Field of the invention

[001] The present invention relates to a method for detection of infiltration points in the soil of the ground. In particular, the present invention relates to a method of determining a vertical infiltration profile over a depth interval of the ground, and to determining well capacity of the soil at the respective infiltration points. Unlocking insights from GeoData, the present invention further relates to improvements in sustainability and environmental developments: together we create a safe and liveable world.

Background art

[002] Infiltration of liquid into the ground may occur both naturally, e.g. due to precipitation, or initiated by human activity. It finds various applications, such as fresh water storage, remediation of contaminated or polluted soil, return or recirculation of water which has been pumped away from the ground during construction works, e.g. during construction works involving a lowering of the ground water level, etc. Fresh water storage and fast removal of excess precipitation water or water resulting from flooding may increase in importance as climate changes, leading to periods of draught alternated with heavy rainfalls.

[003] However, the ability to perform infiltration into the ground, i.e., the degree to which ground, or the soil thereof, is able to receive infiltration liquid, depends on various parameters, including the permeability of the ground and the infiltration rate, i.e., the pressure and/or flow rate of the infiltration liquid.

[004] The permeability of the ground, in particular various layers of the soil, influences various properties of the ground, such as the infiltration capacity of the ground. This may vary throughout the different layers of the subsurface, and may hence be different at different depths throughout the ground.

[005] Infiltration points are conventionally determined through trial and error, e.g., by using a ‘ Diisensauginfiltratiori’ (DSI) technique (‘jet suction infiltration’ in English), which involves pushing an injection probe into the ground, while liquid at a set pressure, and pushing the probe down into the ground until infiltration is observed. However, injecting liquid at too high pressure, or too high flow rate, may lead to various types of disruption or distortion of the ground, such as matrix failure, hydraulic failure, and/or fluidization/ liquefaction, in particular in and around the injection probe aperture and at the infiltration points of the ground. This may lead to the intended infiltration well becoming unsuitable for use, and the process having to be repeated at a different location.

[006] To mention an example, for water remediation processes, conventionally infiltration points may be searched for by measuring injection flow rate and associated pressure response during well installation. However, this does not enable prediction of matrix failures, which may therefore occur during the well installation. If matrix failure occurs during well installation, water will not be infiltrated into the ground but move up to the surface, and the remediation process will not be efficient. Even more, well installation might have to be started anew at a new position.

[007] Attempts have been made to predict, or estimate, various soil parameters relevant for infiltration, such as infiltration flow rate, infiltration cone volume, etc., from permeability values of the ground, wherein the permeability values are assumed to be either previously known or to be determined from measurements.

[008] However, the conventional techniques described above do not allow for estimating or predicting the location of infiltration points, i.e., the depth at which infiltration points occur, nor the vertical infiltration profile of the ground. Consequently, the conventional methods do not allow for predicting matrix failure, nor to properly estimate well capacity.

[009] Such lack of estimation of infiltration points leads to a detrimental effect on the accuracy and resulting uncertainty in asset design, such as wells. If matrix failure occurs, the resulting inefficient remediation process or new well installation leads to extra time and efforts being required. This leads to prolonged exposure of personnel to hazardous surroundings and negatively affects sustainability. There is thus a need for a solution to the abovementioned problems.

Summary of the invention

[010] It is an object of the invention to provide a method of detecting or determining the position of infiltration points in the ground, which method reduces the risks of damages and/or disruption of the ground caused by the measurements processes used for detecting the infiltration points.

[011] The term “infiltration point” for use in the invention is defined as a location, or depth range, at the surface within the ground (deeper than the surface) which is more permeable than its surroundings, and therefore such a location or depth range can take up a certain amount of pressure.

[012] The term “infiltration location” for use in the invention is defined as the point at the surface at which one or more infiltration points vertically aligned penetrates the ground.

[013] The terms ground, soil, and subsurface are used alternatingly throughout the application, denote the material or substance of a formation.

[014] The methods described herein find application, in particular, in the design of injection and/or extraction wells. Injection and/or extraction wells may generally be formed by a substantially solid tubing extending through a well bore in the ground, the solid tubing interrupted by one or more filter regions positioned at infiltration points, such as to enable the injection, or extraction, of liquid into, or out of, the ground. Such wells may, for example, be used for reception of excessive rain water, fresh water reserves, storage of water having been pumped e.g. from construction sites or drained from fields, for example sport fields.

[015] During Cone Penetration Testing, CPT, a probe is pushed into the ground while measuring the tip resistance as it is pushed into the ground and through the various subsurface layers over the depth interval, or penetration depth. This may be measured, e.g., by force sensors, strain gauges or piezo elements provided on or in the CPT probe, which measure forces relating to the tip resistance, the local friction at the probe, and friction ratios.

[016] During Hydraulic Profiling Tool (HPT) measurements, a probe is pushed into the ground while injecting fluid from one or more openings provided on the probe and measuring the pressure response of the ground using one or more pressure sensors provided on the probe. The Hydraulic Profiling Tool (HPT) is used to measure the volume of flow and pressure required to inject water into the soil. The results are called HPT logs or HPT data. The liquid is generally injected at a preset, substantially constant flow rate. In certain applications, one or more additional probes may be provided, located at a lateral distance from the probe and pushed into the ground substantially simultaneously. The one or more additional probes comprise one or more additional pressure sensors, enabling determination of parameters related to the soil, such as relative permeability values, in three dimensions over the infiltration volume.

[017] CPT probing and HPT measurements may be performed in conjunction, referred to as CPT-HPT measurements, using one single probe, which may be referred to as a HPT probe or CPT-HPT probe.

[018] Alternatively, or additionally, during CPT-HPT measurements the probe may be stopped at one or more (set) penetration depths and pressure testing performed at these depths. For example, by performing a plurality, or series, of pressure tests at stepwise increasing flow rates at each penetration depth. A liquid, such as water, is injected into the ground, at each one of the one or more penetration depths, and the resulting pressure response of the soil is measured. Additionally, the injection flow rate may be measured. This may be referred to as mini pumping tests, MPT.

[019] From the HPT and/or the MPT measurements, various parameters, including the permeability of the soil of the subsurface layers, can be determined.

[020] The CPT, HPT and MPT measurements may be performed as described in WO 2017/222372 Al and US 2021/0003492 Al.

[021] In particular, it is an object of the invention to detect potential infiltration points over a depth interval of the ground.

[022] This is achieved by a method as defined in claim 1.

[023] Embodiments of the invention are claimed in dependent claims.

[024] According to a first aspect, a method of detecting one or more infiltration points in ground is provided, the method comprising: providing CPT data, obtained from CPT measurements throughout a depth interval of the ground; providing HPT data, obtained from HPT measurements throughout the depth interval; and determining the one or more infiltration points from analysis of the CPT data in combination with the HPT data.

[025] Infiltration points may be determined using a DSI technique which involves pushing an injection probe into the ground until infiltration is observed, while subtracting liquid near the groundwater level and injecting the subtracted liquid at a set pressure rate into the same borehole, but at a greater depth. That is, at an infiltration point, the ground is capable of receiving the injected liquid at the applied injection flow rate. Further, at these points, no ground disruption should occur during liquid injection.

[026] The method of the invention is hence based on concept of detecting infiltration points from a combined, or conjunct, analysis of CPT measurement data and HPT measurement data, and a realization that infiltration points can be identified as locations within the ground, or portions along the depth interval, at which the ground is able to receive the inj ected liquid, while there being no ground disruption, or limited with respect to its surroundings.

[027] Herein, CPT and HPT data may be obtained according to methods known in the art. For example, the CPT and the HPT measurement data may be obtained by a combined CPT-HPT probing using a CPT-HPT probe. Alternatively, one or both sets of measurement data may be provided as previously known data.

[028] . By combining CPT measurement data and HPT measurement data, insight of the ground properties is improved, leading to gain an insight of the likelihood of disruption, thereby well(s) installation is optimized. Indeed, the method according to the present invention prevents that liquid is injected incontrolably, for example at too high pressure, or too high flow rate and thus prevents various types of disruption or distortion of the ground, such as matrix failure, hydraulic failure, and/or fluidization/ liquefaction, in particular in and around the injection probe aperture and at the infiltration points of the ground. Furthermore, the invention prevents overlooking infiltration points due to an oversight.

[029] By the method as described herein, potential infiltration points can be detected, e.g. during injection well design, while reducing the risk of ground disruption or even well explosion, also commonly designated as blowout. [030] The permeability of the ground, in particular various layers of the soil, influences various properties of the ground, such as the possibility or capacity of infiltration liquid into the ground.

[031] However, often the permeability of the subsurface varies throughout different layers in the subsurface, which influences the ability of the ground, i.e., the soil, to receive the infiltration liquid. If liquid is injected with too high pressure at a depth where the permeability of the ground does not allow infiltration, the infiltration liquid will not be received by the soil, but will flow up through the well to the surface of the ground.

[032] The pressure applied during injection will also influence the soil. The increase in water pressure in the ground caused by the injection of water reduces the effective stress in a formation, which can lead to various types of ground disruption. Typically, during DSI , a pressure of 1 bar, or on the order of magnitude of 1 bar, is used. If injecting liquid at this pressure outside of an infiltration point, i.e., at depths where the ground is not able to receive injected liquid, ground disruption, such as matrix failure, hydraulic fracturing, or even fluidization, may occur around the point of injection. If this happens during installation of an infiltration well, the infiltration well becomes unusable and a new well may need to be installed.

[033] As will be discussed in detail further below, from CPT data various types of ground disruption, such as matrix failure, hydraulic fracturing, and fluidization, can be predicted.

[034] The method may further comprise the steps of: from the CPT data, determining an initial effective vertical stress, c’vi, and/or an initial effective horizontal stress, c’hi, over the depth interval, from the HPT data, determining a corrected overpressure over the depth interval; from the initial effective vertical stress and/or the initial effective horizontal stress in combination with the corrected overpressure, determining ground disruption parameters, the ground disruption parameters predicting onset of one or more types of ground disruption at the corrected overpressure over the depth interval. [035] The corrected overpressure is the pressure measured during HPT probing, corrected for groundwater level. That is, it represents the pressure that is due to the HPT injection.

[036] The increase in water pressure, which occurs in response to the injection of water into the ground, reduces the effective stress in a formation and may lead to ground disruption. Three different types of ground disruption can be distinguished: matrix failure, hydraulic fracturing, and fluidization or liquefaction. These processes are dependent on, e.g., the increase in water pressure as a result of injection, the overload (i.e., the depth), the effective horizontal stress and the effective vertical stress. These types of ground disruptions, and theory behind them, are known in the art. A summary of theory behind these, as well as equations defining where these failures or disruptions occur, are known, e.g., from Chapter 13 of Remediation Hydraulics, F.C. Payne, J.A. Quinman, and S.T. Potter, CRC Press, 2008.

[037] Hydraulic fracturing occurs when the horizontal effective stress of the ground matrix is reduced to zero due to the injection pressure. During hydraulic fracturing, the water pressure is increased by an increase in water pressure which is equal to the effective horizontal stress. Hydraulic fracturing may lead to the uncontrolled development of preferred flow paths and fracturing/cracking.

[038] Mathematically, the onset of the risk of hydraulic fracturing can be expressed as

[039] a'h = a'hi — Aau = 0 , [Eq. 1] or

[040] a'hi = A an [Eq. 2]

[041] wherein c’h is the effective horizontal stress, c’hi is the initial effective horizontal stress, and Acu is the increase in water pressure due to injection.

[042] According to the present invention, it has been observed that the initial effective horizontal stress, o’ hi, can be obtained from CPT data, and the increase in pressure, Aou, caused by the liquid injection, can be obtained from HPT data.

[043] Fluidization/liquefaction occurs when the vertical and horizontal effective stress of the ground matrix are reduced to zero by the applied injection water pressure reaching a value where the overload of the matrix is exceeded. Fluidization/liquefaction hence occurs when the water pressure is increased by an increase in water pressure which is equal to the effective vertical stress:

[044] a'v = a'vi — Aau = 0, [Eq. 3] or

[045] a'vi = Aau [Eq. 4]

[046] wherein o’v is the effective vertical stress, o’vi is the initial effective vertical stress, and Acu is the increase in water pressure due to injection.

[047] According to the present invention, it has been observed that the initial effective vertical stress, o’vi, can be obtained from CPT data, and the increase in pressure can be obtained from HPT data.

[048] Prior to hydraulic fracturing or fluidization/liquefaction, matrix failure occurs. Matrix failure is initiated when the horizontal effective stress is reduced to a level when the ratio of vertical and horizontal effective stress reaches a critical limit. Furthermore, at limited overload (depth) and/or poor well design, water injection may lead to short cuts.

[049] Therefore, differently expressed, the critical limit of applied water pressure caused by injection, at which matrix failure may occur, can be expressed as

[051] wherein 0 is the angle of internal friction (expressed in degrees), o’vi is the initial effective vertical stress, and Aouf is the critical limit of the increase in water pressure due to injection. Again, according to the invention, the initial effective vertical stress can be determined from CPT measurement data.

[052] From the above, it follows that by analyzing the CPT data and HPT data in conjunction, the onset of ground disruption, in particular hydraulic fracture and fluidization or liquefaction, of the formation being probed, may be predicted.

[053] From the CPT data, using the equations included herein above, it can be determined, or estimated, as a function of depth into the ground, at which injection pressures the different types of disruption or ground structure failure are likely to occur. [054] The one or more infiltration points may be determined as one or more locations at which no ground disruption has been predicted.

[055] The infiltration points can be determined from the HPT data, which depends on the flow rate at which the HPT is performed, as points, or portions along the depth interval, where the measured pressure response, at a certain depth, is lower than the pressure at which one or more of the types of ground disruption has been predicted to occur. When using higher injection rates in HPT, the HPT data might show ground disruptions due to matrix failure even in points where no fluidization and no hydraulic fracturing are expected to occur.

[056] The method may further comprise determining a vertical infiltration profile over the depth interval, the vertical infiltration profile indicating a potential infiltration location, representing the one or more infiltration points along the depth interval, and potential ground disruption along the depth interval and the maximum pressure to prevent a matrix failure.

[057] The occurrence, or predicted occurrence, of fluidization, hydraulic fracturing, and matrix failure, as determined from the CPT data, may be indicated versus the depth interval.

[058] From the HPT data, the corrected overpressure as function of depth interval is determined, and set out as the predicted ground disruption. As mentioned above, the infiltration points can be detected as the locations, or portions, along the depth interval where the corrected overpressure is lower than the pressure at which ground disruption is initialized or, when matrix failure is happening, where the corrected overpressure has a low grade of disruption.

[059] The method may further comprise determining an ideal well depth from the vertical infiltration profile. From the determined ideal well depth, and values of an absolute permeability along the depth interval, determining a transmissivity over the well depth.

[060] This may also involve the use of MPT measurement data, i.e., specific absolute permeability as determined from one or more series of pumping tests performed with the CPT-HPT probe halted at one or more penetration depths. The specific absolute permeability as determined from MPT may be combined with relative permeability values, as determined from HPT measurement data, to thereby determine an absolute permeability of the ground as a function of the penetration depth.

[061] Although the permeability is described as preferable being determined using HTP data and MPT data, the permeability can also be determined using any other known method or combination of methods.

[062] The method may further comprise determining a maximum injection pressure profile as function of the depth. The maximum injection pressure profile may be calculated from CPT data.

[063] The maximum injection pressure profile can be determined from the CPT measurements and the ground disruption parameters calculated from the CPT measurements and the pressure responses obtained during HPT measurements. The maximum injection pressure is determined as the maximum pressure allowed as response to the injection, where no ground disruption occurs, in particular, the maximum pressure which can be induced without fluidization or hydraulic fracturing occurring.

[064] The method may further comprise determining a maximum well injection capacity from the maximum injection pressure profile.

[065] The maximum well injection capacity represents a maximum injection capacity of the well, i.e., the maximum flow rate which could be infiltrated with., without risking hydraulic fracturing or fluidization of the surrounding soil. The maximum well injection capacity depends on various parameters, in particular on the filter length along the one or more infiltration points, the permeability of the ground over the filter length, storability and the maximum pressure which can be applied during infiltration, among others.

[066] According to the method, the CPT data and the HPT data are obtained simultaneously during CPT-HPT probing.

[067] The CPT-HPT probing may be performed, for example, using a single probe as described in WO 2017/222372 Al and US 2021/0003492 Al. Alternatively, two different probes, located relatively close to one another, could be used.

[068] Alternatively, one or both of the CPT data and the HPT data may be obtained from previous measurements and/or previously known data. [069] In some embodiments, CPT data may already be known for the site which is considered for the installment of an injection well. Such already known, or pre-collected, CPT data may be used in conjunction with HPT data from measurements.

[070] The method may further comprise providing mini pumping test, MPT, measurement data, which has been obtained by one or more pressure testing series performed at one or more locations along the depth interval. The method may further comprise determining, from the MPT measurement data, a specific absolute permeability over the depth interval, and determining, from the specific absolute permeability and from relative permeability, Q/P, determined from the HPT data, a cohesive strength, C, and an absolute permeability, K, over the depth interval. Alternatively, the specific absolute permeability over the depth interval can be obtained from data different than MPT measurement data.

[071] Such MPT data may be obtained by halting the probe during HPT or CPT-HPT measurements, as described herein above. From the MPT measurement data, soil parameters such as the specific absolute permeability can be calculated.

[072] According to a second aspect, a system for determination of one or more infiltration points in ground along a depth interval is provided, the system comprising: a probe equipped with an opening for injecting fluid at a set injection flow rate and at least one pressure sensor for measuring a pressure response in the subsurface; and a processor, configured to perform the steps of the method according to any one of claims 1-12.

[073] The probe may be a probe as described in WO 2017/222372 Al and US 2021/0003492 Al. In some embodiments, the system may additionally comprise a second probe, the second probe comprising one or more additional pressure sensors for measuring a pressure response in the subsurface, as is also described in WO 2017/222372 Al and US 2021/0003492 Al. The system may be based on a system as described in WO 2017/222372 Al and US 2021/0003492 Al, wherein the processor, controller and/or data acquisition system is adapted or configured to perform the method according to any one of the embodiments described herein above. [074] According to the system, the opening for infecting fluid may be an injection opening on at least one side of the probe, or an injection opening extending round the probe or a combination of both.

[075] In particular, the system according to the second aspect may be configured to perform the method according to any one of the embodiments as described herein above with respect to the first aspect.

[076] According to a third aspect, a computer program product is provided, the computer program product comprising instructions which, when executed by a computer, causes the computer to perform the steps according to any one of the embodiments of the method according to the first aspect.

[077] The method, system and computer program product as described herein can be used in various applications, such as well design (e.g. injection/extraction well design), specifying one or more locations, or depths regions, representing infiltration points. Further, a profile of maximum injection pressure over a depth interval of the ground can be determined. The maximum injection pressure represents an injection pressure, i.e. maximum corrected overpressure, at which ground disruption is avoided. Also, a maximum well capacity can be determined. Hence, the methods according to the various embodiments, comprising the various steps as described herein above, enables the determination of vertical profiles of potential wells, indicating one or more potential infiltration points and associated maximum injection pressure, which can be applied without ground disruptions such as fluidization/liquefaction, hydraulic fracturing, and matrix failure being expected to occur.

[078] Since CPT and HPT data are generally being recorded during probe penetration through ground, these can be represented as vertical profiles of the ground. According to the present invention, the vertical infiltration profile, including infiltration points and the infiltration capacity at the infiltration points, can be determined by combining measurement data obtained from CPT probing and HPT probing. In particular, based on vertical profiles obtained during CPT and during HPT, respectively, the infiltration points can be determined. [079] Although the present disclosure focuses on liquid injection, the methods and associated steps disclosed herein, and the associated mechanisms being used, or occurring, in the methods, as well as the probes and systems, may be applied in analogous manner to extraction, with eventual adaptations as would be understood by the person skilled in the art.

Brief description of the drawings

[080] Further features and advantages of the invention will become apparent from the description of the invention by way of non-limiting and non-exclusive embodiments. These embodiments are not to be construed as limiting the scope of protection. The person skilled in the art will realize that other alternatives and equivalent embodiments of the invention can be conceived and reduced to practice without departing from the scope of the present invention. Embodiments of the invention will be described with reference to the figures of the accompanying drawings, in which like or same reference symbols denote like, same or corresponding parts, and in which:

[081] Figures 1A and IB show a flow charts of methods performing probing of the ground, which are known in the art and which may be used for the present invention;

[082] Figure 2 shows a schematic side view of an embodiment of a system which may be used for probing;

[083] Figures 3a, 3b and 3c show schematic side views of a probe which may be used for gathering measurement data;

[084] Figure 4 shows a graph indicating critical limits of increase in water pressure caused by injection as a function of initial effective vertical stress and the onset of ground disruption;

[085] Figure 5 shows a graph illustrating the combination of HPT and CPT measurement data according to embodiments of the invention; and

[086] Figure 6 shows a flow chart of a method according to embodiments of the invention, including combined analysis of CPT and HPT measurement data. Description of embodiments

[087] Fig. 1A shows a flow chart of a method, which can be used for determining soil properties by use of a probe comprising at least a liquid injection port and a pressure transducer. The probe is pushed into a soil for carrying out one or more pumping tests at predetermined depths. During a pumping test an infiltration liquid, such as water, is pumped though the liquid injection port of the probe. The pressure response resulting from the injection of water through the liquid injection port in the soil is measured by means of the pressure transducer arranged on the probe. The pressure response can be measured for each of the one or more pumping tests. The soil testing system can be used for measuring soil parameters while the probe is penetrated into the soil. This may be referred to as MPT, mini pumping tests.

[088] Fig. IB shows a flow chart of a method wherein the pumping test is combined with a hydraulic profiling tool, HPT, and/or cone penetrometer, CPT, test. The probe is pushed into a soil while an infiltration liquid is pumped though the liquid injection port of the probe. During advancement of the probe through the soil the pressure response of the soil/groundwater system against liquid injection can be determined. This may be referred to as HPT measurements or hydraulic profiling tool measurement. Also, during advancement, mechanical resistance and/or friction experienced by the probe can be determined. This may be measured, e.g., using force sensors or strain gauges provided on the probe. This is referred to as CPT, cone penetration testing.

[089] The probe is halted at one or more predetermined depths. At each predetermined depth, one or more pumping tests, e.g. as described with reference to Fig. 1A, are performed while the probe is halted at the predetermined depth. During a pumping test an infiltration liquid is pumped though the liquid injection port of the probe. The pressure response resulting from the injection of liquid through the liquid injection port in the soil is measured by means of the pressure transducer arranged on the probe. The pressure response can be measured for each of the one or more pumping tests.

[090] Fig. 2 shows a schematic side view of an embodiment of a system 1, which can be employed during soil penetration tests, e.g. as described above with reference to Fig. 1 A and IB, for subsurface characterization of a soil 2. The system 1 comprises a probe 9 comprising at least a liquid injection port and a pressure transducer. The probe 9 is arranged for penetration of the soil 2. The system further comprises a data acquisition system arranged for sampling measurement signals from the probe, a controller or processor arranged to control the system to push the probe 9 into the soil 2 and carry out one or more pumping tests, and measure by means of a pressure transducer, for each of the one or more pumping tests, a pressure response in the soil, resulting from the injection of liquid through the liquid injection port. The system 1 can comprise a truck 3. The truck 3 according to this embodiment has wheels. However, tracks or a combination of wheels and tracks can also be arranged. Other arrangements are also possible, e.g. the system 1 may be movable by another transportation unit. The truck 3 may further comprise a plurality of stabilizers to provide support and to improve stability during the penetration tests. The system 1 can further comprise a rod 7 which is coupled to the probe 9, and means for forcibly penetrating the probe 9 into the soil 2 by pushing the rod 7, wherein a depth of penetration L and a penetration rate of the probe 9 can be controlled by the controller. The rod 7 is used to push the probe 9 into the soil, and can include a plurality of sub-elements, such as a plurality of rod sections connected to each other. Other solutions are possible for pushing the probe 9 into the soil. The pushing force for penetration of the probe into the soil 2 can be supplied by a hydraulic pushing arrangement, arranged in the truck 3. The weight of the truck 3 can provide the reaction force for pushing against the rod 7 which is connected to the probe 9 which is forcibly penetrated into the soil 2. Other solutions for providing the reaction force are possible. Further, the system comprises a pump arranged to provide liquid, such as water, to the probe, so as to enable the injection of liquid into the soil through the liquid injection port arranged on the probe.

[091] The system 1 further comprises a digital computer, including one or more processors, which can be coupled to the probe 9 and its sensors, e.g. force sensor and pressure sensors, to receive measurement data from the sensors. The data acquisition system can be arranged to receive electrical signals from the sensors of the probe 9. Also, the digital computer can be coupled to the data acquisition system so as to receive the acquired electrical signals or signals representative for the acquired electrical signals. The digital computer can be arranged for processing the electrical signals to provide an analysis of the measurement results so as to determine and/or calculate soil parameters and characteristics.

[092] Further, the system can comprise an interface, such as a monitor, coupled to the digital computer for displaying a soil analysis, performed by the one or more processors, which can include the determined soil parameters, such as e.g. permeability and storativity. The analysis may be performed for different depths of penetration L. The results from a measurement campaign may be combined to provide a general overview of the soil parameters over an area or volume.

[093] The digital computer can be arranged in a measurement unit in the truck 3 or at a remote unit. The measured data may be received by a digital computer through a wired connection or wireless connection. In case of wireless data communication, a wireless connection device may be arranged to transfer signals through mobile data transfer protocols such as 3G, 4G, 5G, etc. However, other wireless protocols such as WiFi (e.g., a wireless communication conforming to the IEEE 802.11 standard or other transmission protocol) or LoRa may also be employed to obtain a wireless communication. A combination of wireless protocols is possible.

[094] The system 1 may be implemented in or may take the form of a vehicle. Alternatively, the system may be implemented in or take the form of other vehicles, such as cars, recreational vehicles, trucks, agricultural vehicles, construction vehicles and robotic vehicles. It also perceivable that a plurality of systems 1 are included in a vehicle. [095] Fig. 3a and 3b show embodiments of the probe 9 comprising a liquid injection port 11 and a pressure transducer 13. Fig. 3a shows a schematic side view of the probe 9 having a substantially elongated tubular shape comprising a tip 17 facing in a longitudinal penetration direction 19 of the probe 9 and arranged for penetrating the soil 2. In this embodiment, the tip 17 of the tubular probe 9 has a conical shape, however, other shapes are possible. The liquid injection port 11 and the pressure transducer 13 of the probe 9 are arranged at a distance D from each other with respect to a longitudinal penetration direction of the probe 9. Fig. 3b shows a schematic side view of the probe 9 coupled with rod 7 for being pushed into the soil 2. At a certain depth of penetration L into the soil 2, the one or more pumping tests can be conducted, during which the infiltration liquid is pumped through the liquid injection port 11 of the probe 9 in the liquid infiltration flow direction 15 out of the probe 9. By means of the pressure transducer 13, for the one or more pumping tests, a pressure response in the soil 2 resulting from the injection of a liquid through the liquid injection port 11 can be measured. The one or more pumping tests can be carried out at a predefined/chosen substantially fixed depth of soil penetration L of the probe 9. Liquid, such as water, can be injected into the soil 2 through the water injection port 11 at a certain water injection flow rate Q which can be adjusted and controlled. The one or more pumping tests can be carried out at a substantially constant water injection flow rate Q, while in case of a plurality of pumping tests, successive pumping tests at a certain depth of penetration L can be carried out at different water injection flow rates Q.

[096] The probe 9 may be a hydraulic profiling tool, HPT, probe 9, which may also be used to carry out a cone penetration test, CPT in a hydraulic profiling tool cone penetration test, HPT-CPT. Herein the HPT probe 9 is pushed into the ground or soil 2 at a constant rate while water is injected at a constant flow rate into the soil through a water injection port 11 arranged on the HPT probe 9 . A HPT-CPT measurement can be used to evaluate hydraulic properties of a site sub-surface. The system 1 can comprise a HPT probe 9 comprising a tip or cone equipped with one or more water pressure sensors at a distance D from a HPT probe 9 water injection port 11, i.e. injection point. During a HPT measurement the HPT probe is advanced through the soil while injecting water via the injection port 11 at a constant flow rate. During advancement a pressure response of the soil/groundwater system against water injection is determined. During a CPT measurement the probe 9 is advanced through the soil. During advancement mechanical tip resistance, and optionally sleeve resistance, may be measured, as also described with reference to Fig. 1 A and IB. A HPT-CPT measurement combines the HPT and the CPT measurement. During a HPT measurement, the HPT probe movement can be stopped at a certain depth of penetration L. After dissipation of water pressures generated as a result of the HPT measurement, the system 1 can carry out one or more pumping tests, MPT, wherein water is injected in the soil 2 through the injection port 11. For instance, four pumping tests can be carried out, wherein four different water injection flow rates Q are used for the different pumping tests. The different water injection flow rates can be used to perform a quality assessment of the measurements afterwards by analyzing the pressure response measured by the pressure transducer 13 of the HPT probe 9. The water injection flow rate through the water injection port 11 of the HPT probe 9 can induce water overpressures, which may depend on the local geohydrological conditions, and which can be sensed/measured by the pressure transducer 13. After finishing a field measurement inverse modelling can be performed on the measured water overpressure. The inverse modelling can be performed using analytical solutions or using geohydrogeological numerical modelling. The HPT-CPT measurement may be continued after performing one or more pumping tests at a certain depth. The probe 9 may e.g. be pushed further into the soil 2. The HPT probe 9 may pushed into the soil 2 at the same constant rate while water is injected at the constant flow rate as before the pumping tests. It will be appreciated that the HPT-CPT measurement may be resumed after pore water pressure of the preceding pumping tests has dissipated. It is possible that after the HPT-CPT measurement is resumed after water injection has been restored to the level of the initial HPT-CPT measurement, and water pressure has come to an equilibrium.

[097] Fig. 3c shows an embodiment of a probe system 99 comprising a first probe 9’ and a second probe 9”. Herein, the probe 9’may be similar to the probe 9 described with reference to Fig. 2. The first and second probes 9’, 9” are laterally spaced from each other, and may be pushed into the ground and used for performing HPT-CPT measurements in a manner as described with reference to Fig. 2. The first probe 9’ comprises the liquid injection port 11. The second probe 9”comprises the pressure transducer 13. In this example, the probe system 99 comprises further pressure transducers 13’, 13”. The liquid injection port 11 and the pressure transducer 13 of the probe system 99 are arranged at a distance D from each other with respect to a lateral direction of the probe 9’. The one or more pressure transducers in the 3D space around the injection point can be used to derive horizontal and/or vertical permeability and storativity from the measured pressure response on the injected liquid Q. For example, the pressure transducer 13 can be used to determine the horizontal permeability and storativity. The pressure transducer 13” can be used to determine the vertical permeability and storativity. Optionally the horizontal and/or vertical permeability and storativity can be derived using numerical or analytical calculations, for example with an inverse modelling technique.

[098] Figure 4 shows a graph indicating critical limits of increase in water pressure caused by injection as a function of initial effective vertical stress and the onset of ground disruption. This graphs provides an indication of the critical limits of water pressure increase, i.e., the maximum allowed increase in water pressure (in m H2O), caused by the injection, as a function of initial vertical effective stress and the angle of internal friction for the onset of various types of ground disruption. The short dashed lines, 402, indicate predicted onset of matrix failure. The solid lines, 404, indicated the predicted onset of hydraulic fracture. The long-dashed line, 406, indicates the predicted onset of liquefaction. As can be seen, the expected onset, or initialization, of the different types of disruption is dependent on the soil properties of the formation. In particular, soil or ground layers having a higher initial vertical stress, c’vi, and higher internal friction angle, <b, can withstand higher overpressure caused by injection than layers of lower initial vertical stress. The initial vertical stress can be determined from CPT measurement data, as discussed above.

[099] The point at which ground disruption is initiated can be estimated by recording injection flow rate and injection pressure during HPT probe penetration, and/or during searching for infiltration points. For this, the above equations, Eq 1 - Eq 5, can be used.

[0100] Figure 5 shows a graph illustrating how the HPT and CPT measurement data can be analyzed in conjunction, i.e., can be combined to determine various parameters of the ground over a depth interval. In particular, this graphical representation conceptually illustrates how CPT and HPT data can be combined to determine infiltration points and maximum infiltration capacity, and to create a vertical infiltration profile showing injection points and potential matrix failure locations.

[0101] The diagonally running lines indicates the critical limits when the different types of ground disruption is expected, calculated from CPT data as described herein above. The line 502 indicates the threshold for matrix failure, as a function of depth (probe penetration depth) into the ground. That is, line 502 represents the overpressure, caused by liquid injection, at which matrix failure is predicted to occur. The line 504 indicates the threshold for hydraulic fracturing, as a function of depth (probe penetration depth) into the ground. That is, line 504 represents the overpressure at which hydraulic fracturing is predicted to occur. The line 506 indicates the threshold for fluidization, or liquefaction, as a function of depth (probe penetration depth) into the ground. That is, line 506 represents the overpressure at which fluidization, or liquefaction, is predicted to occur. These failure lines have been determined from CPT measurement data, using the equations and theory which were discussed in the Summary section.

[0102] The quickly fluctuating line, 508, represents the overpressure caused by the liquid injection as a function of probe penetration depth, as measured during HPT probing, using a set substantially constant injection flow rate. Where this fluctuating line crosses one or more of lines 502, 504 and/or 506, it may be concluded that ground disruption, i.e., matrix failure, hydraulic fracturing, or fluidization, respectively, would be expected to occur. The respective type of failure expected is indicated in the line, or bar, 510, in the right hand part of the graphic. Locations, or penetration depth ranges, 510, where substantially no, or at least not matrix failure, is predicted, can be considered potential infiltration points.

[0103] Thereby, by graphically illustrating the pressure fluctuations measured during HPT probing in combination with the thresholds for ground disruption, which have been determined from CPT data, information can be deducted regarding the sensitivity of the ground to ground disruption as a result of the increase in water pressure caused by the injection. From this, infiltration points can be detected.

[0104] CPT and HPT measurement data can be processed and analyzed using methods and algorithms, or equations, as known to the skilled person. The curves indicating prediction of the various types of ground disruption (matrix failure, hydraulic fracturing, fluidization, respectively) can be determined, for example using the theory and equations presented in Chapter 13 of Remediation Hydraulics, 2008, Payne et al.

[0105] As can be seen from Fig. 5, at certain penetration depths no ground disruption or variations in disruption appears to occur, at the injection flow rate of the HPT system. These depth ranges, or intervals, represent possible infiltration points. If injection flow rate is increased, detecting these infiltration points becomes increasingly difficult, since the resulting water pressure increases to a point where the thresholds of fluidization/liquefaction are reached. Further, it can also be deducted that if only considering the resulting increase in water pressure caused by the probing only provides limited information, due to the limited increase in water pressure.

[0106] The above analysis confirms the concept of preferred flow paths and highly permeable layers at infiltration points. At an infiltration point the ground is less prone to disruption by an increase in water pressure than the other ground layers, which do not exhibit good permeability and infiltration properties, since the water pressure can be quickly dissipated. However, the detection of an infiltration point is highly dependent on the flow rate and/or pressure at which is probed. [0107] As an example, in Figure 5 a vertical line has been included at an injection pressure of 1 bar (100 kPa). If searching for infiltration points using an injection pressure of 1 bar, fluidization is expected to occur down to a depth of 9-10 meter below the ground surface. As can be seen, the diagonal line 506 representing fluidization intersects with the 1 bar line at around 9-10 meters. Therefore, above this depth, it will not be possible to find infiltration points unless working with a lower injection pressure, i.e., an injection pressure below the injection pressure at which fluidization is expected. That is, an injection pressure “underneath” the diagonal line indicating the onset of fluidization.

[0108] From pressure measurements performed at the depth of an infiltration point, an indication may be provided of the risk of certain ground disrupting processes. The maximum pressure, at which specific ground disruption is expected, can be deducted from the diagonal lines indicating, respectively, matrix failure, hydraulic fracturing, and fluidization.

[0109] The information deducted as described herein above, e.g., the detected infiltration points, can be used in the design or construction of an injection well to be positioned at the probed location. Such well may be designed with an injection filter at one or more of the infiltration points as determined from the above analysis. Additionally or alternatively, one of the infiltration points may be used for extraction and another of the infiltration points may be used for infiltration, or injection. For example, an upper infiltration point, that is, a point at less depth, may be used for extraction, and a lower lying, i.e., at a deeper depth, infiltration point may be used for infiltration/inj ection.

[0110] Figure 6 shows a flow chart of an embodiment of the method as described herein, which may be used for deduction of a graphical representation as illustrated in Fig. 5, and/or for deduction of specific parameters and specifications, e.g. of the information discussed herein above.

[0111] At step S602, combined CPT-HPT probing is performed in the field, for example as described in the Summary section above. This may be performed using a system as described with reference to Fig. 2, 3a-3c. During CPT-HPT probing, the CPT- HPT probe 9, 9’, 9”, is pushed into ground over a depth interval, at substantially constant penetration speed. While pushing, CPT data, e.g. force relating to tip resistance or local friction, is measured. Simultaneously, an injection liquid, generally water, is injected at a set substantially constant flow rate, through the opening 11, and the resulting water pressure in the soil is measured using the one or more pressure sensors 13, 13’, 13”. At certain, preferably predetermined, depths, the probe is halted, and, preferably once an equilibrium state has been reached, one or more pumping tests is performed at each depth, so called mini pumping tests, MPT. For example, a series of pumping tests may be performed, at stepwise increasing flow rate. Thereby, CPT, HPT and MPT data are provided.

[0112] During these tests and measurements, CPT measurement data, HPT measurement data, and MPT measurement data, are recorded, e.g. by a data acquisition system. These measurement data are subsequently processed and analyzed, as shown in the flow chart.

[0113] In step S604, the CPT measurement data is input into a CPT data processor, e.g. a processor or processing unit of the digital computer of the system. Analogously, in step S606, the HPT measurement data is input into an HPT data processor, or processing unit of the system. Analogously, in step S608, the MPT measurement data is input into an MPT data processor, or processing unit, of the system.

[0114] In step S610, specific absolute permeability of the ground, as function of depth, i.e., the different layers of the ground, is determined from the MPT data. This may be performed as described in WO 2017/222372 Al and US 2021/0003492 Al.

[0115] In step S612, the groundwater level may be determined from the MPT data.

[0116] In step S614, the HPT data is processed, to determine a corrected overpressure P, i.e., the pressure in the ground resulting from the fluid injection. In this step, the pressures as measured by the one or more pressure sensors 13, 13’, 13”, i.e., the pressure measured behind the injection screen, may be corrected using the groundwater level determined in step S612. This corrected overpressure may be represented graphically by the fluctuating line 508 shown in Fig. 5.

[0117] Further, in step S614, the relative permeability as a function of depth is determined from the injection flow rate, Q, and the corrected overpressure, P. This may be determined as Q/P. [0118] In step S616, the relative permeability over the MPT area of influence, i.e., the volume of influence by the MPT, is determined. Herein, the specific absolute permeability determined in step S610 may be taken into account.

[0119] In step S618, the coherence strength C is determined, which links the absolute permeability to the relative permeability. The coherence strength is a constant, which is typical for certain types of ground layers, and depends on the different properties of the ground. In other words, the coherence strength, C, provides an indication of the type, or class, of ground or layer at a certain depth.

[0120] In step S620, the absolute permeability as a function of depth is determined.

[0121] Hence, the HPT and MPT data can be processed and/or analyzed. The above described analyses and processing of the HPT and MPT data, respectively, may include additional steps or details, as will be understood by a person skilled in the art.

[0122] In step S622, the CPT measurement data is processed, to determine the initial vertical stress, c’vi, and the initial horizontal stress, c’hi, over the depth interval. The corrected overpressure, as determined in step S614, is taken as input, to determine the effective vertical stress, o’v, and the effective horizontal stress, c’h, respectively. These parameters may be determined as described in the Summary section above.

[0123] In step S624, the parameters determined in step S622 may be used to calculate, or determine, ground disruption parameters, also as described herein above. These indicate the (predicted or estimated) onset of different types of ground disruption. In particular, critical pressure limits versus depth of matrix failure, hydraulic fracturing, and fluidization are determined. These may be represented graphically by curves 502, 504 and 506 as illustrated in Fig. 5.

[0124] In step S624, the parameters may be determined, for example, using Mohr’s circle analysis of the horizontal and vertical effective stresses. Such analysis may be performed as known to the person skilled in the art, e.g. as described in Chapter 13 of Remediation Hydraulics, F.C. Payne, J. A. Quinman, and S.T. Potter, CRC Press, 2008

[0125] Based on the predictions of the various types of failures or ground disruption, determined in step S624, and the measured overpressure determined in step S614, a vertical infiltration profile is determined in step S626, indicating potential infiltration points and potential failure processes along the depth interval. [0126] In step S628, an ideal well depth may be detected or determined, from the vertical infiltration profile determined in step S626. This may comprise selecting one or more of the infiltration points detected in step S626 as infiltration, or injection points, to be used in an injection, or extraction, well.

[0127] In step S630, the transmissivity over the well depth is determined. This is determined, basically, as a function of the thickness of the infiltration point, as determined from step S630, multiplied by the absolute permeability at the infiltration point, as determined in step S620.

[0128] In step S632, a profile over the maximum injection pressure as a function of depth is determined. This may be determined from the failure ground disruption parameters determined from step S624. Thereby, the maximum injection pressure, which may be applied at the infiltration points without risking hydraulic failure or fluidization, may be determined. The maximum injection pressure which may be applied may be determined as a certain percentage or ration of the injection pressure at which ground disruption is expected or estimated to occur. For example, the maximum allowable injection pressure may be determined as the pressure at which a certain type of ground disruption is predicted to occur, divided by 1.2.

[0129] In step S634, the maximum well injection capacity may be determined from the maximum injection pressure profile determined in step S632 and the transmissivity determined in step S630.

[0130] Hence, based on analysis of CPT measurement data in combination with HPT data, and in particular also using MPT data, infiltration points, maximum injection pressure, and maximum well injection capacity can be determined.

[0131] These parameters may be used in the design and construction of injection and/or extraction wells, comprising substantially solid, or non-permeable, wall sections, along which, at one or more infiltration points as determined above, injection/extraction filters are positioned.

[0132] As will be understood by the person skilled in the art, the different steps indicated in the flow chart of Fig. 6 are not necessarily performed in the order in which they have been described above, but may be performed in different order and/or simultaneously, i.e., in parallel. Further, depending on which information and/or parameters or specifications are desired, all or only some of the different steps may be performed. That is, in some embodiments, it may not be necessary to perform all steps.

[0133] The method described with respect to Fig. 6, in particular the measurement steps or probing S602, may be performed using one or more of the systems described with reference to Fig. 3A-3C.

[0134] It will be clear to a person skilled in the art that the scope of the invention is not limited to the examples discussed in the foregoing, but that several amendments and modifications thereof are possible without deviating from the scope of the invention as defined in the attached claims. While the invention has been illustrated and described in detail in the figures and the description, such illustration and description are to be considered illustrative or exemplary only, and not restrictive. The present invention is not limited to the disclosed embodiments but comprises any combination of the disclosed embodiments that can come to an advantage.

[0135] Variations to the disclosed embodiments can be understood and effected by a person skilled in the art in practicing the claimed invention, from a study of the figures, the description and the attached claims. In the description and claims, the word “comprising” does not exclude other elements, and the indefinite article “a” or “an” does not exclude a plurality. In fact it is to be construed as meaning “at least one”. The mere fact that certain features are recited in mutually different dependent claims does not indicate that a combination of these features cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope of the invention. Features of the above described embodiments and aspects can be combined unless their combining results in evident technical conflicts.