Method for rapidly calculating conductivity of anisotropic stratum of inclined shaft

Abstract

The invention discloses a method for quickly calculating the conductivity of an anisotropic stratum of an inclined shaft, which comprises the following steps of: logging by using a three-dimensional induction logging instrument to obtain a measurement signal of the three-dimensional induction instrument; according to the three-dimensional induction measurement signal, a borehole inclination angle is given, a logging response combination component is solved for each measurement point, and a logging response component combination curve sigma HA is formed; the stratum horizontal conductivity of each measuring point is obtained after skin effect correction; and according to the stratum horizontal conductivity and the borehole inclination angle, the vertical conductivity is solved by utilizing the cross component response combination curve. According to the method, the horizontal conductivity and vertical conductivity parameters of the TI stratum of the inclined shaft can be quickly and accurately solved, so that the logging information of the three-dimensional induction instrument can be better applied to field processing and visual interpretation.

Description

Technical Field

[0001] This invention belongs to the field of petroleum logging technology, specifically a method for rapidly determining the anisotropic formation conductivity of deviated wells. Background Technology

[0002] It is estimated that approximately 30% of the world's oil and gas reserves are located in thin sandstone-mudstone interbedded layers. These thin interbedded reservoirs can be considered equivalent to macroscopic uniaxial anisotropic formations (or, laterally isotropic formations, abbreviated as TI formations). Detecting and identifying these formations is of great significance and a practical necessity for oil and gas resource development. For existing axial induction logging instruments, due to insufficient vertical resolution, these thin interbedded oil reservoirs are often mistakenly identified as high water-saturation layers and missed during logging. Three-dimensional induction logging instruments consist of three perpendicular transmitting coils and three parallel receiving coils. They can detect the horizontal and vertical conductivity information of the formation, identifying formation characteristics from a three-dimensional perspective, and have an inherent advantage in detecting thin and complex reservoirs.

[0003] In deviated wells, the 3D induction logging response is generally related to the formation's horizontal and vertical conductivity, as well as the wellbore dip angle. Furthermore, the influence of adjacent layers on different components of the logging response varies, all of which increase the difficulty of data processing and interpretation. Currently, 3D induction logging data processing mainly relies on multi-parameter nonlinear iterative inversion. While iterative inversion methods can obtain formation parameters close to the true values, they are typically slow, with most of the computation time spent on calculating the Jacobi matrix of the objective function. Simultaneously, the logging data inversion is greatly affected by initial values ​​such as anisotropic formation conductivity parameters; improper initial value selection can lead to significant errors in the formation conductivity results.

[0004] In summary, existing methods for determining the anisotropic formation conductivity of deviated wells suffer from slow calculation speed and large errors. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a method for rapidly determining the anisotropic formation conductivity of deviated wells. This method enables the rapid and accurate determination of the horizontal and vertical conductivity parameters of the TI formation in deviated wells, allowing the logging data from three-dimensional induction instruments to be better applied to field processing and intuitive interpretation.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for rapidly determining the anisotropic formation conductivity of a deviated well includes the following steps:

[0008] Well logging is performed using a three-dimensional induction logging instrument to obtain the measurement signals from the three-dimensional induction instrument;

[0009] Based on the three-dimensional induction measurement signal, given the wellbore inclination angle, for each measurement point, the combined components of the logging response are calculated, and a combined logging response component curve σ is formed. HA ;

[0010] After skin effect correction, the formation horizontal conductivity at each measurement point was obtained.

[0011] The vertical conductivity is determined by using the cross-component response combination curve based on the formation horizontal conductivity and the wellbore dip angle.

[0012] Preferably, the coil system structure of the three-dimensional induction logging instrument includes a transmitting coil system, a receiving coil system, and a shielding coil system;

[0013] The transmitting coil T in the transmitting coil system x Transmitting coil T y Transmitting coil T z The centers of the two points are at the same point and they are perpendicular to each other;

[0014] The receiving coil R in the receiving coil system x Receiver coil R y Receiver coil R z The centers of the two points are at the same point and they are perpendicular to each other;

[0015] Shielding coil B in the shielding coil system x Shielded coil B y Shielded coil B z The centers of the two points are at the same point and they are perpendicular to each other;

[0016] The transmitting coil T z Receiver coil R z and shielded coil B z Coaxial; the transmitting coil T x Receiver coil R x Shielded coil B x Parallel to each other; the transmitting coil T y Receiver coil R y Shielded coil B y They are parallel to each other.

[0017] Furthermore, the winding directions of the shielding coil system and the receiving coil system are opposite, and the direct-coupled electromotive forces generated in the shielding coil system and the receiving coil system cancel each other out.

[0018] Furthermore, when the transmitting coil system emits sinusoidal alternating current into the surroundings, it is possible to simultaneously measure the nine magnetic field components H on the receiving coil system. ij (i = x, y, z; j = x, y, z).

[0019] Furthermore, after the direct-coupled electromotive forces cancel each other out, the magnetic field strength measured by the receiving coil system... The formula is:

[0020]

[0021] In the formula H ij1 H represents the magnetic field generated by the receiving coil. ij2 L1 represents the magnetic field generated by the shielding coil; L2 represents the source distance of the receiving coil; L3 represents the source distance of the shielding coil.

[0022] Preferably, the well logging response component combination curve σ HA The formula is:

[0023]

[0024] Where, σ zx The conductivity curve is for emission in the z-direction and reception in the x-direction; σ xz The conductivity curve is for emission in the x-direction and reception in the z-direction; σ xx The conductivity curve is for transmission and reception in the x-direction; σ zz The conductivity curves are those emitted and received in the z-direction; α is the wellbore inclination angle.

[0025] Preferably, when acquiring the three-dimensional induction logging response in the inclined well, three formation coordinate systems OX are introduced. f Y f Z f Wellbore coordinate system OX w Y w Z w and instrument coordinate system OX t Y t Z t Perform a rotation transformation.

[0026] Preferably, the cross-component response combination curve (σ) is less affected by adjacent layers. zx +σ xz ) Calculate the vertical conductivity.

[0027] Compared with the prior art, the present invention has the following beneficial technical effects:

[0028] This invention provides a method for rapidly determining the anisotropic formation conductivity of deviated wells. It involves acquiring three-dimensional induction logging data, calculating the combined components of the logging response, and obtaining the formation's horizontal conductivity after skin correction. Finally, the formation's vertical conductivity is calculated. This invention enables rapid determination of the horizontal and vertical conductivity parameters of anisotropic formations in deviated wells at each measurement point, significantly shortening logging data processing time, improving the efficiency of logging instruments, and substantially reducing the cost of on-site testing. This allows three-dimensional induction logging data to be better applied to field processing and intuitive interpretation and evaluation, which is of great significance for the widespread application of three-dimensional induction logging instruments in the field. Furthermore, this invention is applicable to determining the anisotropic formation conductivity of any deviated well, especially showing excellent results in highly deviated wells, thus broadening the application range of three-dimensional induction logging instruments. Attached Figure Description

[0029] Figure 1 This is a flowchart for rapidly determining the TI formation conductivity using three-dimensional induction logging data.

[0030] Figure 2 This is a diagram of the coil system structure of a three-dimensional induction logging instrument.

[0031] Figure 3 It is a diagram used to illustrate the relationship between the three coordinate systems: the formation coordinate system, the wellbore coordinate system, and the instrument coordinate system.

[0032] Figure 4 This is the parameter table for the 18-layer TI anisotropic stratum model.

[0033] Figure 5 It is the simulated curve of the principal components (XX / YY / ZZ) of the well logging response.

[0034] Figure 6 The simulated curves of the well logging response cross components (XZ / ZX) and their response sum are shown.

[0035] Figure 7 These are the results of the formation's horizontal and vertical electrical conductivity when the wellbore inclination angle is 60 degrees.

[0036] Figure 8 These are the formation horizontal and vertical electrical conductivity values ​​obtained when the wellbore dip angle is 30 degrees.

[0037] Figure 9 These are the formation horizontal and vertical electrical conductivity values ​​obtained when the wellbore dip angle is 80 degrees. Detailed Implementation

[0038] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0039] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0040] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0041] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0042] The accompanying drawings illustrate various structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0043] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0044] After a detailed investigation and analysis of the logging response characteristics of three-dimensional induction instruments, this invention constructs a logging response component combination curve σ for each measurement point using three-dimensional induction logging data. HA Its vertical conductivity σ v It is irrelevant, only related to the horizontal conductivity σ h It is related to the wellbore dip angle α. Where σ ij (i,j = x,y,z). After skin effect correction, SECσ is obtained. HA This allows for the accurate calculation of the horizontal conductivity σ at the corresponding measurement point. hThen, the response combination curve of the cross component, which is less affected by adjacent layers (σ) is used. zx +σ xz ) Calculate the vertical conductivity σ at the corresponding measurement point. v .

[0045] The method of this invention is designed for transversely anisotropic (TI) formations in deviated wells, and can quickly and accurately determine the horizontal and vertical electrical conductivity of the formation using three-dimensional induction logging data.

[0046] This invention provides a method for rapidly determining the TI formation conductivity using three-dimensional induction logging data, comprising the following steps: Figure 1 As shown:

[0047] Well logging was performed using a three-dimensional induction logging instrument, and the measurement signal of the three-dimensional induction instrument was obtained: the well logging response conductivity curve of the receiving coil system with a shorter source distance and greater signal strength was preferred compared to the receiving coil system with a longer source distance.

[0048] Based on the three-dimensional induction measurement signal, and given the wellbore inclination angle, the well logging response component combination curve σ is obtained for each measurement point. HA After skin effect correction, SECσ was obtained. HA Thus, the horizontal conductivity at each measurement point is obtained;

[0049] The vertical conductivity is determined using the cross-component response combination curve based on the formation horizontal conductivity and wellbore dip angle.

[0050] Example

[0051] like Figure 2 As shown, the coil system of the three-dimensional induction logging instrument consists of three transmitting coils T, which are centered at a common point and perpendicular to each other. x T y T z Three receiving coils R parallel to it x R y R z (source distance is L1) and three shielding coils B x B y B z Composed of (source distance L2). Specifically: The coil system structure of the three-dimensional induction logging instrument includes a transmitting coil system, a receiving coil system, and a shielding coil system; the transmitting coil T in the transmitting coil system x Transmitting coil T y Transmitting coil T z The centers of the two coils are at the same point and perpendicular to each other; the receiving coil R in the receiving coil system x Receiver coil R y Receiver coil R zThe centers of the two coils are at the same point and perpendicular to each other; shielding coil B in the shielding coil system x Shielded coil B y Shielded coil B z The centers of the two coils are at the same point and perpendicular to each other; the transmitting coil T z Receiver coil R z and shielded coil B z Coaxial; transmitting coil T x Receiver coil R x Shielded coil B x Parallel to each other; transmitting coil T y Receiver coil R y Shielded coil B y They are parallel to each other.

[0052] When the transmitting coil emits a sinusoidal alternating current of equal amplitude into the surrounding environment, an alternating electromagnetic field (primary magnetic field) is generated in the medium. According to the principle of electromagnetic induction, an induced electromotive force (EMF) will be generated in the receiving coil and the shielding coil within this magnetic field. To cancel the direct coupling component generated by the transmitting coil in the receiving coil, this invention introduces a shielding coil. Direct coupling refers to the induced signal directly induced in the receiving coil by the closed-loop characteristic of magnetic flux without the transmitted signal passing through a ground layer. The shielding coil and the receiving coil have opposite winding directions and unequal number of turns, and the direct coupling EMFs generated in the shielding coil and the receiving coil cancel each other out in the air.

[0053] When the transmitting coil system emits sinusoidal alternating current into the surroundings, it can simultaneously measure nine magnetic field components H on the receiving coil system. ij (i=x,y,z; j=x,y,z), where H xy This represents the magnetic field strength generated by emission in the x direction and reception in the y direction; other components are defined similarly.

[0054] To examine the three-dimensional induction logging response in inclined wells, three coordinate systems need to be introduced, namely, the formation coordinate system OX. f Y f Z f Wellbore coordinate system OX w Y w Z w and instrument coordinate system OX t Y t Z t (like Figure 3 As shown), the magnetic field tensors in these three coordinate systems satisfy the following rotation transformation rule:

[0055]

[0056] in,

[0057]

[0058] In equations (1) and (2), α is the wellbore dip angle, defined as the Z-axis in formation coordinates (Z... f ) and the Z-axis in the wellbore coordinate system (Z w Angle between them; The instrument azimuth angle is defined as the angle between the instrument's projection onto the XY plane and the X-axis.

[0059] After the direct-coupled electromotive forces cancel each other out, the magnetic field strength measured by the receiving coil system... It can be expressed by the following formula (3),

[0060]

[0061] In the formula H ij1 H represents the magnetic field generated by the receiving coil. ij2 This represents the magnetic field generated by the shielding coil. To facilitate comparison between the logging response and formation electrical parameters, the induction logging response is typically normalized to a quantity in the dimension of conductivity. As shown below:

[0062]

[0063] in, K represents the imaginary part of the magnetic field of the coil system. ij σ is the instrument coefficient for the coil system. ij The apparent conductivity of the coil system.

[0064]

[0065]

[0066] Where ω is the angular frequency and μ is the permeability.

[0067] Forward modeling first calculates the electromagnetic field excited by three orthogonal transmitting coils in the formation coordinate system. Then, through coordinate rotation transformation related to the wellbore inclination angle α, it obtains the three-dimensional induction logging response in the wellbore coordinate system. Finally, it modulates the response with respect to the instrument azimuth angle. The relevant coordinate rotation transformation yields the three-dimensional induction logging response in the instrument coordinate system. Actual logging data is always obtained in the instrument coordinate system. In data processing, it is common practice to obtain the logging response curve in the wellbore coordinate system from the measured data through an inverse transformation of the instrument azimuth angle before further processing.

[0068] In this invention, the process of rapidly obtaining the anisotropic formation conductivity using three-dimensional induction logging data is as follows: obtain three-dimensional induction logging data → obtain the combined components of the logging response → obtain the formation horizontal conductivity after skin correction → obtain the formation vertical conductivity.

[0069] For each measurement point, construct a line perpendicular to the conductivity σ. v It is unrelated to, but only related to, the horizontal conductivity σ h The combined curve σ related to the wellbore dip angle α HA ,

[0070]

[0071] After skin effect correction, SECσ was obtained. HA This yields the required horizontal conductivity σ of the formation. h .

[0072] After obtaining the horizontal conductivity, the cross-component combination curve (σ) is then used. zx +σ xz ) Determine the vertical conductivity σ v .

[0073] Select (σ) zx +σ xz The reason is that the response curve becomes flat within the layer, and is less affected by adjacent layers. In other words, the vertical conductivity of the formation is not limited to the above method; other methods can also be used to determine the vertical conductivity of the formation.

[0074] This invention can quickly obtain the horizontal and vertical conductivity parameters of anisotropic formation deviated wells for each measurement point, greatly shortening the logging data processing time, improving the working efficiency of logging instruments, and significantly reducing the cost of on-site testing. This enables the logging data from three-dimensional sensing instruments to be better applied to field processing and intuitive interpretation and evaluation, which is of great significance for the widespread application of three-dimensional sensing instruments in the field.

[0075] Meanwhile, this invention can be applied to the determination of the electrical conductivity of anisotropic formations in any deviated well, and it works particularly well in highly deviated wells, thus broadening the application scope of three-dimensional sensing instruments.

[0076] Example 2

[0077] The following example, using an inclined well with 18 layers of anisotropic TI formation, illustrates and verifies the method of rapidly determining the electrical conductivity of anisotropic formations using three-dimensional induction logging data. Figure 4 This is a parameter table for an 18-layer anisotropic TI formation model. The three-dimensional induction instrument's transmission frequency is f = 25kHz, and a short source-pitch coil system is selected: main receiving coil source pitch L1 = 30in, shielding coil source pitch L2 = 20.5in. Where 1 inch (1in) = 2.54cm; Figure 5 It is a numerical simulation curve of the principal component logging response of a three-dimensional sensing instrument at a wellbore inclination angle α = 60°, where the horizontal axis is the vertical measurement depth and the vertical axis is the apparent conductivity of the coil system.

[0078] Figure 6 These are numerical simulation curves of the logging response of a three-dimensional sensing instrument at a wellbore inclination angle α = 60°, including cross-component and combined-component logging. From... Figure 6 It can be seen from σ zx and σ xz Compared to the curve, (σ) zx +σ xz The curve flattens out within the layer, indicating less influence from adjacent layers. Therefore, in homogeneous anisotropic TI formations, once the horizontal conductivity and wellbore dip angle are determined, solving for the vertical conductivity becomes a single-parameter problem. A response combination (σ) that is less affected by adjacent layers can be selected. zx +σ xz Using this method to determine the vertical conductivity yields better results.

[0079] Considering the actual measurement conditions, the simulated logging response plus 5% random noise was used as the instrument's measured data to verify the effectiveness of the method. Figure 7 The results of horizontal and vertical conductivity are obtained quickly using this method when the wellbore inclination angle is 60 degrees. In the figure, psh and psv are the horizontal and vertical conductivity results without considering the influence of noise, while pshN and psvN are the horizontal and vertical conductivity results considering the influence of 5% random noise. Figure 8 This method quickly obtains the horizontal and vertical conductivity results when the wellbore inclination angle is 30°. Figure 9 This method quickly calculates the horizontal and vertical conductivity results when the wellbore inclination angle is 80°. Figure 7 , Figure 8 and Figure 9 In the diagram, the horizontal axis represents the vertical measurement depth, and the vertical axis represents the apparent conductivity value.

[0080] from Figure 7 , Figure 8 , Figure 9 As can be seen, the method for rapidly determining the anisotropic formation conductivity of this invention is applicable to determining the conductivity of anisotropic formations in any deviated well, such as small angles of 30°, intermediate angles of 60°, and large angles of 80°. Without considering noise, the obtained anisotropic formation conductivity results are highly accurate. Furthermore, even considering random noise, the obtained conductivity results match the actual horizontal and vertical conductivity curves of the formation very well. Because the method of this invention can obtain the horizontal and vertical conductivity values ​​of the formation with high accuracy, this processing method can accurately identify thin sandstone-mudstone alternating layers, avoiding the misidentification of such thin alternating oil reservoirs as high water-saturation layers during well logging, which is of great significance in well logging.

[0081] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the scope of the invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0082] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that can be understood by those skilled in the art. The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for rapidly determining the anisotropic formation conductivity of a deviated well, characterized in that, Includes the following processes, Well logging is performed using a three-dimensional induction logging instrument to obtain the measurement signals from the three-dimensional induction instrument; Based on the three-dimensional induction measurement signal, given the wellbore inclination angle, for each measurement point, the combined components of the logging response are calculated, and a combined logging response component curve σ is formed. HA ; After skin effect correction, the formation horizontal conductivity at each measurement point was obtained. The vertical conductivity is determined by using the cross-component response combination curve based on the formation horizontal conductivity and the wellbore dip angle.

2. The method for rapidly determining the anisotropic formation conductivity of a deviated well according to claim 1, characterized in that, The coil system structure of the three-dimensional induction logging instrument includes a transmitting coil system, a receiving coil system, and a shielding coil system; The transmitting coil T in the transmitting coil system x Transmitting coil T y Transmitting coil T z The centers of the two points are at the same point and they are perpendicular to each other; The receiving coil R in the receiving coil system x Receiver coil R y Receiver coil R z The centers of the two points are at the same point and they are perpendicular to each other; Shielding coil B in the shielding coil system x Shielded coil B y Shielded coil B z The centers of the two points are at the same point and they are perpendicular to each other; The transmitting coil T z Receiver coil R z and shielded coil B z Coaxial; the transmitting coil T x Receiver coil R x Shielded coil B x Parallel to each other; the transmitting coil T y Receiver coil R y Shielded coil B y They are parallel to each other.

3. The method for rapidly determining the anisotropic formation conductivity of a deviated well according to claim 2, characterized in that, The winding directions of the shielding coil system and the receiving coil system are opposite, and the direct-coupled electromotive forces generated in the shielding coil system and the receiving coil system cancel each other out.

4. The method for rapidly determining the anisotropic formation conductivity of a deviated well according to claim 2, characterized in that, When the transmitting coil system emits sinusoidal alternating current into the surroundings, it can simultaneously measure nine magnetic field components H on the receiving coil system. ij (i = x, y, z; j = x, y, z).

5. The method for rapidly determining the anisotropic formation conductivity of a deviated well according to claim 2, characterized in that, After the direct-coupled electromotive forces cancel each other out, the magnetic field strength measured by the receiving coil system... The formula is: In the formula H ij1 H represents the magnetic field generated by the receiving coil. ij2 L1 represents the magnetic field generated by the shielding coil; L2 represents the source distance of the receiving coil; L3 represents the source distance of the shielding coil.

6. The method for rapidly determining the anisotropic formation conductivity of a deviated well according to claim 1, characterized in that, The well logging response component combination curve σ HA The formula is: Where, σ zx The conductivity curve is for emission in the z-direction and reception in the x-direction; σ xz The conductivity curve is for emission in the x-direction and reception in the z-direction; σ xx The conductivity curve is for transmission and reception in the x-direction; σ zz The conductivity curves are those emitted and received in the z-direction; α is the wellbore inclination angle.

7. The method for rapidly determining the anisotropic formation conductivity of a deviated well according to claim 1, characterized in that, When obtaining the three-dimensional induction logging response in the inclined well, three formation coordinate systems OX are introduced. f Y f Z f Wellbore coordinate system OX w Y w Z w and instrument coordinate system OX t Y t Z t Perform a rotation transformation.

8. The method for rapidly determining the anisotropic formation conductivity of a deviated well according to claim 1, characterized in that, The cross-component response combination curve (σ) with less influence from adjacent layers is adopted. zx +σ xz ) Calculate the vertical conductivity.

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