CN111625976A - Model-based perforated casing acoustic wave measurement method and system - Google Patents

Abstract

The invention discloses a method and a system for measuring acoustic waves of a perforated casing based on a model, and relates to a method and a system for measuring acoustic waves of a perforated casing based on a borehole based on a model, wherein the method and the system comprise numerical modeling, acoustic measurement, computer equipment, software instructions, condition data, E1 peak amplitude, normalization factors, operating parameters and a database, wherein the condition data comprise at least one of estimated CBL amplitude and CBL attenuation. In the present invention, the casing may be provided with a cement plug through a plug and play (P & a) operation and a perforation, flushing and cementing (PWC) operation, the method may further include receiving at least one parameter of the casing and an operating parameter related to the casing, the method may further include accumulating cement evaluation results and parameters into a database to minimize an impact on CBL measurement, and based on data stored in the database, it may make better decisions for the next PWC operation to increase a success rate of the operation while also increasing an accuracy of the acoustic response.

Description

Model-based perforated casing acoustic wave measurement method and system

Technical Field

The invention relates to a method and a system for acoustic measurement of a borehole casing based on a model, in particular to a method and a system for acoustic measurement of a perforated casing based on a model.

Background

When a well is no longer profitable to a petroleum company, they may decide to abandon the well temporarily or permanently after plugging it, depending on the economics and conditions of well re-development. Even if oil companies abandon bad wells for a long time after abandonment, they also have catastrophic consequences for well integrity problems due to poor well quality, and a reliable P & a process and its quality control are critical, both for safety and environmental reasons.

Placing cement plugs in the tubing or casing to ensure zonal isolation or no cross flow behind the pipeline is one of the key and challenging processes for P & a operations. The cement plug is placed by grinding the casing (or tubing) prior to injecting cement in the depth interval for zonal isolation. This grinding operation requires a heavy weight of viscous mud to lift the debris (or steel cuttings) and the borehole cement, which may prevent a multidirectional seal. The density of the cutting mud exceeds the density that the grinding section rock can withstand, resulting in rock failure. In addition to the grinding process, there is a process known as perforating, flushing and cementing (PWC) which utilizes a perforating gun to perforate, clean or flush out perforation debris prior to cementing. While this operation does not risk rock damage, there is uncertainty about the condition of the perforated casing, particularly the success of cement extrusion in hydrocarbon isolation.

Sonic cement evaluation techniques such as ultrasonic cement mapping, ultrasonic Cement Bond Logging (CBL), and CBL variable density logging (CBL-VDL) can be used for oil well cement evaluation. Acoustic cement bond logging tools (CBLs) were developed in 1960 to evaluate the casing, borehole bond quality of oil wells. The CBL-VDL technique is described in HDBrown et al, New developments on in-casing-hole sonic sequencing and analysis, SPWLA, eleventh annual well logging seminar (5.5.3 to 6.1970).

However, these cement evaluation techniques are developed for standard steel casing, logging operations may be performed in P & a wells, but a problem arises in interpreting data, ultrasonic cement mapping can provide local (30-150mm) cement quality after casing, but more than half of the casing surface is lost when casing is severely perforated, ultrasonic response is uncertain due to perforation, CBL can be used for cement quality measurement in large-scale (60mm-1000mm) casing extension, and no suitable database is currently available for quantitative evaluation of cement in porous casing, so a model-based perforated casing sonic measurement method and system are urgently needed to solve the problem.

Disclosure of Invention

The invention aims to: the method and the system for the acoustic measurement of the perforated casing based on the model are provided for solving the problems that more than half of the casing surface is lost when the casing is severely perforated, the ultrasonic response has uncertainty due to the existence of perforations, CBL can be used for measuring the cement quality under the large-scale (60mm-1000mm) casing extension mode, and no proper database is available for quantitatively evaluating the cement in the perforated casing at present.

In order to achieve the purpose, the invention adopts the following technical scheme: a model-based perforated casing sonic measurement method and system, comprising numerical modeling, acoustic measurement, computer equipment, software instructions, estimating at least one of CBL amplitude and CBL attenuation, condition data, E1 peak amplitude, normalization factor, operational parameters, and a database;

the numerical modeling may include a finite difference method and a finite element method, and is used to create an interpretation map for acoustic measurements of a perforated casing in a wellbore, and the perforated casing is evaluated based on the interpretation map, and the evaluation may be an evaluation of a gravel pack in the wellbore;

the computer device and software instructions executable on the computer device to create the acoustic measurement interpretation map for perforated casing, make measurements in the wellbore using the numerical model, and evaluate the perforated casing according to the interpretation map;

the condition data is obtained under the conditions of setting free pipes and 100% cementation, and relates to a common casing model and a porous casing model for the numerical simulation;

the E1 peak amplitude is the E1 peak amplitude for testing the waveforms of the normal casing model and the porous casing model with free pipe and 100% cemented;

the normalization factor is applied to the E1 peak amplitude of the waveform of the perforated casing model;

the operational parameter is at least one parameter of the receiving casing and an operational parameter related to the casing;

the database is used to accumulate cement evaluation results and evaluation parameters, and the evaluation parameters either provide an amplitude that identifies perforation parameters in order to minimize the impact on CBL measurements.

As a further description of the above technical solution:

the interpretation may be an interpretation of Cement Bond Log (CBL) measurements on a porous casing, and the evaluation may be a quantitative evaluation of cement on a porous casing.

As a further description of the above technical solution:

the casing may comprise a special perforated casing, a custom-made perforated casing or an equivalent conduit.

As a further description of the above technical solution:

the E1 peak amplitude is used as a casing-borne signal that can be used for cement bond logging, which is typically the first dominant peak in some cases, but other embodiments may use alternatives such as a peak that arrives after the first peak or an envelope of the casing-borne signal, depending on the measurement implementation.

As a further description of the above technical solution:

the casing can set itself with a cement plug via plug and play (P & a) operations and perforation, flushing and cement (PWC) operations.

As a further description of the above technical solution:

the action flow of the system is as follows:

the method comprises the following steps: summarizing the workflow 100 and the relationship between the field application 110 in the wellsite and creating a model-based CBL interpretation map 120, referring to the example flow of fig. 1, the field application 110 requires operation with a special casing (e.g., a casing for P & a-PWC operations) for which cement bond assessment cannot be made due to the lack of cement bond interpretation tables, a numerical model 122 of CBL measurements in such a special casing is disclosed herein including receiving candidate casing or operating parameters 124, then generating a new CBL interpretation map 126 using the numerical model 122, and performing cement assessment 128 on the special casing based on the CBL interpretation map 126, the cement assessment results and field operating parameters and results being accumulated in a database 140, applying parameter assessments 142;

step two: the above-described processes 110, 122, 128, 140 and 142 are iterated through the processes 110, 122, 128, 140 and 142 in step one, in order to better understand the observations, which iterative process allows for improved and accelerated development of the field application 110, (examples one: users such as PWC operations and oil companies want to evaluate PWC parameters to ensure zonal isolation after abandonment of the well; example two: in heavy perforation, i.e. large and wide casing access holes, need to ensure better cementing, but CBL amplitude for heavy perforation for special perforated casing is very different from that of standard casing), by using the model-based CBL interpretation map 120 in the present disclosure, which can interpret cement bonding of porous casing for cement bond quantitative evaluation, after PWC and CBL field operations, both PWC/CBL measurements and model-based interpretation maps and final zonal isolation information can be accumulated into a database, based on the data stored in the database, it can make better decisions for the next PWC operation to improve the success rate of the operation, during which multiple parameter evaluations of different operations 142 can be made as a result, (e.g., in PWC operations there are parameters for perforating, flushing, cleaning and cementing), the numerical CBL model of the present invention can provide CBL amplitude to identify the perforation parameters that have minimal impact on the CBL measurement, in which case the logarithm of the CBL measurement can be used as is without the need to prepare custom interpretation maps for PWC operations, but without the current modeling results, the perforation parameters will affect the ability of the perforations to clear debris (casing, cement and formation) and how to squeeze the cement into the annular space behind the casing;

step three: calculating and applying the model CBL normalization factor 130 to the numerical model 122 of CBL measurements in a particular casing, as can be seen again with reference to fig. 1, the model CBL normalization factor 130 can be calculated based on CBL amplitude modeling of the common casing (free pipe) 132 using common casing (free pipe) parameters 134, and further, the method can include cross-validation 136 between the current numerical CBL modeling and the experiments of CBL measurements;

step one: as can be seen from steps one through three, the above procedure focuses more on CBL measurements for cement evaluation, but depending on the application and the particular casing used, the method can be applied to the ultrasonic measurement "cement evaluation tool — a new method for cement evaluation" described in the document of b.froelich et al, and furthermore it can extend the present numerical model to ultrasound, using detailed model geometries and frequencies appropriate for ultrasonic measurements, to aid in the evaluation of oilfield operations or applications requiring cement evaluation in special or custom casing or equivalent pipelines, including casings for P & a or WPC operations;

step four: quantitative evaluation of cement in porous casing, an example of a schematic configuration of a CBL measurement using a CBL tool 900, an example result being fig. 2A, followed by an example of a CBL signal waveform measured using the CBL tool 900, an example result being fig. 2B, the CBL tool 900 being used to evaluate cement bond between a porous casing 910 and a cemented cement annulus 912 in a borehole 914 formed in a formation 916, the CBL tool 900 having an acoustic transmitter (pressure source) 902 and an acoustic receiver (pressure receiver) 904 and being deployed in the borehole 914 through an armored electrical cable 908, the CBL measurement being based on an acoustic pitch capture technique in which acoustic waves are excited by the acoustic transmitter (pressure source) 902, coupled into the perforated casing 910 in a uniform well fluid, a portion of the waves propagate inside the porous casing 910 towards the acoustic receiver 904, through the cement slurry 912, energy is lost or reduced due to radiation or acoustic wave refraction to the well fluid 914 and the formation 916, the waves refracted to the receiver 904 are recorded in the tool 900 and transmitted as CBL signals using the armored cable 908;

step five: the amplitude of the first dominant casing signal is measured using a CBL tool to obtain the E-1 peak amplitude, as shown in fig. 2B, where the log magnitude of the E-1 peak amplitude is proportional to the Bond Index (BI), which is defined as a fraction of the casing circumference to which cement 912 is bonded, as can be seen with reference to fig. 3, the E1 peak amplitude is linear with the cement annulus bonding, and the E1 peak amplitude and its attenuation can be predicted when determining the casing geometry (casing inside diameter and thickness), the cement acoustic properties (product of acoustic impedance, density and velocity of propagation of longitudinal waves) and referring to the nomogram of the E1 peak amplitude associated with cement bonding, or as shown in fig. 4, where the E1 peak amplitude or the E1 peak amplitude at BI of a free pipe is 0 is obtained from a plot of the CBL free pipe reference amplitude (CBRA), as a function of casing diameter as shown in fig. 5, CBRA was used, which enables to obtain CBL amplitude (MSA: minimum acoustic or 100% bond amplitude) at 100% cement bond or BI ═ 1, CBL free pipe reference amplitude (CBRA) and CBL amplitude at 100% cement bond, which enables to estimate the value of the Bond Index (BI) from any CBL amplitude between CBRA and MSA, as shown in fig. 6, for perforated casing, no free pipe and 100% cement bond amplitude data, CBL free pipe reference amplitude was initially experimental data of one of the CBL tools in the standard casing in the free tubular state, for E-1 peak attenuation at 100% cement bond, for the same reason there is no database available, perforated casing is not within the conventional CBL measurement range;

and (2) a summary II: the CBL measurements used in steps four through five, measured using a casing extension mode, as shown, casing pull pattern in perforated casing as a function of perforation density (number of perforations per unit length, e.g., spf or perforations per foot), fig. 7A and 7B and single casing entry hole diameter, fig. 7A and 7B show a schematic of perforated casing at perforation densities of 18spf and 12spf, respectively, with multiple perforations 700 distributed over a range of 24 inches in depth (Z) and 0-360 degrees from viewing angle (θ) to casing center, the casing being structurally standard due to the perforations, using numerical simulations to construct custom CBL measurement interpretations for various non-standard casings, including perforated casings;

step six: workflow 300 to build an interpretation graph of CBL measurements:

a1 numerical modeling (step 302 in fig. 8):

as an example shown in fig. 9A, 9B, 10A and 10B, detailed model geometries in the radial (R) and depth (Z) directions for three-dimensional numerical simulation are established, and software for numerical modeling can be divided into various types, in CBL modeling of free pipe, as shown in fig. 9A and 10A, the CBL tool 200 is deployed within the casing 210, and the outer region of the casing 210 and the region between the CBL tool 200 and the casing 210 are filled with brine 212, and in CBL, the 100% cemented condition is modeled, as shown in fig. 9B and 10B, the CBL tool 200 is deployed within the casing 210, and the region between the CBL tool 200 and the casing 210 is filled with brine 212, as in the case of free pipe, however, unlike the above-described free pipe, the outer surface of the casing outer surface 210 that is 100% cemented completely to the formation 216 by cement 214, in which process, internal software is used in one or more computer devices, the internal software is capable of installing and performing various stress velocity propagation in finite difference time domain (FT-DT) calculations by executing software, an alternative being commercial finite element programs such as LS-Dyna, Comsol and ANSYS;

a1a common cannula type:

inputting at least one arbitrary field model source in the numerical modeling, which may be an acoustic pressure near the CBL frequency (e.g., 20kHz), similar to the actual CBL tool, the CBL signal and the waveform of the CBL amplitude are simulated in a common casing in both free pipe and 100% cement bond, as shown in fig. 9A and 9B, which outputs a CBL signal recorded at the transmitter (pressure source) -receiver spacing of 3 feet (arbitrary amplitude);

a1b perforated casing:

a three-dimensional numerical model of the perforated casing is established, and model waveforms of a CBL signal and a CBL amplitude in the perforated casing are simulated by taking two states of a free pipe and 100% cement bonding as an example, as shown in FIGS. 10A and 10B, although free tubular state data does not exist in the actual P & A-PWC operation, the free tubular state data is required to be used for CBL amplitude interpretation in the perforated casing;

A2E1 peak detection (step 304 in fig. 8):

detecting the E1 peak amplitude of the model waveforms for the plain casing in step (1-a) above and the perforated casing in step (1-b) above with free pipe and 100% bond;

CBL amplitude model of a3 perforated casing (step 306 in fig. 8):

calculating the normalized factor of model CBL in the above step (1-a), i.e. the ratio of the amplitude of CBRA to the amplitude of the normal free pipe model E-1, and then, in the above step (1-b), applying the normalized factor to the perforated casing model with the free pipe and 100% cement bonded, the normalized values being referred to as CBRA _ P (perforated casing CBRA value) and MSA _ PWC (minimum sound wave amplitude after perforation, flushing and bonding);

new CBL Chart for A4P & A-PWC:

as shown in fig. 11, the normalized CBL amplitude is plotted in the form of a two-dimensional graph (2-D), referring to the Bond Index (BI) of the plain and perforated sleeves, in fig. 11, at BI ═ 0 and 1, CBL amplitude data of the plain sleeves CBRA (BI ═ 0) and MSA (BI ═ 1) are represented as opaque circles 400 and 402, respectively, in fig. 11, CBL amplitude data of the perforated sleeves CBR (BI ═ 0) and MSA (BI ═ 1) in the free tube (CBRA _ P at BI ═ 0) and 100% bond (MSA _ PWC at BI ═ 1) are represented as clear circles 410 and 412 at BI ═ 0 and 1, respectively;

expected CBL amplitude after A5PWC operation:

CBL logs are typically interpreted using cemented light casing amplitude, at one depth, CBL amplitude is obtained at the amplitude shown by circle 420 in fig. 11, the Bond Index (BI) of the common casing before perforation is calculated, assuming BI is Bix, after PWC (perforation, flushing and bonding) operation the expected CBL amplitude at BI BIx is CBL-PWC, as shown by circle 422 in fig. 11, and after successful consolidation the CBL-PWC amplitude is predicted to be MSA-PWC, as shown by circle 412 in fig. 11, based on the model-derived interpretation map in fig. 11, the CBL-PWC amplitude is converted to the expected CBL amplitude at BI BIx, defined herein as CBLa, as shown by circle 420;

a6 explains:

at the depth discussed in the file of the 35 th annual fall meeting in denver SPE, if the CBL tool observes three different CBL amplitudes, satisfying the following conditions (6a) - (6c), respectively, it can interpret the CBLa amplitude after PWC operation compared to the original CBL amplitude before PWC operation (CBLo as defined herein) and using CBL interpretation maps of common bushings (CBRA, MSA), or alternatively, the CBL-PWC amplitude can also be interpreted using CBRA-PWC and MSA-PWC, as described below;

A6aCBLa>CBL

perforating or PWC operations can reduce the bond of the casing to the cement

Or CBLa > MSA^0.8*CBRA^0.2

The perforated casing bonding index is less than 0.8, indicating poor bonding

Or MSA^0.8*CBRA^0.2＞CBLa＞MSA

The cement bonding index of the perforated casing is greater than 0.8, which indicates good bonding;

a7 data comparison, CBL measurement to model expected value:

FIG. 12 shows an example of a log of recorded CBL amplitudes before and after PWC operation, where curves 500 and 502 show the respective CBL amplitudes in a depth interval of 20m before and after PWC, respectively, with the horizontal axis being an amplitude increasing from left to right, and the dashed line 504 representing the predicted CBL-PWC value of the model after perforation, and comparing the predicted value of the dashed line 504 with the measured value of the solid line 502, a depth interval of improved and deteriorated cement adhesion can be found;

a8 applies to P & A's MCI:

the objective of the CBL measurements is to determine zonal isolation, MCI (minimum cement interval is one of the parameters defining the interval of good cementing required for different casing sizes (in: inches), as shown in fig. 13, h.d. brown et al describe MCI in the document "new development of sonography and analysis in cased hole" SPWLA eleventh annual well logging symposium from 3/1970 to 6, good binding is defined by the binding index limit BILI, typically 0.8 with BILI, 0.8 with standard casing, suitable for P & a operations, CBL-PWC interpretation continuously applicable to actual data, and finally find MCI for P & a operations;

a9 data and puncture quality control-slowness and transit time:

as described in the journal of Petroleum engineering (SPE453), the DT or slowness of the CBL casing pattern helps to determine the importance of perforation interval and perforation in CBL measurements, the slowness value of a normal casing is typically between 57.5 and 58.5 μ s/ft, in the model example provided in this document the slowness value of a perforated casing varies between 57.5 and 61 μ s/ft, which may be greater if the casing is perforated to a greater extent, and TT (transmission time) is delayed by 10 μ s with a T-R (transmitter-receiver) interval of 3ft as the slowness increases; where FIG. 14 shows an example of TT (time of flight) and DT (slope of TT) data in a heavily perforated casing, in FIG. 14 the data shown by curve 602 shows a TT versus T-R spacing curve for a heavily perforated casing, referred to as "perf # 1", showing the increase in TT and DT (slope of TT) shown in the upper left corner of the figure (FIG. 14) compared to a standard or lightweight perforated casing of the same diameter as shown by curves 600 and 604, respectively, the increase in slowness and TT values indicating the significance of the perforation effect, i.e., deviation from a plain casing and amplitude;

a10 alternative measurement:

as with CBL measurements in standard casing, attenuation measurements can also be evaluated as a replacement for acoustic cement measurements based on amplitude, and are effective, especially when there is significant uncertainty in fluid and environmental effects, CBL amplitude measurements depend on acoustic pressure excitation and key characteristics (e.g., capacitance, sensitivity, etc.) of sensors such as transmitters (pressure sources) and receivers, which typically have non-negligible sensitivity to the environment, and casing mode attenuation is measured using at least two pairs of transmitters (pressure sources) 202 and two receivers 204 deployed in a borehole compensated configuration (BHC) within casing 210, as shown in fig. 15, as described in the document "cement bond tool" by l.h.gollwizer et al, the SPWLA twenty-third year lumberwork seminar, array acoustic receivers can also be used to derive casing mode attenuation as an E-1 amplitude gradient across the array, attenuation measurements are not affected by fluid properties and environmental influences because they are offset by BHC measurements, as described above in the production operations workshop document SPE21690, held in oklahoma, 4.7.9.1991, casing mode attenuation is sensitive to cement properties, bond index and perforations (density and entrance hole diameter), so it can identify the cement bond status of perforated casing, and is or is superior to amplitude-based CBL measurements, where casing mode attenuation can be calculated by CBL modeling using multiple receivers, e.g., at 3.5ft-4.5ft or 3ft-5ft emitter-receiver (T-R) spacing, attenuation values can be calculated from two CBL amplitudes at known R-R spacing (1 and 2ft, respectively), while figure 16 shows one example of a linear relationship between casing mode Attenuation (ATT) and Bond Index (BI), mode attenuation can be computed separately for two states: the free pipe condition and the 100% cement bonded condition, named ATTfp (free pipe attenuation) and MATT (maximum attenuation), respectively, at one key index (BI), the casing expresses the ATT as a linear relationship, as shown by the ATT ═ 1-BI ATTfp + BI MATT equation, for perforated casing, the numerical simulations in this disclosure provide ATTfp _ PWC and MATT _ PWC, which attenuate the perforated casing in the free pipe and 100% cement bonded conditions, respectively;

use of a11 sonic tool in the evaluation of downhole substandard cement applications:

in addition to standard cement evaluation, there is also the use of sonic logging tools such as CBL tools, for example as described in us patent 4742496, which use sonic measurements to evaluate gravel pack quality, and the present method in the context of the present invention may be applied to applications other than the standard cement evaluation case, based on quantitative analysis or model-based interpretation;

and (3) a summary III: conventional CBL measurements are provided at sonic logging frequencies, typically near 20kHz, and casing extension models can be excited at higher frequencies (e.g., 100kHz or 200kHz), and thus embodiments of the model-based interpretation development method are not limited to conventional CBLs at conventional frequencies, but also include higher frequencies.

In summary, due to the adoption of the technical scheme, the invention has the beneficial effects that:

in the present invention, the casing can be provided with a cement plug by a plug and play (P & a) operation and a perforation, flushing and cement (PWC) operation, the method may further include receiving at least one parameter of the casing and an operating parameter associated with the casing, the method may further include accumulating cement evaluation results and parameters into a database, and evaluating the parameters or providing amplitudes identifying perforation parameters, so as to minimize the impact on CBL measurements, in current methods and systems, the evaluation may be an evaluation of gravel packing in the wellbore, after PWC and CBL field operations, the PWC/CBL measurements and model-based interpretations and final regional isolation information can be accumulated into a database, based on the data stored in the database, the method can make better decision for the next PWC operation, so as to improve the success rate of the operation and improve the accuracy of the acoustic wave reaction.

Drawings

FIG. 1 is a schematic diagram of one example of the relationship between workflow and wellsite field application in a model-based perforated casing sonic measurement method and system of the present invention and the creation of a model-based CBL interpretation map;

FIG. 2A is a schematic diagram depicting an example of CBL measurement using a CBL tool in a model-based perforated casing sonic measurement method and system in accordance with the present invention;

FIG. 2B is a schematic diagram depicting an example of a CBL signal waveform measured using a CBL tool in a model-based perforated casing sonic measurement method and system in accordance with the present invention;

FIG. 3 is a schematic diagram depicting an example of a peak amplitude profile of E1 in a model-based perforated casing sonic measurement method and system in accordance with the present invention;

FIG. 4 is a schematic diagram depicting an example of a cement evaluation interpretation map, referred to as the "M-1" map, in a model-based perforated casing sonic measurement method and system in accordance with the present invention;

FIG. 5 is a schematic diagram showing a free pipe reference amplitude as a function of casing diameter in a model-based perforated casing sonic measurement method and system of the present invention;

FIG. 6 is a schematic diagram depicting an example of a CBL-based interpretation map in a model-based perforated casing sonic measurement method and system in accordance with the present invention;

FIGS. 7A and 7B are schematic diagrams depicting examples of perforated casings based on two different injection densities in a model-based perforated casing sonic measurement method and system in accordance with the present invention;

FIG. 8 is a schematic diagram depicting an example of a workflow for constructing CBL interpretations using numerical modeling in a model-based perforated casing sonic measurement method and system in accordance with the present invention;

FIGS. 9A and 9B are schematic diagrams illustrating an example of detailed model geometry for numerical CBL modeling of a conventional casing in each free pipe and 100% bonded pipe in a model-based perforated casing sonic measurement method and system in accordance with the present invention;

FIGS. 10A and 10B are examples of detailed model geometries for numerical CBL modeling of perforated casing at each free pipe and 100% bond condition in a model-based perforated casing sonic measurement method and system in accordance with the present invention;

FIG. 11 is a schematic diagram of an example of a CBL interpretation map as a function of the perforated casing's Bonding Index (BI) for P & A-PWC based on normalized CBL amplitude in a model-based perforated casing sonic measurement method and system in accordance with the present invention;

FIG. 12 is a schematic diagram depicting an example of the log of CBL amplitudes recorded before and after PWC operation in a model-based perforated casing sonic measurement method and system in accordance with the present invention;

FIG. 13 is a schematic diagram of an example of Minimum Cement Intervals (MCI) depicting different casing sizes in a model-based perforated casing sonic measurement method and system in accordance with the present invention;

fig. 14 is a schematic diagram depicting an example of TT (transit time) and DT (slope of TT) data in a model-based perforated casing sonic measurement method and system in accordance with the present invention;

FIG. 15 is a schematic diagram depicting an example of casing mode attenuation by a CBL tool in a borehole compensation configuration (BHC) in a model-based perforated casing sonic measurement method and system of the present invention;

FIG. 16 is a schematic diagram depicting an example of a linear relationship between casing mode Attenuation (ATT) and Bond Index (BI) in a model-based perforated casing sonic measurement method and system in accordance with the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Referring to fig. 1-16, the present invention provides a technical solution: a model-based perforated casing sonic measurement method and system, comprising numerical modeling, acoustic measurement, computer equipment, software instructions, estimating at least one of CBL amplitude and CBL attenuation, condition data, E1 peak amplitude, normalization factor, operational parameters, and a database;

the numerical modeling involving model-based wellbore casing acoustic measurement methods and systems may include finite difference methods and finite element methods, and the interpretation map for acoustic measurements of perforated casing in the wellbore is created using the method involving model-based wellbore casing acoustic measurement methods and systems numerical modeling, and the perforated casing is evaluated based on the method involving model-based wellbore casing acoustic measurement methods and systems interpretation map, and the method involving model-based wellbore casing acoustic measurement methods and systems evaluation may be an evaluation of gravel packing in the wellbore;

computer means and software instructions executable on the computer means to create acoustic measurement methods and system acoustic measurement interpretations relating to model-based wellbore casing for perforating casing, to take measurements in the wellbore using the acoustic measurement methods and system numerical models relating to model-based wellbore casing, and to evaluate the perforated casing according to the acoustic measurement methods and system interpretations relating to model-based wellbore casing;

the system comprises a model-based acoustic measurement method for borehole casing and a system, wherein condition data are obtained under the conditions of setting free pipe and 100% cementation, and a common casing model and a porous casing model which are used for numerical simulation of the model-based acoustic measurement method for borehole casing and the system;

the method and system relating to model-based borehole casing acoustic measurements the E1 peak amplitude is the E1 peak amplitude for the detection of the common casing model and porous casing model waveforms under free pipe and 100% cemented conditions;

to the E1 peak amplitude of the waveform applied to a perforated casing model by model-based borehole casing acoustic measurement methods and system normalization factors;

to a model-based borehole casing acoustic measurement method and system operating parameters for receiving at least one parameter of the casing and operating parameters related to the casing;

to model-based wellbore casing acoustic measurement methods and system databases for accumulating cement evaluation results and evaluation parameters, and to model-based wellbore casing acoustic measurement methods and systems for evaluating parameters or providing amplitudes identifying perforation parameters in order to minimize the impact on CBL measurements.

In particular, as shown in fig. 1, the interpretation chart relating to the model-based acoustic measurement method and system of the borehole casing may be an interpretation chart relating to the measurement result of Cement Bonded Logging (CBL) of the porous casing, and the evaluation relating to the model-based acoustic measurement method and system of the borehole casing may be a quantitative evaluation relating to cement of the porous casing.

In particular, as shown in FIG. 1, the casing may comprise a special perforated casing, a custom-made perforated casing, or an equivalent conduit.

In particular, as shown in FIG. 1, the E1 peak amplitude is used as a casing-borne signal that may be used for cement bond logging, which in some cases is typically the first dominant peak, but other embodiments may use alternatives such as a peak that arrives after the first peak or an envelope of the casing-borne signal, depending on the measurement implementation.

Specifically, as shown in FIG. 1, the casing may itself be provided with a cement plug via a plug and play (P & A) operation and a perforation, flushing and cementing (PWC) operation.

In particular, as shown in figure 1,

the action flow of the system is as follows:

the method comprises the following steps: summarizing the workflow 100 and the relationship between the field application 110 in the wellsite and creating a model-based CBL interpretation map 120, referring to the example flow of fig. 1, the field application 110 requires operation with a special casing (e.g., a casing for P & a-PWC operations) for which cement bond assessment cannot be made due to the lack of cement bond interpretation tables, a numerical model 122 of CBL measurements in such a special casing is disclosed herein including receiving candidate casing or operating parameters 124, then generating a new CBL interpretation map 126 using the numerical model 122, and performing cement assessment 128 on the special casing based on the CBL interpretation map 126, the cement assessment results and field operating parameters and results being accumulated in a database 140, applying parameter assessments 142;

step two: the above-described processes 110, 122, 128, 140 and 142 are iterated through the processes 110, 122, 128, 140 and 142 in step one, in order to better understand the observations, which iterative process allows for improved and accelerated development of the field application 110, (examples one: users such as PWC operations and oil companies want to evaluate PWC parameters to ensure zonal isolation after abandonment of the well; example two: in heavy perforation, i.e. large and wide casing access holes, need to ensure better cementing, but CBL amplitude for heavy perforation for special perforated casing is very different from that of standard casing), by using the model-based CBL interpretation map 120 in the present disclosure, which can interpret cement bonding of porous casing for cement bond quantitative evaluation, after PWC and CBL field operations, both PWC/CBL measurements and model-based interpretation maps and final zonal isolation information can be accumulated into a database, based on the data stored in the database, it can make better decisions for the next PWC operation to improve the success rate of the operation, during which multiple parameter evaluations of different operations 142 can be made as a result, (e.g., in PWC operations there are parameters for perforating, flushing, cleaning and cementing), the numerical CBL model of the present invention can provide CBL amplitude to identify the perforation parameters that have minimal impact on the CBL measurement, in which case the logarithm of the CBL measurement can be used as is without the need to prepare custom interpretation maps for PWC operations, but without the current modeling results, the perforation parameters will affect the ability of the perforations to clear debris (casing, cement and formation) and how to squeeze the cement into the annular space behind the casing;

step three: calculating and applying the model CBL normalization factor 130 to the numerical model 122 of CBL measurements in a particular casing, as can be seen again with reference to fig. 1, the model CBL normalization factor 130 can be calculated based on CBL amplitude modeling of the common casing (free pipe) 132 using common casing (free pipe) parameters 134, and further, the method can include cross-validation 136 between the current numerical CBL modeling and the experiments of CBL measurements;

step one: as can be seen from steps one through three, the above procedure focuses more on CBL measurements for cement evaluation, but depending on the application and the particular casing used, the present method is applicable to the "cement evaluation tool-a new method for cement evaluation" in the b.froelich et al literature involving model-based borehole casing acoustic measurement methods and systems, and furthermore, it can extend the current numerical model to ultrasound, using detailed model geometries and frequencies appropriate for the ultrasound measurements, to aid in the evaluation of oilfield operations or applications requiring cement evaluation in special or customized casings or equivalent pipelines, including casings for P & a or WPC operations;

step four: quantitative evaluation of cement in porous casing, an example of a schematic configuration of a CBL measurement using a CBL tool 900, an example result being fig. 2A, followed by an example of a CBL signal waveform measured using the CBL tool 900, an example result being fig. 2B, the CBL tool 900 being used to evaluate cement bond between a porous casing 910 and a cemented cement annulus 912 in a borehole 914 formed in a formation 916, the CBL tool 900 having an acoustic transmitter (pressure source) 902 and an acoustic receiver (pressure receiver) 904 and being deployed in the borehole 914 through an armored electrical cable 908, the CBL measurement being based on an acoustic pitch capture technique in which acoustic waves are excited by the acoustic transmitter (pressure source) 902, coupled into the perforated casing 910 in a uniform well fluid, a portion of the waves propagate inside the porous casing 910 towards the acoustic receiver 904, through the cement slurry 912, energy is lost or reduced due to radiation or acoustic wave refraction to the well fluid 914 and the formation 916, the waves refracted to the receiver 904 are recorded in the tool 900 and transmitted as CBL signals using the armored cable 908;

step five: the amplitude of the first dominant casing signal was measured using a CBL tool to obtain the E-1 peak amplitude, as shown in figure 2B, where the log magnitude of the E-1 peak amplitude is proportional to the bond index (B I), the Bond Index (BI) being defined as the fraction of the casing circumference to which the cement 912 is bonded, as can be seen with reference to figure 3, the E1 peak amplitude is linear with the cement annulus bond, and the E1 peak amplitude and its attenuation can be predicted when determining the casing geometry (casing inside diameter and thickness), the cement acoustic properties (product of acoustic impedance, density and velocity of propagation of longitudinal waves) and referring to the nomogram of the E1 peak amplitude associated with the cement bond, or as shown in figure 4, where the E1 peak amplitude or the E1 peak amplitude at BI ═ 0 for the free pipe is obtained from the CBL free pipe reference amplitude (CBRA) plot, as a function of casing diameter as shown in fig. 5, CBRA was used, which enables to obtain CBL amplitude (MSA: minimum acoustic or 100% bond amplitude) at 100% cement bond or BI ═ 1, CBL free pipe reference amplitude (CBRA) and CBL amplitude at 100% cement bond, which enables to estimate the value of the Bond Index (BI) from any CBL amplitude between CBRA and MSA, as shown in fig. 6, for perforated casing, no free pipe and 100% cement bond amplitude data, CBL free pipe reference amplitude was initially experimental data of one of the CBL tools in the standard casing in the free tubular state, for E-1 peak attenuation at 100% cement bond, for the same reason there is no database available, perforated casing is not within the conventional CBL measurement range;

and (2) a summary II: the CBL measurements used in steps four through five, measured using a casing extension mode, as shown, casing pull pattern in perforated casing as a function of perforation density (number of perforations per unit length, e.g., spf or perforations per foot), fig. 7A and 7B and single casing entry hole diameter, fig. 7A and 7B show a schematic of perforated casing at perforation densities of 18spf and 12spf, respectively, with multiple perforations 700 distributed over a range of 24 inches in depth (Z) and 0-360 degrees from viewing angle (θ) to casing center, the casing being structurally standard due to the perforations, using numerical simulations to construct custom CBL measurement interpretations for various non-standard casings, including perforated casings;

step six: workflow 300 to build an interpretation graph of CBL measurements:

a1 numerical modeling (step 302 in fig. 8):

as an example shown in fig. 9A, 9B, 10A and 10B, detailed model geometries in the radial (R) and depth (Z) directions for three-dimensional numerical simulation are established, and software for numerical modeling can be divided into various types, in CBL modeling of free pipe, as shown in fig. 9A and 10A, the CBL tool 200 is deployed within the casing 210, and the outer region of the casing 210 and the region between the CBL tool 200 and the casing 210 are filled with brine 212, and in CBL, the 100% cemented condition is modeled, as shown in fig. 9B and 10B, the CBL tool 200 is deployed within the casing 210, and the region between the CBL tool 200 and the casing 210 is filled with brine 212, as in the case of free pipe, however, unlike the above-described free pipe, the outer surface of the casing outer surface 210 that is 100% cemented completely to the formation 216 by cement 214, in which process, internal software is used in one or more computer devices, the internal software is capable of installing and performing various stress velocity propagation in finite difference time domain (FT-DT) calculations by executing software, an alternative being commercial finite element programs such as LS-Dyna, Comsol and ANSYS;

a1a common cannula type:

inputting at least one arbitrary field model source in the numerical modeling, which may be an acoustic pressure near the CBL frequency (e.g., 20kHz), similar to the actual CBL tool, the CBL signal and the waveform of the CBL amplitude are simulated in a common casing in both free pipe and 100% cement bond, as shown in fig. 9A and 9B, which outputs a CBL signal recorded at the transmitter (pressure source) -receiver spacing of 3 feet (arbitrary amplitude);

a1b perforated casing:

a three-dimensional numerical model of the perforated casing is established, and model waveforms of a CBL signal and a CBL amplitude in the perforated casing are simulated by taking two states of a free pipe and 100% cement bonding as an example, as shown in FIGS. 10A and 10B, although free tubular state data does not exist in the actual P & A-PWC operation, the free tubular state data is required to be used for CBL amplitude interpretation in the perforated casing;

A2E1 peak detection (step 304 in fig. 8):

detecting the E1 peak amplitude of the model waveforms for the plain casing in step (1-a) above and the perforated casing in step (1-b) above with free pipe and 100% bond;

CBL amplitude model of a3 perforated casing (step 306 in fig. 8):

calculating the normalized factor of model CBL in the above step (1-a), i.e. the ratio of the amplitude of CBRA to the amplitude of the normal free pipe model E-1, and then, in the above step (1-b), applying the normalized factor to the perforated casing model with the free pipe and 100% cement bonded, the normalized values being referred to as CBRA _ P (perforated casing CBRA value) and MSA _ PWC (minimum sound wave amplitude after perforation, flushing and bonding);

new CBL Chart for A4P & A-PWC:

as shown in fig. 11, the normalized CBL amplitude is plotted in the form of a two-dimensional graph (2-D), referring to the Bond Index (BI) of the plain and perforated sleeves, in fig. 11, at BI ═ 0 and 1, CBL amplitude data of the plain sleeves CBRA (BI ═ 0) and MSA (BI ═ 1) are represented as opaque circles 400 and 402, respectively, in fig. 11, CBL amplitude data of the perforated sleeves CBR (BI ═ 0) and MSA (BI ═ 1) in the free tube (CBRA _ P at BI ═ 0) and 100% bond (MSA _ PWC at BI ═ 1) are represented as clear circles 410 and 412 at BI ═ 0 and 1, respectively;

expected CBL amplitude after A5PWC operation:

CBL logs are typically interpreted using cemented light casing amplitude, at one depth, CBL amplitude is obtained at the amplitude shown by circle 420 in fig. 11, the Bond Index (BI) of the common casing before perforation is calculated, assuming BI is Bix, after PWC (perforation, flushing and bonding) operation the expected CBL amplitude at BI BIx is CBL-PWC, as shown by circle 422 in fig. 11, and after successful consolidation the CBL-PWC amplitude is predicted to be MSA-PWC, as shown by circle 412 in fig. 11, based on the model-derived interpretation map in fig. 11, the CBL-PWC amplitude is converted to the expected CBL amplitude at BI BIx, defined herein as CBLa, as shown by circle 420;

a6 explains:

at the depth discussed in the file of the 35 th annual fall meeting of denver SPE, if the CBL tool observes three different CBL amplitudes, respectively satisfying the following conditions (6a) - (6c), it can interpret the CBLa amplitude after PWC operation compared to the original CBL amplitude before PWC operation (CBLo as defined herein) and using CBL interpretation maps of common casing (CBRA, MSA), or alternatively, the CBL-PWC amplitude can also be interpreted using CBRA-PWC and MSA-PWC, as described below in relation to model-based borehole casing acoustic measurement methods and systems;

A6aCBLa>CBL

perforating or PWC operations can reduce the bond of the casing to the cement

Or CBLa > MSA^0.8*CBRA^0.2

The perforated casing bonding index is less than 0.8, indicating poor bonding

Or MSA^0.8*CBRA^0.2＞CBLa＞MSA

The cement bonding index of the perforated casing is greater than 0.8, which indicates good bonding;

a7 data comparison, CBL measurement to model expected value:

FIG. 12 shows an example of a log of recorded CBL amplitudes before and after PWC operation, where curves 500 and 502 show the respective CBL amplitudes in a depth interval of 20m before and after PWC, respectively, with the horizontal axis being an amplitude increasing from left to right, and the dashed line 504 representing the predicted CBL-PWC value of the model after perforation, and comparing the predicted value of the dashed line 504 with the measured value of the solid line 502, a depth interval of improved and deteriorated cement adhesion can be found;

a8 applies to P & A's MCI:

the objective of the CBL measurements is to determine zonal isolation, MCI (minimum cement interval is one of the parameters defining the interval of good cementing required for different casing sizes (in: inches), as shown in fig. 13, h.d. brown et al describe MCI in the document "new development of sonography and analysis in cased hole" SPWLA eleventh annual well logging symposium from 3/1970 to 6, good binding is defined by the binding index limit BILI, typically 0.8 with BILI, 0.8 with standard casing, suitable for P & a operations, CBL-PWC interpretation continuously applicable to actual data, and finally find MCI for P & a operations;

a9 data and puncture quality control-slowness and transit time:

as the Petroleum engineering journal (SPE453) relates to model-based borehole casing acoustic measurement methods and systems, the DT or slowness of the CBL casing modes helps determine the importance of perforation intervals and perforations in CBL measurements, the slowness values of conventional casings are typically between 57.5 and 58.5 μ s/ft, in the model examples provided in this document the slowness values of perforated casings vary between 57.5 and 61 μ s/ft, which may be greater if the casing is perforated to a greater extent, with TT (transmission time) also being delayed by 10 μ s with a T-R (transmitter-receiver) interval of 3ft as the slowness increases; where FIG. 14 shows an example of TT (time of flight) and DT (slope of TT) data in a heavily perforated casing, in FIG. 14 the data shown by curve 602 shows a TT versus T-R spacing curve for a heavily perforated casing, referred to as "perf # 1", showing the increase in TT and DT (slope of TT) shown in the upper left corner of the figure (FIG. 14) compared to a standard or lightweight perforated casing of the same diameter as shown by curves 600 and 604, respectively, the increase in slowness and TT values indicating the significance of the perforation effect, i.e., deviation from a plain casing and amplitude;

a10 alternative measurement:

as with CBL measurements in standard casing, attenuation measurements can also be evaluated as an alternative to acoustic cement measurements based on amplitude, and are effective, especially when there is significant uncertainty in fluid and environmental effects, CBL amplitude measurements depend on acoustic pressure excitation and key characteristics of sensors such as transmitters (pressure sources) and receivers (e.g., capacitance, sensitivity, etc.) that typically have non-negligible sensitivity to the environment, and CBL based on discrimination or attenuation measures casing mode attenuation using at least two pairs of transmitters (pressure sources) 202 and two receivers 204 deployed in a borehole compensated configuration (BHC) within casing 210, as shown in fig. 15, e.g., the document "cement bond tool" by l.h.gollwizer et al relates to model-based borehole casing acoustic measurement methods and systems, SPWLA, the twenty-third year lumberjack seminar, array acoustic receivers can also be used to derive casing mode attenuation as an E-1 amplitude gradient across the array, attenuation measurements are not affected by fluid properties and environmental influences because they are offset by BHC measurements, as described above in relation to model-based borehole casing acoustic measurement methods and systems, and in relation to model-based borehole casing acoustic measurement methods and systems in the production operations workshop document SPE21690, held back in oklahoma, from 7.4.1991 to 9, casing mode attenuation is sensitive to cement properties, bond index and perforations (density and entrance hole diameter), so it is able to identify the cement bond status of the borehole casing, and or better than amplitude-based CBL measurements, where casing mode attenuation can be calculated by CBL modeling using multiple receivers, for example, at 3.5ft-4.5ft or 3ft-5ft transmitter-receiver (T-R) spacings, according to two CBL amplitudes at known R-R spacings (1 and 2ft, respectively), attenuation values can be calculated while fig. 16 shows an example of a linear relationship between casing mode Attenuation (ATT) and the Bond Index (BI), which can be calculated separately for two states: the free pipe condition and the 100% cement bonded condition, named ATTfp (free pipe attenuation) and MATT (maximum attenuation), respectively, at one key index (BI), the casing expresses the ATT as a linear relationship, as shown by the ATT ═ 1-BI ATTfp + BI MATT equation, for perforated casing, the numerical simulations in this disclosure provide ATTfp _ PWC and MATT _ PWC, which attenuate the perforated casing in the free pipe and 100% cement bonded conditions, respectively;

use of a11 sonic tool in the evaluation of downhole substandard cement applications:

in addition to standard cement evaluation, there is also the use of sonic logging tools such as CBL tools, for example in us 4742496 relating to model-based borehole casing acoustic measurement methods and systems, sonic logging tools using sonic measurements to evaluate gravel pack quality, and the present method in the context of the present invention may be applied to applications other than the standard cement evaluation case, based on quantitative analysis or model-based interpretation;

and (3) a summary III: conventional CBL measurements are provided at sonic logging frequencies, typically near 20kHz, and casing extension models can be excited at higher frequencies (e.g., 100kHz or 200kHz), and thus embodiments of the model-based interpretation development method are not limited to conventional CBLs at conventional frequencies, but also include higher frequencies.

The above-mentioned method and system for acoustic measurement of a borehole casing based on a model are only preferred embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can substitute or change the technical solution and the inventive concept of the present invention within the technical scope of the present invention.

Claims (6)

1. A method and a system for measuring the sound wave of a perforated casing based on a model are characterized in that: including numerical modeling, acoustic measurements, computer equipment, software instructions, estimating at least one of CBL amplitude and CBL attenuation, condition data, E1 peak amplitude, normalization factor, operating parameters, and a database;

the numerical modeling may include a finite difference method and a finite element method, and is used to create an interpretation map for acoustic measurements of a perforated casing in a wellbore, and the perforated casing is evaluated based on the interpretation map, and the evaluation may be an evaluation of a gravel pack in the wellbore;

the computer device and software instructions executable on the computer device to create the acoustic measurement interpretation map for perforated casing, make measurements in the wellbore using the numerical model, and evaluate the perforated casing according to the interpretation map;

the condition data is obtained under the conditions of setting free pipes and 100% cementation, and relates to a common casing model and a porous casing model for the numerical simulation;

the E1 peak amplitude is the E1 peak amplitude for testing the waveforms of the normal casing model and the porous casing model with free pipe and 100% cemented;

the normalization factor is applied to the E1 peak amplitude of the waveform of the perforated casing model;

the operational parameter is at least one parameter of the receiving casing and an operational parameter related to the casing;

the database is used to accumulate cement evaluation results and evaluation parameters, and the evaluation parameters either provide an amplitude that identifies perforation parameters in order to minimize the impact on CBL measurements.

2. The model-based perforated casing sonic measurement method and system of claim 1 wherein the interpretation map may be an interpretation map of Cement Bond Log (CBL) measurements on porous casing and the evaluation may be a quantitative evaluation of cement on porous casing.

3. The model-based perforated casing sonic measurement method and system of claim 1 wherein the casing may comprise a special perforated casing, a custom perforated casing, or an equivalent conduit.

4. The model-based perforated casing sonic measurement method and system of claim 1 in which the E1 peak amplitude is used as a casing-borne signal that can be used for cement bond logging, in some cases this is usually the first dominant peak, but other embodiments may use alternatives such as a peak that arrives after the first peak or an envelope of the casing-borne signal, depending on the measurement implementation.

5. The model-based perforated casing sonic measurement method and system of claim 1 wherein the casing can set itself with a cement plug via plug and play (P & a) and perforation, washout and cement (PWC) operations.

6. The method and system of claim 1 wherein the system is configured to perform the following steps:

the method comprises the following steps: summarizing the workflow 100 and the relationship between the field application 110 in the wellsite and creating a model-based CBL interpretation map 120, referring to the example flow of fig. 1, the field application 110 requires operation with a special casing (e.g., a casing for P & a-PWC operations) for which cement bond assessment cannot be made due to the lack of cement bond interpretation tables, a numerical model 122 of CBL measurements in such a special casing is disclosed herein including receiving candidate casing or operating parameters 124, then generating a new CBL interpretation map 126 using the numerical model 122, and performing cement assessment 128 on the special casing based on the CBL interpretation map 126, the cement assessment results and field operating parameters and results being accumulated in a database 140, applying parameter assessments 142;

step two: the above-described processes 110, 122, 128, 140 and 142 are iterated through the processes 110, 122, 128, 140 and 142 in step one, in order to better understand the observations, which iterative process allows for improved and accelerated development of the field application 110, (examples one: users such as PWC operations and oil companies want to evaluate PWC parameters to ensure zonal isolation after abandonment of the well; example two: in heavy perforation, i.e. large and wide casing access holes, need to ensure better cementing, but CBL amplitude for heavy perforation for special perforated casing is very different from that of standard casing), by using the model-based CBL interpretation map 120 in the present disclosure, which can interpret cement bonding of porous casing for cement bond quantitative evaluation, after PWC and CBL field operations, both PWC/CBL measurements and model-based interpretation maps and final zonal isolation information can be accumulated into a database, based on the data stored in the database, it can make better decisions for the next PWC operation to improve the success rate of the operation, during which multiple parameter evaluations of different operations 142 can be made as a result, (e.g., in PWC operations there are parameters for perforating, flushing, cleaning and cementing), the numerical CBL model of the present invention can provide CBL amplitude to identify the perforation parameters that have minimal impact on the CBL measurement, in which case the logarithm of the CBL measurement can be used as is without the need to prepare custom interpretation maps for PWC operations, but without the current modeling results, the perforation parameters will affect the ability of the perforations to clear debris (casing, cement and formation) and how to squeeze the cement into the annular space behind the casing;

step three: calculating and applying the model CBL normalization factor 130 to the numerical model 122 of CBL measurements in a particular casing, as can be seen again with reference to fig. 1, the model CBL normalization factor 130 can be calculated based on CBL amplitude modeling of the common casing (free pipe) 132 using common casing (free pipe) parameters 134, and further, the method can include cross-validation 136 between the current numerical CBL modeling and the experiments of CBL measurements;

step one: as can be seen from steps one through three, the above procedure focuses more on CBL measurements for cement evaluation, but depending on the application and the particular casing used, the method can be applied to the ultrasonic measurement "cement evaluation tool — a new method for cement evaluation" described in the document of b.froelich et al, and furthermore it can extend the present numerical model to ultrasound, using detailed model geometries and frequencies appropriate for ultrasonic measurements, to aid in the evaluation of oilfield operations or applications requiring cement evaluation in special or custom casing or equivalent pipelines, including casings for P & a or WPC operations;

step four: quantitative evaluation of cement in porous casing, an example of a schematic configuration of a CBL measurement using a CBL tool 900, an example result being fig. 2A, followed by an example of a CBL signal waveform measured using the CBL tool 900, an example result being fig. 2B, the CBL tool 900 being used to evaluate cement bond between a porous casing 910 and a cemented cement annulus 912 in a borehole 914 formed in a formation 916, the CBL tool 900 having an acoustic transmitter (pressure source) 902 and an acoustic receiver (pressure receiver) 904 and being deployed in the borehole 914 through an armored electrical cable 908, the CBL measurement being based on an acoustic pitch capture technique in which acoustic waves are excited by the acoustic transmitter (pressure source) 902, coupled into the perforated casing 910 in a uniform well fluid, a portion of the waves propagate inside the porous casing 910 towards the acoustic receiver 904, through the cement slurry 912, energy is lost or reduced due to radiation or acoustic wave refraction to the well fluid 914 and the formation 916, the waves refracted to the receiver 904 are recorded in the tool 900 and transmitted as CBL signals using the armored cable 908;

step five: the amplitude of the first dominant casing signal is measured using a CBL tool to obtain the E-1 peak amplitude, as shown in fig. 2B, where the log magnitude of the E-1 peak amplitude is proportional to the Bond Index (BI), which is defined as a fraction of the casing circumference to which cement 912 is bonded, as can be seen with reference to fig. 3, the E1 peak amplitude is linear with the cement annulus bonding, and the E1 peak amplitude and its attenuation can be predicted when determining the casing geometry (casing inside diameter and thickness), the cement acoustic properties (product of acoustic impedance, density and velocity of propagation of longitudinal waves) and referring to the nomogram of the E1 peak amplitude associated with cement bonding, or as shown in fig. 4, where the E1 peak amplitude or the E1 peak amplitude at BI of a free pipe is 0 is obtained from a plot of the CBL free pipe reference amplitude (CBRA), as a function of casing diameter as shown in fig. 5, CBRA was used, which enables to obtain CBL amplitude (MSA: minimum acoustic or 100% bond amplitude) at 100% cement bond or BI ═ 1, CBL free pipe reference amplitude (CBRA) and CBL amplitude at 100% cement bond, which enables to estimate the value of the Bond Index (BI) from any CBL amplitude between CBRA and MSA, as shown in fig. 6, for perforated casing, no free pipe and 100% cement bond amplitude data, CBL free pipe reference amplitude was initially experimental data of one of the CBL tools in the standard casing in the free tubular state, for E-1 peak attenuation at 100% cement bond, for the same reason there is no database available, perforated casing is not within the conventional CBL measurement range;

and (2) a summary II: the CBL measurements used in steps four through five, measured using a casing extension mode, as shown, casing pull pattern in perforated casing as a function of perforation density (number of perforations per unit length, e.g., spf or perforations per foot), fig. 7A and 7B and single casing entry hole diameter, fig. 7A and 7B show a schematic of perforated casing at perforation densities of 18spf and 12spf, respectively, with multiple perforations 700 distributed over a range of 24 inches in depth (Z) and 0-360 degrees from viewing angle (θ) to casing center, the casing being structurally standard due to the perforations, using numerical simulations to construct custom CBL measurement interpretations for various non-standard casings, including perforated casings;

step six: workflow 300 to build an interpretation graph of CBL measurements:

a1 numerical modeling (step 302 in fig. 8):

as an example shown in fig. 9A, 9B, 10A and 10B, detailed model geometries in the radial (R) and depth (Z) directions for three-dimensional numerical simulation are established, and software for numerical modeling can be divided into various types, in CBL modeling of free pipe, as shown in fig. 9A and 10A, the CBL tool 200 is deployed within the casing 210, and the outer region of the casing 210 and the region between the CBL tool 200 and the casing 210 are filled with brine 212, and in CBL, the 100% cemented condition is modeled, as shown in fig. 9B and 10B, the CBL tool 200 is deployed within the casing 210, and the region between the CBL tool 200 and the casing 210 is filled with brine 212, as in the case of free pipe, however, unlike the above-described free pipe, the outer surface of the casing outer surface 210 that is 100% cemented completely to the formation 216 by cement 214, in which process, internal software is used in one or more computer devices, the internal software is capable of installing and performing various stress velocity propagation in finite difference time domain (FT-DT) calculations by executing software, an alternative being commercial finite element programs such as LS-Dyna, Comsol and ANSYS;

a1a common cannula type:

inputting at least one arbitrary field model source in the numerical modeling, which may be an acoustic pressure near the CBL frequency (e.g., 20kHz), similar to the actual CBL tool, the CBL signal and the waveform of the CBL amplitude are simulated in a common casing in both free pipe and 100% cement bond, as shown in fig. 9A and 9B, which outputs a CBL signal recorded at the transmitter (pressure source) -receiver spacing of 3 feet (arbitrary amplitude);

a1b perforated casing:

a three-dimensional numerical model of the perforated casing is established, and model waveforms of a CBL signal and a CBL amplitude in the perforated casing are simulated by taking two states of a free pipe and 100% cement bonding as an example, as shown in FIGS. 10A and 10B, although free tubular state data does not exist in the actual P & A-PWC operation, the free tubular state data is required to be used for CBL amplitude interpretation in the perforated casing;

A2E1 peak detection (step 304 in fig. 8):

detecting the E1 peak amplitude of the model waveforms for the plain casing in step (1-a) above and the perforated casing in step (1-b) above with free pipe and 100% bond;

CBL amplitude model of a3 perforated casing (step 306 in fig. 8):

calculating the normalized factor of model CBL in the above step (1-a), i.e. the ratio of the amplitude of CBRA to the amplitude of the normal free pipe model E-1, and then, in the above step (1-b), applying the normalized factor to the perforated casing model with the free pipe and 100% cement bonded, the normalized values being referred to as CBRA _ P (perforated casing CBRA value) and MSA _ PWC (minimum sound wave amplitude after perforation, flushing and bonding);

new CBL Chart for A4P & A-PWC:

as shown in fig. 11, the normalized CBL amplitude is plotted in the form of a two-dimensional graph (2-D), referring to the Bond Index (BI) of the plain and perforated sleeves, in fig. 11, at BI ═ 0 and 1, CBL amplitude data of the plain sleeves CBRA (BI ═ 0) and MSA (BI ═ 1) are represented as opaque circles 400 and 402, respectively, in fig. 11, CBL amplitude data of the perforated sleeves CBR (BI ═ 0) and MSA (BI ═ 1) in the free tube (CBRA _ P at BI ═ 0) and 100% bond (MSA _ PWC at BI ═ 1) are represented as clear circles 410 and 412 at BI ═ 0 and 1, respectively;

expected CBL amplitude after A5PWC operation:

CBL logs are typically interpreted using cemented light casing amplitude, at one depth, CBL amplitude is obtained at the amplitude shown by circle 420 in fig. 11, the Bond Index (BI) of the common casing before perforation is calculated, assuming BI is Bix, after PWC (perforation, flushing and bonding) operation the expected CBL amplitude at BI BIx is CBL-PWC, as shown by circle 422 in fig. 11, and after successful consolidation the CBL-PWC amplitude is predicted to be MSA-PWC, as shown by circle 412 in fig. 11, based on the model-derived interpretation map in fig. 11, the CBL-PWC amplitude is converted to the expected CBL amplitude at BI BIx, defined herein as CBLa, as shown by circle 420;

a6 explains:

at the depth discussed in the file of the 35 th annual fall meeting in denver SPE, if the CBL tool observes three different CBL amplitudes, satisfying the following conditions (6a) - (6c), respectively, it can interpret the CBLa amplitude after PWC operation compared to the original CBL amplitude before PWC operation (CBLo as defined herein) and using CBL interpretation maps of common bushings (CBRA, MSA), or alternatively, the CBL-PWC amplitude can also be interpreted using CBRA-PWC and MSA-PWC, as described below;

A6aCBLa>CBL

perforating or PWC operations can reduce the bond of the casing to the cement

A6b

Or CBLa > MSA^0.8*CBRA^0.2

The perforated casing bonding index is less than 0.8, indicating poor bonding

A6c

Or MSA^0.8*CBRA^0.2＞CBLa＞MSA

The cement bonding index of the perforated casing is greater than 0.8, which indicates good bonding;

a7 data comparison, CBL measurement to model expected value:

FIG. 12 shows an example of a log of recorded CBL amplitudes before and after PWC operation, where curves 500 and 502 show the respective CBL amplitudes in a depth interval of 20m before and after PWC, respectively, with the horizontal axis being an amplitude increasing from left to right, and the dashed line 504 representing the predicted CBL-PWC value of the model after perforation, and comparing the predicted value of the dashed line 504 with the measured value of the solid line 502, a depth interval of improved and deteriorated cement adhesion can be found;

a8 applies to P & A's MCI:

the objective of the CBL measurements is to determine zonal isolation, MCI (minimum cement interval is one of the parameters defining the interval of good cementing required for different casing sizes (in: inches), as shown in fig. 13, h.d. brown et al describe MCI in the document "new development of sonography and analysis in cased hole" SPWLA eleventh annual well logging symposium from 3/1970 to 6, good binding is defined by the binding index limit BILI, typically 0.8 with BILI, 0.8 with standard casing, suitable for P & a operations, CBL-PWC interpretation continuously applicable to actual data, and finally find MCI for P & a operations;

a9 data and puncture quality control-slowness and transit time:

as described in the journal of Petroleum engineering (SPE453), the DT or slowness of the CBL casing pattern helps to determine the importance of perforation interval and perforation in CBL measurements, the slowness value of a normal casing is typically between 57.5 and 58.5 μ s/ft, in the model example provided in this document the slowness value of a perforated casing varies between 57.5 and 61 μ s/ft, which may be greater if the casing is perforated to a greater extent, and TT (transmission time) is delayed by 10 μ s with a T-R (transmitter-receiver) interval of 3ft as the slowness increases; where FIG. 14 shows an example of TT (time of flight) and DT (slope of TT) data in a heavily perforated casing, in FIG. 14 the data shown by curve 602 shows a TT versus T-R spacing curve for a heavily perforated casing, referred to as "perf # 1", showing the increase in TT and DT (slope of TT) shown in the upper left corner of the figure (FIG. 14) compared to a standard or lightweight perforated casing of the same diameter as shown by curves 600 and 604, respectively, the increase in slowness and TT values indicating the significance of the perforation effect, i.e., deviation from a plain casing and amplitude;

a10 alternative measurement:

as with CBL measurements in standard casing, attenuation measurements can also be evaluated as a replacement for acoustic cement measurements based on amplitude, and are effective, especially when there is significant uncertainty in fluid and environmental effects, CBL amplitude measurements depend on acoustic pressure excitation and key characteristics (e.g., capacitance, sensitivity, etc.) of sensors such as transmitters (pressure sources) and receivers, which typically have non-negligible sensitivity to the environment, and casing mode attenuation is measured using at least two pairs of transmitters (pressure sources) 202 and two receivers 204 deployed in a borehole compensated configuration (BHC) within casing 210, as shown in fig. 15, as described in the document "cement bond tool" by l.h.gollwizer et al, the SPWLA twenty-third year lumberwork seminar, array acoustic receivers can also be used to derive casing mode attenuation as an E-1 amplitude gradient across the array, attenuation measurements are not affected by fluid properties and environmental influences because they are offset by BHC measurements, as described above in the production operations workshop document SPE21690, held in oklahoma, 4.7.9.1991, casing mode attenuation is sensitive to cement properties, bond index and perforations (density and entrance hole diameter), so it can identify the cement bond status of perforated casing, and is or is superior to amplitude-based CBL measurements, where casing mode attenuation can be calculated by CBL modeling using multiple receivers, e.g., at 3.5ft-4.5ft or 3ft-5ft emitter-receiver (T-R) spacing, attenuation values can be calculated from two CBL amplitudes at known R-R spacing (1 and 2ft, respectively), while figure 16 shows one example of a linear relationship between casing mode Attenuation (ATT) and Bond Index (BI), mode attenuation can be computed separately for two states: the free pipe condition and the 100% cement bonded condition, named ATTfp (free pipe attenuation) and MATT (maximum attenuation), respectively, at one key index (BI), the casing expresses the ATT as a linear relationship, as shown by the ATT ═ 1-BI ATTfp + BI MATT equation, for perforated casing, the numerical simulations in this disclosure provide ATTfp _ PWC and MATT _ PWC, which attenuate the perforated casing in the free pipe and 100% cement bonded conditions, respectively;

use of a11 sonic tool in the evaluation of downhole substandard cement applications:

in addition to standard cement evaluation, there is also the use of sonic logging tools such as CBL tools, for example as described in us patent 4742496, which use sonic measurements to evaluate gravel pack quality, and the present method in the context of the present invention may be applied to applications other than the standard cement evaluation case, based on quantitative analysis or model-based interpretation;

and (3) a summary III: conventional CBL measurements are provided at sonic logging frequencies, typically near 20kHz, and casing extension models can be excited at higher frequencies (e.g., 100kHz or 200kHz), and thus embodiments of the model-based interpretation development method are not limited to conventional CBLs at conventional frequencies, but also include higher frequencies.

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