample in the fluid chamber.

According to some embodiments, the fluid chamber has a second fluid outlet and the device comprises a second core holder configured to comprise a core and extending from the second fluid outlet, along a core axis which is transversal to the fluid chamber axis.

According to some embodiments, the first and second core holders are located on opposite sides of the fluid chamber.

According to some embodiments, the first core holder has a core fluid outlet and the device further comprises a collecting chamber extending from the core fluid outlet. According to some embodiments, the collecting chamber comprises a collecting chamber fluid outlet comprising a filter.

According to some embodiments, the first piston is removable from the fluid chamber.

According to some embodiments, the second piston is removable from the fluid chamber.

According to some embodiments, the device comprises at least one pressure sensor in the first core holder and optionally in the second core holder.

According to some embodiments, comprises an enclosure around the first core holder and optionally the second core holder, the enclosure being configured to contain a pressurizing fluid.

The present invention further relates to a method for determining at least one property of at least one core by using the device described above, the method comprising: placing a core into the first core holder; introducing a fluid sample into the fluid chamber, between the first piston and the second piston; pressurizing the core in the first core holder; pressurizing the fluid sample in the sample chamber so as to inject it into the first core, by displacing at least one of the first piston and second piston ; measuring a parameter in the core.

According to some embodiments, the at least one property is chosen from permeability, the content in limestone, the content in clay, the degree of crack, the propagation speed of the fluid and the pore volume to breakthrough, and wherein preferably the at least one property is permeability.

According to some embodiments, the at least one parameter is pressure.

According to some embodiments, the method comprises, prior to the injection of the fluid sample into the core, a step of moving the fluid sample from an initial position in the fluid chamber to a final position in the fluid chamber facing the first fluid outlet.

According to some embodiments, the introduction of the sample fluid in the fluid chamber is carried out by removing the first piston from the device, by introducing the fluid in the fluid chamber and by placing the first piston so as to seal the fluid chamber.

According to some embodiments, the fluid sample to be injected comprises an acid and/or suspended solid material. According to some embodiments, the acid is chosen from acetic acid, formic acid, hydrochloric acid, esters which hydrolyze and give the above mentioned acids, and mixtures of such acids and esters.

According to some embodiments, the suspended solid material is chosen from lost circulation material and fibers.

According to some embodiments, the method comprises: placing a core into the second core holder; pressurizing the core in the second core holder; pressurizing the fluid sample in the fluid chamber so as to inject the fluid into the cores comprised into the first and second core holder at the same time by displacing at least one of the first piston and second piston ; measuring a parameter in each of the first and second core.

According to some embodiments, the core placed in the first core holder and the core placed in the second core holder have different permeabilities.

According to some embodiments, the device is heated at a temperature from 20 to 250°C.

According to some embodiments, a counter-pressure is applied at the core fluid outlet of the core holder, so that the core is at a core pressure of from 1 to 500 bar, and preferably from 300 to 400 bar.

According to some embodiments, at the moment of the injection of the fluid sample, the fluid sample is pressurized to an injection pressure higher than the core pressure.

According to some embodiments, the core holder is a flexible membrane, and wherein a confinement pressure is applied external to the flexible membrane, which is from 1 to 50 bar, and preferably from 10 to 40 bar above the core pressure.

The present invention enables to meet the abovementioned need. In particular the invention provides a device for injecting a fluid in at least one core preferably from a subterranean formation, advantageously in two cores, notably of different permeabilities, that makes it possible to study at least one property of the core(s), without the risk of plugging the equipment.

This is achieved by using the device of the present invention. More particularly, this device comprises a fluid chamber extending along a fluid chamber axis and having a first fluid outlet; a first core holder configured to comprise the core and extending from the first fluid outlet, along a core axis which is transversal to the fluid chamber axis; and a first piston and a second piston slidably arranged in the fluid chamber, configured for displacing and compressing a fluid sample in the fluid chamber. The fact that the first core holder extends from the first fluid outlet of the fluid chamber makes it possible to avoid any tube or conduit used for the injection of the fluid in the core. In other words, the first and second pistons are configured to displace and compress the fluid in the fluid chamber so that the fluid can be directly injected (without intermediate tubes or conduits) into the core in the core holder through the first fluid outlet. Thus, the risk of plugging the device is avoided.

Advantageously, the fluid chamber of the device according to the invention comprises a second fluid outlet and the device comprises a second core holder configured for comprising a core and extending from the second fluid outlet, along a core axis which is transversal to the fluid chamber axis. This makes it possible to simultaneously inject a fluid sample with or without suspended particles into both cores (without the use of intermediate tubes or conduits). This is of particular importance when two cores of different permeabilities should be studied. For example, in case the first core is a high permeability core, and the second core is a low permeability core, the device and method of present invention make it possible to inject a single fluid sample into both cores so as to analyze the response of both cores to the fluid injection without the risk of plugging the device. In this case, the injection of the fluid sample may for example allow to (permanently or temporarily) increase the permeability of the low permeability core and at the same time (during the same injection) decrease the permeability of the high permeability core. Otherwise, the injection of the fluid sample may for example allow to (permanently or temporarily) increase the permeability of both cores (of low and high permeability core).

In addition, the present invention makes it possible to study the effect of the injection of a fluid comprising an acid on the cores, in order to implement for example an acid retardation process.

Furthermore, the present invention makes it possible to study the effect of the injection of a fluid on the clogging of the reservoir during drilling for example in the event of mud damage, or in the event of any damaged (cracked) core.

Brief description of the drawings

Figure 1 is a cross-sectional view of part of the device according to one embodiment of the invention.

Figure 2 is a perspective view of part of the device according to one embodiment of the invention.

Figure 3 is a front view of the device according to one embodiment of the invention. Figure 4 is a cross-sectional view of part of the device according to one embodiment of the invention.

Figure 5 is a cross-sectional view of part of the device according to another embodiment of the invention.

Figures 6 and 7 are cross-sectional views of part of the device according to one embodiment of the invention.

Detailed description

The invention will now be described in more detail without limitation in the following description.

Device for injecting a fluid in at least one core

The device 1 according to the present invention will be described by making reference to figures 1 to 7.

First of all, such device 1 comprises a fluid chamber 2 extending along a fluid chamber axis and having a first fluid outlet 2d. During use, the device 1 according to the invention may be placed vertically or horizontally such that the fluid chamber axis of the fluid chamber 2 is oriented in the vertical or horizontal direction. The vertical orientation of the device 1 is illustrated figure 1.

The fluid chamber 2 may comprise an upper extremity 2a and a lower extremity 2b. The fluid chamber 2 may also be defined by a tubular sidewall 2c which extends along the fluid chamber axis, between the upper extremity 2a and the lower extremity 2b of the fluid chamber 2. The tubular sidewall 2c defines an internal space, wherein a fluid sample can be placed. In addition, the upper and lower extremities 2a, 2b are preferably open.

By the term “tubular is meant a shape of a cylinder with a circular or non-circular base. For example, the base may be a disc, an oval, a square, a rectangle, a regular or non-regular polygon, or a combination of planar surfaces and/or curved surfaces. Preferably, the base is a circular disc.

The fluid chamber 2 (or in other words the tubular side wall 2c) may have an inner diameter from 20 to 100 mm, and preferably from 30 to 70 mm. This inner diameter may notably be from 20 to 25 mm; or from 25 to 30 mm; or from 30 to 35 mm; or from 35 to 40 mm; or from 40 to 45 mm; or from 45 to 50 mm; or from 50 to 55 mm; or from 55 to 60 mm; or from 60 to 65 mm; or from 65 to 70 mm; or from 70 to 75 mm; or from 75 to 80 mm; or from 80 to 85 mm; or from 85 to 90 mm; or from 90 to 95 mm; or from 95 to 100 mm. The inner diameter of the fluid chamber 2 is the maximum inner dimension of the fluid chamber 2 in a plane orthogonal to the fluid chamber axis. The fluid chamber 2 may have a volume from 0.1 to 2 L, and preferably from 500 mL to 1 L.

The fluid chamber 2 (notably the tubular sidewall 2c of the fluid chamber 2) may have a length from 100 mm to 500 mm, and preferably from 200 mm to 300 mm.

The fluid chamber 2 may be manufactured from a material chosen from a nickel-based and especially a chromium-nickel alloy (such as Hastelloy®), stainless steel 316L.

The device 1 according to the present invention further comprises a first core holder 3 which is configured to comprise a core. The first core holder 3 extends from a first fluid outlet 2d of the fluid chamber 2, along a core axis which is transversal (preferably orthogonal) to the fluid chamber axis. For example, the core axis may be horizontal, as shown in the figures. The fluid sample can enter the first core holder 3 through the first fluid outlet 2d, and exit the first core holder 3 through a core fluid outlet 3b.

The first core holder 3 may also be defined by a tubular sidewall which extends along the core axis, between the first fluid outlet 2d of the fluid chamber

2 and the core fluid outlet 3b of the first core holder 3. The tubular sidewall defines an internal space, wherein the core can be placed. Thus, the tubular sidewall of the core holder 3 is perpendicular to the tubular sidewall 2c of the fluid chamber 2.

The first core holder 3 (or in other words the tubular side wall) may have an inner diameter from 20 to 80 mm, and preferably from 30 to 60 mm. This inner diameter may notably be from 20 to 25 mm; or from 25 to 30 mm; or from 30 to 35 mm; or from 35 to 40 mm; or from 40 to 45 mm; or from 45 to 50 mm; or from 50 to 55 mm; or from 55 to 60 mm; or from 60 to 65 mm; or from 65 to 70 mm; or from 70 to 75 mm; or from 75 to 80 mm. The inner diameter of the first core holder

3 is the maximum inner dimension of the first core holder 3 in a plane orthogonal to the core axis.

In addition, the first core holder 3 may have a length from 50 to 500 mm, and preferably from 100 to 300 mm. Such length may be from 50 to 100 mm; or from 100 to 150 mm; or from 150 to 200 mm; or from 200 to 250 mm; or from 250 to 300 mm; or from 300 to 350 mm; or from 350 to 400 mm; or from 400 to 450 mm; or from 450 to 500 mm.

The first core holder 3 may also have a volume from 1 L to 5 L, and preferably from 2 L to 3 L. According to some preferred embodiments, the device 1 may comprise a second core holder 3 which extends from the second fluid outlet 2d, along a core axis which is transversal to the fluid chamber axis.

The second core holder 3 may be as described above.

According to preferred embodiments, the first and second core holders 3 are located on diametrically opposite sides of the fluid chamber 2 as illustrated for example in figures 1 and 2. Thus, the fluid sample exiting the fluid chamber 2 from the first (and optionally the second) fluid outlet 2d may enter the first and optionally the second core holders 3.

According to some embodiments, the first and second core holders 3 have the same dimensions (inner diameter, length). According to other embodiments, the first and second core holders 3 differ in at least one dimension.

Although not illustrated here, the device 1 may comprise more than two core holders extending from the fluid chamber 2. In this case, they may in particular be regularly spaced around the fluid chamber 2.

The core holder(s) 3 may be a flexible membrane, in particular a polymer membrane preferably a fluoroelastomer membrane, for example a Viton® membrane).

The core holder(s) 3 is/are fixed to the fluid chamber 2. The interior of the flexible membrane (and therefore the core) is in a sealed fluidic connection with the fluid chamber 2. A sealing member can be provided to this end.

According to some embodiments, the core fluid outlet 3b of a core holder 3 may be connected to a tubing or a channel 4 (as illustrated for example in figure 5). For example, the core holder(s) 3 may be fixed to a fixation piston 21 , wherein the channel 4 runs within the fixation piston 21. The interior of the flexible membrane (and therefore the core) is in a sealed fluidic connection with this channel 4.

In addition, a filter 17 (as illustrated in figure 5) can be present between the core fluid outlet and the tubing. In this case, the fluid sample exiting the core fluid outlet 3b may be transferred via the tubing or channel 4 to a unit such as a scaling unit, a flow meter, pH meter, conductometer, viscosimeter.

According to other embodiments, the core fluid outlet 3b of a core holder 3 may be connected to a collecting chamber 5 (as illustrated in figure 4). The collecting chamber 5 may be defined by a tubular sidewall extending along a collecting chamber axis (such axis preferably being a continuation of the core axis) from the core fluid outlet 3b to a collecting chamber fluid outlet 5b. Such collecting chamber 5 allows to collect any solid material present in the fluid sample and exiting the core holder 3, in order to avoid blocking any narrow channel or tubing with such solid material. The internal transversal dimensions (e.g. the diameter) of the collecting chamber 5 may be more than the internal transversal dimensions (e.g. the diameter) of the core holder 3. The core holder 3 in this case can be maintained in place owing to a support which may be for example in the form of an annular sealing member. The interior of the flexible membrane is in fluid communication with the collecting chamber 5.

The collecting chamber fluid outlet 5b of the collecting chamber 5 may then be connected to a tubing or a channel so as to transfer the fluid sample exiting the collecting chamber 5 to a unit such as a scaling unit, a flow meter, pH meter, conductometer, viscosimeter.

The collecting chamber 5 may have an inner diameter from 20 to 90 mm, and preferably from 30 to 80 mm. This inner diameter may notably be from 20 to 25 mm; or from 25 to 30 mm; or from 30 to 35 mm; or from 35 to 40 mm; or from 40 to 45 mm; or from 45 to 50 mm; or from 50 to 55 mm; or from 55 to 60 mm; or from 60 to 65 mm; or from 65 to 70 mm; or from 70 to 75 mm; or from 75 to 80 mm; or from 80 to 85 mm; or from 85 to 90 mm. The inner diameter of the collecting chamber 5 is the maximum inner dimension of the collecting chamber 5 in a plane orthogonal to the collecting chamber axis.

In addition, the collecting chamber 5 may have a length from 30 to 250 mm, preferably from 50 to 200 mm and more preferably from 100 to 180 mm.

The collecting chamber 5 may also have a volume from 50 to 1500 mL, preferably from 300 to 1000 mL, and more preferably from 500 to 900 mL.

Preferably, the collecting chamber fluid outlet 5b of the collecting chamber 5 is provided with a filter so as to block the exit of solid material in the collecting chamber 5. Such filter may be for example a grid made from stainless steel.

According to some preferred embodiments, when the device 1 comprises a first core holder 3 and a second core holder 3, one of the first and second core holders 3 is connected to a collecting chamber 5 while the other of the first and second core holders 3 is directly connected to a channel or tubing 4. This is particularly advantageous in case the two cores to be studied are of different permeabilities and the solid material present in the fluid sample only exits one of the two core holders 3.

Alternatively, both core holders 3 may be connected to a channel or tubing 4; or both core holders 3 may be connected to a collecting chamber 5.

In any of these embodiments, the dimensions of the core holders and cores contained therein, in particular the longitudinal dimension, may be the same or different. Advantageously, the device 1 is adaptable to cores having different dimensions. Advantageously, at least some of the elements engaging the core holders 3 (such as the fixation piston 21 ) may be removable, so that the configuration of the device 1 may be modified to be adapted to different cores and different protocols.

The collecting chamber 5 may be manufactured from a material chosen from a nickel-based alloy (such as Hastelloy®).

According to some embodiments, the device 1 may comprise at least one sensor (not illustrated in the figures) associated with a core holder 3 in order to measure at least one property in each core holder 3. Preferably, such sensor is a pressure sensor. The sensor may for example be connected to the device 1 via the sensor inlets 7 illustrated in figure 1 . For example, the device 1 may comprise at least two sensor inlets 7.

According to some embodiments, a single sensor may be connected to the different sensor inlets 7.

According to other embodiments, each sensor inlet 7 is connected to a different sensor.

Preferably, each core holder 3 is equipped with at least one sensor. Therefore, in case the device 1 comprises a first and a second core holder 3 it is preferable that both core holders 3 are equipped with a sensor, notably a pressure sensor.

Alternatively or additionally, the device 1 may comprise an enclosure 6 around a core holder 3, preferably around each core holder 3. Thus, in case the device 1 comprises a first core holder 3 and a second core holder 3, an enclosure 6 is preferably located around the first core holder and around the second core holder 3. In case the device 1 further comprises a collecting chamber 5, the enclosure 6 preferably also encloses the collecting chamber 5.

The enclosure 6 may be configured to confine the core(s) in the core holder(s) 3 by a pressurizing fluid, for example at a pressure (called external confinement pressure) from 1 to 50 bar, and preferably from 10 to 40 bar above the pressure in the core. This pressure is measured at the outlet 3b of the core holder 3. The pressurizing fluid may be for example water, a mineral oil or gas (such as nitrogen, helium, compressed air). Thus, the enclosure 6 comprises a tubular sidewall extending around the first core holder 3 and/or the second core holder 3. An internal space 6a is thus formed between the tubular sidewall of the enclosure 6 and the sidewalls of the first core holder 3 and/or the second core holder 3. The pressurized fluid may thus circulate in the internal space 6a and confine the core in the membrane of the core holder 3. The introduction of the pressurized fluid in the internal space 6a may be carried out through inlets 18. In addition, the pressurized fluid may exit the internal space 6a from outlets 19. The enclosure 6 may be manufactured from a material chosen from a nickel based alloy and especially a chromium-nickel (such as Hastelloy®), or stainless steel 316L.

The device 1 according to the invention further comprises a first piston 8 and a second piston 9 slidably arranged in the fluid chamber 2. More particularly, the first piston 8 may be inserted in the fluid chamber 2 from the upper extremity 2a of the fluid chamber 2. Similarly, the second piston 9 may be inserted in the fluid chamber 2 from the lower extremity 2b of the fluid chamber 2. When both pistons are in the fluid chamber 2, an internal space A (as illustrated in figures 6 and 7) in the fluid chamber 2 is defined between the pistons 8, 9. This internal space A is configured to comprise a fluid sample. In addition, when both pistons are in the fluid chamber 2, they seal this internal space A in a fluid-tight manner.

While the first piston 8 and the second piston 9 are in the fluid chamber 2, they are configured to slide in the fluid chamber 2 so as to displace and compress a fluid sample in the fluid chamber 2 (more particularly in the internal space A). In addition, as will be explained below, depending on the compression of the fluid sample and the location of the internal space A formed by the first and second pistons 8, 9 and the fluid chamber 2, the fluid sample may exit the fluid chamber 2 from the first and/or second fluid outlet 2d and enter the core(s) in the core holder(s) 3.

The first and second pistons 8, 9 can be driven manually, mechanically, electrically or hydraulically. Preferably both pistons 8, 9 can be driven electrically. This makes it possible to accurately control the pressure in the internal space A and displace the first and second pistons 8, 9 with a high synchronization.

Still making reference to figures 6 and 7, each piston 8, 9 comprises an upper extremity 10, a lower extremity 11 and a sidewall 12. In the context of the present invention by “upper extremity’ is meant the extremity of the piston that forms and defines the internal space A in the fluid chamber 2. In other words, the internal space A formed in the fluid chamber 2 is defined by the tubular sidewall 2c of the fluid chamber 2 and the upper extremities 10 of each of the first and second pistons 8, 9.

The first piston 8 and/or the second piston 9 may comprise a conduit extending from the lower extremity 11 to the upper extremity 10 of each piston. Such conduit makes it possible to eliminate any gas present in the internal space A.

Each piston 8, 9 may have a cylindrical shape with a circular or non-circular base. Preferably, the base is a circular disc. Each piston 8, 9 may have a length from to 500 mm, and preferably from 150 to 300 mm.

Each piston 8, 9 may have an outer diameter which is equal to or less than the inner diameter of the fluid chamber 2, so that each piston 8, 9 can be inserted in the fluid chamber 2. Therefore, the outer diameter of the from 20 to 100 mm, and preferably from 30 to 70 mm. This outer diameter may notably be from 20 to 25 mm; or from 25 to 30 mm; or from 30 to 35 mm; or from 35 to 40 mm; or from 40 to 45 mm; or from 45 to 50 mm; or from 50 to 55 mm; or from 55 to 60 mm; or from 60 to 65 mm; or from 65 to 70 mm; or from 70 to 75 mm; or from 75 to 80 mm; or from 80 to 85 mm; or from 85 to 90 mm; or from 90 to 95 mm; or from 95 to 100 mm.

Preferably, the outer diameter of each piston 8, 9 is equal to the inner diameter of the fluid chamber 2.

According to some preferred embodiments, the outer shape of the first and/or the second pistons 8, 9 may substantially match the inner shape of the fluid chamber 2 (for example they can both have a cylindrical shape with a circular base of the same diameter). Thus, according to some preferred embodiments, and as shown in figure 1, the second piston 9 has an outer diameter which is uniform along its length and matches the inner shape of the fluid chamber 2.

According to other embodiments, the first and/or the second pistons 8, 9 may have an outer shape that does not substantially match the inner shape of the fluid chamber 2 (for example they can both have a cylindrical shape with a circular base, the base of the upper extremity 10 of the first and/or the second pistons 8, 9 having a different outer diameter from the inner diameter of the base of the fluid chamber 2). In this case, the upper extremity 10 of the first and/or the second pistons 8, 9 may have substantially the same outer diameter as the inner diameter of the fluid chamber 2, so that the first and/or the second pistons 8, 9 can seal in a fluid-tight manner the fluid chamber 2.

As illustrated in figure 1 , the upper extremity 10 of each piston 8, 9 may a planar (flat) surface which is perpendicular to the sidewall 12 of each piston 8, 9. Alternatively, the upper extremity 10 of each piston 8, 9 may have a different shape, such as a conical shape.

According to preferred embodiments, the first piston 8 is removable from the fluid chamber 2. This makes it possible to remove the first piston 8 so as to supply the fluid chamber 2 with a fluid sample and then place the first piston 8 in the fluid chamber 2 so as to seal the fluid sample in the internal space A formed by the tubular sidewall 2d of the fluid chamber 2 and the upper extremities 10 of each of the first and second pistons 8, 9. This is especially useful when the fluid sample comprises suspended solid material which is prone to clogging tubing.

The second piston 9 may also be removable from the fluid chamber 2. This makes it possible to facilitate the maintenance of the device 1 .

The first and second pistons 8, 9 may be manufactured from a material chosen from a nickel-based alloy (such as Hastelloy®), stainless steel (such as 316L). It is advantageous that the materials used for the pistons 8, 9 present a sufficient resistance to acids.

The device 1 according to the invention may further comprise an additional fluid inlet 13a (as illustrated in figures 2 and 3) and an additional outlet (not illustrated in the figures. Such inlet 13a is useful for the injection of additional fluid samples into the fluid chamber 2 (for example for a fluid sample devoid of suspended solid material that can block the intermediate tubing) such as water or brine solutions. When an additional fluid sample is injected into the fluid chamber 2 via the additional fluid inlet 13a, it may then be injected into the cores owing to an external pump.

As illustrated in figure 2, the additional inlet 13a and additional outlet may be disposed on diametrically opposite sides of the fluid chamber 2. They may be disposed substantially in the same plane as the fluid outlets 2d of the fluid chamber. As illustrated, the fluid chamber may comprise four fluid connections arranged substantially in a same plane and spaced by approximately 90° from each other, two of these fluid connections being fluid outlets 2d to respective core holders 3 and two of these fluid connections being the additional inlet 13a and additional outlet.

The device 1 according to the invention may also comprise a frame 14 as illustrated in figure 3. Such frame 14 makes it possible to support the assembly comprising the fluid chamber 2, the core holder(s) 3, the first and second pistons 8, 9 and optionally the collecting chamber 5.

The frame 14 may further comprise wheels 15 which make it possible to easily transport and move the device 1 .

The frame 14 may be manufactured from a material chosen from aluminum and steel.

The device 1 according to the invention may have the following dimensions:

- A height from 500 to 3000 mm and preferably from 1000 to 2000 mm.

- A length from 500 to 2500 mm and preferably from 800 to 1500 mm.

- A width from 100 to 1500 mm and preferably from 400 to 1000 mm.

In addition, the device 1 according to the invention may have a weight from 50 to 500 kg, and preferably from 200 to 500 kg. According to some embodiments, and as illustrated in figure 3, the device 1 according to the invention may comprise an upper (optionally motorized) part 16 configured to remove the first piston 8 from the device 1 and to put the first piston 8 in place. Thus, such upper part 16 may remove the first piston 8 from the device 1 so as to introduce the fluid sample in the fluid chamber 2. For example, the upper part 16 may displace the first piston 8 up and down in order to engage it into the fluid chamber 2 and to make it slide within the fluid chamber 2. It may also displace the first piston 8 horizontally when it is not engaged in the fluid chamber 2, in order to allow an easier access to the interior of the fluid chamber 2. Such upper part 16 may comprise for example pneumatic or electric cylinders.

Alternatively or additionally, the device 1 may comprise a lower (optionally motorized) part (not illustrated in the figures) configured to remove the second piston 9 from the device 1 and to put the second piston 9 in place. For example, the lower part may displace the second piston 9 up and down in order to engage it into the fluid chamber 2 and to make it slide within the fluid chamber 2. It may also displace the second piston 9 horizontally when it is not engaged in the fluid chamber 2, in order to allow an easier access to the interior of the fluid chamber 2. This makes it possible to facilitate the maintenance of the device 1 . Such lower part may comprise for example pneumatic or electric cylinders.

The device 1 according to the invention may further comprise a support element 20 able to pivot the core holder(s) 3 and the fluid chamber 2 (for example at an angle of 90° relative to the initial orientation of the core holder(s) 3 and the fluid chamber 2). Preferably this support element 20 is motorized.

Method for determining at least one property of at least one core

The method of the present invention makes it possible to determine at least one property of at least one core. This method is preferably implemented in the above device 1 .

According to preferred embodiments, the at least one core derives from a subterranean formation.

Alternatively, the at least one core may derive from a quarry, or from 3D printing (which may for example represent the rock with a certain porosity).

The property determined by the method according to the invention may be chosen from permeability, the nature of the core (content in limestone, content in clay, degree of crack), propagation speed of the fluid, pore volume to breakthrough. Preferably, the property determined by the method according to the invention is permeability.

The method generally comprises steps of: - placing core(s) into the or each core holder 3;

- introducing a fluid sample into the fluid chamber 2, between the first piston 8 and the second piston 9;

- pressurizing the core(s) in the core holder(s) 3;

- pressurizing the fluid sample in the sample chamber 2 so as to inject it into the core(s);

- measuring a parameter in the core;

- determining the property based on the parameter measurements.

The or each core may be for example collected from a subterranean formation . The core may consist of a sample of rock of the subterranean formation or an artificial core made to present certain desired properties. Preferably, it has a cylindrical shape.

In order to place the core into each core holder 3, it is preferable to rotate a part of the device 1 comprising the fluid chamber 2 and the core holder(s) 3 by an angle of 90° so that one core holder 3 is oriented in the vertical position and disposed above the fluid chamber 2. When the core is placed in the core holder 3, such part of the device 1 may further be rotated back to its initial position. If needed, the part of the device 1 comprising the fluid chamber 2 and the core holder(s) 3 may then be rotated in the opposite direction by an angle of 90° so that the other core holder 3 is oriented in the vertical position and disposed above the fluid chamber 2. After placing the core in this other core holder 3, this part of the device 1 may be rotated back to its initial position. Other rotations are possible if more than two core holders are present, or if the core holders are not aligned with respect to one another. This rotation is made possible for example by using the support element 20. Before any rotation is performed, it is preferable that the pistons 8, 9 are removed from the fluid chamber 2. In this case, the method according to the present invention may further comprise a step of removing the first piston 8 and/or the second piston 9 prior to introducing the core(s) into the core holder(s) 3 and a step of putting the first piston 8 and/or the second piston 9 in place in the fluid chamber 2, after the introduction of the core(s) into the core holder(s) 3. Such steps may be carried out by the upper (optionally motorized) part 16, and the lower (optionally motorized) part as described above.

The core may have a permeability from 0.01 to 10 000 mD. Therefore, the permeability of the core may be from 0.1 to 1 mD; or from 1 to 100 mD; or from 100 to 250 mD; or from 250 to 500 mD; or from 500 to 1 000 mD; or from 1 000 to 2 000 mD; or from 2 000 to 3 000 mD; or from 3 000 to 4 000 mD; or from 4 000 to 5 000 mD; or from 5 000 to 6 000 mD; or from 6 000 to 7 000 mD; or from 7 000 to 8 000 mD; or from 8 000 to 9 000 mD; or from 9 000 to 10 000 mD. Furthermore, the core may present a Young’s modulus from 1 to 10 Mpsi.

In case the device 1 comprises a second core holder 3, it is preferable that the core placed in the first core holder 3 has at least one different property, preferably a different permeability from the core placed in the second core holder 3.

Preferably a high permeability core, such as a fractured core, is placed in the first core holder 3 (on the left in figure 1) and a low permeability core, such as a non-fractured core, is placed in the second core holder 3 (on the right in figure 1).

The method further comprises a step of introducing a sample fluid into the fluid chamber 2, between the first piston 8 and the second piston 9.

The introduction of the sample fluid in the fluid chamber 2 may preferably be carried out by removing the first piston 8 from the device 1 in order to pour the fluid directly into the fluid chamber 2 and then by putting the first piston 8 in place so as to seal the fluid chamber 2. Thus, the fluid sample is then located in the internal space A defined by the tubular sidewall 2c of the fluid chamber 2 and the upper extremities 10 of each of the first and second pistons 8, 9. This mode of introduction is preferred when the fluid sample comprises suspended solid material which may lead to tubing clogging.

Alternatively, the sample fluid may be introduced directly into the sealed internal space A, between the pistons 8, 9, by way of the additional inlet 13a. This mode of introduction is appropriate when the fluid sample does not comprise suspended solid material which may lead to tubing clogging. The injection may be carried out by connecting an external pump to the additional fluid inlet 13a.

The fluid sample may be an aqueous solution. Such fluid sample may optionally comprise a polymer.

According to some embodiments, the fluid sample may comprise at least one acid. Such acid may be chosen from acetic acid, formic acid, hydrochloric acid, lactic acid, esters which hydrolyze and give the above mentioned acids, and mixtures of such acids and esters. The presence of the acid in the fluid sample makes it possible to increase the permeability of the core located in the core holder 3 when the fluid sample is injected in the core.

Alternatively or additionally, the fluid sample may comprise suspended solid material. By “suspended solid material’ is meant material which is solid and in suspension in the fluid sample. Such material may include particles (for example deriving from a biodegradable polymer such as polylactic acid), fibers and/or lost circulation material. By “lost circulation material" is meant substances added to drilling fluids when drilling fluids are being lost to the formations downhole. Commonly used lost circulation materials are fibrous (cedar bark, shredded cane stalks, mineral fiber and hair), flaky (mica flakes and pieces of plastic or cellophane sheeting) or granular (glass beads, ground and sized limestone or marble, wood, nut hulls, Formica, corncobs and cotton hulls).

The presence of the suspended solid material in the fluid sample makes it possible to decrease the permeability of the core located in the core holder 3 when the fluid sample is injected in the core (by plugging the core with such material).

In case the suspended solid material is in the form of particles, the volume median particle diameter of these particles (Dv50) may preferably be from 50 to 2000 pm, and preferably from 70 to 700 pm. The particle size distribution can be determined by laser diffraction.

According to preferred embodiments, the fluid sample comprises acid and suspended solid material (notably when the device comprises two core holders 3) preferably solid particles and/or fibers. This makes it possible to inject a single fluid sample in both cores so as to decrease the permeability of a high permeability core and at the same time increase the permeability of a low permeability core as desired.

According to other embodiments, the fluid sample comprises lost circulation material. The presence of lost circulation material is useful for clogging a fissured or fractured core sample in order to avoid losses during drilling.

As detailed above, after the fluid sample has been introduced in the fluid chamber 2, it is located in the internal space A defined by the tubular sidewall 2c of the fluid chamber 2 and the upper extremities 10 of each of the first and second pistons 8, 9 as illustrated in figure 6.

According to some embodiments, at this initial position, the fluid sample is sealed in the internal space A and is not in contact with the first and/or second fluid outlet 2d of the fluid chamber 2.

According to other embodiments, at this initial position, the fluid sample is sealed in the internal space A and is already in contact with the first and/or second fluid outlet 2d of the fluid chamber 2.

The internal space A may contain a volume of fluid sample from 1 to 2000 mL, and preferably from 50 to 800 mL.

The device 1 may be heated at a temperature from 20 to 250°C. This makes it possible to simulate the temperature in the subterranean reservoir. Such heating may be performed by a heating collar and/or heating cartridges.

The method according to the invention further comprises a step of pressurizing the core(s). This may be carried out by applying a counter-pressure at the core fluid outlet 3b of the core holder(s) 3, for example by using a counter- pressure valve. This counter-pressure makes it possible to achieve a desired core pressure so as to for example simulate subterranean reservoir conditions. The core pressure may be from 1 to 500 bar, and preferably from 300 to 400 bar.

Additionally, an external confinement pressure may be applied to the core (as described above), which is higher than the core pressure. The external confinement pressure may e.g. be from 1 to 50 bar, and preferably from 10 to 40 bar above the core pressure.

This external confinement pressure may be applied by a pressurized fluid that may circulate in the enclosure 6 of the device 1. This external confinement pressure makes it possible to avoid the deformation of the core during the implementation of the method according to the invention.

In order for the fluid sample to be injected into the core(s), the fluid sample must come into contact with the first and/or second fluid outlet 2d of the fluid chamber 2. As described above, according to some embodiments, the fluid sample in the internal space A is already in contact with the first and/or second fluid outlet 2d of the fluid chamber 2 at the initial position. According to other embodiments, the fluid sample may be moved from the initial position in the fluid chamber 2 (at which the fluid sample is not in contact with the first and/or second fluid outlet 2d of the fluid chamber 2) to a final position in the fluid chamber 2 facing the first and/or second fluid outlet as illustrated in figure 7. This may be carried out by displacing at least one of the first piston 8 and second piston 9, preferably at least the second piston 9, and more preferably both pistons 8, 9. During this step, it is preferable that the first piston 8 and the second piston 9 be displaced simultaneously in order to maintain the volume of internal space A as well as the pressure inside such internal space constant.

Once the fluid sample is at the final position facing the first and/or second fluid outlet 2d, the method according to the invention further comprises pressurizing the fluid sample in the sample chamber 2 so as to inject it into the first core and optionally in the second core. Such pressurization and therefore injection is carried out by displacing at least one of the first piston 8 and second piston 9.

According to some embodiments, during this step only the first piston 8 is displaced.

According to other preferred embodiments, during this step only the second piston 9 is displaced.

According to other embodiments, during this step both pistons are displaced. The fact that at the final position the fluid sample in the internal space A is in direct contact with the fist and/or second fluid inlet 2d (without intermediate tubes and channels) makes it possible to inject the fluid sample in the core(s) without risking plugging the device 1 .

In addition, at the moment of the injection of the fluid sample in the core(s) through the first and/or second fluid inlet 2d of the fluid chamber 2, the pressure of the fluid sample (injection pressure) should be higher than the counter-pressure applied at the core fluid outlet 3b of the core holder 3. For example, such injection pressure may be higher than the counter-pressure applied at the core fluid outlet 3b of the core holder 3 by 0.5 to 100 bar.

Thus, the fluid sample enters the core holder(s) 3 from the first and/or second fluid outlet 2d and passes through the core to exit the core holder(s) 3 through the core fluid outlet 3b.

The method according to the invention further comprises a step of measuring a parameter in the core.

The measured parameter may be chosen from pressure, flow rate of the fluid flowing in the core, pH of the fluid flowing in the core, conductivity of the fluid flowing in the core and viscosity of the fluid flowing in the core. Preferably, the measured parameter is pressure.

Such step may be carried out by sensors (preferably pressure sensors) connected at different points on the core holder(s) 3. In addition, such step makes it possible to study the influence of the fluid sample on the determined property (preferably permeability) of the core and measure such property (preferably permeability) of the core.

The permeability may be measured using the Darcy law.

The parameter may be measured at at least two different points in the core. For example, the parameter may be measured at 2 to 10 different points in the core.

According to some embodiments, the fluid exiting the core holder 3 may enter the collecting chamber 5 and then exit the collecting chamber 5 via the collecting chamber fluid outlet 5b in order to be transferred to a unit such as a scaling unit, a flow meter, a pH meter, a conductometer via a tube or a channel. Such embodiments are useful in order to recover in the collecting chamber 5 solid material (particles, fibers) deriving from the fluid sample. In addition, the presence of a filter at the collecting chamber fluid outlet 5b makes it possible to maintain such solid material in the collecting chamber 5 so as to avoid plugging the device 1 during the transport of the remaining fluid from the collecting chamber 5 to the unit (scaling unit, flow meter, pH meter, conductometer). According to other embodiments, the fluid exiting the core holder 3 may be transferred to a unit such as a scaling unit, a flow meter, a pH meter or a conductometer via a tube or a channel 4 without passing through a collecting chamber 5.

Thus, the remaining fluid can be recovered and analyzed in a unit such as a flow meter or a scaling unit. This makes it possible for example to conduct a material balance and calculate the initial permeability of the core(s).

The method according to the invention may further comprise one or more steps of injecting an additional fluid sample, different from the fluid sample injected through the fluid inlet of the fluid chamber 2. Such additional fluid sample may be or comprise, water, a brine solution, an acid solution, oil or mud. The injection of such additional fluid makes it possible to define the characteristics of a drilling mud to be used for a given well and to test the lost circulation material to be used.

According to some embodiments, this step may be carried out prior to the injection of the fluid sample.

Alternatively or additionally, this step may be carried out after the injection of the fluid sample.

For example, the method according to the invention may comprise a first step of injecting an additional fluid such as brine into the core(s) (in order to determine an initial permeability for example), and a second step of injecting into the core(s) the fluid sample as described above, in order to determine the permeability after such injection. Preferably, the first injection may be carried out through the additional inlet 13a, while the second injection may be carried out by pouring the fluid sample in the fluid chamber 2 (as detailed above).

Claims

1. A device (1 ) for injecting a fluid in at least one core comprising: a fluid chamber (2) extending along a fluid chamber axis and having a first fluid outlet (2d); a first core holder (3) configured to comprise a core and extending from the first fluid outlet (2d), along a core axis which is transversal to the fluid chamber axis; a first piston (8) and a second piston (9) slidably arranged in the fluid chamber (2), configured for displacing and compressing a fluid sample in the fluid chamber (2).

2. The device (1 ) according to claim 1 , wherein the fluid chamber (2) has a second fluid outlet (2d) and the device (1 ) comprises a second core holder (3) configured to comprise a core and extending from the second fluid outlet (2d), along a core axis which is transversal to the fluid chamber axis.

3. The device (1 ) according to any one of claims 1 or 2, wherein the first and second core holders (3) are located on opposite sides of the fluid chamber (2).

4. The device (1 ) according to any one of claims 1 to 3, wherein the first core holder (3) has a core fluid outlet (3b) and the device (1 ) further comprises a collecting chamber (5) extending from the core fluid outlet (5b).

5. The device (1 ) according to claim 4, wherein the collecting chamber (5) comprises a collecting chamber fluid outlet (5b) comprising a filter.

6. The device (1 ) according to any one of claims 1 to 5, wherein the first piston (8) is removable from the fluid chamber (2).

7. The device (1 ) according to any one of claims 1 to 6, wherein the second piston (9) is removable from the fluid chamber (2).

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8. The device (1 ) according to any one of claims 1 to 7, comprising at least one pressure sensor in the first core holder (3) and optionally in the second core holder (3).

9. The device (1 ) according to any one of claims 1 to 8, comprising an enclosure (6) around the first core holder (3) and optionally the second core holder (3), the enclosure (6) being configured to contain a pressurizing fluid.

10. A method for determining at least one property of at least one core by using the device (1 ) according to any one of claims 1 to 9, the method comprising: placing a core into the first core holder (3); introducing a fluid sample into the fluid chamber (2), between the first piston (8) and the second piston (9); pressurizing the core in the first core holder (3); pressurizing the fluid sample in the sample chamber (2) so as to inject it into the first core, by displacing at least one of the first piston (8) and second piston (9); measuring a parameter in the core.

11. The method according to claim 10, wherein the at least one property is chosen from permeability, the content in limestone, the content in clay, the degree of crack, the propagation speed of the fluid and the pore volume to breakthrough, and wherein preferably the at least one property is permeability.

12. The method according to claim 10 or 11 , wherein the at least one parameter is pressure.

13. The method according to claim 10 to 12, comprising, prior to the injection of the fluid sample into the core, a step of moving the fluid sample from an initial position in the fluid chamber (2) to a final position in the fluid chamber (2) facing the first fluid outlet (2d).

14. The method according to any one of claims 10 to 13, wherein the introduction of the sample fluid in the fluid chamber (2) is carried out by removing the first piston (8) from the device (1 ), by introducing the fluid in the fluid chamber (2) and by placing the first piston (8) so as to seal the fluid chamber (2).

15. The method according to any one of claims 10 to 14, wherein the fluid sample to be injected comprises an acid and/or suspended solid material.

16. The method according to claim 15, wherein the acid is chosen from acetic acid, formic acid, hydrochloric acid, esters which hydrolyze and give the above mentioned acids, and mixtures of such acids and esters.

17. The method according to claim 15, wherein the suspended solid material is chosen from lost circulation material and fibers.

18. The method according to any one of claims 10 to 17, comprising: placing a core into the second core holder (3); pressurizing the core in the second core holder (3); pressurizing the fluid sample in the fluid chamber (2) so as to inject the fluid into the cores comprised into the first and second core holder (3) at the same time by displacing at least one of the first piston (8) and second piston (9); measuring a parameter in each of the first and second core.

19. The method according to claim 18, wherein the core placed in the first core holder (3) and the core placed in the second core holder (3) have different permeabilities.

20. The method according to any one of claims 10 to 19, wherein the device (1 ) is heated at a temperature from 20 to 250°C.

21. The method according to any one of claims 10 to 20, wherein a counter-pressure is applied at the core fluid outlet (3b) of the core holder (3), so that the core is at a core pressure of from 1 to 500 bar, and preferably from 300 to 400 bar.

22. The method according to claim 21 , wherein at the moment of the injection of the fluid sample, the fluid sample is pressurized to an injection pressure higher than the core pressure. The method according to any one of claims 10 to 22, wherein the core holder (3) is a flexible membrane, and wherein a confinement pressure is applied external to the flexible membrane, which is from 1 to 50 bar, and preferably from 10 to 40 bar above the core pressure.

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