A method for electrical measurement of radial horizontal well trajectory

Abstract

The present invention belongs to the field of oil and gas exploration and development, and specifically relates to an electrical measurement method for radial horizontal well trajectories. Using the radial horizontal well jet nozzle and the adjacent well or ground as electrodes, an artificial electric field is applied to the formation to form a potential difference between various points in the formation. Assuming the formation to be an infinitely large uniform medium with isotropic resistivity, the potential difference between various points in the formation is positively correlated with their relative distance. Multiple groups of measuring point electrodes with different orientations and vertical depths are added to the radial horizontal well diverter to measure the potential difference between these electrodes and the radial horizontal well jet nozzle electrodes. Based on the potential difference measured at each measuring point, the relative distance between the nozzle and each measuring point is inferred. Using a multi-point positioning method, the coordinate position of the diffracted jet nozzle in a Cartesian coordinate system with the center of the diverter end measuring point as the origin is deduced to map the actual drilling trajectory of the radial horizontal well. The method has the advantages of simple operation and calculation, no cumulative error, and the ability to form a spatial trajectory.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas development, and in particular to an electrical measurement method for radial horizontal well trajectories. Background Art

[0002] Controlling the actual drilling trajectory and accurately hitting the target are important requirements for oil and gas resource exploration and development. Measuring and mapping the actual drilling trajectory is an inevitable means to achieve these requirements.

[0003] Conventional trajectory measurement devices are currently inadequate for radial horizontal well trajectory mapping due to their small radius of curvature, large doglegs, and small borehole diameters. Therefore, there are currently only two technical solutions for mapping radial horizontal well trajectories. The first employs micro-electromechanical (MEMS) inertial devices to measure the jet nozzle attitude in radial horizontal wells, combining this with the coiled tubing lowering and raising speeds or lengths to cumulatively estimate the wellbore trajectory. However, due to device vibration and external environmental interference during the mapping process, errors in the measured data are present, which are gradually amplified during the cumulative estimation process, ultimately leading to significant deviations between the mapped wellbore trajectory and the actual wellbore. The second approach, based on the principle of potential measurement, uses the actual wellbore and another adjacent wellbore as electrodes to supply a highly stable current into the formation to generate an initial formation electric field. Highly conductive fluid is then injected into the formation during drilling to induce changes in the initial formation electric field. Multiple groups of potential observation points arranged in a circular pattern on the surface monitor the potential changes to infer the radial horizontal well trajectory.

[0004] The existing technology presents at least the following problems: Due to measurement errors, trajectory extrapolation based on the inertial principle inevitably leads to the accumulation of surveying and mapping errors, ultimately resulting in low accuracy of the calculated wellbore trajectory parameters and low reliability of the mapped wellbore trajectory. Limited by the precision of understanding formation characteristics and employing only multiple ring-shaped measurement points on the surface, the measured potential changes only reflect the drilling trend of the radial horizontal well in its horizontal projection, not the horizontal projection parameters of the actual trajectory, and even less so the radial horizontal well trajectory within a spatial range. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for electrical measurement of radial horizontal well trajectories in response to the deficiencies in the prior art.

[0006] The radial well trajectory measurement is achieved by using the radial horizontal well jet nozzle and the adjacent well or the ground as electrodes and the potential difference between the radial horizontal well diverter and the nozzle as the measured parameter.

[0007] The technical solution is as follows:

[0008] A method for electrical measurement of radial horizontal well trajectories, comprising:

[0009] Using the radial horizontal well jet nozzle and the adjacent well or ground as electrodes E1 and E2 respectively, an artificial electric field is applied to the formation to form a potential difference between various points in the formation;

[0010] Assuming the stratum to be an infinite homogeneous medium with isotropic resistivity, the potential difference between points in the stratum is positively correlated with their relative distance;

[0011] Add multiple sets of measuring point electrodes at different azimuths and vertical depths at the end of the radial horizontal well diverter to measure the potential difference between them and the radial horizontal well jet nozzle electrodes;

[0012] According to the potential difference measured at each measuring point, the relative distance between the nozzle and each measuring point is inferred;

[0013] The coordinate position of the anti-diffraction jet nozzle in the Cartesian coordinate system with the center of the diverter end measuring point as the origin is measured by the multi-point positioning method to map the actual drilling trajectory of the radial horizontal well.

[0014] In a preferred embodiment, the method of inferring the relative distance between the nozzle and each measuring point based on the potential difference measured at each measuring point includes:

[0015] The conversion coefficient is obtained by using the potential difference and vertical depth difference between measuring points at different vertical depths;

[0016] The relative distance between the nozzle and the measuring point is obtained using the conversion coefficient and the potential difference between the nozzle and the measuring point.

[0017] In a preferred embodiment, the coordinate position of the anti-diffraction jet nozzle in a Cartesian coordinate system with the center of the diverter end measuring point as the origin by the multi-point positioning method includes:

[0018] Use the relative deviation between the measurement point data to eliminate outliers;

[0019] Using the principles of spatial geometry, we can obtain a set of nonlinear statically indeterminate equations;

[0020] Calculating the Jacobian matrix of the nonlinear statically indeterminate equations;

[0021] The Jacobian matrix is used to iteratively calculate the least square solution of the jet nozzle coordinates.

[0022] The beneficial effects of the present invention are:

[0023] Radial well trajectory measurement is achieved by using the radial horizontal well jet nozzle and the adjacent well or the ground as electrodes and the potential difference between the radial horizontal well diverter and the nozzle as the measured parameter. It has the advantages of simple operation and calculation, no cumulative error, and the ability to form a spatial trajectory. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The diagram is a schematic diagram of electrical measurement using the adjacent well and jet nozzle as power supply electrodes;

[0025] Figure 2 It is the horizontal projection diagram of the relative positions of measuring points M1 to M5;

[0026] Figure 3 Schematic diagram of measurement point arrangement. DETAILED DESCRIPTION

[0027] To make the objectives, technical solutions, and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. It should be understood that these descriptions are merely exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present invention.

[0028] Example 1:

[0029] A method for electrical measurement of radial horizontal well trajectories, the method comprising:

[0030] Using the radial horizontal well jet nozzle and the adjacent well or ground as electrodes E1 and E2 respectively, an artificial electric field is applied to the formation to form a potential difference between various points in the formation;

[0031] Assuming the stratum to be an infinite homogeneous medium with isotropic resistivity, the potential difference between points in the stratum is positively correlated with their relative distance;

[0032] Add multiple sets of measuring point electrodes at different azimuths and vertical depths at the end of the radial horizontal well diverter to measure the potential difference between them and the radial horizontal well jet nozzle electrodes;

[0033] According to the potential difference measured at each measuring point, the relative distance between the nozzle and each measuring point is inferred;

[0034] The coordinate position of the anti-diffraction jet nozzle in the Cartesian coordinate system with the center of the diverter end measuring point as the origin is measured by the multi-point positioning method to map the actual drilling trajectory of the radial horizontal well.

[0035] In a preferred embodiment, the method of inferring the relative distance between the nozzle and each measuring point based on the potential difference measured at each measuring point includes:

[0036] The conversion coefficient is obtained by using the potential difference and vertical depth difference between measuring points at different vertical depths;

[0037] The relative distance between the nozzle and the measuring point is obtained using the conversion coefficient and the potential difference between the nozzle and the measuring point.

[0038] In a preferred embodiment, the coordinate position of the anti-diffraction jet nozzle in a Cartesian coordinate system with the center of the diverter end measuring point as the origin by the multi-point positioning method includes:

[0039] Use the relative deviation between the measurement point data to eliminate outliers;

[0040] Using the principles of spatial geometry, we can obtain a set of nonlinear statically indeterminate equations;

[0041] Calculating the Jacobian matrix of the nonlinear statically indeterminate equations;

[0042] The Jacobian matrix is used to iteratively calculate the least square solution of the jet nozzle coordinates.

[0043] Example 2:

[0044] like Figure 1 、 Figure 3 As shown in the figure, for radial horizontal well operations requiring trajectory measurement, a variable-diameter support arm is installed at the end of the diverter before operations begin. Two groups of eight measuring points are installed on the diverter support arm in a double-layer array at 0°, 90°, 180°, and 270° angles. The measuring point lines are transported to the surface via tubing. After the diverter is lowered to the operating zone, the hydraulic anchor is opened and set. The support arm is propped up to the wellbore wall under the action of axial force, bringing measuring points M2 to M9 into contact with the wellbore wall.

[0045] A coiled tubing unit (CTU) transports a high-pressure hose and jet nozzle to the bottom of the well for jet drilling. Electrodes and measurement lines at the nozzle are transported to the surface via CTU. A surface generator, using the adjacent wellbore and jet nozzle as electrodes, continuously delivers electricity to the formation, creating an artificial electric field.

[0046] The lines between the measuring point on the steering gear end support arm and the measuring point at the nozzle are connected on the ground, and real-time potential measurement and data analysis and processing are carried out on the ground.

[0047] Example 3:

[0048] For the nozzle measuring point M1 at any spatial position, its horizontal projection relative to the upper layer measuring points M2 to M5 is as follows: Figure 2 As shown in Figure 2. Since the radial horizontal well branch borehole scale is much smaller than the geological structure scale and the vertical displacement of its trajectory is much smaller than the reservoir thickness, the formation within its operating range can be regarded as an infinite homogeneous formation with isotropic resistivity. Therefore, the formation between different measuring points can be regarded as a resistor, and its potential difference is proportional to the relative distance:

[0049] V=f(h)≈kh

[0050] Then there is

[0051] V 21 :V 31 :V 41 :V 51 =f(h 21 ):f(h 31 ):f(h 41 ):f(h 51 )≈h 21 :h31 :h 41 :h 51

[0052] Similarly, the same relationship exists between the measuring point M1 at the nozzle and the measuring points M6 to M9 at the lower layer of the steering end support arm.

[0053] V 61 :V 71 :V 81 :V 91 =f(h 61 ):f(h 71 ):f(h 81 ):f(h 91 )≈h 61 :h 71 :h 81 :h 91

[0054] Since the formation is homogeneous and has isotropic resistivity,

[0055] V 21 :V 31 :V 41 :V 51 :V 61 :V 71 :V 81 :V 91 :V 26 ≈h 21 :h 31 :h 41 :h 51 :h 61 :h 71 :h 81 :h 91 :h 26

[0056] Example 4:

[0057] like Figure 1 、 Figure 3 As shown, measuring points M2 through M9 on the steering arm's end are connected to measuring point M1 on the nozzle surface via cables. Measuring points M2 and M6 are also connected via cables on the surface. Measurements are performed simultaneously with radial horizontal well construction.

[0058] During each sampling, the ground obtains the potential difference between M2 and M6, and between M2 to M9 and M1:

[0059] V 26 、V 21 、V 31 、V 41 、V 51 、V 61 、V 71、V 81 、V 91

[0060] Combined with the installation dimensions of the measuring points, the distance between M2 and M6 measuring points is 2L z The diameter of the vertical wellbore where the support arm is located is 2L. The center of the support arm is used as the origin to establish a Cartesian coordinate system, and the spatial coordinates of the measuring points M2 to M9 in the coordinate system are:

[0061]

[0062] Let the coordinates of the measuring point M1 at the nozzle be (x, y, z)

[0063] Then, according to the geometric relationship:

[0064]

[0065] There is a conversion factor

[0066] k=V 26 / (2L z )

[0067] Compare the deviations between measurement points, identify outliers and remove them, and establish the Jacobian matrix

[0068] ΔV i,j =|(V i1 -V j1 )-k(h i1 -h j1 )|≥δmin{V i1 ,V j1}

[0069]

[0070] Taking the point without distinct values as an example, there is the Jacobian matrix

[0071]

[0072] The Gauss-Newton iteration method is used to solve the least squares solution of the above nonlinear overdetermined equations, and the coordinates of the measuring point M1 at the nozzle (x c ,y c ,z c ).

[0073] Link the coordinates of the M1 measuring point at each moment to obtain the radial horizontal well trajectory

[0074] T={(x c ,y c ,z c ) t}| t＝1,2λn

[0075] Get the trajectory parameters at each measuring point

[0076]

[0077] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for electrical measurement of radial horizontal well trajectory, characterized in that: The steps include: a: Using the radial horizontal well jet nozzle and the adjacent well or ground as electrodes, an artificial electric field is applied to the formation to form a potential difference between points in the formation. The formation is assumed to be an infinitely large homogeneous medium with isotropic resistivity. b: Add multiple sets of measuring point electrodes at different orientations and vertical depths to the end of the radial horizontal well diverter, and measure the potential difference between them and the radial horizontal well jet nozzle electrodes; c: The coordinate position of the anti-diffraction jet nozzle in the Cartesian coordinate system with the center of the diverter end measuring point as the origin is measured by the multi-point positioning method to map the actual drilling trajectory of the radial horizontal well; The step c specifically includes: c1: Determine the relative distance between the nozzle and each measuring point based on the potential difference measured at each measuring point; c2: coordinate position of the anti-diffraction jet nozzle in the Cartesian coordinate system with the center of the measuring point at the end of the diverter as the origin by the multi-point positioning method; c3: Mapping the actual drilling trajectory of radial horizontal wells; The step c1 specifically includes: The conversion coefficient is obtained by using the potential difference and vertical depth difference between measuring points at different vertical depths; The relative distance between the nozzle and the measuring point is obtained using the conversion coefficient and the potential difference between the nozzle and the measuring point.

2. The electrical measurement method for radial horizontal well trajectory according to claim 1, characterized in that: The step b specifically includes: A variable diameter support arm is installed at the end of the steering gear, and multiple measuring points of multiple groups of measuring point electrodes are installed on the support arm at the end of the steering gear in the form of multi-layer arrays in different orientations.

3. The electrical measurement method for radial horizontal well trajectory according to claim 2, characterized in that: The step c2 specifically includes: Eliminate outlier points based on the relative deviation between the measurement point data; The coordinates of the measuring points at the jet nozzle are obtained by iteratively calculating the least square solution of the nonlinear hyperstatic equations and the Jacobian ratio matrix obtained using the principles of spatial geometry.

4. The electrical measurement method for radial horizontal well trajectory according to claim 3, characterized in that: The step c3 specifically includes: sequentially linking the coordinates of the measuring points at the jet nozzle at each moment to obtain the radial horizontal well trajectory.

5. The electrical measurement method for radial horizontal well trajectory according to any one of claims 2 to 4, characterized in that: The measuring points are divided into two groups, with four measuring points in each group.

6. The electrical measurement method for radial horizontal well trajectory according to claim 5, characterized in that: The four measuring points of each group are installed on the steering gear end support arm at orientations of 0°, 90°, 180° and 270°.

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