System, method, and composition for pressure, flow, and containment monitoring using active-source electromagnetics and streaming potential

Abstract

An exemplary geophysical monitoring system and method are disclosed for an active-source EM with streaming potential (SP), termed EM-SP, for subsurface fluid flow characterization and monitoring, and for assessment of containment structures that are subject to fluid flow, such as groundwater, oil and gas reservoirs, geothermal reservoirs, and carbon-storage sites. In some embodiments, the active-source EM-SP combines the principles of SP and active-source EM monitoring to provide real-time, non-invasive monitoring of subsurface fluid dynamics without requiring direct access to wells or boreholes.

Description

Attorney Docket No. 10046-668W018602 AHM SYSTEM, METHOD, AND COMPOSITION FOR PRESSURE, FLOW, AND CONTAINMENT MONITORING USING ACTIVE-SOURCE ELECTROMAGNETICS AND STREAMING POTENTIALRelated Application

[0001] This application claims priority to, and the benefit of, U.S. Provisional Patent Application No. 63 / 753,888, filed February 4, 2025, entitled “SUBSURFACE FLUID FLOW MONITORING SYSTEM AND METHOD,” which is incorporated by reference herein in its entirety.Background

[0002] Electromagnetic (EM) surveys have been widely utilized for the real-time, non¬ in vasive characterization and monitoring of subsurface man-made and natural structures (Ziolkowski and Slob, 2019). Conventional EM survey techniques primarily rely on variations in electrical conductivity to identify subsurface features. However, these methods face limitations in formations with low conductivity contrasts and typically do not provide direct information about the flow direction or rate of subsurface fluids. Furthermore, conventional EM surveys have difficulty detecting slow subsurface fluid movement, such as early-stage leaks, due to background geological noise and cultural interference (e.g., power lines).

[0003] The integration of streaming potential (SP) could enable these surveys to monitor subsurface fluid flow as well. SP is a phenomenon in which pressure-driven fluid flow drags ions from the diffuse layer of the Electrical Double Layer (EDL) through a porous medium and generates an electrical potential (Revil and Jardani, 2013). The measured potentials arise from natural processes, such as groundwater flow or electrokinetic effects. Traditionally, this survey is conducted passively. Unlike active methods like electrical resistivity or induced polarization, no artificial current is injected into the ground.

[0004] Ahmadian et al. (2023) discovered that SP could contribute to the interpretation of active-source EM surveys. Active-source EM monitoring involves the injection of electric current over the area of investigation and the collection of the resulting electric voltage and magnetic fields by receivers deployed in the survey. An example of this technique is the controlled source electromagnetic (CSEM) method used for monitoring subsurface fracture and fluid flow (Ziolkowski and Slob, 2019). Ahmadian and Haddad proposed that activesource EM-SP could be utilized for higher fidelity real-time monitoring of subsurface fluidAttorney Docket No. 10046-668W018602 AHM flow and containment in various applications such as groundwater, oil and gas reservoirs, geothermal reservoirs, and carbon-storage sites (Ahmadian and Haddad, 2025).Summary

[0005] An exemplary geophysical monitoring system and method are disclosed for an active-source EM with streaming potential (SP), termed EM-SP, for subsurface fluid flow characterization and monitoring, and for assessment of containment structures that are subject to fluid flow, such as groundwater, oil and gas reservoirs, geothermal reservoirs, and carbon- storage sites. In some embodiments, the active-source EM-SP combines the principles of SP and active-source EM monitoring to provide real-time, non-invasive monitoring of subsurface fluid dynamics without requiring direct access to wells or boreholes.

[0006] The exemplary system and method extend the application of the active-source EM-SP method to monitoring plugged-and-abandoned (P& A) wells, a critical use for safeguarding environmental safety, public health, and regulatory compliance. Notably, despite its potential advantages of being non-invasive and cost-effective, the SP method has not been used to monitor P& A wells. Unlike current methods, which often rely on direct access to the wellhead and are limited in their ability to detect leaks in real time, this exemplary system and method enable remote, continuous monitoring of P& A wells using the EM-SP technique. This capability enhances operational safety by enabling early leak detection without direct access to wells, thereby improving response times and reducing risks.

[0007] In some implementations, the exemplary system and method can improve the strength of the SP signal by altering the porous media and injectates, enabling detection and monitoring of fluid flow rate, direction, pressure, type, spatial distribution, and fracturing pressure, and offering greater resolution and sensitivity than current technologies. By adjusting factors such as surface charge density, electrolyte concentration in the fluid, fluid viscosity, and the size and shape of pores in the material, and appropriately deploying an active source, the exemplary system and method enable a broad range of monitoring applications in both subsurface and surface environments. The same compositional changes could also enhance passively gathered SP signals. The extensive energy and environmental applications can include and are not limited to: (i) containment monitoring (e.g., wellbore cement, P& A, cap rock containment in storage complexes), (ii) containment monitoring of other engineered structures utilizing cement as the main barrier to contain fluids in reservoir (e.g., dams, nuclear facilities), and (iii) fluid dynamics monitoring (e.g., waterflooding in conventional reservoirs, fracture flow in stimulated unconventional reservoirs).Attorney Docket No. 10046-668W018602 AHM

[0008] In some implementations, containment monitoring can be improved using containment structures having cement admixtures that are emplaced during the construction of the containment system, to enhance the SP signal attained by active-source SP monitoring.

[0009] In some implementations, fluid dynamics monitoring applications can be improved with the introduction of SP-signal-enhancing injected fluids into porous media (e.g., by coating the pore walls), particulate admixtures, or a combination thereof. The injectates can be introduced during the stimulation and fluid injection campaigns to enhance the SP signal attained by the methods described below.

[0010] In some implementations, the exemplary system and method (i) integrates active-and passive-source EM-SP data to refine fluid flow and direction information and (ii) introduces external stimuli such as contrast-agent coatings, tailored electrolytes, tuned fluid viscosity, modified medium composition, post-setting treatment, and optimized pore size and geometry, to amplify SP signals in challenging environments.

[0011] The exemplary system and method employ synergistic interaction between an active source and fluid flow and employ GPS synchronization for high-precision measurements, minimizing the influence of geological and cultural noises.

[0012] The exemplary system and method are applicable across industries such as oil and gas, Carbon Capture and Storage (CCS), geothermal energy, environmental monitoring, mining, and agriculture, for tasks such as leak detection, fluid migration tracking, reservoir characterization, and resource management optimization. It enhances safety, improves environmental protection, and increases operational efficiency. Potential future applications could expand into new fields, such as infrastructure and construction, volcanology and seismology, and space exploration.

[0013] In an aspect, a method (e.g., for measurement and analysis) is disclosed comprising: monitoring of flow dynamics or containment via EM and SP sensitive instruments positioned over a site (e.g., Oil & Gas site, e.g., hydraulic fracturing, waterflood, gas injection) or structure (e.g., dam, containment O& G structure, e.g., P& A wells), and collecting multi-frequency active-source EM-SP data, augmented by SP generated when a pressure-driven fluid flow drags ions from a diffuse layer of an EDL through a porous medium; determining, via an EM-SP simulation or analysis, fluid flow and containment characteristics at a plurality of subsurface depths of fluid flow or containment barriers; and outputting the fluid flow and containment characteristics, wherein the output fluid flow characteristics are employed for site / structure survey, site / structure operation integrity, or site / structure compliance.Attorney Docket No. 10046-668W018602 AHM

[0014] In some embodiments, the method described herein further comprises: injecting a fluid with a pre-defined (e.g., known / characterized) frequency-dependent signature into the site or structure: and determining via the simulation or analysis using the pre-defined frequency-dependent signature to determine the fluid flow characteristics at the plurality of subsurface depths of the fluid flow.

[0015] In some embodiments, the method described herein further comprises: injecting a fluid with an enhanced SP signature into the site or structure; and determining via the simulation or analysis using the pre-defined frequency-dependent signature to determine the fluid flow characteristics at the plurality of subsurface depths of the fluid flow.

[0016] In some embodiments, the fluid is mixed with electrically active contrast agents, electrolyte, or mineral admixtures to improve sensitivity of the fluid to active- and passive¬ source EM monitoring.

[0017] In another aspect, a composition of matter (e.g., modified injectates for hydraulic fracturing) is disclosed comprising: an injectate; and an SP-enhanced additive added to the injectate, the SP-enhanced additive including graphite, metal, composite, or a combination thereof added to the injectate that enhances active- and passive-source EM-SP monitoring.

[0018] In another aspect, a composition of matter (e.g., modified cement) is disclosed comprising: electrically active particulate, admixture; a binder for forming a construction structure that sets, hardens, and adheres to bind them together to form a containment structure (e.g., in P& A well, dam, caprock); and an SP-enhanced additive including graphite, metal, composite, or a combination thereof mixed in the binder that enhances active- and passive¬ source EM-SP monitoring.

[0019] In another aspect, a construction structure is disclosed being formed of aggregates and a binder that sets, hardens, and adheres to bind them together to form a containment structure (e.g., in P& A well, dam, caprock), wherein the structure is embedded with an SP- enhanced additive including graphite, metal, composite, or a combination thereof mixed in the aggregate and / or binder that enhances active- and passive-source EM-SP monitoring of the containment structure or conditions thereby.

[0020] In some embodiments, the aggregates and binder include at least one of: alite (3CaO·SiO2), belite (2CaO·SiO2), tricalcium aluminate (3CaO·Al2O3), and brownmillerite (4CaO·Al2O3·Fe2O3).

[0021] In some embodiments, the fluid flow is flowing through a geologic formation in a subsurface porous medium with low conductivity contrast.Attorney Docket No. 10046-668W018602 AHM

[0022] In some embodiments, the determined fluid flow characteristics include a rate of the subsurface fluid flow at different depths.

[0023] In some embodiments, the determined fluid flow characteristics include a direction of subsurface fluid flow at different depths.

[0024] In some embodiments, the determined fluid flow characteristics include pressure within the subsurface fluid flow at different depths.

[0025] In some embodiments, the method described herein comprises: determining, via the simulation or analysis, a frequency-dependent profile for a subsurface fluid flow; and determining a fluid type based on the determined frequency-dependent profile.

[0026] In some embodiments, the method described herein comprises: deploying a transmitter and receivers around a borehole or zone of interest, and transmitting electric current to the borehole or the zone of interest to apply the current to a subsurface region connected to the borehole or over the zone of interest.

[0027] In some embodiments, the method described herein comprises: deploying a transmitter and receivers around a borehole or zone of interest, and passively monitoring electric fields induced solely by the fluid flow of a subsurface region connected to the borehole or over the zone of interest.

[0028] In some embodiments, the structure includes a plugged-and-abandoned well, a dam subsurface structure, or a nuclear plant structure.

[0029] In some embodiments, the stiucture is formed in part of cement, wherein the cement of the structure is embedded with an admixture that enhances electromagnetic or streaming potential signal sensing, wherein the admixture includes graphitic, metallic, composite, or a combination thereof.

[0030] In some embodiments, the active-source simulation or analysis identifies an infinite- base station as a reference point in the simulation or analysis.

[0031] In yet another aspect, a method (e.g., for the analysis portion only) is disclosed comprising: receiving measurement data of flow dynamics or containment acquired via electromagnetic (EM) and streaming potential (SP) sensitive instruments positioned over a site (e.g., Oil & Gas site, e.g., hydraulic fracturing, waterflood, gas injection) or structure (e.g., dam, containment O& G structure like P& A wells), wherein the measurement data includes multi-frequency active-source EM-SP data, augmented by SP generated when a pressure-driven fluid flow drags ions from a diffuse layer of an Electrical Double Layer (EDL) through a porous medium; determining, via an EM-SP simulation or analysis, fluid flow and containment characteristics at a plurality of subsurface depths of fluid flow orAttorney Docket No. 10046-668W018602 AHM containment barriers; and outputting the fluid flow and containment characteristics, wherein the output fluid flow characteristics are employed for site / structure survey, site / structure operation, or site / structure compliance.Brief Description of Drawings

[0032] Fig. 1A shows a schematic of an example active-source EM-SP survey of a permanently P& A well.

[0033] Fig. IB shows a schematic of an example active-source EM-SP survey of hydraulic fracturing.

[0034] Fig. 2A shows an aerial view of the example surface EM-SP survey configuration with an active source of Fig. 1 A or IB.

[0035] Fig. 2B shows an EM-SP field configuration, e.g., for surveying a hydraulic fracturing target.

[0036] Fig. 2C shows an example geometry of a synthetic P& A well, e.g., at a Devine Field Test Site, used to demonstrate the benefit of the exemplary system and method.

[0037] Fig. 3A shows experimental results of compared SP results obtained using either an active or passive source in the presence of an exemplary Electrically Active Additives (EAAs), coke breeze, in a field demonstration case.

[0038] Fig. 3B shows SP temporal variations in a one -dimensional (ID) four-electrode sand pack subjected to four active-source potentials during a stepwise tap water injection.

[0039] Fig. 3C shows a comparison of SP from freshwater and carbonated water injections using a passive source at three stations.

[0040] Fig. 3D shows a comparison of SP in cement capillary tubes with 15% sand, in cement capillary tubes with 15% EAA mix-in, and SP over time for both tubes.

[0041] Fig. 3E shows a controlled test conducted to demonstrate the influence of water flow direction on SP.

[0042] Fig. 3F shows SP voltage measurements at the Advanced Energy Consortium (AEC) lab and the Devine Field Test Site using different fluid flow rates.

[0043] Fig. 3G shows a quick well integrity test using an air compressor to pressurize the borehole and evaluate water leakage through the cemented borehole.

[0044] Fig. 4 shows an example EM-SP analysis method for monitoring P& A wells, dams, and nuclear plants.

[0045] Fig. 5A shows an example of radially distributed surface receiver electrodes.

[0046] Fig. 5B shows an example of uniformly distributed surface receiver electrodes.Attorney Docket No. 10046-668W018602 AHM Detailed Description

[0047] Some references, which may include various patents, patent applications, and publications, are cited in a reference list and discussed in the disclosure provided herein. The citation and / or discussion of such references is provided merely to clarify the description of the disclosed technology and is not an admission that any such reference is “prior art” to any aspects of the disclosed technology described herein. In terms of notation, “[n]” corresponds to the nth reference in the list. For example, [1] refers to the first reference in the list. All references cited and discussed in this specification are incorporated herein by reference in their entirely and to the same extent as if each reference were individually incorporated by reference.

[0048] Example Active-Source EM-SP Survey System

[0049] Fig. 1A shows a schematic of an example active-source EM-SP survey 100a of a permanently P& A well 101. Fig. IB shows a schematic of an example active-source EM-SP survey 100b of hydraulic fracturing.

[0050] In each of the Figs. 1A and IB, the EM-SP survey system includes a transmitter (e.g., 102a) and multiple receivers 104. The transmitter 102a is coupled to one or more surface transmission electrodes 106 and is configured to inject a current waveform into the survey site. In some embodiments, and as shown in Figs. 1A and IB, the transmitter (e.g., 102b) may be coupled to one or more borehole transmission electrodes 108. The receivers 104 are connected via electric wires 110 to a set of surface and / or subsurface electrodes 112a-112b positioned over a survey site. Integrating subsurface electrodes 112b (e.g., deep-seated electrodes) into the set can enable high-resolution monitoring of subsurface flow by facilitating three-dimensional (3D) streaming potential (SP) signal acquisition and overcoming the two-dimensional (2D) limitations of surface-only configurations. Subsurface electrodes 112b can also be less susceptible to surface-level cultural noise. By installing the surface and / or subsurface electrodes 112a- 112b at various strategic depths, the set can be fully optimized for comprehensive 3D SP characterization.

[0051] Locations of electrodes 112a- 112b, electrode spacing, length of transmitter lines 103a-103b, or the position of the infinite base station (not shown), and parameters thereof, may be properly positioned and selected based on the P& A well configuration (e.g., material, structure configuration, and casing direction), surface cultural interference (e.g., nearby interference objects), and the intended depth of investigation.Attorney Docket No. 10046-668W018602 AHM

[0052] Typical current waveforms injected via the surface transmission electrodes 106 and the borehole transmission electrodes 108 may have magnitudes of 1 A - 1000 A, e.g., 1 A - 10 A, 1 A - 20 A, 1 A - 30 A, and frequencies of 0 Hz - 1000 Hz.

[0053] The design of the conductor casing 114 can vary between different states in the U. S. and other countries. Additionally, variations in geological environments may influence the length and placement of the cement plug 116. Despite the differences, the schematic represents the general structure of a P& A well 101. In the example shown in Fig. 1A, the permanently P& A well 101 includes a production casing 118 that, at a first location, has a primary cement plug 120 prior to a production zone 122 with perforated casing holes 124. The production casing 118 may be coupled at its end to an intermediate casing 126 having a cement plug 116 at one end and a surface casing 128 (shown as “surface plug” 128) at another end. Fluid spills 130 can exit through cracks 132 in the plugs (e.g., cement plug 116, surface plug 128) of the production casing 118 and intermediate casing 126 to release reservoir fluid leaks 134.

[0054] Fig. IB provides a schematic of an example active-source EM-SP survey 100b of hydraulic fracturing. Hydraulic fracturing is a procedure that can increase the flow of oil or gas from a well. It is conducted by pumping liquids 140 down a well into subsurface rock units 142 at pressures high enough to fracture the rock (e.g., 144). The goal is to create a network of interconnected fractures 144 that can serve as pore spaces for the movement of oil and natural gas to the wellbore 146. Fracture placement monitoring can be conducted by the EM-SP signal induced by fluid flow at high rates and pressures during hydraulic fracturing. As with earlier figures, this schematic does not represent the exact surface and / or subsurface electrode locations, electrode spacing, transmitter line length, or infinite base station position. These parameters depend on factors such as the hydraulic fracturing target, surface cultural interference, and investigation depth.

[0055] In the embodiments other than the one shown in Fig. IB, the formation 142 could not be fractured, and the EM-SP signal is enhanced by a fluid additive, for instance, in waterflooding or gas injection into hydrocarbon reservoirs. In another embodiment, the formation 142 may be fractured but not full of proppant 148, and only the fluid injectate 140 modifies the active-source SP signal.

[0056] Example top view of surface EM-SP survey configuration. Fig. 2A illustrates an aerial view of the example surface EM-SP survey configuration 200a with an active source of Fig. 1A or IB. The actual locations of electrodes 112a-ll2b, electrode spacing, length of transmitter lines 103a-103b, or the position of the infinite base station 202, and parametersAttorney Docket No. 10046-668W018602 AHM thereof, would vary depending on the P& A well 101, surface cultural interference, and the depth of investigation. The EM-SP survey could produce a contour map with isolines of constant value distributed concentrically around the central P& A well 101, as shown by dashed circles 204 in the schematic.

[0057] Fig. 2A also illustrates how the electric field between any electrode pair within the grid is calculated. In the field, data is collected only between each grid electrode and the infinite base station, such as E and E2(see Fig- 2A). Direct measurement between Electrode 1 and Electrode 2 does not occur. However, the electric field between them can be computed using vector subtraction using Equation 1:E⃗12= E⃗2− E⃗1(Eq. 1)

[0058] In Equation 1, the electric field between any electrode pair in the grid, as shown in Fig. 2A, may be oriented either parallel or perpendicular to the flow direction that is normal to the subsurface fluid front. Multi-directional EM-SP measurements enable inference of flow direction, rate, and other dynamic properties by leveraging established EM-SP signal signatures correlated with various electrode pair orientations relative to the flow vector.Exemplary signatures were empirically derived under controlled laboratory conditions.

[0059] Design parameters may include, but are not limited to, considerations outlined in Table 1A.Table 1ADesign Consideration DescriptionInfinite base station I'he infinite base station 202 should be positioned far from the P& A consideration well 101, e.g., at least three times the lateral extent of the receiver grid (e.g., 200a) or three times the maximum transmitter-receiver separation distance from the P& A well 101.Length of the transmitter The length of the transmitter line 103a-103b should be adjusted based line 103a- 103b on the depth of investigation and the level of cultural interference in tire survey area, usually in several hundred meters.Position of the The position of the transmitter line 103a-103b may be optimized transmitter line 103a- according to the investigation requirements and cultural interference.103b For higher resolution, multiple transmitter lines can be deployed. Borehole-to-borehole or If applicable, borehole-to-borehole or surface-to-borehole transmitter surface-to-borehole lines can be utilized. For example, a borehole-to-borehole transmitter transmitter lines line may be employed as outlined in the OESI report.Borehole electrodes 108 Where applicable, borehole electrodes 108 can also be deployed.

[0060] Fig. 2B shows an EM-SP field configuration 200b, e.g., for surveying a hydraulic fracturing target. For hydraulic fracturing, electrodes 112a- 112b are arranged in a uniformlyAttorney Docket No. 10046-668W018602 AHM distributed grid. The actual locations of electrodes 112a- 112b, electrode spacing, length of transmitter line 103a-103b, or the position of the infinite base station 202, and parameters thereof, would vary depending on the hydraulic fracturing target, surface cultural interference, and the depth of investigation.

[0061] Design parameters may include, but are not limited to, considerations outlined in Table IB.Table IBDesign DescriptionConsiderationInfinite base station The infinite base station 202 should be positioned far from the hydraulic consideration fracturing site, e.g., at least three times the lateral extent of the receiver grid (e.g., 200b) or three times the maximum transmitter-receiver separation distance.Length of the The length of the transmitter line 103a- 103b should be adjusted based on transmitter line the depth of investigation and the level of cultural interference in the 103a- 103b survey area, usually in several hundred meters.Position of the The position of the transmitter line 103a- 103b may be optimized according transmitter line to the investigation requirements and cultural interference. For higher 103a- 103b resolution, multiple transmitter lines 103a- 103b can be deployed.Surface-to-borehole A surface-to-borehole transmitter configuration often yields better results transmitter lines for hydraulic fracturing targets.Borehole electrodes Where applicable, borehole electrodes 108 can also be deployed.108

[0062] Fig. 2C shows an example geometry of a synthetic P& A well (e.g., 101), e.g., at the Devine Field Test Site, used to demonstrate the benefit of the exemplary system and method. Pass-through tubing 210 may be included, e.g., to inject through in the P& A wells. As shown, the bottom 6.5-ft-long annular section 213 of the well is filled with coarse sand for the sufficient injectivity of water from the central polyvinyl chloride (PVC) casing 210 into the annular space 215, and the top 24.5-ft-long annular section 212 is filled with (i) crushed cement or (ii) a mixture of crushed cement and electrically active additives, simulating a defective cement plug.

[0063] The results of the controlled injection experiment in synthetic P& A wells (e.g., at the Devine Field Test Site), as shown in Fig. 2C, have been detailed by Ahmadian and Haddad (2025).

[0064] Example Active-Source EM-SP Measurement. Fig. 3A shows field experimental results of compared SP results obtained using either an active or passive source in the presence of an exemplary Electrically Active Additives (EAAs), coke breeze, in a fieldAttorney Docket No. 10046-668W018602 AHM demonstration case. In both cases, SP signals exhibited distinct responses to water injection. The signals increased as the injections progressed, with a 1-gpm flow rate followed by a 0.5- gpm flow rate, peaking at shut-in. Strong correlations were observed during pulse tests, with the 2-gpm test yielding higher signal values than the 1-gpm test. Furthermore, SP signal amplitudes decreased with distance from the injection source in both cases, indicating attenuation of SP responses with spatial distance. SP signals from an active source are stronger than those from a passive source (no active source), indicating that the active source amplifies SP signals.

[0065] To validate the amplification of SP signals via an active source, laboratory experiments, as shown in Fig. 3B, were conducted using a ID four-electrode cell (e.g., 1-inch internal diameter) packed with 20 / 40 mesh silica sand. Electrodes were placed at 1.5 -inch intervals. By injecting tap water at a stepwise rate (e.g., up to 8 mL / min) and applying varying electric potentials to the outer electrodes, including a zero-potential control for passive source comparison, the resulting SP at the inner electrodes was monitored. In Fig. 3B, the induced SP increased in correlation with the active-source potential, corroborating the field experimental results.

[0066] Influence of injected fluids on SP measurement. A controlled test conducted at the Devine Field Test Site showed that injected fluids (water or pH-adjusted water produced by carbonation) can affect SP measurements. SP signals obtained using a passive source during freshwater and carbonated water injections were compared (Fig. 3C). Notably, carbonation acidifies water, reducing its pH. The SP signals from carbonated water injection were slightly stronger than those from freshwater injection, suggesting that the mild increase in water acidity from pH 8.4 to 6.15, caused by CO2dissolution in water, increased SP signal intensity.

[0067] In a saturated medium, SP is sensitive to flow dynamics controlled by flow path geometries and surface interactions with the fluid. Changes in flow path systems caused by rock dissolution or chemical precipitation can be detected using SP. Additionally, some fluid¬ rock chemistry can be monitored because SP couples strongly to the rock or mineral interface, where these interactions occur. CSEM methods are limited in their ability to detect geochemistry beyond processes that change fluid salinity. Together, these methods can produce enhanced real-time geochemical maps, which would be essential for adaptive engineering practices.

[0068] Influence of media composition on SP. Fig.3D shows the results of a laboratory demonstration using a controlled lab test in which the only variable is the mediumAttorney Docket No. 10046-668W018602 AHM composition. This laboratory demonstration compared the SP induced by fluid flow through two cement capillary tubes: one with a 15% sand mix-in (subpanel (a)) and the other with a 15% EAA mix-in (subpanel (b)). The EAA-modified tube generated an SP more than twice as high as the sand-modified tube (subpanel (c)).

[0069] Influence of water flow direction and SP. Fig.3E shows a controlled test conducted to demonstrate the influence of water flow direction on SP. Subpanel (a) shows the electrode and flow setup. The results compare SP measurements obtained using electrode pairs with axes normal or parallel to the flow direction. An electrode pair aligned parallel to the flow direction shows polarity changes correlating with fluid movement (subpanel (b)). An electrode pair oriented perpendicular to the flow direction reveals distinct voltage patterns influenced by cross-flow dynamics (subpanel (c)). These configurations show the relationship between flow direction and voltage variations across the electrode pairs. The relationship provides a robust and reliable method for detecting and mapping subsurface fluid flow dynamics. The exemplary SP system and method go beyond current approaches by leveraging vector-summation-and-subtraction techniques. These allow the electric field to be captured not only in the parallel and perpendicular directions but also along the axes of maximum and minimum coupling between the electric field and subsurface fluid flow. This multi-directional measurement approach improves the accuracy and precision of subsurface fluid-flow direction mapping by capturing a broader spectrum of electric-field responses. Second, the enhanced directional data may increase the density of collected information, contributing to the creation of high-resolution subsurface maps.

[0070] Influence of water flow rate and SP. Controlled tests were conducted at the Advanced Energy Consortium (AEC) lab and Devine Field Test Site that demonstrate the influence of fluid flow rate on SP. Fig. 3F shows experimental results comparing SP induced by different fluid flow rates. Generally, SP signal strength positively correlates with fluid flow rate. In Fig. 3F, a 7.9-ml / min flow rate was observed to induce higher SP signals than the 3.9-ml / min flow rate in the lab (subpanel (a)). At the field test site, a 2-gpm flow rate produced stronger SP signals than a 1-gpm flow rate (subpanel (b)).

[0071] Broad P& A Application: As shown in Fig. 3F, SP signal strength is positively correlated with fluid flow rate, offering a reliable method for identifying defective permeable paths in cement. P& A wells with accessible wellheads could be instrumented with a conduit through which a pressure pulse (water or gas) could be introduced at the top of the cement plug while collecting active-source EM-SP. If there is a leak, the fluid (liquid or gas) can flow through the permeable zone and generate the strong EM-SP signature as shown in Fig.Attorney Docket No. 10046-668W018602 AHM 3G, through pulsing flows through permeable zones. When defects are present, increased pressure may exceed the capillary entry pressure, leading to flow through these defects (pulsing the top of the cement plug with gases or liquids) and generating an SP signal anomaly. The method not only identifies defective zones but also quantifies their severity, improving the precision of barrier integrity assessments and enabling targeted remediation.

[0072] For new P& A wells where the top of the well is buried, a conduit can be attached at the time of construction and later be used for such pressure pulse testing.

[0073] Man-made Media Perturbations. SP signal strength may be positively correlated with fluid flow rate (Fig. 3F), offering a reliable method for identifying common pulsing flows through barrier defects. By applying controlled pressure changes above the barrier, potential defects can be illuminated using SP signal pulses. When defects are present, increased pressure may exceed capillary entry pressure, leading to flow through permeable thief zones and generating an SP signal anomaly. This method not only identifies defective zones but also quantifies their severity, improving the precision of barrier integrity assessments and enabling targeted remediation. For instance, in a dam application, this pressure change can be achieved by a limited rise in the water reservoir level, which can occur naturally during rainy seasons or artificially by controlling the outflow gates.

[0074] Example EM-SP / CSEM Method. Fig. 4 shows an example EM-SP analysis method 400 for monitoring P& A wells, dams, and nuclear plants. In the example shown in Fig. 4, the method 400 includes (i) positioning (402) a transmitter (e.g., 102a- 102b) (e.g., CSEM transmitter, ERT transmitter, or other transmitters described herein) on the ground surface or within a borehole relative to the target areas, (ii) deploying (404) a radially or uniformly distributed grid of electrodes (e.g., 200a-200b, 500a-500b) on the ground surface centered at the target area(s) or inside the borehole, (iii) installing (406) a base station sufficiently far from the target area to minimize interference (i.e., infinite base station), (iv) installing (408) multiple EM-SP receivers (e.g., 104), recording electric fields between the electrodes of the grid and the base station, synchronized (410) with transmitter, (v) injecting (411) electric currents into the ground using transmitter (e.g., 102a-102b) within a frequency range of 0 to 1000 Hz; (vi) recording (412) active-source EM-SP signals induced by transmitter (e.g., 102a-102b) and subsurface fluid flow; (vii) processing (414) the data to acquire electric fields at each frequency; and (viii) conducting (416) modeling and inversion on the EM-SP responses induced by both the transmitter (e.g., 102a-102b) and the subsurface fluid flow to analyze and characterize (418) the subsurface fluid flow dynamics.Attorney Docket No. 10046-668W018602 AHM

[0075] In some embodiments, inversion of the EM-SP responses to determine the subsurface fluid flow dynamics is performed using a history-matching method. In this method, multiple plausible fluid-flow patterns and containment characteristics are received, and corresponding EM-SP field is calculated via Equations 2-7. A set of fluid-flow pattern and containment characteristics that yields the most consistent EM-SP field with the field measurements can be identified as a history match. Alternatively, inversion of the EM-SP responses can be performed using regularization methods; however, this approach needs further refinement to address the increased non-uniqueness of the solution because of including pore pressure changes alongside conductivity as independent variables.

[0076] The EM-SP acquisition and analysis method 400 shown in Fig. 4 can enhance the EM-SP signal strength using multi-frequency EM data. The enhanced signal may then be used to detect and analyze fluid dynamics, including the type of fluid flow, its direction, and the pressure within the fluid. This system has the potential to enable a wide range of monitoring applications, both within the subsurface and on the surface, by adjusting factors such as surface charge density, electrolyte concentration, fluid viscosity, and pore size and shape.

[0077] A numerical model can quantify the SP response to fluid flow, enabling the interpretation of complex EM survey data. When no man-made source is present (e.g., in the presence of a natural SP source only), the current density induced by subsurface fluid movement can be expressed asJsp= (Jxsp, Jysp, Jzsp)e (Eq.2) where Jspis the current density vector, e is the unit vector in the coordinate direction,JxP, JyP, and are the current densities in x, y, and z directions. These current densities are influenced by fluid flow rate, pressure, and fluid type. They can be indirectly measured on the Earth's surface using the exemplary system and method. JxP, JyP, JzPcan be expressed in terms of pore-pressure gradient (Vp) (Fitterman, 1979):Jsp= -L∇p, (Eq.3) where L is the electrokinetic coupling coefficient. L is highly dependent on the ionic charge balance and could be used to determine the fluid type using EM-SP surveys. When an active source is deployed, the total current density becomes a summation of natural and man-made contributions (Pugh et al., 2024):Jt = kp + Ja = J“)e, (Eq.4)Attorney Docket No. 10046-668W018602 AHM where Jtis the total current density, Jspis the natural current density vector induced by subsurface fluid movement, Jais the current density induced by an active source with three components J£, Jy, and / “ in x, y, and z directions. Theoretically, the magnitude of Jx y z can be controlled. To include SP effects in the forward simulation, Jtincluding SP source current density, Jsp, can be incorporated into equations of Ampere’s law in the frequency domain (Eldad, 2015):∇ × E − iωμH = 0, (Eq. 5) ∇ × H − σE = Jt, (Eq. 6)n x H = 0, (Eq. 7) where E is the electric field, H is the magnetic field, ω is the angular frequency, μ is the magnetic permeability, and is the electrical conductivity. A numerical solution to this system of equations yields the electric field and, if desired, the magnetic field from it. These electric and magnetic fields are composed of the electric field generated by an active transmitter and the electric field induced by the fluid-flow-driven SP. Jsptypically exhibits low-frequency or DC characteristics, while Jaspans a broad frequency range. The exemplary EM-SP system and method combine multi-frequency EM-SP data to infer subsurface fluid dynamics. Vp can be obtained from a poroelastic or reservoir model.

[0078] Regarding the limitations of modeling and inversion, the exemplary EM-SP system and method focus on the SP and EM signals induced by subsurface fluid movement. The EM-SP method utilizes a time-lapse approach. Baseline data are used to comprehensively minimize the influences of surrounding geological structures, cultural noise, background primary fields, and other persistent noise sources, allowing the modeling and inversion process to target the subsurface fluid exclusively. This enhances the accuracy of imaging and characterizing subsurface fluid dynamics.

[0079] Multi-frequency EM-SP data. The exemplary EM-SP system and method combine the strengths of traditional SP and EM techniques (e.g., CSEM), addressing their individual limitations. By integrating SP measurements, which are sensitive to the rate of fluid flow, with multi-component, multi-frequency EM data, the exemplary system and method can directly determine the direction of subsurface fluid flow at different depths, and fluid type and composition. At specific active-source frequencies, resonance phenomena may occur within the porous media, enhancing the accuracy of fluid type identification. The multi¬ frequency differences among various fluids provide a reliable means of determining fluid types and can potentially be applied to detect subsurface fluid paths. For example, injecting aAttorney Docket No. 10046-668W018602 AHM fluid with a known frequency-dependent signature into the subsurface could aid in locating fluid pathways.

[0080] Synergies of Combining SP and EM Measurements. The method involves deploying an EM transmitter and a network of receivers around a borehole or zone of interest, and either transmitting electric current into the subsurface or passively monitoring electric fields induced solely by fluid flow. By combining EM (e.g., CSEM) and SP data, comprehensive subsurface fluid dynamics can be assessed.

[0081] Reservoir Fluid Type. The SP signal can be affected by the ionic composition of flowing fluids, including resident water, connate water, hydrocarbon reservoir brine, hydrocarbon-associated ions, and ions from dissolved gases (e.g., CO2 in water), coated proppant, tailored electrolytes, and mineral admixtures. Recent field data from the OESI project, which involved injecting freshwater and carbonated water into synthetic P& A wells, confirms this dependence.

[0082] The exemplary method 400 in Fig. 4 can be used to monitor the integrity and environmental safety of P& A wells by detecting and analyzing fluid leakage or migration from the wellbore into the surrounding subsurface. An example method 400 includes the step of: (i) positioning (402) a transmitter (e.g., 102a-102b) (e.g., CSEM transmitter, ERT transmitter, or other transmitters described herein) at the surface or in a nearby borehole close to the P& A well; (ii) deploying (404) a grid of electrodes (e.g., 200a-200b, 5OOa-5OOb) around the P& A well (e.g., 101) to record variations in electric fields; (iii) installing (406) an infinite base station at a distance to ensure stable reference measurements; (iv) installing (408) multiple SP receivers (e.g., 104), recording electric fields between the electrodes of the grid and the base station, synchronized (410) with transmitter; (v) injecting electric currents (411) into the ground using transmitter (e.g., 102a-102b) within a frequency range of 0 to 1000 Hz to generate an active-source EM-SP field that interacts with any migrating fluids; (vi) recording (412) active-source EM-SP signals induced by transmitter (e.g., 102a-102b) and subsurface fluid flow; (vii) processing (414) the data to acquire electric fields at each frequency; and (viii) conducting (416) modeling and inversion on the EM-SP responses induced by both the transmitter (e.g., 102a-102b) and the subsurface fluid flow to model and invert (418) the behavior of subsurface fluid flow, generating a detailed map of fluid pathways, flow directions, and possible leakage zones.

[0083] Over time, repeated measurements can be conducted to monitor changes in subsurface fluid dynamics and identify emerging issues, such as annular gas migration or fluid seepage through the wellbore plug. The information may enable operators to takeAttorney Docket No. 10046-668W018602 AHM proactive measures to remediate the P& A well, such as replugging or sealing leakage pathways, to ensure environmental safety and regulatory compliance.

[0084] Dam monitoring. Method 400 in Fig. 4 can be used to monitor structural integrity and detect potential seepage or fluid migration within and beneath dams, which is critical for ensuring the safety and longevity of these structures. The method 400 may include (i) placing (402) a transmitter (e.g., 102a-102b) (e.g., CSEM transmitter, ERT transmitter, or other transmitters described herein) on the surface near the dam or embedded within boreholes drilled into key structural or foundational areas of the dam; (ii) arranging (404) a grid of electrodes (e.g., 200a-200b, 500a-500b) across the dam structure, the reservoir, and downstream areas to monitor potential seepage paths and fluid flow, where the grid (e.g., 200a-200b, 500a-500b) can be radial or uniformly distributed to cover areas of concern; (iii) setting up (406) a base station far from the dam to provide stable reference measurements for electric field recordings; (iv) installing (408) multiple EM-SP receivers (e.g., 104), recording electric fields between the electrodes of the grid and the base station, synchronized (410) with transmitter; (v) injecting, e.g., with the transmitter (e.g., 102a-102b) activated using a frequency range of 0 to 1000 Hz, controlled currents into the subsurface, generating an active-source EM field that interacts with any migrating fluids such as seepage through fractures, erosion of material, or piping; (vi) recording (412) active-source EM-SP signals induced by the transmitter and subsurface fluid flow; (vii) processing (414) the data to acquire electric fields at each frequency; and (viii) conducting (416) modeling and inversion on the EM-SP responses induced by both the transmitter (e.g., 102a-102b) and the subsurface fluid flow to model and invert (418) the behavior of subsurface fluid flow, generating detailed maps of seepage locations, flow velocities, and potential erosion zones.

[0085] Regular measurements may enable continuous monitoring of seepage dynamics and early detection of changes, such as increased seepage rates, which may indicate structural weakening or potential failure. Identified problem areas, such as seepage hotspots or zones of material loss, can guide targeted repairs, including grouting or sealing. Rapid detection of abnormal seepage patterns or significant fluid migration may provide early warnings to prevent catastrophic dam failures. The method may be particularly valuable for monitoring aging dams, those in seismically active regions, or those experiencing high reservoir pressures.

[0086] Nuclear plant monitoring. Method 400 in Fig. 4 can be used to monitor subsurface fluid dynamics around nuclear plants, ensure the structural integrity of containment systems, detect fluid leakage, and assess the risk of contamination in the surrounding environment.Attorney Docket No. 10046-668W018602 AHM The method 400 may include (i) positioning (402) a transmitter (e.g., 102a-102b) (e.g., CSEM transmitter, ERT transmitter, or other transmitters described herein) on the surface or within boreholes near critical areas of the nuclear plant, such as beneath storage tanks, waste containment areas, or cooling water discharge zones; (ii) installing (404) a grid of electrodes (e.g., 200a-200b, 500a-500b) on the ground surface or within boreholes surrounding the plant; (iii) setting up (406) a base station far from the plant to provide stable reference measurements for electric field recordings; (iv) installing (406) multiple EM-SP receivers (e.g., 104), recording electric fields between the electrodes of the grid and the base station, synchronized (410) with transmitter; (v) injecting (411) with the transmitter (e.g., 102a-102b) activated using a frequency range of DC to 1000 Hz, controlled currents are injected into the subsurface, generating an active-source EM field that interacts with any migrating fluids such as leakage from cooling systems, waste tanks, or underground storage structures; (vi) recording (412) active-source EM-SP signals induced by transmitter (e.g., 102a-102b) and subsurface fluid flow; (vii) processing (414) the data to acquire electric fields at each frequency; and (viii) conducting (416) modeling and inversion on the EM-SP responses induced by both the transmitter (e.g., 102a- 102b) and the subsurface fluid flow to model and invert (418) the behavior of subsurface fluid flow to identify zones of leakage, flow pathways, and contamination spread in high detail.

[0087] Regular monitoring of fluid leakage may be crucial for proactive environmental and safety management. By detecting fluid leakage or contamination early, the measurements may provide valuable data to demonstrate regulatory compliance. The non-invasive and cost- effective approach may minimize environmental and safety risks by enabling continuous monitoring of containment fluid dynamics without disrupting plant operations. Early detection can help mitigate risks from groundwater contamination, structural failures, and radioactive waste leaks, ensuring safer, more sustainable operations.

[0088] Unconventional O& G resources monitoring. Method 400 in Fig. 4 can be used to monitor subsurface fluid dynamics and well integrity in unconventional O& G resources, such as shale oil and gas reservoirs, to optimize extraction techniques and prevent issues such as fluid migration, fracturing inefficiencies, or environmental contamination. The method 400 may include (i) placing (402) a transmitter (e.g., 102a-102b) (e.g., CSEM transmitter, ERT transmitter, or other transmitters described herein) on the surface above the target reservoir or within the borehole, depending on the specific area of interest (e.g., near horizontal wells or hydraulic fracturing zones); (ii) positioning (404) a grid of electrodes (e.g., 200a-200b, 500a-500b) in a grid layout either at the surface or within nearby boreholes, centered over theAttorney Docket No. 10046-668W018602 AHM target reservoir or hydraulic fracture zones; (iii) installing (406) a base station sufficiently far from the target area to minimize interference (i.e., infinite base station); (iv) installing (408) multiple EM-SP receivers (e.g., 104), recording electric fields between the electrodes of the grid and the base station, synchronized (410) with transmitter; (v) injecting, with the transmitter (e.g., 102a-102b) activated within a frequency range of 0 to 1000 Hz, controlled currents are injected into the subsurface, generating an active-source EM field that interacts with the subsurface fluid and fracture network; ((vi) recording (412) active-source EM-SP signals induced by transmitter (e.g., 102a-102b) and subsurface fluid flow; (vii) processing (414) the data to acquire electric fields at each frequency; and (viii) conducting (416) modeling and inversion on the EM-SP responses induced by both the transmitter (e.g., 102a- 102b) and the subsurface fluid flow to provide (418) more precise information about the location, size, and permeability of fractures, as well as the overall fluid flow characteristics, which are crucial for optimizing hydraulic fracturing and extraction processes.

[0089] Continuous monitoring of fluid flow through fractures may optimize hydraulic fracturing by enabling adjustments to pressures and fluid compositions to enhance fracture propagation and resource recovery. It may detect leaks to neighboring formations, preventing unwanted fluid migration and associated environmental risks or decreased well productivity. The real-time reservoir health assessment may identify site areas with suboptimal injection rates, guiding corrections to the current stage or redesigning subsequent stimulations.Monitoring may also detect the migration of fracking fluid outside target zones, enabling preventive measures to protect groundwater and ecosystems.

[0090] CCS site monitoring. Method 400 in Fig. 4 can be used to monitor CO2 injection and storage in CCS sites, e.g., enabling continuous monitoring of CO? migration, integrity of the storage site, and potential leakage pathways, ensuring safe, effective, and environmentally responsible CO2 sequestration. The method 400 may include (i) placing (402) a transmitter (e.g., 102a-102b) (e.g., CSEM transmitter, ERT transmitter, or other transmitters described herein) on the surface above the CO2 injection well or within a nearby borehole. The transmitter (e.g., 102a-102b) may be positioned to monitor the subsurface regions most likely to be affected by CO2 injection and migration. The method 400 may then include (ii) placing (404) a grid of electrodes (e.g., 200a-200b, 500a-500b) either on the surface or within surrounding boreholes, positioned over the injection zone or potential CO2migration paths; (iii) installing (406) a base station sufficiently far from the target area to minimize interference (i.e., infinite base station); (iv) installing (408) multiple EM-SP receivers (e.g., 104), recording electric fields between the electrodes of the grid and the base station,Attorney Docket No. 10046-668W018602 AHM synchronized (410) with transmitter; (v) injecting (411), with the transmitter (e.g., 102a- 102b) activated within a frequency range of 0 to 1000 Hz, controlled currents are injected into the subsurface, generating an active-source EM field that interacts with the CO2, and other fluids in the reservoir; (vi) recording (412) active-source EM-SP signals induced by transmitter (e.g., 102a-102b) and subsurface fluid flow; (vii) processing (414) the data to acquire electric fields at each frequency; and (viii) conducting (416) modeling and inversion on the EM-SP responses induced by both the transmitter and the subsurface fluid flow to provide (418) a high-resolution analysis of CO2behavior, including mapping the depth and lateral extent of the CO2plume, evaluating pressure buildup, and identifying areas of high permeability or potential leakage.

[0091] Continuous monitoring of CO2migration may enable real-time tracking of injected CO2, ensuring it remains within the designated reservoir. The method may detect potential leaks to the surface or surrounding formations, enabling timely corrective actions such as adjusting injection rates or implementing remedial measures. Real-time data measurement can provide an ongoing assessment of reservoir integrity and long-term CO2containment, ensuring regulatory compliance. The feedback may optimize injection techniques by enabling adjustments to rates, pressures, and fluid compositions, improving storage efficiency, and minimizing leakage risks for safe long-term CO2sequestration.

[0092] In lab-controlled systems, it has been observed that sampling across material boundaries can produce unique SP responses. The feature can generate information about when fluid is moving into another geologically distinct region, which is particularly useful for determining whether the fluid intended to be contained is leaking into other regions. Specific applications include reservoir-sequestered CO2.

[0093] Enhanced Geothermal Systems. Method 400 in Fig. 4 can be used to monitor subsurface fluid dynamics and reservoir conditions in Enhanced Geothermal Systems (EGS). EGS often relies on injecting fluid into hot, dry rock formations to enhance geothermal energy extraction. This method provides real-time monitoring of fluid flow, temperature variations, and reservoir integrity, helping optimize geothermal energy recovery and improve the efficiency and safety of the system.

[0094] The method 400 may include (i) deploying (402) a transmitter (e.g., 102a-102b) (e.g., CSEM transmitter, ERT transmitter, or other transmitters described herein) on the surface above the EGS reservoir or within a nearby borehole to monitor the geothermal reservoir's subsurface conditions, including the extent of induced fractures and fluid pathways; (ii) placing (404) a grid of electrodes (e.g., 200a-200b, 500a-500b) on the surfaceAttorney Docket No. 10046-668W018602 AHM or within the boreholes in a grid pattern, centered above the reservoir or targeted fracture zones; (iii) installing (406) base station sufficiently far from the target area to minimize interference (i.e., infinite base station); (iv) installing (408) multiple EM-SP receivers (e.g., 104), recording electric fields between the electrodes of the grid and the base station, synchronized (410) with transmitter; (v) injecting (411), with the transmitter (e.g., 102a- 102b) activated within a frequency range of 0 to 1000 Hz, controlled currents are injected into the subsurface, generating an active-source EM field that interacts with the fluid and heat flow within the induced fractures, as well as the interaction between the injected fluid and surrounding rock; (vi) recording (412) active-source EM-SP signals induced by transmitter (e.g., 102a-102b) and subsurface fluid flow; (vii) processing (414) the data to acquire electric fields at each frequency; and (viii) conducting (416) modeling and inversion on the EM-SP responses induced by both the transmitter (e.g., 102a-102b) and the subsurface fluid flow to provide (418) a high-resolution image of the geothermal reservoir, including the location and extent of induced fractures, fluid pathways, and heat distribution.

[0095] The method 400 may provide real-time monitoring of geothermal fluid flow, allowing operators to optimize injection and extraction rates, ensuring efficient heat recovery while avoiding reservoir heat depletion or overuse. Continuous monitoring of EM-SP signals may help assess the integrity of induced fractures and the overall stability of the geothermal reservoir. If signs of fracture closure or fluid leakage occur, the method 400 may provide early warnings to adjust the operational parameters. By detecting fluid migration outside the target reservoir, the method may identify potential leakage points or inefficiencies in fluid circulation, allowing for corrective actions, such as adjusting injection zones or pressure settings to ensure fluid remains confined within the target reservoir. Continuous monitoring of the EGS system may enable the tracking of reservoir performance over time. Long-term data may be crucial for understanding reservoir behavior under sustained fluid injection and extraction, helping ensure the sustainability of geothermal energy production.

[0096] Fracturing pressure monitoring. Method 400 in Fig. 4 can be used to determine fracturing pressure during injections into subsurface reservoirs. Hydraulic fractures increase aperture at pressures above the fracturing pressure, thereby influencing fluid dynamics and, consequently, the generation of EM-SP signals. Conversely, in CO2 storage sites, the SP is strongly influenced by the magnitude of the injection / production flow rate while operating below the fracturing pressure. Maximizing EM-SP necessitates maximizing the flow rate, subject to the constraint imposed by the fracturing pressure, to prevent damage to the host rock. This may be of paramount importance in carbon storage sites. Consequently, knowingAttorney Docket No. 10046-668W018602 AHM the fracturing pressure from an EM-SP survey helps determine the CO2 injection rate that yields maximum SP without damaging the host rock. This capability expands the applicability of the exemplary system and method to both unconventional reservoirs and CO2storage sites.

[0097] The monitoring method 400 may include (i) deploying (402) a transmitter (e.g., 102a-102b) (e.g., CSEM transmitter, ERT transmitter, or other transmitters described herein) on the surface above the injection reservoir or within a nearby borehole to monitor the injection reservoir’s subsurface conditions; (ii) placing (404) a grid of electrodes (e.g., 200a-200b, 500a-500b) on the surface or within the boreholes in a grid pattern, centered above the reservoir; (iii) installing (406) a base station sufficiently far from the target area to minimize interference (i.e., infinite base station); (iv) installing (408) multiple EM-SP receivers (e.g., 104), recording electric fields between the electrodes of the grid and the base station, synchronized (410) with transmitter; (v) injecting (411), with the transmitter (e.g., 102a-102b) activated within a frequency range of 0 to 1000 Hz, controlled currents are injected into the subsurface, generating an active-source EM field that interacts with the fluid flow within the reservoir; (vi) recording (412) active-source EM-SP signals induced by transmitter (e.g., 102a-102b) and subsurface fluid flow; (vii) processing (414) the data to acquire electric fields at each frequency; and (viii) conducting (416) modeling and inversion on the EM-SP responses induced by both the transmitter and the subsurface fluid flow to provide (418) a high-resolution image of reservoir pressure, which will be then postprocessed to determine any abrupt pressure changes such as fracturing pressure.

[0098] The method 400 may provide real-time monitoring of reservoir pressure, allowing operators to optimize injection rates and ensure efficient injection while avoiding fracturing pressure exceedance. Continuous monitoring of EM-SP signals may help assess the overall stability of reservoirs. If the fracturing pressure is exceeded, the system may provide early warnings to adjust operational parameters, such as injection rates.

[0099] Active-Source Utilization to Enhance SP Signal

[0100] The presence of an active source during an SP survey can enhance the SP signal when the active source is strategically positioned relative to the flow-induced SP source. This has been validated by recent field data acquisitions from the OESI project. This approach enables the EM-SP method to acquire high-resolution subsurface images by enhancing data quality. This enhancement is attributed to increased ion mobility, modifications to the EDL, and synergistic effects with other optimization strategies.Attorney Docket No. 10046-668W018602 AHM

[0101] Implementation requires careful consideration of electrode placement, selecting an appropriate voltage magnitude to avoid adverse effects, adjusting electrolyte conductivity for optimal efficiency, and understanding the medium's porosity, permeability, and surface charge. By addressing these factors, effective amplification of SP signals can be achieved.

[0102] Enhanced SP Configuration

[0103] Infinite-based station guidelines. Traditional SP surveys, often employing gradient-based (Heinson et al., 2005) or fixed-base configurations, are logistically complex and costly because SP signals vary slowly over time, necessitating frequent remeasurements (Wightman et al., 2003). The exemplary SP configuration can utilize GPS synchronization to enable simultaneous measurements across multiple stations. To further enhance efficiency and accuracy, the location of stations can be determined using an infinite- base station concept and guidelines to minimize the influence of a fixed reference point. An infinite base station is defined as a station positioned at least three times the lateral extent of the receiver grid or three times the maximum transmitter-receiver separation distance from the target zone.

[0104] The EM-SP method may require a surface and / or subsurface grid of receiver electrodes to accurately locate subsurface fluid information.

[0105] The grid size and electrode spacing depend on the target's size and depth: (i) larger and deeper targets require sparser electrode spacing, (ii) the grid’s spatial extent should exceed the target’s depth, and (iii) electrode spacing should be smaller than half the target's lateral size.

[0106] A fixed-base station (infinite base station) should be positioned sufficiently far from the target area to minimize its potential impact. This ensures that variations in subsurface fluid flow do not influence the potential field at the base station. Specific guidelines include (i) for passive measurements, the base station should be positioned at least three times the lateral extent of the receiver grid away from the target zone; (ii) for active¬ source measurements, the base station should be located at least three times the maximum transmitter-receiver separation distance away from the target zone; and (iii) the base station should avoid cultural interferences such as power lines, fences, and metallic structures. The base station should also be placed away from areas with abrupt variations in subsurface resistivity.

[0107] Vertical subsurface fluid movement. For vertical subsurface fluid movement (e.g., flow in P& A wells), surface receivers 112a- 112b should be deployed radially (e.g., Fig. 5A). In some embodiment, (i) the center of the radial distribution should align with the target's center; (ii) the inner electrode spacing should be smaller than outer spacing to account forAttorney Docket No. 10046-668W018602 AHM larger signal gradients near the target; (iii) a fixed-base station (not shown) should be installed far enough away to ensure its potential remains constant; and (iv) the EM-SP measurements should compute potential differences between electrode pairs to derive directional information. Permutations of electrode pairs enable imaging of subsurface fluid movement.

[0108] Horizontal or inclined fluid movement. For horizontal or inclined fluid movement (e.g., underground rivers, dam leakages, or seepage studies), surface receiver electrodes 112a- 112b should be uniformly distributed in a grid (e.g., Fig. 5B). In some embodiment, (i) the grid's center should align with the surface projection of the target; (ii) the lateral extent of the grid should be 2-4 times the target's lateral size and exceed its depth; and (iii) the electrode spacing should be smaller than half the target's lateral size.

[0109] Deep subsurface fluid targets. For deep subsurface fluid targets (e.g., CO2storage sites), the receiver grid often extends several miles, making the deployment of a fixed-base station logistically expensive. To address this, the exemplary EM-SP method can be adapted to a traditional CSEM configuration, reducing field operation costs.

[0110] Active-source configuration. The active source for the EM-SP method can be configured in various setups, including surface -based, surface-to-borehole, or borehole -to- borehole, e.g., per Table 2.Table 2Design Considerations DescriptionSurface-Based Active Sources Suitable for inducing horizontal (x or y) currents.Borehole-to-Borehole Active Effective for inducing vertical (z) currents.SourcesAlignment with Fluid The active source should ideally align with the fluid flow Movement direction. If unknown, iterative adjustments can maximize polarization, indicating the flow direction. Distance from Receiver Grid To minimize noise, the active source should be at least twice the receiver grid's lateral extent for shallow targets. For deep targets, borehole-to-borehole transmitters aretypically more effective.

[0111] Transmitter configuration. In traditional CSEM surveys, the transmitter is often deployed using a dipole line of copper wire positioned away from the target zone or inside a borehole. In contrast, in some embodiments, an unconventional transmitter configuration may be employed that leverages the preexisting cables embedded for cathodic protection ofAttorney Docket No. 10046-668W018602 AHM nearby infrastructure. The configuration may allow for the investigation of structural integrity and the detection of potential leakages from P& A wells.

[0112] Example Particulate and Medium Modifications for Enhancing EM-SP / CSEM Monitoring

[0113] Cement containment monitoring. The inclusion of tailored chemistry / compositions can enhance the SP signal. The combination of particulate and medium modifications may enhance SP signal detection by integrating advanced modifications in particulate materials, the composition of the surrounding medium, and injected electrolytes, all together.

[0114] Pore modifiers: The approach may involve a surface functionalization technique to modify particulate surfaces with various minerals such as clay (e.g., montmorillonite, kaolinite, bentonite), metal oxides (e.g., titanium dioxide, manganese dioxide, magnesium oxide, iron oxide), and silica-based materials (e.g., silica nanoparticles, fumed silica, aluminosilicates). These minerals enhance surface charge density, stability, and ion mobility, making them effective for EDL modification. Additionally, carbon-based materials (e.g., graphene, carbon nanotubes, coke-breeze) and polymers (e.g., polyelectrolytes, polyvinylidene fluoride, polydopamine, polyacrylamide, polyethyleneimine, chitosan, and conductive polymers) can improve ion transport, reduce fouling, and tailor wettability.Advanced techniques such as plasma treatment, electrodeposition, and chemical etching modify surface chemistry, while methods such as self-assembled monolayers, layer-by-layer assembly, and nano-structuring enable precise control of surface properties. Hybrid approaches, including metal-organic frameworks and composite coatings of polymers with nanoparticles, may synergistically enhance EDL behavior. Finally, optimizing the size, shape, and structural properties of these particulates — including the use of uniformly sized and mechanically robust materials— -may ensure efficient fluid flow and sustained SP signal generation under high-stress conditions.

[0115] Admixtures: In addition to particulate modifications, the method may also incorporate changes to the composition of the medium surrounding the particulate matrix. The addition of mineral admixtures (e.g., fly ash, silica fume, calcium carbonate) enhances the pore structure, increases surface area, and influences the surface chemistry of the host matrix, indirectly boosting surface charge density and improving SP signal response.Chemical admixtures, including water-reducing agents, superplasticizers, retarders, and accelerators, may help control the rheology of the medium, optimizing fluid flow and improving the uniformity of the particulate matrix. The use of organic admixtures, such asAttorney Docket No. 10046-668W018602 AHM surfactants and dispersants, may further improve the wettability and dispersion of particulates in the medium, enhancing overall electrokinetic properties. Post-treatment adjustments, including pH modification, ionic strength control, and chemical treatments such as crosslinking agents, can further improve surface charge density and modify the electrokinetic behavior of the matrix. These treatments allow for finer control over the properties of the flow-hosting medium, enhancing ion transport and reducing fouling. Field data, including results from the OESI project, highlight the substantial impact of electrically conductive additives (contrast agents) on the modulation of SP signals, confirming the efficacy of this method.

[0116] Application. In an example using the method 400 shown in Fig. 4, tailored chemistries may be employed to enhance the detection of pressure and flow rate. Method 400 in Fig. 4 can be used to determine fracturing pressure during injections into subsurface reservoirs. The monitoring method 400 may include (i) deploying (402) a transmitter (e.g., 102a- 102b) (e.g., CSEM transmitter, ERT transmitter, or other transmitters described herein) on the surface above the injection reservoir or within a nearby borehole to monitor the injection reservoir's subsurface conditions; (ii) placing (404) a grid of electrodes (e.g., 200a-200b, 500a-500b) on the surface or within the boreholes in a grid pattern, centered above the reservoir; (iii) installing (406) a base station sufficiently far from the target area to minimize interference (i.e., infinite base station); (iv) installing (408) multiple EM-SP receivers (e.g., 104), recording electric fields between the electrodes of the grid and the base station, synchronized (410) with transmitter; (v) injecting (411) tailored electrolytes into the fracturing network; (vi) injecting, with the transmitter (e.g., 102a- 102b) activated within a frequency range of 0 to 1000 Hz, controlled currents into the subsurface, generating an active-source EM field that interacts with the fluid flow within the reservoir; (vii) recording (412) active-source EM-SP signals induced by transmitter (e.g., 102a- 102b) and subsurface fluid flow; and (viii) processing (414) the data to acquire electric fields at each frequency; and (ix) conducting (416) modeling and inversion on the EM-SP responses induced by both the transmitter and the subsurface fluid flow to provide (418) a high-resolution image of reservoir pressure, which will be then postprocessed to determine any abrupt pressure changes such as fracturing pressure.

[0117] SP signal enhancement composition with the inclusion of tailored chemistries. The composition of the injectate, whether liquid or gas, may be modified to improve fluid¬ flow monitoring. The modification may be applied to waterflooding or polymer flooding that decorates the matrix.Attorney Docket No. 10046-668W018602 AHM

[0118] Tailored Electrolytes: The exemplary EM-SP method may incorporate injection fluids containing specifically designed electrolytes to amplify the generation of EM-SP signals. The electrolyte concentration may have a critical influence on the strength of the SP signal, with higher concentrations generally reducing it. Through the judicious selection of fluids and electrolytes tailored to the specific subsurface conditions, a more pronounced EM- SP response can be elicited. Candidates are provided in Table 3.Table 3Injection fluids with Descriptiondesigned electrolytesIonic Liquids Ionic liquids exhibit high ionic conductivity, enhancing the streaming current and, consequently, the SP. Their properties, such as the solvation characteristics of protic ionic liquids and molecular solvents, can be tuned to meet specific requirements.Polymer Electrolytes Polymer electrolytes provide a suitable environment for ion transport, which can increase SP current. They may be designed to ensure compatibility with cement-based materials.Nanofluids Nanoparticles dispersed in the electrolyte can increase charge carrier density and modify interfacial properties, thereby enhancing SP. The type and concentration of nanoparticles can be tailored to achieve desired outcomes.Surfactants Surfactants can modify the surface charge of cement particles,influencing the formation of the EDL. They may improve the wettability of cement surfaces, facilitating efficient ion transport. Low-Salinity Water In offshore applications, seawater desalination can improve SP signal Injection detection by substantially reducing the electrical conductivity of the injected fluid.Organic Solvents Organic solvents (e.g., ethylene carbonate, dimethyl carbonate) can be used to create non-aqueous electrolytes with high ionic conductivity. Hybrid Electrolytes Combining water, ionic liquids, and organic solvents yields hybrid (Water + Ionic Liquid electrolytes with high ionic conductivity while maintaining desirable + Organic Solvent) properties for specific applications.Chelating Agents Chelating agents, such as ethylenediaminetetraacetic acid, can be incorporated into the electrolyte to enhance metal-ion mobility in subsurface environments. These agents can form complexes with metal ions, altering the ion distribution and enhancing the electrical conductivity and overall SP signal.Acidic or Basic In addition to carbonation, pH adjustments with acidic or basic Additives (pH additives can help optimize the surface charge density of the EDL. Adjusters) Acidic solutions, such as hydrochloric or sulfuric acid, can lower thepH, thereby increasing surface protonation, while alkaline solutionsAttorney Docket No. 10046-668W018602 AHM can enhance electrochemical reactions, promoting stronger SP responses.Salt-Based Salt-based electrolytes, such as sodium chloride (NaCl), potassium Electrolytes (Salts chloride (KCl), and magnesium sulfate (MgSO4), remain common like NaCl, KCl, choices for modifying the electrical conductivity of the injected fluid. MgSO<) By varying the concentration and type of salt, the ion strength and overall conducti vity of the electrolyte can be adjusted, influencing the magnitude of SP signals.Bio-Based Bio-based electrolytes, such as chitosan derived from shrimp shells, Electrolytes can be used to create a sustainable, environmentally friendly alternative for fluid injection. These natural polymers offer the potential for applications where bio-degradability is a consideration while still maintaining sufficient ionic conductivity to enhance EM-SP signals.Battery electrolytes These battery electrolytes typically contain lithium salts (e.g., lithium hexafluorophosphate (LiPF6amp;) or lithium perchlorate (LiClO4)) dissolved in organic solvents such as ethylene carbonate or dimethyl carbonate, which provide very high ionic conductivity. This high conductivity boosts SP and enhances ion mobility in the subsurface, making them ideal for improving SP signal sensitivity. These electrolytes can be adapted from battery technology to optimize EM- SP responses for subsurface monitoring, particularly for detectingfluid flow and characterizing reservoirs.

[0119] Consideration should be given to the compatibility of the solvents with sandstone and the environmental impact. For electrolyte selection, the electrolytes should be compatible with cement, have high ionic conductivity, remain stable under operating conditions, and be environmentally friendly. Field data, including those from the OESI project, highlight the substantial influence of water carbonation, a pH-adjustment process, on SP signal amplification.

[0120] Tuning Fluid Viscosity: Increasing the viscosity of the injection fluid is commonly utili zed for 1) enhanced oil recovery from hydrocarbon reservoirs through blockage of thief zones and 2) hydraulic fracturing for the proppant placement. The diversion of the injection fluid flow to other depth intervals or hydraulic fracture placement via viscosity modifications could be monitored using the exemplary system and method because fluid viscosity changes can alter the SP signal. Higher viscosity generally leads to weaker SP signals due to increased resistance to fluid flow.

[0121] To enhance SP signals, tuning fluid viscosity may be considered, e.g., per Table 4.Table 4Attorney Docket No. 10046-668W018602 AHM Fluid Viscosity DescriptionModifierTemperature Increase For most liquids, viscosity decreases with increasing temperature. Adding Diluents Diluting a viscous solution with a less viscous solvent (e.g., water) can effectively reduce the overall viscosity.Surfactant Addition Some surfactants can interact with the fluid and reduce its interfacial tension, which can indirectly lower viscosity.Use of Polymers Polymers can be tailored to break under specific conditions (e.g., (Thickeners) temperature or pressure), reducing viscosity at a later stage of injection, thus improving fluid mobility for temporal changes in the SP signal. Crosslinking Agents Crosslinkers (e.g., chromium(III) acetate, borate compounds) can be and Gel Breakers added to hydroxypropyl guar gum or other polymer-based fluids to form a crosslinked network that enhances viscosity and flow properties in a controlled manner. Crosslinking can result in a gelled structure that improves flow control. On the other hand, a gel breaker (e.g., bromate or persulfate salts) breaks the gel to enhance fracturing-fluid flowback. This abrupt reduction in viscosity could be used to enhance the SP signal and monitor hydraulic fractures.Nanoparticles Nanoparticles such as silica nanoparticles, clay particles, or carbon nanotubes can be used to tune the fluid viscosity. These particles can interact with the fluid to modify the flow properties, and depending on the size, shape, and concentration of the nanoparticles, they can increase or decrease viscosity and improve the fluid’s electrokinetic properties for enhanced SP signal generation.Inorganic Additives Certain inorganic salts (e.g., calcium chloride or magnesium sulfate) can increase fluid viscosity by promoting the aggregation of fines or by affecting the interaction between water and other fluid components. These salts may be especially useful in systems where other additives are not desirable or for enhancing electrokinetic responses in high- salinity environments.Emulsions and Oil-water emulsions or microemulsions can be used to adjust the Microemulsions viscosity of the injected fluid. By controlling the droplet size and the proportion of oil and water, the viscosity can be fine-tuned. This method can provide enhanced control over fluid dynamics and can be useful for applications requiring controlled fluid movement within subsurface formations, such as CO2sequestration or hydraulic fracturing.Superabsorbent Superabsorbent polymers, which can absorb and retain large amounts Polymers of liquid, may be used to adjust fluid viscosity by absorbing water and increasing the fluid’s internal resistance. This can be effective in scenarios where fluids need to be thickened temporarily and then reliquefied for certain subsurface applications, such as enhanced oilrecovery.Attorney Docket No. 10046-668W018602 AHM Gels and Gel -like Fluids such as hydrogels and microgels can be used to tune viscosity. Systems These gel-like materials provide enhanced control over fluid mobility, especially for controlled fracturing or fluid diversion. Gels also offer potential in wellbore cleanout operations, where a temporary increase in viscosity is required to carry debris while still allowing for effective SP signal tracking.Ionic Liquids as Ionic liquids (e.g., table salt) can help enhance the electrochemical Viscosity Modifiers response, potentially boosting the SP signal. Their ability to alter the structure of the surrounding liquid makes them useful for modifying fluids.Thermally Thermally responsive fluids (also known as smart fluids) can change Responsive Fluids their viscosity in response to temperature changes. These fluids can be controlled dynamically and may be particularly useful in geothermal ordeep-well applications where temperature gradients are significant.

[0122] Increasing the viscosity of the injection fluid could enhance oil recovery from hydrocarbon reservoirs by blocking thief zones. The diversion of the injection fluid flow to other depth intervals during this process could be monitored using the exemplary system and method.

[0123] Potential Applications

[0124] The exemplary system and method can be used for a number of different industrial applications. Examples are listed in Table 5.Table 5Industry Example ApplicationHydrogeology and - Mapping aquifers and groundwater flow paths.water resource - Detecting groundwater recharge and discharge zones. management - Locating subsurface barriers to flow (e.g., faults or impermeable layers).- Monitoring changes in water table levels.Subsurface energy - Monitoring fluid injection and enhanced oil recovery (EOR) storage, exploration, processes.and production - Detecting subsurface fluid migration pathways and thief zones.- Characterizing hydrocarbon reservoirs with associated water flows.- Monitoring fracturing pressure- Monitoring compressed air energy storage or hydrogen storage - Real-time detection of gas leaks (methane or hydrogen) Carbon Capture and - Monitoring CO2plume migration within the subsurface.Storage (CCS) - Assessing the integrity of storage formations by detecting fluid leakage or caprock failure.- Mapping brine displacement caused by CO2injection.Attorney Docket No. 10046-668W018602 AHM Geothermal energy - Identifying geothermal reservoirs.- Monitoring fluid circulation and heat transport within geothermal systems.- Assessing fractures and permeability in geothermal fields. Environmental and - Monitoring leakage from landfills or subsurface waste engineering repositories.applications - Detecting seepage in dams, levees, or embankments.- Locating underground contamination plumes.- Monitoring tailings dams.- Monitoring tunnel and underground construction fluid flow - Monitoring nuclear reactor leakageVolcanology and - Tracking fluid movement in volcanic systems.Seismology - Monitoring hydrothermal systems for volcanic activity prediction.- Investigating fault zone hydrology and fluid pressure changes related to induced seismic events.Mining - Locating ore deposits associated with hydrothermal fluid flow.- Monitoring groundwater inflow in open-pit or underground mines.- Monitoring engineered salt-cavern solution mining operations. Agricultural - Mapping soil moisture dynamics.Management - Identifying regions of subsurface water accumulation for irrigation planning.Space exploration and -Monitoring of subsurface conditionssubsurface mapping of -Mapping underground water iceother planets -Detecting geological structures-Analyzing subsurface fluid dynamics

[0125] Conclusion

[0126] The construction and arrangement of the systems and methods, as shown in the various implementations, are illustrative only. Although only a few implementations have been described in detail in this disclosure, many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes, proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.). For example, the position of elements may be reversed or otherwise varied, and the nature or number of discrete elements or positions may be altered or varied. Accordingly, all such modifications are intended to be included within the scope of the present disclosure. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative implementations. Other substitutions, modifications, changes, and omissions mayAttorney Docket No. 10046-668W018602 AHM be made in the design, operating conditions, and arrangement of the implementations without departing from the scope of the present disclosure.

[0127] The present disclosure contemplates methods, systems, and program products on any machine-readable media for accomplishing various operations. The implementations of the present disclosure may be implemented using computer processors, or by a special purpose computer processor for an appropriate system, incorporated for this or another purpose, or by a hardwired system. Implementations within the scope of the present disclosure include program products, including machine-readable media for carrying or having machine-executable instructions or data structures stored thereon. Such machine-readable media can be any available media that can be accessed by a general-purpose or special -purpose computer or other machine with a processor. By way of example, such machine -readable media can comprise RAM, ROM, EPROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to cany or store desired program code in the form of machine¬ executable instructions or data structures, and which can be accessed by a general purpose or special purpose computer or other machine with a processor.

[0128] When information is transferred or provided over a network or another communications connection (either hardwired, wireless, or a combination of hardwired or wireless) to a machine, the machine properly views the connection as a machine-readable medium; thus, any such connection is properly termed a machine -readable medium.Combinations of the above are also included within the scope of machine-readable media. Machine-executable instructions include, for example, instructions and data that cause a general-purpose computer, special-purpose computer, or special-purpose processing machine to perform a certain function or group of functions.

[0129] Although the figures show a specific order of method steps, the order of the steps may differ from what is depicted. Also, two or more steps may be performed concurrently or with partial concurrence. Such variation will depend on the software and hardware systems chosen and on the designer's choice. All such variations are within the scope of the disclosure, likewise, software implementations could be accomplished with programming techniques with rule-based logic and other logic to accomplish the various connection steps, processing steps, comparison steps, and decision steps.

[0130] It is to be understood that the methods and systems are not limited to specific synthetic methods, specific components, or to particular compositions. It is also to beAttorney Docket No. 10046-668W018602 AHM understood that the terminology used herein is for the purpose of describing particular implementations only and is not intended to be limiting.

[0131] As used in the specification and the appended claims, the singular forms “a,” “an” and “the” include plural referents unless the context clearly dictates otherwise. Ranges may be expressed herein as from “about” one particular value, and / or to “about” another particular value. When such a range is expressed, another implementation includes from the one particular value and / or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another implementation. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

[0132] “Optional” or “optionally” means that the subsequently described event or circumstance may or may not occur and that the description includes instances where said event or circumstance occurs and instances where it does not.

[0133] Throughout the description and claims of this specification, the word “comprise” and variations of the word, such as “comprising” and “comprises,” means “including but not limited to,” and is not intended to exclude, for example, other additives, components, integers or steps. “Exemplary” means “an example of” and is not intended to convey an indication of a preferred or ideal implementation. “Such as” is not used in a restrictive sense but for explanatory purposes.

[0134] Disclosed are components that can be used to perform the disclosed methods and systems. These and other components are disclosed herein, and it is understood that when combinations, subsets, interactions, groups, etc. of these components are disclosed while specific reference of each various individual and collective combinations and permutation of these may not be explicitly disclosed, each is specifically contemplated and described herein, for all methods and systems. This applies to all aspects of this application, including, but not limited to, steps in disclosed methods. Thus, if there are a variety of additional steps that can be performed it is understood that each of these additional steps can be performed with any specific implementation or combination of implementations of the disclosed methods.

[0135] The following patents, applications, and publications, as listed below and throughout this document, are hereby incorporated by reference in their entirety herein.

[0136] References[1] Ahmadian, M., Haddad, M., Cui, L. el al. 2023. Real-Time Monitoring of Fracture Dynamics with a Contrast- Agent- Assisted Electromagnetic Method. Presented at the SPEAttorney Docket No. 10046-668W018602 AHM Hydraulic Fracturing Technology Conference and Exhibition, The Woodlands, Texas, USA, 31 January-2 February 2023. SPE-212376-MS. https: / / doi.org / 10.2118 / 212376- MS.[2] Ahmadian, M., and Haddad, M. 2025. Demonstration of a Real-Time Electromagnetic Method to Monitor Plugged-and- Abandoned Wells. OESI final report.[3] Eldad, H. 2015. Computational Methods in Geophysical Electromagnetics. Society for Industrial and Applied Mathematics.[4] Fitterman, D. V. 1979. Calculations of Self-Potential Anomalies Near Vertical Contacts.Geophysics 44 (2): 195-205. https: / / doi.org / 10.1190 / 1.1440961.[5] Heinson, G., White, A., Robinson, D., and Fathianpour, N. 2005. Marine Self-Potential Gradient Exploration of the Continental Margin. Geophysics 70 (5): G109-G118. https: / / doi.org / 10.1190 / 1.2057981.[6] Pugh, T. K. C., et al. 2024. System and Method for Combined Streaming Potential and Controlled-Source Electromagnetic Modeling. US Patent 2024 / 0085584 A1.[71 Revil, A., and Jardani, A. 2013. The Self-Potential Method. Cambridge University Press, https: / / doi.org / 10.1017 / CBO9781139094252.[8] Sheffer, M. R., and Oldenburg, D. W. 2007. Three-Dimensional Modelling of Streaming Potential. Geophys. J. Int. 169: 839-848. https: / / doi.org / 10.1111 / j.1365-246X.2007.03397.x.[9] Wightman, W. E., Jalinoos, F., Sirles, P., and Hanna, K. 2003. Application of Geophysical Methods to Highway Related Problems. U. S. Department of Transportation. Publication No. FHWA-IF-04-021.

[0010] Ziolkowski, A. and Slob, E. 2019. Introduction to Controlled-Source Electromagnetic Methods: Detecting Subsurface Fluids. Cambridge University Press; 1stedition.

Claims

Attorney Docket No. 10046-668W018602 AHM What is claimed:

1. A method comprising:monitoring of flow dynamics or containment via electromagnetic (EM) and streaming potential (SP) sensitive instruments positioned over a site or structure, and collecting multi¬ frequency active-source EM-SP data, augmented by SP generated when a pressure-driven fluid How drags ions from a diffuse layer of an Electrical Double Layer (EDL) through a porous medium;determining, via an EM-SP simulation or analysis, fluid flow and containment characteristics at a plurality of subsurface depths of fluid flow or containment barriers; and outputting the fluid flow and containment characteristics, wherein the output fluid flow characteristics are employed for site / structure survey, site / structure operation integrity, or site / structure compliance.

2. The method of claim 1, further comprising:injecting a fluid with a pre-defined frequency-dependent signature into the site or structure; anddetermining via the simulation or analysis using the pre-defined frequency-dependent signature to determine the fluid flow characteristics at the plurality of subsurface depths of the fluid flow.

3. The method of claim 1 or 2, further comprising:injecting a fluid with an enhanced SP signature into the site or structure; and determining via the simulation or analysis using a pre-defined frequency-dependent signature to determine the fluid flow characteristics at the plurality of subsurface depths of the fluid flow.

4. The method of claim 3, wherein the fluid is mixed with electrically active contrast agents, electrolyte, or mineral admixtures to improve sensitivity of the fluid to active- and passive-source EM monitoring.

5. The method of any one of claims 1-4, wherein the fluid flow is flowing through a geologic formation in a subsurface porous medium with low conductivity contrast.Attorney Docket No. 10046-668W018602 AHM 6. The method of any one of claims 1-5, wherein the determined fluid flow characteristics include a rate of the subsurface fluid flow at different depths.

7. The method of any one of claims 1-6, wherein the determined fluid flow characteristics include a direction of subsurface fluid flow at different depths.

8. The method of any one of claims 1-7, wherein the determined fluid flow characteristics include pressure within the subsurface fluid flow at different depths.

9. The method of any one of claims 1-8, comprising:determining, via the simulation or analysis, frequency-dependent profile for a subsurface fluid flow; anddetermining a fluid type based on the determined frequency-dependent profile.

10. The method of any one of claims 1-9, comprising:deploying a transmitter and receivers around a borehole or zone of interest, and transmitting electric current to the borehole or the zone of interest to apply the current to a subsurface region connected to the borehole or over the zone of interest.

11. The method of any one of claims 1-10, comprising:deploying a transmitter and receivers around a borehole or zone of interest, and passively monitoring electric fields induced solely by the fluid flow of a subsurface region connected to the borehole or over the zone of interest.

12. The method of any one of claims 1-11, wherein the structure comprises a plugged-and- abandoned well, a dam subsurface structure, or a nuclear plant structure.

13. The method of any one of claims 1-12, wherein the structure is formed in part of cement, wherein the cement of the structure is embedded with admixture that enhances electromagnetic or streaming potential signal sensing, wherein the admixture includes graphitic, metallic, composite, or a combination thereof.

14. The method of any one of claims 1-13, wherein the active-source simulation or analysis identifies an infinite-base station as a reference point in the simulation or analysis.Attorney Docket No. 10046-668W018602 AHM15. A composition of matter comprising:an inj ectate; andan SP-enhanced additive added to the injectate, the SP-enhanced additive comprising graphite, metal, composite, or a combination thereof, added to the injectate that enhances active- and passive-source EM-SP monitoring.

16. The composition of matter of claim 15, wherein the composition of matter is employed in the method of claims 1-14 or 19.

17. A composition of matter comprising:electrically active particulate, admixture;a binder for forming a construction structure that sets, hardens, and adheres to bind them together to form a containment structure; andan SP-enhanced additive comprising graphite, metal, composite, or a combination thereof mixed in the binder that enhances active- and passive-source EM-SP monitoring.

18. The composition of matter or construction structure of claim 17, wherein the aggregates and binder include at least one of:alite (3CaO·SiO2), belite (2CaO-Si()2), tricalcium aluminate (3CaO A12O3), and brownmillerite (4CaO • A12O3 • Fe2O3).

19. The composition of matter of claim 17 or 18, wherein the composition of matter is employed in the method of claims 1-14.

20. A construction structure formed of aggregates and a binder that sets, hardens, and adheres to bind them together to form a containment structure, wherein the structure is embedded with an SP-enhanced additive comprising graphite, metal, composite, or a combination thereof mixed in the aggregate and / or binder that enhances active- and passivesource EM-SP monitoring of the containment structure or conditions thereby.

21. The construction structure of claim 19, wherein the construction structure is employed in the method of claims 1-14.Attorney Docket No. 10046-668W018602 AHM 22. A method comprising:receiving measurement data of flow dynamics or containment acquired via electromagnetic (EM) and streaming potential (SP) sensitive instruments positioned over a site or structure, wherein the measurement data comprises multi-frequency active-source EM-SP data, augmented by SP generated when a pressure-driven fluid flow drags ions from a diffuse layer of an Electrical Double Layer (EDL) through a porous medium;determining, via an EM-SP simulation or analysis, fluid flow and containment characteristics at a plurality of subsurface depths of fluid flow or containment barriers; and outputting the fluid flow and containment characteristics, wherein the output fluid flow characteristics are employed for site / structure survey, site / structure operation, or site / structure compliance.23 A system to perform the method of any one of claims 1-14 and 19.24 A non-transitory computer-readable medium having instructions stored thereon, wherein execution of the instructions causes the processor to perform the method of any one of claims 1-14 and 19.

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