Hybrid saturation recovery-inversion recovery pulse sequence for improved nmr logging of boreholes.

(54) Title: SEQUENCE OF RECOVERY IMPULSES BY HYBRID SATURATION-RECOVERY BY INVESTMENT FOR IMPROVED NMR RECORD OF SOUNDINGS.

(54) Title: HYBRID SATURATION RECOVERY-INVERSION RECOVERY PULSE SEQUENCE FOR IMPROVED NMR LOGGING OF BOREHOLES.

(57) Summary

A nuclear magnetic resonance (NMR) recording method includes providing a hybrid pulse sequence having a saturation pulse, an inversion pulse, and a detection sequence; The method also includes measuring echo signals in response to the hybrid pulse sequence; The method also includes deriving a spin-net time constant (T1) from the measured echo signals; An NMR system includes a hybrid pulse sequence module for providing a hybrid pulse sequence with a saturation pulse, a reversal pulse, and a detection sequence; the NMR system also includes a control module for selecting a time interval between the saturation pulse and the reversal pulse.

(57) Abstract

A nuclear magnetic resonance (NMR) logging method ineludes providing a hybrid pulse sequence having a saturation pulse, an inversion pulse, and a detection sequence. The method also ineludes measuring echo signals in response to the hybrid pulse sequence. The method also includes deriving a spin-lattice time constant (T1) distribution from the measured echo sign. A NMR system ineludes a hybrid pulse sequence module to provide a hybrid pulse sequence with a saturation pulse, an inversion pulse, and a detection sequence. The NMR system also includes a control module to select a time interval between the saturation pulse and the inversion pulse.

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Mexican Property Institute

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PATENT TITLE NO. 344841

<td>Headlines):</td><td>HALLIBURTON ENERGY SERVICES, INC.</td>

<td>Home:</td><td>10200 Bellaire Boulevard, Houston, Texas, 77072, USA</td>

<td>Denomination:</td><td>SEQUENCE OF RECOVERY IMPULSES BY HYBRID SATURATION-RECOVERY BY INVESTMENT FOR IMPROVED NMR RECORD OF SOUNDINGS.</td>

<td>Classification:</td><td>Int.CI.8: E21B47 / 12; G01N24 / 08; G01R33 / 44; G01V3 / 32</td>

<td>Inventor (s);</td><td>LILONG Ll; SONGHUACHEN</td>

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Number

International filing date:

MX / a / 2014/012436 May 2013

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<td>US</td><td>May 16, 2012</td><td> 61/647,671</td>

Validity: Twenty years

Expiration Date: May 16, 2033 'The reference patent will be granted based on articles 1, 2^or fraction V, 6th fraction III,

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Issue Date: January 9, 2017

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SEQUENCE OF RECOVERY IMPULSES BY HYBRID SATURATION RECOVERY BY INVESTMENT FOR IMPROVED NMR RECORD OF

SURVEYS

BACKGROUND OF THE INVENTION

Understanding the structure and properties of geological formations can improve the efficiency of oil field operations, such as drilling, well completion, and production. The collection of information related to downhole conditions, commonly referred to as logging, can be accomplished through various methods including nuclear magnetic resonance (NMR) logging.

NMR logging tools operate using an imposed static magnetic field, B_or to provide the nucleus with nonzero nuclear spin divided energy levels (nonzero magnetic moment and angular momentum). Because lower energy levels are preferred, an assembly of nuclei will show an anisotropic distribution of energy states, giving the nuclear spins a preferential polarization parallel to the imposed field. This state creates a lattice magnetic moment and produces bulk magnetization. The nuclei converge in their equilibrium alignment with a time constant of ₂ IMPI ^

INSTITUTO M &amp; XiCANO ȣ THE INDUSTRIAL PROPERTY exponential relaxation characteristic. When this convergence occurs after the cores have been placed in an initial cooperative state (discussed below), this is known as recovery. The time constant for recovery is called the longitudinal relaxation time or spin-network (Ti).

During or after the polarization period, the tool applies a disturbance field, usually in the form of a radio frequency electromagnetic pulse whose magnetic component (Bi) is perpendicular to the static field (B_or). This perturbation field moves the orientation of the magnetization to the transverse (perpendicular) plane. The pulse frequency can be chosen for specific target nuclei (eg hydrogen). The polarized nuclei are simultaneously disturbed and, when the disturbance ends, they rotate around the static magnetic field gradually prepolarizing to align with the static field once again while losing coherence in the transverse plane (relaxation T₂). The precession of the nuclei generates a detectable radio frequency signal that can be used to mediate the static distributions of Ti, T₂, porosities and / or diffusion constants. To retrieve NMR measurements, data sampling is performed during a pulse sequence

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OF THE fMPIEOAD tA ^ -Sag jjgl industrial generating echoes of spin or decay of free induction. The data sampling process is limited by the timing constraints of the receiver electronics as well as the timing criteria of the NMR experiment.

For NMR-based training evaluation, Ti measurements are sometimes preferred over T measurements.₂ because they can be less vulnerable to vibrations. Furthermore, the interpretation of the Ti data may be simpler than the interpretation of the T data.₂ because Ti data is unaffected by additional signal decay caused by molecular diffusion in magnetic field gradients. Furthermore, the Ti / T data₂ provide additional fluid and formation information than the T data₂ for themselves. Despite these benefits, Ti measurements can suffer from a very long measurement time using the Inversion Recovery (IR) data acquisition method, or reduced sensitivity in the short relaxation time range using the saturation recovery (SR).

BRIEF DESCRIPTION OF THE FIGURES

Accordingly, several nuclear magnetic resonance (NMR) analysis methods and systems using a hybrid pulse sequence to mediate Tasmeasurements Ti. ——

The. Figure 1 is a block diagram of an illustrative NMR tool.

Figure 2 shows an illustrative hybrid pulse sequence.

Figure 3 shows an illustrative two-step reversal.

Figures 4A through 4F show illustrative high signal-to-noise ratio (SNR) inversion results.

Figures 5A to 5F show illustrative results of the inversion of the low signal-to-noise ratio (SNR).

Figure 6 shows a graph comparing illustrative relaxation times.

Figures 7A and 7B show illustrative graphs comparing Ti inversion results using a hybrid pulse sequence and a saturation recovery pulse sequence.

Figure 8A shows a graph with illustrative waiting time (TW) information related to the use of a hybrid pulse sequence in a heavy oil environment.

Figure 8B shows a graph with illustrative TW information related to the use of a sequence of

INSTITUTO MEXICANO DE IA INDUSTRIAL PROPERTY hybrid impulses in a shale-oil environment.

Figure 9 shows an illustrative NMR system.

Figure 10 shows an illustrative logging environment while drilling (LWD).

Figure 11 shows an illustrative wired logging environment.

Figure 12 shows an illustrative computer system for managing logging operations.

Figures 13 and 14 are illustrative NMR method flow charts.

However, it should be understood that the specific embodiments provided in the drawings and the following detailed description do not limit the disclosure. Rather, they provide the basis for one of ordinary skill in the art to discern alternative forms, equivalents, and other modifications that are encompassed within the scope of the appended claims.

DETAILED DESCRIPTION OF THE INVENTION

Disclosed herein are methods and systems for nuclear magnetic resonance (NMR) analysis using a hybrid pulse sequence combining saturation recovery (SR) and inversion recovery (IR). Data acquisition using the pulse sequence₆ IMPI ^

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INDUSTRIAL 1-hybrids retains the efficiency of SR while ensuring the characteristics of increased sensitivity of IR, thus improving the performance of NMR analysis for fast-relaxation components abundant in shale gas, heavy oil, and for microporosity in carbonates.

As an exemplary application, an NMR logging tool using hybrid pulse sequence can measure the longitudinal relaxation time (Ti) distribution in a sample, where multiple Ti times may be present. Such distributions are useful for evaluation of the downhole formation due to the different types of fluids that reside in different sized pores. Therefore, the combined fluids produce widely different Ti values ​​in NMR measurements. With the disclosed hybrid pulse sequence, the sensitivity of the NMR recording tool to rapidly relaxing Ti components (components with very small Ti) is improved without significantly prolonging the measurement time.

Figure 1 is a block diagram of an illustrative NMR tool 100. In some embodiments, the NMR tool 100 is part of a downhole wired log string or a log-while-drilling (LWD) string for analyzing attributes. Of the information. In another modality the

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DE LA FKOWEDAD INDUSTRIAL The NMR 100 tool corresponds to laboratory equipment to analyze samples. As shown, the NMR logging tool 100 includes a static magnetic field source (B_or) 102, such as one or more strong permanent magnets (eg, samarium cobalt magnets). The NMR recording tool 100 also includes a pulsed magnetic field source (Bi) 104 for emitting pulses of an alternating radio frequency (RF) magnetic field using one or more antennas with convenient electronic circuitry. Note that these antennas and electronic circuits can act in a dual mode, also functioning to receive and detect rotating echo signals. Alternatively, such reception can be done with separate antennas and electronic circuits.

The NMR logging tool 100 further includes a hybrid pulse sequence generator 110 in communication with the pulsed magnetic field source 104. In some embodiments, the hybrid pulse sequence generator 110 includes a processor and memory with software instructions. executables. In alternative embodiments, the hybrid pulse sequence generator 110 corresponds to hardware modules such as application specific integrated circuits (ASICs) or programmable logic configured to provide any of the following.

INSTITUTO MEXICANO DE LA PROPIEDAD INDUSTRIAL variations of sequence of hybrid impulses described here. The hybrid pulse sequence generator 110 directs the pulsed magnetic field source 104 to emit a particular pulse sequence and listen for the NMR phenomenon related to the pulse sequence. More specifically, the hybrid pulse sequence generator 110 includes a hybrid pulse sequence module 112 that stores information or parameters for one or more saturation pulses, a reversal pulse, and a detection sequence that constitutes each pulse sequence. hybrid drives.

Hybrid pulse sequence generator 110 also includes a control module 114 that allows selection or updates of hybrid pulse sequence options. For example, the time interval between the last saturation pulse and the reversal pulse can be selected or updated to increase or decrease the sensitivity to rapidly relaxing components. Furthermore, the number of saturation pulses can be increased or decreased. In addition, the detection sequence can be selected or switched between a pulse-free induction decay (FID), a CarrPurcell sequence, a Carr-Purcell-Meiboom-Gill (CPMG) sequence, or another sequence with different phase cycling schemes. . It should be understood that the refocusing impulse or impulses in₀ IMPI and INSTITUTE Μ εχιΟκΝΓ.

0Ε INDUSTRIAL PROPERTY These sequences are not restricted to 180 degrees.

The NMR tool 100 also includes a measurement storage unit 116 for storing measurements of NMR phenomena related to the hybrid pulse sequence. The measurement storage unit 116 is accessible via wired or wireless data transmissions to provide the measurements to processing logic for analysis. For example, stored measurements can be used to derive Ti distributions as described here. In at least some embodiments, the measurements or values ​​derived from the measurements can be displayed on a computer.

Figure 2 shows an illustrative hybrid pulse sequence with a saturation pulse, a reversal pulse, and a detection sequence. Also, various time intervals for the hybrid pulse sequence are illustrated, including: a wait time (TW) between the saturation pulse and the reversal pulse; a reversal time interval (TI) between the reversal pulse and the detection sequence; and an inter-echo interval (TE) between pulses of the detection sequence. In operation, the saturation pulse places the target nuclei in an essentially demagnetized state. After TW in which the nuclei begin to repolarize parallel to the field

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INDUSTRIAL ^ r ™ static, the reversal impulse is applied to reverse the (partial) polarization along the z axis. After TI, measurements are ensured using a standard CPMG sequence, in which a 90 ° pulse is followed by a sequence of 180 ° pulses separated in accordance with TE to generate echo signals (displayed along the line bottom in figure 2). Ti and T measurements₂ they can be derived from the echo signal amplitudes in the usual way. In various modes, the time intervals can be modified to improve the sensitivity and robustness of the measurement. Furthermore, through the use of gradients and frequency variation, NMR measurements can be spatially resolved.

Some variations can be envisaged for the hybrid pulse sequence of Figure 2. For example, for TI = 0, the reversal pulse can be eliminated, but the resulting signals will be mathematically inverted. At larger values ​​for TI, the reversal pulse can also be eliminated, resulting in a sequence of saturation recovery pulses. The time interval prior to the reversal pulse TW can be adjusted, or made variable, according to the specific needs of the application. In addition, the number of CPMG echoes acquired may change with TI, or a

WST1TU ΤΟ MiXICAN INDI 1STRIAL PROPERTY direct FID measurement instead of CPMG echo train when field homogeneity is sufficient. Furthermore, a Carr-Purcell sequence can be used, or another sequence with different phase cycling schemes. Also, although the pulses illustrated in Figure 2 have a square shape, other pulse shapes can be used. For example, a smooth impulse or a fast step that involves frequency sweep would also work.

The disclosed hybrid pulse sequence for Ti measurements is a combination of a saturation recovery sequence and an inversion recovery sequence. The CPMG saturation recovery method can be symbolically described as (sat) -TW- π / 2-TE / 2- (π TE / 2-echo-TE / 2) n, where (sat) represents a pulse or pulses of saturation, and π and π 12 are RF pulses. Meanwhile, the CPMG payback method can be symbolically described as jr-TI-fl · / 2-TE / 2- (π-ΤΕ / 2-echoTE / 2)_n.

Compared to the IR sequence, the SR sequence does not require a long time to reach full polarization between the measurements of two TWs. In contrast, the IR sequence requires a very long wait time (eg, at least three times the longest Ti component) to repolarize the magnetization. Therefore, from

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The increase in polarization followed by the saturation pulse is described by

MW) = M₀(l - expC-TW '/ TO) (1) for a single component Ti system. For a system containing multi-component fluid fractions and / or multi-component pore sizes the increase can be described by

M (W) = Σ ^ Μ ^ Ι - expC-TW / η,)) _(2}

From equations (1) and (2) it can be seen that the polarization accumulation curve starts from almost zero at low TW. On the other hand, using the IR sequence, the evolution of polarization is described by

Mm = M „[1 - 2exp (- 2)]

LX íJ / J (□) for a single component system Ti, and for a system containing fluid fractions and / or multi-component pore sizes, the increase can be described by

Mm = 2 ^ 0, (1-2 ^ (- ^ -)] ₍₄₎

The evolution of magnetization starts at near -Mo to very low TI.

A Ti distribution can be obtained by reversing the evolution of the magnetization polarization curve with a multi-exponential decay model described by equation (2) or (4). Because the signals corresponding to different T_n should be greater than or equal to zero, a non-negative restriction is included in the investment. The sensitivity of the inversion to resolve the individual components depends, among other factors, on the signal-to-noise ratio (SNR) of the evolution of the polarization curve data. For the SR approach, the initial data points, corresponding to the short TWs, may have a very poor SNR; therefore, the rapidly relaxing components may suffer a greater error. On the other hand, for short CTs in the inversion recovery sequence, the signal amplitude of the initial data points can be close to M_or but opposite in phase. Therefore, SNR may be adequate.

The hybrid pulse sequence is convenient as it exceeds the long time required to run the IR sequence but maintains the advantage of this sequence sensitivity to rapidly falling Ti components. The hybrid pulse sequence can be described as saturation (partial recovery) - inversion-recovery (HSIR) sequence and can symbolically be written as:

(sat) - TW_t - π - —n / 2-TE / 2- &amp; - TE / 2 - echo - ΤΕ / 2)_η (5)

The TWi can be fixed or variable but is generally

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an interval of. _ _. INPySTftJA !. -_r short time, which allows only the fast relaxation component to be fully polarized. The first saturation pulse establishes the defined state of the well. After TWi,

MR) M₀(l - expi-m / n »(6a) is the polarized magnitude of the magnetization. The next pulse π reverses this signal M (TWi) to the -z direction, and the

TW_tremaining unpolarized magnetization, M_andand ^Ti _t continues its course of accumulation of polarization. Subsequently, after the payback over time TIj,

M = M_and

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(6b)

With algebraic simplification, equation (6a) can be rewritten as:

(6c)

From this expression it can be seen that if a TW value is large enough than a Ti component value to be quantized, the third term in the bracket can be pulled, and TIs can be modified to estimate this component. Furthermore, TW optimization is possible as described below.

At the end of the CPMG echo train with n number of echoes, the ¹⁵ IMPI ^ iNSTrniTOMexiCANo magnetization is described by sjSwC

ITij r / j + nríi «rs ____ l-2en + en · &lt;(Μ) ~ -— (7) for a single relaxation time component system, where R = Ti / T2 is used instead of explicitly T₂. On the other hand, for a multiple component system, [Ti_F Tfi + TWjj »τε

1-2 «η * + β e (^TiM. (8) The disclosed hybrid pulse sequence retains the time saving advantage of the saturation recovery sequence while increasing the dynamic range and thus the accuracy of the measurement of the fast relaxation components. The amplitude of the echoes in figure 2 is:

E. = Σ, Μ, {(1 - «-” ^ * 0 (1 - 2 «^ · /) + · (1 - .- *«)}, - «« A (9) where Mj is the magnetization equilibrium with a longitudinal relaxation time Tij, and Rj the ratio Ti / T₂ of that component. From equation 9 it can be seen that in the extreme case where TI = 0, this is the same as the saturation recovery case:

AND_n = Σ, Μ, (1 - ₍x ₀)

In another extreme case where TW is several times the

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D £ LA α »ογιε:&gt; αγ, _ industrial component Ti longer (then consuming much more time), equation 9 reduces to:

ü = Σ, Μ, (1 - I- V^Tv ₍! i) the same as for IR. However, if a TW (or several TWs) is chosen that is several times the Ti of the sample fast relaxation components for smaller TI, and a TW of zero for larger TI, the accuracy improvements of the Equation 11 are achieved for fast relaxation components without introducing too much overload time compared to saturation recovery (Equation 10).

The performance of the hybrid pulse sequence is here compared to SR and IR sequences. While the total porosity is straightforward for comparison, quantifying the fidelity of the Ti distribution derived from the inversion of the Ti evolutions of these sequences is more challenging. In the comparison, the Fréchet distance quantifies the similarity between two Ti distributions. More specifically, the Fréchet distance is calculated to compare the true Ti distribution (model) and the inverted Ti distribution of the magnetization evolutions of either the hybrid or SR sequence. As presented here, the Fréchet distance is shorter for Ti distributions derived from the hybrid sequence than those derived from the SR sequence.

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For comparison, random noise is added to the time domain magnetization evolution data so that the noise reaches the typical levels found in either laboratory NMR core plug measurements or log data from open hole, respectively. Also, the systems are modeled with different Ti / T ratios.₂ underlying due to the ability to resolve the relaxation time spectrum and quantify the fast relaxation components depends on the Ti / T ratio₂. In each model, the simulation is repeated at least 100 runs with fresh random noises in the magnetization evolution data, and the conclusion is based on the statistical measurements of the entire data set. From the simulations, the improvements obtained using the hybrid pulse sequence can be observed for both the core and the noise level of log data but are more significant in the high level noise data, indicating that the sequence of in fact it is beneficial to the downhole logging environment. To objectively compare the ability to derive petrophysical information from the two data acquisition methods, the simulation of the evolutions of magnetization in response to the same input models is generated with random noise additive to the comparative level.

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INDUSTRIAL&gt; SC typically found in core plug NMR measurements and NMR log data.

Formation rock models used for comparison are drawn from observing actual NMR log data in: (1) a North American shale gas well with dominant porosity in a short relaxation time range; (2) a heavy oil formation containing heavy oil and moving water; and (3) T distributions₂ of a carbonate reservoir that has micro and macro porosities. To add to the complexity of the model, a variable R = Ti / T ratio is applied₂. The R values ​​are set to be 3 for the shortest relaxation time component and 1 for the longest relaxation time component and progressively decrease from 3 to 1 for the intermediate components. Such a pattern of variation R is especially reasonable for heavy oil and shale gas formations. The values ​​of TWs and TIs in the hybrid sequence are listed in Table 1.

TABLE 1

The TW and TI times used in the hybrid sequence simulation

<td>YOU</td><td> 0</td><td> 0.5</td><td> 1</td><td> 2</td><td> 3</td><td> 4</td><td> 8</td><td> 16</td><td> 40</td><td> 100</td><td> 300</td><td> 500</td><td> 1000</td><td> 3000</td>

<td>TW</td><td> 8</td><td> 8</td><td> 8</td><td> 8</td><td> 8</td><td> 0</td><td> 0</td><td> 0</td><td> 0</td><td> 0</td><td> 0</td><td> 0</td><td> 0</td><td> 0</td>

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For simulations, the inter-echo time of the echo trains following the hybrid sequence and SR is 0.3 ms and the number of echoes is 15. With these parameters, the difference in the total data acquisition time between this hybrid and the SR sequences is less than 1% (approximately equal). Note that the TW value is chosen to be zero for TI values ​​greater than 4 ms, because longer TIs are no longer needed and this saves time as well. For the SR sequence, the TW values ​​are chosen to be the same as the TI values ​​of the hybrid sequence listed in Table 1. Note that the clear IR sequence is not included in the comparison, because it would take too long a time, (the downside is obvious).

The simulation data is inverted in two steps. The first step reverses the echo trains with a multi-T decay model₂ to obtain the apparent porosity vector, φ (ΤΉ4, Τ ^). The second step inverts the vector with a multi-Ti polarization accumulation model. The two-step inversion is illustrated in Figure 3. The two-step inversion is illustrated in Figure 3. The two-step inversion technique eliminates the need to estimate Ti / T₂ unknown in the investment process. The inversion processing algorithm included a regularization term where normal regularization has been used for all data.

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The regularization coefficient is adjusted based on the intensity of the signal and the noise level.

For the quantitative comparison of the investment Ti distributions with the true Ti relaxation time distribution models, the Fréchet distances between the inversion results and the true models are calculated. The Fréchet distance is a measure of similarity between two curves that takes into account the location and ordering of the points along the curves. The shorter the Fréchet distance, the greater the degree of similarity between the investment result and the Ti distribution of the model. In the comparison, the vertical scale of the partial porosity model is normalized to the same as the horizontal log scale (Ti). The investment results are normalized by the same factor. A discrete Fréchet distance computation algorithm can then be used to calculate the distance. This can also be used to compare the log and kernel derived relaxation time distributions. For comparison, the curve misfit is calculated as:

Figures 4A-4C show simulated inversion results using a recovery sequence by ₇₁ IMPIAS

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OF INDUSTRIAL PROPERTY saturation. Similarly, Figures 4D-4F show simulated inversion results using a hybrid recovery sequence. In Figures 4A-4F, the Ti model distributions and the multiple noise performance of the inversion results are displayed for carbonate, heavy oil with moving water, and black shale formations. The total porosity of these simulations is 22 porosity units (pu) for carbonate, 15 pu for heavy oil, and 6 pu for gas shale, respectively. To perform the simulations of Figures 4A-4F, a fixed signal-to-noise ratio (SNR) of 200 is used, in the range for measurements

Convenient laboratory core plug NMR.

In Figures 4A-4F, each model curve is represented as a line with diamonds, and the other lines are the results of the inversion. Using the naked eye, the high SNR data inversion results derived from both the hybrid pulse sequence and SR are seen as quite good. For the heavy oil and shale cases, the hybrid pulse sequence results recover the model distribution patterns more closely, particularly for the short relaxation time ranges. This is consistent with the expectation that the hybrid pulse sequence

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it has better sensitivity for rapidly relaxing components.

The Fréchet distances calculated for the simulations of Figures 4A-4F compare the inversion results derived from these two sequences. The Fréchet distance and mismatch values ​​are shown in Table 2 indicating non-trivial improvements for the hybrid pulse sequence data versus the SR pulse sequence data. The values ​​listed in the table are the means of the values ​​calculated from individual noise realizations.

TABLE 2

Statistical Analysis of Fréchet Distance and Misfit for the cases shown in figures 4A-4F

<td></td><td>Distance Fréchet Half</td><td>STD of Distance Fréchet</td><td>I loosened Means, medium</td><td>STD of I loosened</td>

<td>Carbonate-SR</td><td> 2.75</td><td> 0.23</td><td> 0.2123</td><td> 0.0103</td>

<td>Carbonate-HSIR</td><td> 2.72</td><td> 0.25</td><td> 0.2100</td><td> 0.0107</td>

<td>Petroleum Heavy-SR</td><td> 2.22</td><td> 0.19</td><td> 0.1285</td><td> 0.0080</td>

<td>Petroleum Heavy-HSIR</td><td> 2.13</td><td> 0.20</td><td> 0.1097</td><td> 0.0080</td>

<td>Esguisto-SR</td><td> 1.30</td><td> 0.19</td><td> 0.0325</td><td> 0.0032</td>

<td>Esguisto-HSIR</td><td> 1.11</td><td> 0.01</td><td> 0.0291</td><td> 0.0033</td>

The most significant improvements are seen when the data has higher noise levels. In operations of

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FROM THE PKOmDAT record, the noise level is determined by l ^ TÓ '^ macionT' the borehole environment, configurations5 "CTe" nérramientaand acquisition, and data weighting. In simulations, 0.5 pu of random noise was added to all model data. For the 22 pu, 15 pu, and 6-pu model formations the corresponding SNR is 44, 30, and 12 respectively, and is the typical range of log data locations.

Compared to high SNR simulations shown in Figures 4A-4F, the improvements using the hybrid pulse sequence are more significant for the low SNR simulations in Figures 5A-5F. Statistical, quantitative analysis of the Fréchet distance shows an improvement for all simulations with more significant improvements achieved for heavy oil and shale gas simulations. The less significant improvement for carbonates with small amounts of microporosity is understandable due to the weak signal amplitudes in the short relaxation time range, where the hybrid pulse sequence shows the advantage, it does not contribute significantly to the Fréchet distance nor to the mismatch. . However, for both high SNR and low SNR simulations, the hybrid pulse sequence results consistently still show an advantage. In other words,

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INUUSTF.IAi the consistency of inversion results for hybrid pulse sequence data in the microporosity ranges for varying noise realizations is better than that of SR data in the same region. The Fréchet distance and mismatch calculation values ​​are shown in Table 3 indicating non-trivial improvements for hybrid pulse sequence data versus SR pulse sequence data.

TABLE 3

Statistical Analysis of Fréchet Distance and Misfit for the cases shown in Figures 5A-5F

<td></td><td>Distance Fréchet Half</td><td>STD of Distance ia Fréchet</td><td>Maladjustment Means, medium</td><td>STD of I loosened</td>

<td>Carbonate-SR</td><td> 4.07</td><td> 0.23</td><td> 0.2545</td><td> 0.0105</td>

<td>Carbonate- HSIR</td><td> 4.04</td><td> 0.23</td><td> 0.2508</td><td> 0.0101</td>

<td>Petroleum Heavy-SR</td><td> 5.03</td><td> 0.29</td><td> 0.2127</td><td> 0.0105</td>

<td>Petroleum Heavy-HSIR</td><td> 3.48</td><td> 0.24</td><td> 0.1688</td><td> 0.0106</td>

<td>Shale-SR</td><td> 5.20</td><td> 0.35</td><td> 0.0705</td><td> 0.0056</td>

<td>Schist-HSIR</td><td> 3.76</td><td> 0.41</td><td> 0.0513</td><td> 0.0051</td>

In Figures 5A-5F, each model curve is represented as a line with diamonds, and the other lines are the results of the inversion. Once again, 0.5 pu of

<img file="MX344841B_D0013.tif" />

random noise is added to all model data. For 22 pu, 15 pu, and 6 pu model formations, the corresponding SNR is 44, 30, and 12, respectively, and is in the typical range for log data quality. The hybrid pulse sequence results recover the model distribution patterns more closely, and the improvements over the SR results are more significant for the low SNR (poorer quality) data from Figures 5A-5F than for the data. high SNR of Figures 4A-4F.

Figure 6 compares the investment results Ti and T₂from experimental data collected with different NMR sequences using a water-saturated North American shale plug. An obvious difference between hybrid pulse sequence Ti and SR measurements is that the hybrid pulse sequence provides a highly anticipated Ti component (^ 0.1 ms) and a second peak centered at approximately 1 ms. The SR sequence, meanwhile, only provides a broader peak, albeit with some polarization towards previous components. This polarization becomes more pronounced with a higher number of scans. However, even with four times as many scans, the SR sequence still cannot separate the two peaks. Said separation of peaks should be real, as confirmed by T₂

<img file="MX344841B_D0014.tif" />

and the IR results shown in Figure 6. In shale, the Ti ^ 0.1 ms components should almost certainly arise from organic matter. Therefore, the hybrid pulse sequence, just like the IR sequence, is more sensitive to prior relaxation components and can even distinguish between the signal from organic matter and that from other materials. Conveniently, the hybrid pulse sequence can achieve this sensitivity at a fraction of the time used in IR measurements. For example, to get the result using 512 scans, it will take slightly more than 1.5 hours for the hybrid sequence, but more than 16 hours for the IR sequence if three seconds is used as the timeout.

Figures 7A and 7B show the comparison of the Ti distribution of a North American carbonate plug using ISR hybrid pulse sequences, respectively, with various numbers of scans. The carbonate sample had many bumps, as evidenced by the large peak at more than one second in relaxation times. At the same time, the sample had a certain degree of microporosity and meso-porosity, as indicated by the previous peaks in the Ti distribution pattern. It can be seen that at 128 scans, the hybrid impulse sequence separates the two previous peaks very well, with

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INSTITUTO MEXICANO I heard the ρκόνεοαπ t \ eJBLrí. INDUSTRIAL correct amplitudes. Compared to SR, 384 scans are needed 'to have a good separation. For the hybrid pulse sequence, at a higher number of scans, more features appear for the second peak, while these features are absent in SR results. All these observations suggest that the hybrid pulse sequence is in fact more sensitive to previous components of the Ti distribution and offers better characterization at minimal time cost if these components exist in the sample. Compared to IR, the hybrid pulse sequence has a significant advantage because for IR, each scan needs an additional delay of more than 15 seconds to fully relax the nuclear turns, and each Ti measurement includes 40 timeouts. As an example, the time savings for a 128 scan experiment would be more than 128 * 15 * 40 seconds = 21.3 hours.

From equation (8), it can be recognized that the advantage of using the hybrid pulse sequence over the SR sequence depends on the selection of the TW and TI values, as well as the Ti distribution of the sample under investigation. In some embodiments, simulations can be carried out to determine an optimal TW value. Such simulations can be performed to test models of

<img file="MX344841B_D0015.tif" />

heavy oil and shale gas with different TW values. Subsequently, the corresponding Fréchet distance and curve mismatch values ​​are calculated. Without limitation, the simulation SNR is kept at 20. Figures 8A and 8B show two exemplary simulation results for heavy oil and shale gas, respectively.

For both simulations, the minimum Fréchet distance and mismatch consistently reside at approximately 10 ms. The fact that the optimal TW does not vary significantly from one training scenario to another is useful in implementing the hybrid pulse sequence in a log data acquisition scheme. Because pore sizes and fluid saturations inevitably vary from depth to depth, and the variations are not predictable before logging operations, it is desirable to use one set of parameters to log an entire well.

Figure 9 shows a blogged diagram of an illustrative NMR system 300. The NMR registration system 300 includes a computer 302, which in at least some embodiments directs the operations of the hybrid pulse sequence generator 110. In such embodiments, the computer stores and executes instructions to enable NMR registration with ₂₉ ΪΜΡΙ ^

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based on a hybrid pulse sequence as described herein. Computer 302 is configured to provide commands, programming, and / or data to transmitter 304. Transmitter 304 may include a programmable pulse sequence device or storage, a radio frequency synthesizer (RE), a phase shifter, a pulse gate, an amplifier, and / or other components to control the pulsed magnetic field for pulse operations. NMR recording including the hybrid pulse sequence operations described herein. In different embodiments, the hybrid pulse sequence generator 110 allows adjustment of the hybrid pulse sequence options based on a default configuration, user selection, and / or calibration. For example, the time interval (TW) between the last saturation pulse and the reversal pulse can be selected or updated to increase or decrease the sensitivity to low relaxation components. Furthermore, the number of saturation pulses can be increased or decreased. Furthermore, the detection sequence can be selected or switched between an FID pulse, a Carr-Purcell sequence, a CPMG sequence, or another sequence with different phase cycling schemes. In short, transmitter 304 is configured to output any of the sequence variations of

INSTITUTO MEXICANO DE LA PRORIEPAD INDUSTRIAL hybrid impulses described here.

The NMR 300 logging system also includes NMR 306 spectrometer components used for NMR logging operations. Examples of NMR 306 spectrometer components include one or more magnets, offset coils, probes / antennas, and / or field frequency blocking components. In addition, the NMR 306 spectrometer components may include a duplexer that allows separation between the transmitter stream and the receive stream. The receiver 308 of the NMR recording system 300 is configured to receive and decode NMR signals. Receiver 310 may include an analog-to-digital converter (ADC), filters, mixers, dividers, preamps, and / or other components to receive NMR signals and retrieve measurement data. According to embodiments, receiver 310 is configured to retrieve free induction decay or spin echo data using available receiver window options. The retrieved measurement data is output from receiver 308 to computer 310 for storage and analysis. Thus, the computer 302 can communicate with the transmitter 304 and receiver 308 of the system 300 to allow NMR logging operations in which a hybrid pulse sequence is used to retrieve the gyro echo data and / or signal data. free induction decay.

<img file="MX344841B_D0016.tif" />

Figure 10 shows an illustrative environment while drilling (LWD), which serves as an exemplary use context for the NMR 100 tool or NMR 300 system described herein. A drilling rig 2 supports a tower 4 that has a displacement block 6 for raising and lowering a drillstring 8. A drillstring drag bar 10 supports the remainder of drillstring 8 as it is lowered to through a turntable 12. Turntable 12 rotates drillstring 8, thus rotating a bit 14. As bit 14 rotates, it creates a hole 16 that passes through various formations 18. A pump 20 circulates drilling fluid through feed tube 22 to drawbar 10, downhole through the interior of drillstring 8, through holes in bit 14, back to the surface. through ring 9 around drillstring 8 and into a holding pit 24. Drilling fluid carries cuts from hole 16 into hole 24 and helps maintain the integrity of the hole.

The bit 14 is just one piece of an open hole LWD assembly that includes one or more drill collars and registration tools 28, 32. The collars of

<img file="MX344841B_D0017.tif" />

Drilling 26 are thick, pima aram tubing sections that provide weight and rigidity for the drilling process. Recording tools 28, 32 (some of which can be built into drill collars) collect measurements of various drilling or formation parameters. Any of the registration tools 28, 32 may include an NMR registration tool configured to run and / or be driven by the calibration techniques described herein. Measurements from the recording tools 28, 32 can be acquired by a telemetry subassembly (eg, built in the recording tool 28) to be stored in internal memory and / or communicated to the surface via a communications link. Mud pulsed telemetry is a common technique for providing a communications link to transfer log measurements to a surface receiver 30 and to receive commands from the surface, but other telemetry techniques can also be used.

At various times during the drilling process, drillstring 8 can be withdrawn from hole 16 as shown in Figure 11. Once drillstring 8 has been removed, logging operations can be performed using a drill string. wired registration 34 (i.e., an assembly of hardwired registration tools

INSTITUTO MEXICan. . Dfc THE PROPERTY \ λ r nwrici / M! ..¹ or INDUSTRIAL suspended by a cable 42 that has conductors to carry power to the tools and telemetry from the tools to the surface). It should be noted that various types of formation property sensors can be included with the wired log probe 34. For example, illustrative wired logging probe 34 includes logging tool 32, which may correspond to an NMR logging tool configured to execute or be driven by the hybrid pulse sequence techniques described herein. The registration tool 32 can be coupled to other wired registration probe modules 34 by one or more adapters 33.

A wired logging facility 44 collects measurements from logging tool 32, and includes computing facilities 45 for managing logging operations, acquiring and storing measurements collected by wired logging probe 34, and optionally processing the measurements for deployment to a user. For the logging environments of Figures 10 and 11, the measured parameters can be logged and displayed in the form of a log, that is, a two-dimensional graph showing the measured parameter as a function of position or depth of the tool.

Figure 12 shows a computer system

<img file="MX344841B_D0018.tif" />

Illustrative 43 to manage registry operations. The computer system 43 may correspond, for example, to an on-site registration facility for the drilling rig of Figure 10, the computing facility 45 of the hard-line registration facility 44 of Figure 11, or a system remote computing that manages registry operations. Computer system 43 may include wired wireless communication interfaces to direct log operations and / or receive log measurements. As shown, illustrative computer system 43 includes user workstation 51 with computer chassis 46 coupled to display device 48 and user input device 50. Computer chassis 46 includes one or more information storage devices for accessing software (shown in FIG. 12 in the form of a removable, non-transient information storage medium 52) that configures the computer system to interact with a user, allowing the user to process registration data and, in the case of local registration facilities, manage logging operations including analysis of borehole conditions. The software may also be downloaded software that is accessed through. a network (for example, via the Internet). In

<img file="MX344841B_D0019.tif" />

In some embodiments, the illustrative computer system 43 executes software that performs the hybrid pulse sequence techniques described herein and / or directs the recording operations of an NMR recording tool (e.g., NMR recording tool 100 or 32) using the disclosed hybrid pulse sequence techniques.

In some embodiments, the computer system 43 includes a non-transient computer-readable medium with a hybrid pulse sequence software tool. The software tool, when executed, causes a computer system processor 43 to provide a sequence of hybrid pulses or convenient parameters from which a sequence of hybrid pulses can be generated.

Figure 13 is a flow chart of an illustrative NMR method 702. The NMR method 702 may be performed, for example, by a downhole wired logging tool, a LWD tool, or a laboratory tool. In method 702, a hybrid pulse sequence is provided at block 704. The hybrid pulse sequence can correspond to any of the hybrid pulse sequence variations described herein. The hybrid pulse sequence provided may include, for example, a saturation pulse, a reversal pulse, and

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6 MEXICAN INSTITUTE

DF ΙΑ PROPERTY C · »-INDUSTRIAL a detection sequence. The detection sequence can correspond to a FID sequence, a Carr-Purcell sequence, a CPMG sequence, or another sequence with different phase cycling schemes. In some embodiments, the hybrid pulse sequence includes multiple saturation pulses. At block 706, echo signals are measured in response to the hybrid pulse sequence provided at block 704. At block 708, a Ti distribution is derived from the measured echo signals. The derived Ti distribution can be displayed to a user using a computer. Additionally or alternatively, a property of the formation can be displayed as a function of the tool position based on the derived Ti distribution.

In some embodiments, the NMR 702 method includes additional steps. For example, the NMR 702 method may include selecting a time interval between the saturation pulse and the reversal pulse. Selection criteria can be based on default metrics, user input, or other factors. In some embodiments, the NMR 702 method may include setting a time interval between the saturation pulse and the reversal pulse from a first value to a second value that is different from the first value.

Figure 14 is a flow chart of another NMR method

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INSTITUTO MEXICANO 'Oí THE ILLUSTRATIVE INDUSTRIAL IROIITY 802. Once again, the NMR 802 method can be formed, for example, through a wired downhole logging tool, an LWD tool, or a laboratory tool. In method 802, a measurement region is exposed to a static magnetic field in block 804. In block 806, a sequence of hybrid pulses is repeatedly applied to the measurement region. In at least some embodiments, the hybrid pulse sequence includes, in order: a saturation pulse, a reversal pulse, a 90 ° pulse, and optionally one or more 180 ° pulses to induce echo signals. The measurements, corresponding to the hybrid pulse sequence, are collected in block 808. The collected measurements may correspond to a decay signal

<img file="MX344841B_D0020.tif" />

free induction caused by the 90 ° pulse or to an echo signal caused by one or more 180 ° pulses. A Ti distribution is derived from measurements collected at block 810. Finally, a representation of the Ti distribution is displayed at block 812.

In some embodiments, the 802 NMR method includes additional steps. For example, the NMR 802 method may include a variation of the time interval (TW) between the reversal pulse and the 90 ° pulse between repeated applications of the hybrid pulse sequence. In addition, the NMR 802 method³⁸ IΜ ΡI INSTmrK'MtXíCANu □ ϊ ÚA EftWEiMC can include the separation of the variable TW likewise ?? Ee^WAon a logarithmic scale. The 802 NMR method may include separation, on a logarithmic scale, of the variable TW more narrowly for lower values ​​than for higher values.

Numerous other modifications, equivalents and alternatives will be apparent to those skilled in the art once the foregoing description is fully appreciated. The following claims 10 are intended to be construed to encompass all such modifications, equivalents and alternatives where applicable.

9

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