DETAILED ACTION
The amendment and RCE filed on 07/09/2026 has been entered and fully considered. Claims 1-15 and 25-27 are pending, of which claims 1, 3-4, 6, 9-10, 12 and 14-15 are amended, and claim 25-27 are newly added.
Response to Amendment
In response to amendment, the examiner maintains rejection over the prior art established in the previous Office action.
Notice of Pre-AIA or AIA Status
The present application, filed on or after March 16, 2013, is being examined under the first inventor to file provisions of the AIA .
Claim Rejections - 35 USC § 103
The text of those sections of Title 35, U.S. Code not included in this action can be found in a prior Office action.
Claim(s) 1-3, 8-9, 14-15 and 27 is/are rejected under 35 U.S.C. 103 as being unpatentable over Baban et al. (International Journal of Greenhouse Gas Control, 2021) (Baban).
Regarding claim 1, Baban teaches a method (abstract) comprising:
acquiring two or more 1H nuclear magnetic resonance (NMR) transverse relaxation time measurements from a formation sample exposed to different CO2 exposure states (Fig. 5, page 2, par 3, page 3, par 1, page 5, par 2), wherein at least one transverse relaxation time measurement is associated with a first CO2 exposure state and at least one other transverse relaxation time measurement is associated with a second exposure CO2 state different from the first CO2 exposure state (Fig. 5, page 2, par 3, page 3, par 1, page 5, par 2);
determining a CO2 gas wettability index, a CO2 supercritical fluid wettability index, or both based at least on a comparison of the transverse relaxation time shift and the baseline proton response (Table 1, page 4, par 1; page 5, par 3; page 6, par 0-1, abstract).
Baban does not specifically teach calibrating the NMR measurements based on a shift in the at least one transverse relaxation time measurement and the at least one other transverse relaxation time measurement to form baseline measurement, wherein the shift is based at least on the different CO2 containing states. However, Baban teaches a relationship between the NMR measurements and the wettability index (WI) as Equation 8 (page 3).
T1/T2 = -2.25 WI + 2.25 (8)
A person skilled in the art would have appreciated that Equation 8 is a linear function typically written in the form of "y = mx + b", where "m" determines the slope of the line and "b" indicates where the line crosses the y-axis, and that m and b can be calibrated in order to fit the equation to the data. In this case, y is T1/T2, which involves the shift (change) in one or more of the two or more 1H nuclear magnetic resonance (NMR) relaxation time measurements. Thus, it would have been obvious to one of ordinary skill in the art to calibrate the NMR measurements based on a shift in the at least one transverse relaxation time measurement and the at least one other transverse relaxation time measurement to form baseline measurement, wherein the shift is based at least on the different CO2 containing states, in order to fit the equation to the data.
Further, Baban teaches that “T1-T2 and T2 measurements (note that T1 is the longitudinal relaxation time and T2 is the transverse relaxation time) were performed and then 10 PV of live brine were injected into the core at the same conditions as above to displace all dead brine with live brine. Once the pressure drop stabilized, T1-T2 and T2 responses for live-brine saturated core were obtained. Prior to scCO2 injection, the outlet pressure was maintained constant at 8 MPa (using an ISCO pump as a back-pressure regulator). Subsequently, capillary drainage pressures were measured by injecting 20 PV of scCO2 into the core plug at a constant flowrate of 0.1 ml/min, which was incrementally increased to 0.5, 1, 2, 4, 6 and 8 ml/min (Ramakrishnan and Cappiello, 1991) with multiple T1-T2 and T2 scans taken for each flow rate.” (page 2, par 3), “ “Furthermore, the capillary pressure measurements were made at the inlet of the core sample by successively increasing the CO2 flow rate, while average fluid saturations were measured via NMR T2.” (page 3, par 1). Fig. 5 notes “The entire T2 drainage curve (red) shifted left which depicts that CO2 displaced water from the large pores during drainage.”. Thus, Baban teaches that wherein the shift of T1 and T2 is based at least on the different CO2 containing states.
Baban teaches that WI denotes a wettability index, which is a general measure of wettability on a continuum (e.g., WI ≈ +1 strongly water-wet, WI ≈ −1 strongly oil-wet) (page 3, par 14), and is not limited to “water wettability”. The WI value is derived from NMR measurements reflecting fluid–rock interactions present in the system under study.
Baban explicitly teaches determining wettability indices (WI) for CO₂–brine–rock systems using NMR measurements under different CO₂-containing states, including conditions where CO₂ is present as a separate supercritical phase. Baban reports NMR-derived wettability indices after live brine saturation, CO₂ drainage, and CO₂ imbibition, and explains that: “CO₂ (either molecularly dissolved or as a separate supercritical phase) significantly reduced the hydrophilicity of the sandstone…”(abstract).
Further, Baban expressly characterizes the property being evaluated as CO₂ wettability, stating in its conclusion that: “CO₂-wettability of storage and caprock is a vital parameter as it determines storage capacities and containment security.” (page 5, par 3). This statement unambiguously demonstrates that Baban is directed to CO₂ wettability, not merely water wettability. The wettability indices reported by Baban therefore inherently correspond to CO₂ gas and CO₂ supercritical fluid wettability, as recited in amended claim 1.
Regarding claim 2, Baban teaches that the method further comprising injecting the formation sample with CO2 gas (page 2, par 2).
Regarding claim 3, Baban teaches that the method further comprising taking a set of brine signals from the formation sample with the CO2 gas injected in the formation sample (Fig. 5, page 5, par 2).
Regarding claim 8, Baban teaches that the method further comprising injecting the formation sample with a scCO2 gas (page 2, par 2).
Regarding claim 9, Baban teaches that the method further comprising taking a set of brine signals from the formation sample with the scCO2 gas injected in the formation sample (page 5, par 2).
Regarding claim 14, Baban teaches that wherein one of the different CO2 exposure states is a CO2 free state (Table 1, page 4, par 1).
Regarding claim 15, Baban teaches that wherein one of the different CO2 exposure states are at a first time during a CO2 injection into the formation sample and a second time during a storing of the formations sample this is injected with CO2 (page 5, par 2).
Regarding claim 27, Baban teaches the method of claim 1 as set forth above. Baban further teaches that the baseline proton response is associated with a zero CO₂-containing state (page 2, par 3).
Specifically, Baban teaches that the sandstone core sample was initially saturated with dead brine before introduction of CO₂-saturated brine or scCO₂. Baban states that the sample was injected with dead brine, left for 24 hours “to ensure full brine saturation was achieved,” and that T1-T2 and T2 measurements were then performed (page 2, par 3). Baban subsequently injected live brine and thereafter scCO₂ into the same sample (page 2, par 3). Thus, the initial NMR response obtained from the fully dead-brine-saturated sample corresponds to a baseline proton response associated with a zero CO₂-containing state.
Accordingly, Baban teaches the additional limitation of claim 27, “wherein the baseline proton response is associated with a zero CO₂ containing state.”
Claim(s) 4-7 and 10-13 is/are rejected under 35 U.S.C. 103 as being unpatentable over Baban et al. (International Journal of Greenhouse Gas Control, 2021) (Baban) in view of Li et al. (J. Geophys. Eng., 2015) (Li).
Regarding claim 4 and 10, Baban does not specifically teach that the method further comprising performing a multiexponential inversion kernel matrix with two or more brine signals from the formation sample and the set of brine signals to find a brine distribution. However, in the analogous art of core analysis, Li teaches performing a multiexponential inversion kernel matrix with at least the set of brine signals to find a brine distribution (abstract). Li teaches that “The multi-exponential inversion of a NMR relaxation signal plays a key role in core analysis and logging interpretation in the formation of porous media.” (abstract). It would have been obvious to one of ordinary skill in the art to select multiexponential inversion kernel matrix with two or more brine signals from the formation sample and at least the set of brine signals to find a brine distribution, because the selection is based on its suitability for the intended use.
Regarding claim 5 and 11, Baban teaches that the method further comprising cross-validating a contact angle wettability measurement with an NMR based wettability index (Table 1, page 4, par 1).
Regarding claim 6, Baban teaches that the method further comprising forming a brine wettability index from the two or more 1H NMR relaxation time measurements of the formation sample at different CO2 exposure states and two or more brine signals from the formation sample (Table 1, page 4, par 1).
Regarding claim 7, Baban teaches forming the CO2 gas wettability index, the CO2 supercritical fluid wettability index, or both from the brine wettability index (page 5, par 3, abstract).
Regarding claim 12, Baban teaches that the method further comprising forming the brine wettability index from one or more NMR measurements of the formation sample that is scCO2 free, the formation sample with scCO2, and the two or more brine signals from the formation sample (Table 1, page 4, par 1).
Regarding claim 13, Baban teaches forming the CO2 gas wettability index, the CO2 supercritical fluid wettability index, or both from the brine wettability index (page 5, par 3, abstract).
Claim(s) 26 is/are rejected under 35 U.S.C. 103 as being unpatentable over Baban et al. (International Journal of Greenhouse Gas Control, 2021) (Baban) in view of Galford et al. (US 2003/0094946) (Galford).
Regarding claim 26, Baban teaches the method of claim 1 as set forth above. However, Baban does not explicitly teach that “the baseline proton response is associated with the fully aqueous solution phase of a rock sample different from the formation sample.”
Galford teaches using laboratory NMR measurements from separate rock samples to obtain calibration data for NMR measurements associated with a formation. Galford explains that laboratory NMR measurements are performed on samples of core material that are “selectively drilled and removed from a much larger core retrieved from the formations of interest.” (par [0012]). Galford further teaches that “[t]he extracted samples are cleaned and saturated with brine prior to making an initial laboratory NMR measurement,” (par [0012]), and that the resulting data are used “to derive a calibrated transformation that can be applied to the saturated measurements (and NMR logs in the same formations) … in the same, or similar, formations.” (par [0012]). Thus, Galford teaches obtaining an initial proton response from the fully aqueous, brine-saturated phase of a separate rock sample and using that response as calibration data for NMR measurements of another formation sample or formation.
Baban and Galford are analogous art because both concern NMR measurements of fluid-containing rock or formation samples and calibration or comparison of NMR responses to determine formation properties. It would have been obvious to one of ordinary skill in the art before the effective filing date to modify Baban’s method by obtaining the baseline proton response from the fully brine-saturated phase of a separate rock sample, as taught by Galford. One would have been motivated to do so because Galford teaches that NMR data obtained from separate brine-saturated core samples can be used to derive a calibrated transformation applicable to measurements from the same or similar formations, thereby providing a representative fully aqueous baseline without requiring the formation sample under evaluation itself to be returned to the fully aqueous condition.
Allowable Subject Matter
Claim 25 is objected to as being dependent upon a rejected base claim, but would be allowable if rewritten in independent form including all of the limitations of the base claim and any intervening claims.
The following is a statement of reasons for the indication of allowable subject matter: The prior art of record does not teach or fairly suggest the equation as recited in claim 25.
Response to Arguments
Applicant's arguments filed 07/09/2026 have been fully considered but they are not persuasive.
Applicant argues that Baban’s Equation 8 merely establishes a relationship between a single T1/T2 ratio and a wettability index and does not demonstrate a shift between at least two transverse-relaxation-time measurements. The Examiner agrees that Equation 8, considered alone, expresses the relationship (T1/T2=-2.25WI+2.25). However, the rejection does not rely solely on Equation 8 for the claimed transverse-relaxation-time shift.
Baban separately acquires T2 measurements from the same sandstone sample under different CO2 exposure states, including dead-brine saturation, live-brine saturation, scCO2 drainage, and subsequent imbibition. Baban expressly states that “T1-T2 and T2 measurements were performed,” that T1-T2 and T2 responses were obtained after live-brine saturation, and that “multiple T1-T2 and T2 scans” were taken during scCO2 injection (page 2, par 3). Baban therefore teaches at least one transverse-relaxation-time measurement associated with a first CO2 exposure state and at least one other transverse-relaxation-time measurement associated with a second, different CO2 exposure state.
Moreover, Baban expressly compares the T2 measurements obtained under those different states and identifies a shift between them (Fig. 5, page 5, par 2). In particular, Baban states:
“the T2 relaxation time peak shifted to the left (from pores with radii larger than 20 µm to pores with radii less than 10 µm).” (page 5, par 2).
Baban further explains that “the entire T2 drainage curve … shifted left” because CO2 displaced water from the larger pores (Fig. 5). Thus, contrary to Applicant’s argument, Baban expressly teaches a transverse-relaxation-time shift between measurements obtained under different CO2 exposure states.
Baban also provides the claimed aqueous baseline or reference condition (page 2, par 3). Baban first fully saturates the sandstone sample with dead brine, leaves the sample for 24 hours “to ensure full brine saturation,” and obtains the corresponding NMR measurements before introducing CO2-saturated brine or scCO2 (page 2, par 3). This fully brine-saturated condition constitutes a baseline proton response associated with a fully aqueous solution phase against which the later CO2-containing measurements and T2 shifts are compared (page 2, par 3). Baban subsequently introduces known, non-zero CO2 states in the form of live brine and a separate scCO2 phase (page 2, par 3). The observed difference in T2 between the baseline condition and the CO2-containing conditions represents a difference in transverse relaxation behavior, and therefore corresponds to the recited NMR relaxation-rate difference.
Applicant also repeatedly characterizes Baban’s WI as a “water wettability index.” This characterization is inaccurate. Baban defines “WI” simply as “Wettability index.” Baban explains that the index extends from approximately (+1), indicating a strongly water-wet system, to approximately (-1), indicating a strongly oil-wet system (page 3, par 14). WI is therefore a general wettability scale, not an index limited to water wettability (page 3, par 4). Baban applies that scale to CO2-brine-rock systems and reports WI values under scCO2 drainage and imbibition conditions. Baban expressly states that “CO2-wettability of storage and caprock is a vital parameter” (page 5, par 3), and reports a WI of 0.26 for the two-phase CO2-brine systems (page 6, par 1). Accordingly, Baban determines a wettability index associated with CO2 and supercritical-CO2 exposure, rather than merely calculating a separate “water wettability index” from which CO2 wettability is inferred.
Accordingly, Baban teaches or renders obvious acquiring transverse-relaxation-time measurements under different CO2 exposure states, comparing the measurements to identify a transverse-relaxation-time shift relative to a fully aqueous baseline proton response, and determining a wettability index for the CO2-brine-rock system based on the resulting NMR measurements. The amendments to claim 1 therefore do not overcome the rejection of claims 1-3, 8, 9, 14, and 15 under 35 U.S.C. §103 over Baban.
Applicant’s arguments regarding claims 4-7 and 10-13 rely on the same asserted deficiency of Baban with respect to claim 1. For the reasons discussed above, that asserted deficiency is not present. Applicant has not separately identified an error in the teachings relied upon from Li for the additional limitations of those claims. Therefore, the rejection of claims 4-7 and 10-13 under 35 U.S.C. §103 over Baban in view of Li is maintained.
Conclusion
Any inquiry concerning this communication or earlier communications from the examiner should be directed to XIAOYUN R XU, Ph. D. whose telephone number is (571)270-5560. The examiner can normally be reached M-F 8am-5pm.
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/XIAOYUN R XU, Ph.D./ Primary Examiner, Art Unit 1797
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