MX2007007535A - Process of electromagnetic, electric, and seismic micro time-lapse for the direct detection of hydrocarbons, saline intrusions and abnormalities in live tissues. - Google Patents

Abstract

Process of electromagnetic, electric and seismic micro time-lapse consisting in the detection, mapping and quantification of the dissipative linear behaviour in materials, which results from the presence of one or several attenuation mechanisms related to the presence of porosity, permeability, hydrocarbons (oil and gas), saline intrusions and abnormalities in live tissues. The present process is applied to different science fields, including the exploration, development and production of oil wells, the non-destructive evaluation of materials in laboratory or in-situ, as well as the geotecnics and detection of abnormalities in tissues by means of medical imaging processes. The inventive process is characterised in that it uses a dual offset wavefield diffused by the material as a single wavetrain and which phase is in compliance with the creep time of the medium. The process is based on the linear dissipative behaviour of materials. Mechanical waves are known as Pilot and Tracer which have their electromagnetic equivalent. The mechanical or electromagnetic waves may be generated by one or several sources in a synchronous but offset manner. The purpose of the pilot wave is to measure the transitory fluctuation of the physical properties of the material resulting from the tracer wave stimulation. The process may further use a single wavetrain which phase is modified to simulate a dual wavefield.

Description

PROCESS OF SEISMIC, ELECTRICAL AND ELECTROMAGNETIC MICROLAPS FOR DIRECT DETECTION OF HYDROCARBONS, SALIN INTRUSIONS AND ABNORMALITIES IN LIVE TISSUES DESCRIPTION OBJECT OF THE INVENTION Detection, mapping and quantification of the alanstic linear response due to the presence of one or several attenuation mechanisms which are associated, and among other causes, to the saturation of hydrocarbons in porous materials, to porosity, permeability, to intrusions saline in porous materials, abnormalities in living tissues, etc. through the use of seismic, electrical or electromagnetic microlapses.

BACKGROUND This invention relates to the kind of processes used for the non-destructive (remote) characterization of materials with applications in: a) -The exploration, development, production and recovery of hydrocarbons in deposits in the subsoil, b) -The characterization of nuclei, plugs and samples of material in laboratories, c) -The characterization of the shallow geological structure in geotechnics, d) -The detection of abnormalities in living tissues using techniques and processes of medical imaging.

In these processes, a single wave field is typically used to determine the structural (geometric) and petrophysical characteristics of the materials. This field is usually the result of the in-phase summation of multiple wave fields generated by one or several sources to improve the signal-to-noise ratio. The accuracy of the images depends on the resolution of the method used to acquire, process and interpret the information contained in the waves. However, due to the state of the art of technologies and processes, structural images have greater precision than petrophysical ones. To improve the resolution of petrophysical images Khan, T. and McGuire, S., 2001 (United States Patent 6,614,717, filing date 08/30/2001, publication 09/02/2003) propose a new process that uses two wave fields of different frequencies, unlike traditional processes that use only one wave field. The Khan and MgGuire process has applications for the detection of fracturing and the presence of hydrocarbons from rocks in the subsoil. The effectiveness of this process is that the elastic deformations of the materials must be non-linear, which is an atypical mechanical response, especially for the range of measurements observed in the field and laboratory (~ 10"6 m). of non-linearity, a new material characterization process is proposed, which also uses two wave fields, however these are out of phase.The process is based on the alanstic linear response, which is a typical response of the materials in the presence of porosity , permeability, saturation of hydrocarbons and saline intrusions in the subsoil, as well as abnormalities in living tissues.

BRIEF DESCRIPTION OF THE FIGURES. - Figures 1 and 2 present a cross section of some of the applications of the invention for the mechanical case (seismic). They schematically exemplify configurations or source-detector arrangements used in the data acquisition phase, either in the laboratory (Figure 1) or in the field (Figure 2) with a focus on the exploration and production of hydrocarbons. The process is roughly similar to the one used for medical imaging. The wave fronts in figures 1 and 2 correspond to the Pilot wave (No.l) and the Tracer wave (2). These are offset by a range (55) and are added linearly in a modulating wave (3) which is injected into a sample of material (44) with a function generator (7) through a piezoelectric transducer (5). The output wave (33), after being transmitted through the sample of the material, is detected by another piezoelectric transducer and registered in an oscilloscope (8). Figure 2 shows a cross section of a geological model showing different configurations of source-detector arrays with applications to the exploration and exploitation of hydrocarbons. In dashed lines we can observe some possible trajectories of the wave (3) that corresponds to the sum of the wave fronts (1) and (2). The arrangements include: • Surface seismic, either marine or terrestrial, with source (71) and surface detectors (81), although it can also be used in combination with detectors (82 and 83) in wells (9 and 10). • Seismic between wells (X-Well), with source (72) in one well (9) and detectors (83) in the other well (10), although they can also be used in combination with surface detectors (81) and / or in the same well (82). • Well-Logging records with source (73) and receivers in a well (84) in well (10). • Vertical Seismic Profiling (VSP) with source (71) on surface and detectors (82) and / or (81), or with source (72) and detectors (82) in well (9) and / or detectors (83) in another well (10).

The phase of acquisition of data (measurements) in any of the aforementioned arrangements of figures 1 and 2 can be seen synthesized in figures 3, 4 and 5. That same description can be used for medical imaging. First, two waves (1) and (2) separated by a time interval (55) are generated which are propagated through the material (44) as a single wave (3) and are recorded as a filtered signal (33). ). Alternatively, a single signal (3) can be generated whose phase has been modulated to simulate two phase-shifted waves. Subsequently, they are injected separately (1) and (2) through the material to obtain the filtered signals (1 1) and (22). The process of wave decomposition, analysis and quantification of the effects is simplified in Figures 6, 7 and 8. In a simplified way, the spectral decomposition of the wave field (Figure 6) is equivalent to performing the operation between the waves. Wave records: (33) - (1 1) = (222). This last signal may be different from (22) if the material is dissipative. In the next step, you can graph (222) vs. (22) of Figure 7 or alternatively, spectral differences are calculated by obtaining an amount proportional to the differential energy of the two waves (Figure 8). The procedure is described in detail in the next section. In figures 9 and 10 the results of a real example of a laboratory application can be observed using samples of non-dissipative linear material (figure 9) and dissipative material (figure 10).

In figure 11 the spectral differences of the signals 222 and 22 of figure 10 are quantified as a function of the phase shifting between them and the results are also included with other material samples. Figures 12, 13 and 14 show the theoretical results of an effort-deformation test carried out on a viscoelastic material. The two out-of-phase stress loads (s0 and s?) In Figure 12 simulate the pilot (1) and tracer (2) waves. The composite deformation (Figure 13) corresponds to the sum effect of both waves. This is equivalent to the signal (33) of Figures 1 and 3. Figure 14 shows the compliance, which has two non-relaxed modules, and a relaxed module JR.

DETAILED DESCRIPTION OF THE INVENTION The characterization of the physical properties of materials is often carried out through the analysis and interpretation of measurements made in the materials either to preserve their integrity, as for example in medical imaging or in the analysis of samples in the laboratory or because the material to be characterized is inaccessible, as for example in oil exploration where the deposits are located at depth km. The exploration of hydrocarbons is generally carried out indirectly, since instead of detecting, mapping and directly quantifying the presence of oil (gas and oil) in the subsoil, the aim is to determine the most probable structural, lithological and geochemical conditions for your storage. Therefore, the success rate may be low, especially in new areas where there is not enough information yet. On the other hand, seismic methods of direct detection of hydrocarbons have had less success than the first ones due mainly to theoretical and computational limitations. The exploration methods invariably employ a single wave field, which is the result of the in-phase summation of multiple fields generated by one or more sources in a synchronized manner both spatially and temporally. The objective is to improve the signal-to-noise ratio. The process described in the present invention employs two out of phase wave fields to detect, map and quantify the linear dissipative properties of materials which are due to one or multiple attenuation mechanisms, which may be associated with porosity, permeability, viscosity of fluids, presence of saline intrusions, abnormalities in living tissues, etc. The dissipative linear behavior consists in that the magnitude of the deformation induced by a disturbance is dependent on the frequency of each one of the phases of it. For materials with normal dispersion, this means that the magnitude of the properties of the material such as compressibility, rigidity, etc. it increases with time, or decreases with frequency. This behavior is known as creep. The dissipative rheology of materials is also known as anelastic or inelastic. The process generally consists of three phases: acquisition, processing and interpretation of data. The first phase consists of synchronizing the generation phase two waves by a time interval (55) that depends on the times of creep of the material (Figure 1). The first of the waves is called pilot (1) and the second tracer (2). You can also simulate the two phase-shifted waves by means of a single one by modulating their phase. This is called a modulating wave (3). The objective of the wave (2) is to quantify the magnitude of the temporal fluctuations of the physical properties (acoustic, electrical or electromagnetic) of the materials induced by the stimulation (acoustic, electrical or electromagnetic) of the wave (1). When the medium is dissipative, the waves (1) and (2) have different scattering functions and therefore travel with different speeds, resulting in different waveforms. This behavior is equivalent to wave (1) propagating under initial conditions of equilibrium (deformation, velocity, acceleration approximately zero) while wave (2) propagates through a disturbed medium or imbalance caused by the wave ( 1). This type of behavior can also be interpreted as both waves propagate through different means, however their physical properties are the same. The out-of-phase waves can be of the same or different types, either of the body, longitudinal or compressional (known as P), transverse or cut waves with particle movement in the plane of propagation (known as SV) or outside it (known as SH). They can also be surface waves such as Rayleigh and Love or interphase waves such as Stoneley, and in general any variant of body, surface or interface waves due to the presence of dissipation and / or anisotropy.

The spectral bandwidth of these waves depends on the applications and is generally similar to the processes used in the remote and non-destructive characterization of materials. However, the two out-of-phase waves may have the same or different spectral content. When the material is purely elastic and the spectral band of the waves is approximately the same, the propagation velocities of both waves are constant and equal, as well as their waveforms. Therefore, the tracer wave (2) finds the same initial equilibrium conditions as (1) and propagates with its same velocity, resulting in the waveforms being exactly the same. Even if the initial spectral content of the pilot (1) and tracer (2) waves is different, their propagation speeds will be approximately the same and therefore the only spectral differences will be those initially contained in them and not due to the linear response elastic of the material. Therefore, the presence of hydrocarbons in the subsoil is detected when spectral differences of the waves different from those originally contained in them are generated. This type of behavior is shown later in theoretical and experimental studies for the mechanical case. The same type of behavior can be observed for the electrical and electromagnetic case. The processing phase of the process consists of the decoupling of the pilot and tracer waves from the modulating wave train and the quantification of spectral differences generated by the linear inelastic response of the material. In the interpretation phase, it is determined through a process of mathematical inversion of the measurements and based on a physical model, the cause or causes of the differences between the two waves when the medium is dissipated. When there are no differences between the waves, except those introduced initially, it is an indicator that the material is approximately linear elastic. The spatial resolution of the process depends only on the temporal frequency of sampling of the signals, which may be greater than the methods of characterization of traditional materials in which the resolution depends on the frequency of the waves. For the experimental tests real samples of materials were used: Lyon and Berea sandstone sedimentary cores and aluminum and lucite nuclei, the latter a polymer that induces a strong attenuation of acoustic energy at high frequencies. All the experiments were carried out at room temperature, except for a test with Berean sandstone which was heated to 80 ° C. The procedure used can be observed schematically in figure 1. Since the material creep times are unknown, in these experimental tests 20 phase shifts were used, (55) in Figure 1. Figures 9 and 10 show the results of two cases, the first for the aluminum sample (figure 9) whose behavior is elastic and therefore independent of the phase shift. In this case 222 and 22 are practically the same as expected. Figure 10 corresponds to the results obtained with the heated Berea sandstone sample, for a 10 μß design. The differences between 222 and 22 are remarkable and are due to the dissipative behavior of the material. To quantify the effect that results from the difference of the dispersion functions of the waves (1) and (2), the differential energy En, of (222) and (22) is calculated, which corresponds to the sum of the squares of the differences between the two signals as a function of the phase shift. Figure 1 1 shows the calculation of the differential energy for each of the samples for different phase shifts between the pilot and tracer waves. The Em function for the aluminum core (AL in Figure 1 1) shows the expected result. Since the material responds with an elastic mechanical behavior, there is no difference between the waves (1) and (2) for any of the shifts, as seen in Figure 9. This means that the material is instantly recovered from the deformation induced by (1) such that (2) find the same initial equilibrium conditions as (1). Therefore, both waves propagate with the same speed and therefore have the same waveform. For the Lyon sandstone sample (LY in Figure 1 1), the result is also the expected one, since En, is constant, indicating that the mechanical behavior of the material is practically elastic since it is a compact rock of low porosity and permeability , besides that the sample is practically dry and at room temperature. This response will probably be different in the case of saturation with hydrocarbons. It should be noted that the magnitude of Em in this case is greater than for the aluminum sample, as expected, since the medium is porous and saturated with air. For the Berea sandstone sample (BR in Figure 11) at room temperature, the results are also similar to the previous case, since Em is almost constant, although its magnitude is greater. This last effect is clearly correlated with the presence of greater porosity and permeability of the nucleus. A small maximum can be observed at 25 μ8, which could indicate that a relaxation mechanism has caused that (1) and (2) have slightly different spectra for that phase shift. When the sandstone sample is heated (BC in Figure 1 1), noticeable differences between both waves can be observed. This effect is due to the thermomechanical coupling by the compression and expansion of the longitudinal waves, which cause that (1) and (2) have different dispersion functions. Therefore, the aplastic behavior is clearly associated to the thermal differences generated during the propagation of the waves. This example of dry and heated Berean sandstone would simulate approximately a rock saturated with hydrocarbons. In the last example, it is considered a lucite sample (LC in figure 1 1) whose attenuation properties are well documented in the literature. Although the mechanism or mechanisms of dissipation are different from those of a sedimentary porous rock saturated with hydrocarbons, the experimental test would also approximate that mechanical behavior. The result observed in Em is also the expected, since due to the dissipative behavior of the material, the pilot (1) and tracer (2) waves have different dispersive spectra, which causes both to propagate with different speeds and have waveforms. different Therefore, the experimental results observed using real samples of materials confirm the mechanical effects expected by this new process: 1. When the mechanical behavior of the material is dissipative, as in the case of porous rocks saturated with hydrocarbons, the pilot and tracer waves they have different dispersive spectra so they propagate with different speeds and have dissimilar waveforms. 2. When the material is elastic, which can be associated with the absence of hydrocarbons, the waves propagate with exactly the same speed and therefore have the same spectrum.

To better understand the phenomenon on which the process is based, figures 12, 13 and 14 show the theoretical calculation of an effort-strain test to simulate the mechanical behavior of the material in response to the pilot and tracer waves in a regime quasi-static For this case, a viscoelastic model known as SLS-I is considered with a single relaxation mechanism to simulate the dissipative response. The individual efforts s0 and s? (Figure 12) each correspond to a step function. The effort s0 represents the analog of the pilot wave and s? to the tracer. Both have the same magnitude and spectrum but a 0.3 μß interval is out of phase. When the dissipative material, which is in initial conditions of equilibrium (deformation and zero velocity) is applied a load s? (figure 12), this responds to a time to an instantaneous initial deformation and ?, which subsequently tends to increase asymptotically to a maximum value 8ma (figure 13). For this purpose it is known as creep. During this creep period, an additional load s applies? and the material responds instantaneously with a deformation Si which corresponds to the sum of the individual deformations of e < > and e ?. This is calculated using the Boltzman linear superposition principle. The total or composite deformation grows asymptotically at a maximum stot value (Figure 13). The most interesting result is obtained by calculating the compliance J (Figure 14) that is equal to the quotient that results from dividing the resulting deformation between the applied stress as a function of time. Since J is inversely proportional to the compressibility of the medium and the speed of the waves is proportional to the square root of compressibility, the discontinuity in J indicates that at short times (high frequencies) the wave velocities are different since their non-relaxed modules and they are different. At long times (low frequencies), the magnitude of the relaxed module JR of the pilot and tracer waves is equal. Therefore, the discontinuity in J at high frequencies implies that the dispersion function of both stresses must be different, resulting as a consequence that the waveforms are different, as was observed in the ultrasonic experiments described in FIGS. 10. This behavior is equivalent to that if both waves had propagated through slightly different materials. In the case of the application of a single effort, either s0 and s ?, or the simultaneous application of both but in phase, function J would not present any discontinuity and would increase continuously over time (or decrease with frequency) and therefore it would have a single non-relaxed module Jy. For the purely elastic case, which may be associated with the absence of hydrocarbons, the function J is constant with time and the modules of the waves is exactly the same JR = Su. Therefore, the two waves have the same spectrum and propagate with the same speed, so there is no spectral difference between them, as was demonstrated in the case of elastic samples (aluminum and Lyon sandstone). This serves as a diagnostic to determine the presence or absence of oil, or high porosity and permeability, or saline intrusions, or abnormalities in animal tissues.

Claims (10)

I I CLAIMS Having sufficiently described my invention, I consider as a novelty and therefore claim as my exclusive property, what is contained in the following clauses:

1. It is a process of nondestructive and remote characterization of materials that consists in the detection, mapping and quantification of the dissipative linear behavior, also known as inelastic or anelastic, which is associated, among others, with the porosity and permeability, with the viscosity of saturating fluids such as oil and gas hydrocarbons, changes in temperature of materials induced by the propagation of waves, saline intrusions, abnormalities in living tissues and, in general, any attenuation mechanism or group of originating the dissipation of the energy and the consequent decrease -of wave amplitudes and dispersion of the phase velocities and is characterized by the following steps: (a) Selection of the shifts between the pilot waves (1) and the tracer (2) in base to the times of creep of the materials. (b) Reception of the signals by means of sensors that measure the deformations of the material (c) Recording of the signals using sampling methods and digital equipment used in the different applications of said process. (d) Signal processing using algorithms designed to decouple the pilot1 and tracer1 waves from the modulating wave train1. Superscript 1 indicates that the signals have been filtered after propagating through the material. (e) Estimation of the spectral differences of the tracer1 and tracer1 waves using any algorithm developed to calculate parameters proportional to residual residual energy or another parameter that estimates the spectral differences. These are equivalent to those that would result from comparing the pilot1 and tracer1 waves. (f) Estimation of the dispersion functions of the pilot1 and tracer1 waves (g) Estimation of the causes that give rise to the spectral differences between the pilot1 and tracer1 waves.

2. The process, as claimed in clause 1, is characterized by using two out-of-phase wave fields, called pilot and tracer, which are propagated by the material as a single wave train called a modulating wave.

3. The process, as claimed in clause 2, is characterized in that for the case of sources whose waveforms can be electronically controlled, the temporary forms of the pilot and tracer wave, either zero or minimum phase, can be chosen. , to obtain the modulating wave by means of the linear superposition of both.

4. The process, as claimed in clause 3, is characterized in that for the case of sources whose waveforms can not be controlled electronically, the spatial form and areal arrangement can be chosen to synchronize the individual discharge of the pilot waves and tracer by two sources or more.

5. The process, as claimed in clause 2, is characterized because alternatively it is possible to use only the modulating wave, instead of the pilot and tracer waves, and whose phase corresponds to the sum of the phases of both.

6. The process, as claimed in clause 2, is characterized because the pilot wave induces a state of creep in dissipative materials and because the tracer wave quantifies the transitory fluctuations of the physical properties of the materials such as compressibility, rigidity, density, etc. induced by the pilot wave.

7. The process, as claimed in clause 2, is characterized by the fact that the linear aplastic material causes the pilot and tracer waves to develop different dispersion functions than they had initially and as a consequence their spectral properties and waveforms are different.

8. The process, as claimed in clause 6, is characterized because, nevertheless, pilot and tracer waves travel coupled by the same material, this behaves as if they were two different materials.

9. The process, as claimed in clause 8, is characterized by the initial conditions of the subject! they are different for the pilot and tracer waves. For the pilot wave, the initial conditions are approximately equilibrium and for the tracer the initial conditions are of imbalance originated by the pilot wave.

10. The process, as claimed in clause 1, is characterized in that it can use the same or different types of sources, including explosive, implosive, impulsive, etc. eleven . The process, as claimed in clause 2, is characterized in that, in order to decouple the pilot and tracer waves, the pilot and tracer waves can alternatively be injected separately into the material and subsequently the quantification of the spectral differences between the waves is carried out. to determine the causes of the attenuation. 12. The process, as claimed in clause 2, is characterized by a higher spatial resolution than conventional and non-conventional material characterization processes. This is because the resolution of the process is proportional to the temporal frequency of sampling of the signals, while in the others the resolution depends on the spectral content of the waves.