CN-121993176-A - Near-window coupling electromagnetic wave measurement while drilling method for cased well

CN121993176ACN 121993176 ACN121993176 ACN 121993176ACN-121993176-A

Abstract

The invention relates to the technical field of petroleum and natural gas drilling measurement and the technical field of downhole information transmission, in particular to a near-window coupling electromagnetic wave measurement while drilling method of a cased well, which comprises the following steps of S1, off-line establishing a composite medium equivalent model; the method comprises the steps of S2, scanning and determining a near window optimal selection interval according to a composite medium equivalent model, S3, generating a typical impedance interval and a near window parameter set according to the near window optimal selection interval, S4, matching the typical impedance interval on line, judging a near window transition section according to characteristics, S5, triggering a near window mode and closed loop fine adjustment in the near window transition section, and S6, safely degrading according to a protection rule and outputting a result. According to the method, a multi-layer medium model is built by a well logging measuring method, a near window coupling interval is calculated according to the model, so that the signal transmission stability of the insulating nipple in the well logging measuring process is improved, a short-distance stable chain building in a casing window is realized, the problem of downhole touch typing is solved, and the electromagnetic performance reliability is improved.

Inventors

ZHANG ZHENHUA
ZHAI XIPING
LI RUNQI
WANG HAIQI
XU YUEQING
CAI WEI
ZHAO ZHIXUE
GAO MING
PEI FEI
XU YUNLONG
WANG ZHENLEI
WANG SHUQING
LIU HAIBO
YU HONGBO

Assignees

大庆钻探工程有限公司
中国石油天然气集团有限公司

Dates

Publication Date: 20260508
Application Date: 20251225

Claims (8)

1. A method for measuring near-window coupling electromagnetic waves of a cased well while drilling is characterized by comprising the following steps of: S1, establishing a composite medium equivalent model offline; s2, scanning and determining a window-near optimal interval according to the composite medium equivalent model; step S3, generating a typical impedance interval and a near window parameter set according to the near window optimal selection interval; S4, online matching a typical impedance interval, and judging as a near window transition section according to the characteristics; Step S5, triggering a near window mode and closed loop fine tuning in a near window transition section; and S6, safely degrading according to the protection rule and outputting a result.
2. The method for measuring the near-window coupling electromagnetic wave while drilling of the cased well according to claim 1, wherein the step of establishing the composite medium equivalent model offline comprises the following steps: Equivalent the propagation environment near the shaft to a coaxial multilayer conductive medium structure constructed by multilayer concentric cylinders; the coaxial multilayer conductive medium structure comprises a well bore layer, a casing layer, a cement layer and a stratum layer, wherein the well bore layer, the casing layer, the cement layer and the stratum layer are concentrically distributed in the radial direction; Establishing complex dielectric constant forms by different level media : , Wherein: Is the conductivity of the dielectric of the ith layer, mu S/cm; Is the dielectric constant of the dielectric of the i layer; is vacuum dielectric constant; The angular frequency of the dielectric of the i layer is rad/s; The i is the medium of the current level, and j is used for representing the phase difference of 90 DEG in the electromagnetic field, and j = ; In the coaxial multilayer conductive medium model, the electromagnetic field satisfies the axisymmetric condition, the main propagation direction of the electromagnetic field is along the well axis direction, and in each radial layered medium, the propagation characteristic of the electromagnetic wave can be represented by an equivalent propagation constant k i , and the equivalent propagation constant k i is: , Wherein mu 0 is vacuum permeability; epsilon ̃ i is the complex dielectric constant of the i-th layer medium; The epsilon ̃ i is used for representing attenuation and phase characteristics of electromagnetic waves in each medium layer under different frequency conditions; At the radial interface of any adjacent dielectric layers, the electromagnetic field needs to meet the continuity condition of the tangential electric field and the tangential magnetic field, so that the coupling of electromagnetic response of each dielectric layer is realized, and the coaxial multilayer conductive medium is formed.
3. The method for measuring the near window coupling electromagnetic wave while drilling of the cased well according to claim 2, wherein the method for scanning and determining the near window optimization interval according to the composite medium equivalent model comprises the following steps: Obtaining well structure design parameters and logging data to obtain a casing inner diameter thickness D c , a casing wall thickness t c , a casing conductivity sigma c , a cement ring thickness t cem , a cement conductivity sigma m , a formation resistivity rho f , a drilling fluid resistivity rho m and an adopted working frequency range f, inputting the casing inner diameter thickness D c , the casing wall thickness t c , the casing conductivity sigma c , the cement ring thickness t cem , the cement conductivity sigma m , the formation resistivity rho f , the drilling fluid resistivity rho m and the adopted working frequency range f into a coaxial multilayer conductive medium model, obtaining an equivalent load impedance Z eq of a transmitting end and a ratio SNR (L win ) of effective signal energy to system equivalent input noise energy by calculation, wherein the equivalent load impedance represents a ratio of equivalent voltage to equivalent current generated by an insulation nipple in a drilling process, and the equivalent load impedance Z eq of the transmitting end is as follows: , Wherein U tx is equivalent voltage, V under the action of a coaxial multilayer conductive medium model; I tx is equivalent current under the action of a coaxial multilayer conductive medium model, A; The method comprises the steps of obtaining an axial distance L b from a gap sub to the end face of a drill bit, an axial distance L win from the center of the gap sub to a sleeve window, and a window adjacent leakage field intensity E w , wherein the window adjacent leakage field intensity E w is used for representing the leakage degree of electromagnetic energy near a shaft window.
4. The method for measuring the near-window coupling electromagnetic wave while drilling of the cased hole according to claim 3, wherein the coaxial multilayer conductive medium model is calculated to obtain an electric field intensity amplitude E w （L win ) at the neighborhood of the casing window under the condition of an axial distance L win from the center of the insulating nipple to the casing window, and the electric field intensity amplitude E w （L win ) is: , h E () is the electric field transmission coefficient of the composite medium and the window structure; I tx is equivalent current under the action of a coaxial multilayer conductive medium model, A; I eff equivalent dipole length, m; Under the condition of an axial distance L win from the center of the insulating nipple to a sleeve window, obtaining a ratio SNR (L win ) of effective signal energy of a target electromagnetic wave signal in the window to equivalent input noise energy of a system, wherein the ratio SNR (L win ) of the effective signal energy to the equivalent input noise energy of the system is used for measuring the influence of different window lengths on weak signal detection performance, and calculating the SNR (L win ) to obtain an L win continuous interval which not only meets a signal-to-noise ratio threshold value but also does not destroy a near window hypothesis: SNR(L win )=20log 10 (V RX (L win )/V n ) v RX is the amplitude of the received signal; V n is signal noise; The received signal amplitude V RX is: , k RX is the voltage value, V, finally received after the receiving end is affected by all factors; The signal noise V n is: , Wherein e n,eq is the equivalent input noise voltage density of the receiving link, V +. ; B is demodulation equivalent bandwidth, hz; And selecting a near window near leakage field threshold E thr as a near window preferred interval, wherein the near window preferred interval is Ew (L win )≥E thr and SNR (L win )≥SNR thr , thr is the minimum value in the near window preferred interval, and L winmin ≤L win ≤L winmax is obtained), L winmin is the minimum distance of the gap sub at the position of casing opening, and L winmax is the maximum distance of the gap sub at the position of casing opening.
5. The method of measuring a cased hole near window coupled electromagnetic wave while drilling of claim 4, wherein generating a representative impedance interval and a near window parameter set from the near window preferred interval comprises: Generating a sleeve inner section typical impedance interval Z casing , a near window transition section typical impedance interval Z window and an open hole section typical impedance interval Z open in an offline stage, recording the amplitude and phase range of equivalent load impedance Z eq through the working condition, and forming an interval by the sleeve inner section impedance phase interval phi casing , the near window transition section phase interval phi window and the open hole section impedance phase interval phi open : Z casing ：|Z casing |∈[Z c1 ,Z c2 ],φ casing ∈[φ c1 ,φ c2 ], Z window ：|Z window |∈[Z w1 ,Z w2 ],φ window ∈[φ w1 ,φ w2 ], Z open ：|Z open |∈[Z o1 ,Z o2 ],φ open ∈[φ o1 ,φ o2 ], Wherein phi is the impedance phase; c1 and c2 are the typical impedance interval of the inner section of the sleeve and the value range of the impedance phase interval of the inner section of the sleeve; w1 and w2 are the value ranges of typical impedance intervals of the near window transition section; o1 and o2 are the value ranges of typical impedance intervals of the naked eye segment; extracting a change threshold value delta Z thr of impedance amplitude between adjacent windows and a change threshold value delta phi thr of impedance phase phi between adjacent windows; In the near window optimal selection interval, combining an operation tool and temperature rise constraint to obtain a near window optimal selection interval special data set f win and U win , wherein f win is a working carrier frequency in a near window mode and is used for obtaining signal-to-noise ratio and coupling efficiency in a near window area; allowing adjustment of the emission voltage during the well-down to form an emission voltage final control value U set ; the close window transmitting duty ratio parameter D set is obtained by adjusting the pulse width of the transmitting end.
6. The method for measuring the near window coupling electromagnetic wave while drilling of the cased well according to claim 5, wherein the method for measuring the near window coupling electromagnetic wave while drilling of the cased well is characterized by matching a typical impedance interval on line, judging the near window transition section according to the characteristics, and comprising the following steps: Obtaining a drill bit sounding MD bit and a sounding MD win in the center of a casing near window, and calculating a gap sub center sounding MD ins on line by combining a structural constant L b to obtain L win : , , By sampling the transmitting nipple, voltage and current generated by transmitting the transmitting nipple are obtained, equivalent load impedance Z eq is obtained, and equivalent load impedance amplitude |Z eq | is obtained through online calculation according to equivalent load impedance Z eq : , Performing exponential smoothing on the equivalent load impedance amplitude |Z eq | to inhibit noise and transient disturbance, and calculating the change rate delta Z (k) of the equivalent impedance amplitude along the well depth direction and the equivalent impedance phase delta phi (k); the delta Z (k) is the variation of the equivalent impedance amplitude after the exponential smoothing between adjacent receiving windows, and is used for representing the variation rate of the impedance amplitude along the well depth direction; the delta phi (k) is the variation of the equivalent impedance phase between adjacent windows and is used for representing the variation rate of electromagnetic propagation phase characteristics; The near window transition is determined when |Δz (k) | is equal to or greater than a change threshold Δz thr of the impedance magnitude and |Δφ (k) | is equal to or greater than a change threshold Δφ thr of the impedance phase φ between adjacent windows.
7. The method for measuring the near window coupling electromagnetic wave while drilling of the cased hole according to claim 6, wherein triggering the near window mode and the closed loop fine tuning at the near window transition section comprises switching the system to the near window mode when the gap sub currently enters the near window transition section and the axial distance L win from the center of the gap sub to the casing window is within a near window optimal interval (L winmin ≤L win ≤L winmax ), loading a near window mode working frequency control parameter to control the target emission current of a target in a closed loop mode, and feeding back the current at the emission end, wherein the voltage set value U set during the operation of the more recent window mode and the average emission power modulation parameter D set in the near window mode.
8. The method for measuring the near-window coupling electromagnetic wave while drilling of the cased well according to claim 7, wherein the method comprises the steps of safely degrading and outputting a result according to a protection rule, wherein the method comprises the following steps of: When the detected temperature in the near window section exceeds a temperature protection threshold value, the equivalent load impedance amplitude deviates from a target interval for a long time, and the target emission current value of closed-loop control abnormally floats up and down; Triggering a protection rule in a near window section, and triggering a safety degradation operation, wherein the safety degradation operation comprises automatically reducing the transmitting power, reducing the duty ratio or exiting the near window mode to return to the common mode; After the measurement is completed, the system outputs off-line parameters and on-line parameters; The offline parameters comprise a near window optimal selection interval (L winmin ≤L win ≤L winmax ), a sleeve inner section typical impedance interval Z casing , a near window transition section typical impedance interval Z window and an open hole section typical impedance interval Z open , and near window optimal selection interval special data sets f win and U win ; The online parameters comprise online equivalent load impedance Z eq , online judgment result, current mode and emission set value (U set ,D set ); And the system generates a log for subsequent model verification and parameter convergence according to the offline parameters and the online parameters.

Description

Near-window coupling electromagnetic wave measurement while drilling method for cased well Technical Field The invention relates to the technical field of petroleum and natural gas drilling measurement and the technical field of downhole information transmission, in particular to a near-window coupling electromagnetic wave measurement while drilling method for a cased well. Background At present, the underground-ground data transmission technology based on electromagnetic waves in the measurement while drilling field is applied more under the conditions of conventional well diameter and open hole, foreign service companies disclose various electromagnetic wave while drilling telemetry systems which utilize insulation pup joints to establish electric dipoles between the upper part and the lower part of a drill string, the basic principle is that the insulation pup joints are arranged at the upper part of a drilling tool to electrically isolate upper and lower metal drilling tools, an electromagnetic field which spreads along the axial direction of the well is formed in a stratum, and the upward transmission of measurement data is realized. Meanwhile, the typical form of 'insulating pup joint arranged on the upper part of an electromagnetic instrument string or an upper drill collar section' is adopted. Under the arrangement mode, the effective dipole is mainly formed by a large section of drill string above the insulating pup joint and a far loop together, and a metal structure near the bottom of the well bears more current backflow and mechanical bearing functions and is not used as a main radiation area, so that an electromagnetic field can be effectively leaked to the ground after a tool is required to be integrally separated from a casing shoe for a long open hole distance under the casing well working condition, and a longer no-signal area exists near a casing window and the casing shoe. For reentry well and ultra-short radius guided operations, the lack of real-time telemetry support in this critical section can only rely on pre-designed trajectories and intermittent measurements for "empirical guidance", short-time "downhole touch typing" is prone to occur, and the accuracy and timeliness of trajectory control are both limited. The electromagnetic wave instrument breaks a current loop through the insulating nipple so as to radiate an electric field like the surrounding, but the insulating nipple is not closer to the drill bit, so that signals can be radiated faster, a metal sleeve is a good conductor, a strong eddy current shielding effect can be generated, if the insulating nipple is tightly attached to the drill bit and a window, after the drill bit is windowed, energy of a transmitting circuit can be mainly consumed in a local short circuit loop formed by a narrow gap at the edge of the insulating nipple-window-sleeve, so that strong local circulating current is formed, and cannot be effectively leaked into a stratum at a distance, but if the insulating nipple is far away from the drill bit, the strong disturbance area of the window is avoided, the drill bit is windowed, the insulating nipple is still buried deeply inside the sleeve, a longer signal-free area exists near the well section, and the requirements of sidetrack guiding on real-time measurement and transmission cannot be met. Aiming at the situation, a near-window coupling electromagnetic wave measurement while drilling method for a cased well is provided. Disclosure of Invention In order to solve the problems that in the prior art, the insulation pup joint cannot guarantee the stability of signal transmission in the measurement process along with the well, short-distance stable chain establishment is difficult to realize at the positions of a sleeve window and a sleeve shoe, underground touch typing of a key section is easy to cause, and the reliability of electromagnetic performance is difficult to guarantee, the invention provides a measurement method along with drilling of a sleeve well near window coupling electromagnetic wave, which shortens the chain establishment distance through a near window coupling structure and reduces the risk of touch typing of a sleeve windowing section; the device arranges the insulating nipple at a position close to a drill bit, establishes a multi-layer medium model by a measurement method along with a well, calculates a near window coupling interval according to the model, ensures that a radiation area with larger contribution to the external field near the insulating nipple stably falls in an open hole section adjacent to a casing window. The technical scheme of the invention is that the near-window coupling electromagnetic wave measurement while drilling method of the cased well is characterized in that: S1, establishing a composite medium equivalent model offline; s2, scanning and determining a window-near optimal interval according to the composite medium equivalent model; step S3, generating a typ