A high-precision velocity field construction method based on well-seismic integration for horizontal well development

Abstract

The present invention discloses a high-precision velocity field construction method for horizontal well development combined with well-seismic data. The method is first based on the fine structural interpretation of small layers under the constraints of sequence stratigraphy. Through velocity simulation under seismic constraints, the technical problems of low vertical resolution of velocity fields and inter-well modeling in conventional methods are effectively solved, and a high-precision velocity field in the medium and deep layers is established. Secondly, in order to solve the problem of missing velocity curves in shallow layers, the velocity spectrum after well calibration is used to establish a near-surface velocity field. Then, an adaptive optimal value selection algorithm is used to effectively integrate the shallow layer velocity field with the medium and deep layer velocity field to form a complete high-precision three-dimensional velocity field model. Finally, the marker layer inverted triangle layer-by-layer approximation method is used, relying on new drilling data, to continuously correct the velocity model and achieve high-precision structural model updates that accompany the entire life cycle of oil reservoir development. The present invention belongs to the field of oil and gas extraction technology and can reduce the structural error of the "sweet spot" of thin shale oil layers, thereby ensuring the precise entry of horizontal wells into the target.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and gas production and is used in the process of oil and gas reservoir evaluation and development. Specifically, it is a well-seismic combined high-precision velocity field construction method for horizontal well development. Background Art

[0002] With the rapid economic development, people's urgent demand for energy and the uncertainty of the international situation, my country is facing severe energy security, and the development of unconventional energy such as shale oil is imperative.

[0003] Currently, shale oil has become a key area of ​​focus for domestic oilfield capacity development. Compared to conventional oil and gas reservoirs, shale oil has geological characteristics such as thin vertical thickness and rapid lateral changes. Precise velocity field construction is key to improving the accuracy of micro-structural characterization in target areas, guiding the precise placement of horizontal wells, and increasing the drilling rate of oil and gas reservoirs.

[0004] Early velocity field construction research primarily used well velocity interpolation, model tomography, and the Dix formula. These methods have been widely used in conventional oil and gas reservoirs, but their relative errors are large for unconventional reservoirs, where high targeting accuracy is crucial, making them ineffective in guiding precise horizontal well placement.

[0005] In recent years, integrated velocity field construction based on well-seismic analysis has gradually begun to be applied in unconventional oil and gas reservoirs. The basic idea is to first subtract the pseudo-well curve extracted from the interval velocity volume generated by velocity spectrum field construction from the uphole velocity curve to generate residual velocities. Then, a reasonable stratigraphic framework model is established through stratigraphic interpretation, and the residual velocity curve is interpolated using this established stratigraphic framework model to obtain a residual velocity volume. Finally, the interval velocity volume and the residual velocity volume are added together to obtain the final velocity volume. This method has a good application effect on thick, lateral-stable, tight sandstone unconventional reservoirs. However, for areas with thinner sweet spots, faster lateral changes, and higher requirements for micro-structural accuracy, such as a shale oil field in the Junggar Basin, where the structural error requirement is less than 5 meters, the velocity field construction accuracy is far from meeting the requirements of field development. This is specifically reflected in the following aspects: (1) The thickness of the single sweet spot of shale oil in the depression is relatively thin, averaging 1-3 meters, and it is impossible to use the above method to accurately establish a reasonable stratigraphic framework model at the internal small layer level; (2) When subtracting the uphole velocity curve from the extracted pseudo-well curve, due to the difference in sampling rate between the uphole velocity curve and the pseudo-well curve, the residual curve can only reflect the overall trend and cannot accurately represent the error; (3) When the velocity volume is interpolated using the residual velocity curve, although the stratigraphic model is established using the layer position for constraint, the overall interpolation algorithm ignores the lateral constraints of the earthquake; (4) There is a lack of a solution for subsequent iterative correction. Summary of the Invention

[0006] The purpose of this invention is to provide a high-precision velocity field construction method for horizontal well development by combining well-seismic data to reduce the structural error of the "sweet spot" of thin shale oil layers, thereby ensuring accurate targeting of horizontal wells.

[0007] In order to achieve the above-mentioned purpose, the present invention adopts the following technical solutions:

[0008] A high-precision velocity field construction method based on well-seismic integration for horizontal well development is carried out in the following steps:

[0009] S1, Curve environment correction

[0010] The multivariate fitting method is used to carry out curve environment correction on the acoustic time difference curve and the density curve to obtain the corrected acoustic time difference curve and the corrected density curve;

[0011] S2. Interpretation of small-layer structures under high-precision sequence stratigraphic constraints

[0012] Select m interfaces with the most obvious velocity changes as marker layers, conduct well-seismic joint analysis, and complete the structural interpretation of the marker layers in the entire area; for the sweet spots that cannot be identified by seismic, use the method of linear tracing of sequence stratigraphy under the constraint of marker layers to establish a small layer stratigraphic model, and use the residual between the interpreted layer and the well logging layer to correct the initial interpreted layer to ensure the consistency of well-seismic analysis and obtain high-precision interpreted layers; m ≥ 4;

[0013] S3, high-precision and rapid field construction with combined well-seismic and

[0014] S31, complete the velocity field construction of the middle and deep layers and the shallow surface layer;

[0015] S32, fusion of shallow surface velocity field and mid-deep velocity field;

[0016] S4, iterative correction of the marker layer inverted triangle layer-by-layer approximation method

[0017] Based on the high-precision velocity field initially obtained and according to subsequent horizontal well data, the marker layer inverted triangle layer-by-layer approximation method is adopted to correct the velocity body in real time and continuously improve the accuracy of the structural model.

[0018] As a limitation, in step S1, a multivariate fitting method is used for the collapsed section curve, and firstly, a multivariate fitting and correction is performed on the curve whose influence rate of wellbore collapse is less than 5%.

[0019] The acoustic time difference curve is corrected using the following formula:

[0020] P_AC=125.878-0.472*(GR)-0.0914*(RT) Formula ①

[0021] Where, P_AC is the acoustic time difference, unit is μs / m;

[0022] For the density curve, correction is performed using the following formula:

[0023] DEN=2.655+0.00027*(GR)-0.00195*(RT) Formula②

[0024] Where: DEN is density, unit is g / cm 3 ; RT is resistivity, unit is Ω·m; GR is natural gamma, unit is API.

[0025] As a second limitation, step S2 is performed in the following order:

[0026] S21. Establish a high-precision sequence stratigraphic framework that is unified with well and seismic data.

[0027] Select n seismically traceable horizons from m well logging marker layers, complete the structural interpretation of the marker layers in the entire area through well-logging and seismic comparison, and establish a high-precision sequence stratigraphic framework unified by well logging and seismic analysis; n≤m;

[0028] S22. Linear tracing of small layers under sequence stratigraphic constraints

[0029] Based on the marker layers of structural interpretation, the linear tracing method of small layers under the constraints of sequence stratigraphy is applied to realize the intelligent interpretation of small layers.

[0030] S23, Well Seismic Residual Correction

[0031] S231, gridding the interpretation horizon, extracting the interpretation horizon value at the well point, subtracting the layer time value at the well point from the interpretation horizon time value to obtain the well-seismic error;

[0032] S232, gridding the obtained well seismic errors on each well to obtain a well seismic error trend surface;

[0033] S233, gridding the interpreted horizon and adding the resulting error trend surface to obtain a corrected horizon surface;

[0034] S234. Convert the corrected horizon surface into horizon data for subsequent velocity field framework establishment and timely depth conversion.

[0035] As a third limitation, the deep velocity field building in step S31 is performed in the following order:

[0036] S311, converting the acoustic time difference curve corrected in step S1 into an instantaneous velocity curve using formula ③

[0037] V=1000000 / P_AC formula ③

[0038] Where, V is the longitudinal wave velocity, in m / s; P_AC is the acoustic wave time difference, in us / m;

[0039] The instantaneous velocity curve and the density curve corrected in step S1 are calculated using formula ④ to generate the longitudinal wave impedance curve.

[0040] Longitudinal wave impedance = velocity × density (Formula ④);

[0041] S312, establishing a stratigraphic framework model using the high-precision interpretation horizon obtained in step S2;

[0042] S313, obtain the P-wave impedance body through waveform phase-controlled geostatistical inversion;

[0043] S314. Using the longitudinal wave impedance body as a constraint, carry out seismic waveform phase-controlled geostatistical simulation of the velocity curve to obtain a velocity simulation body constrained by seismic data, obtain the mid-deep velocity body, and complete the mid-deep velocity field establishment.

[0044] As a fourth limitation, step S31 shallow surface velocity field establishment is performed in the following order:

[0045] P311. Convert the velocity spectrum into a reference surface for measurement, and correct any abnormal points in the velocity spectrum to obtain a corrected velocity spectrum.

[0046] P312, using the Dix formula, convert the corrected velocity spectrum into the average velocity field;

[0047] P313, use existing drilling information to correct the average velocity field;

[0048] P314. Select the marker layer of the shallow layer, extract the instantaneous velocity of this layer, and interpolate the instantaneous velocity longitudinally to obtain a velocity body with the same longitudinal velocity at each X and Y point and varying lateral velocity. Treat this velocity body as the shallow layer velocity body, and the shallow layer velocity field construction is completed.

[0049] As a fifth limitation, step S32 includes the following process:

[0050] For the same working area Ω, the speed x1∈Ω1, the speed x2∈Ω2, and the boundary between Ω1 and Ω2 Set the fusion width between speed x1 and speed x2 to Then, the fusion operator is

[0051] J(x1, x2)=λ(x)x1+(1-λ(x))x2 Formula ⑤

[0052]

[0053] Further, the total fusion operator is

[0054]

[0055] The mid-deep velocity body obtained in the mid-deep velocity field construction process and the shallow velocity body constructed in the shallow surface velocity field construction process are fused using the fusion operators of formulas ⑤⑥⑦.

[0056] As a sixth limitation, step S4 is performed in the following order:

[0057] S41, using the high-precision velocity field established in step S3, performing time-depth conversion to obtain a depth-domain seismic data volume;

[0058] S42. Design well trajectory before drilling based on deep-domain seismic data.

[0059] S43. During the real-time drilling process of the horizontal well, when a marker layer is encountered, the actual drilling layer data of the marker layer is input, the velocity field is corrected in real time, and the time-depth conversion is re-performed to obtain a corrected depth domain seismic data volume;

[0060] S44. Utilize the corrected depth-domain seismic data volume to optimize the remaining marker layers and predicted target depth, continuously iterate the correction, and improve the horizontal well target accuracy.

[0061] Due to the adoption of the above technical solution, the present invention has achieved the following technical advancements compared with the prior art:

[0062] (1) The present invention can solve the problem of not being able to take into account both the longitudinal velocity accuracy and the lateral velocity trend, thereby improving the accuracy of structural implementation and reducing the structural error in the study area;

[0063] (2) The present invention is based on the fine structural interpretation of small layers under sequence stratigraphic constraints and can effectively solve the technical problems of low vertical resolution of velocity field and inter-well modeling in conventional methods through velocity simulation under seismic constraints;

[0064] (3) The present invention establishes a high-precision velocity field in the middle and deep layers. Secondly, to address the problem of missing velocity curves in the shallow layer, the velocity spectrum after well calibration is used to establish a near-surface velocity field. Then, an adaptive optimal value selection algorithm is used to effectively integrate the shallow velocity field with the middle and deep velocity field to form a complete high-precision three-dimensional velocity field model. Finally, the marker layer inverted triangle layer-by-layer approximation method is used to continuously calibrate the velocity model based on new drilling data, which can achieve high-precision structural model updates throughout the entire life cycle of reservoir development.

[0065] (4) Currently, the main frequency of newly acquired and processed seismic data is mainly around 40 Hz. According to the Widess criterion (resolution = λ / 8), only a 12.5 m reservoir can be identified. The thickness of the shale oil sweet spot is relatively thin, with the minimum thickness of a single sweet spot being only 2-5 m. Seismic data cannot effectively identify the small layers inside the sweet spot, and manual interpretation of the small layers inside the sweet spot cannot be achieved. The present invention is based on the interpreted marker layer and applies a small layer linear tracking method under sequence stratigraphic constraints to achieve intelligent interpretation of the small layers.

[0066] (5) There is a certain difference in the resolution between the well logging curve and the seismic. Even on the basis of the detailed interpretation of the well logging curve and the seismic curve, there is still a certain error. Therefore, according to the errors existing in the interpretation layers and stratifications, the method provided by the present invention can be used to achieve the well logging curve and seismic residual correction.

[0067] The present invention belongs to the technical field of oil and gas extraction, and can reduce the structural error of the "sweet spot" of a thin shale oil layer, thereby ensuring that the horizontal well accurately enters the target. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention.

[0069] In the attached figure:

[0070] Figure 1 Flowchart of the well-seismic combined velocity field construction method according to an embodiment of the present invention

[0071] Figure 2 This is a cross-sectional diagram of the interval velocity body through the well constructed using different velocity field construction methods in an embodiment of the present invention;

[0072] in, Figure 2 a is a layer velocity profile obtained by a velocity field construction method based on multi-well time-depth relationship interpolation according to an embodiment of the present invention;

[0073] Figure 2 b is a velocity profile obtained by numerical interpolation of velocity curves according to an embodiment of the present invention;

[0074] Figure 2 c is an interval velocity profile obtained based on the well-seismic combined velocity field construction of this invention in an embodiment of the present invention;

[0075] Figure 3 a is a target layer structural map drawn based on velocity field construction by interpolating time-depth relationship curves of multiple wells according to an embodiment of the present invention;

[0076] Figure 3 b is a target layer structure map drawn based on well-seismic combined velocity field construction according to an embodiment of the present invention. DETAILED DESCRIPTION

[0077] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention and are not used to limit the present invention.

[0078] A method for combining wellbore seismic with high-precision velocity field construction for horizontal well development

[0079] like Figure 1 As shown, this embodiment is carried out in the following steps in sequence:

[0080] S1, Curve environment correction

[0081] The multivariate fitting method is used to carry out curve environment correction on the acoustic time difference curve and the density curve to obtain the corrected acoustic time difference curve and the corrected density curve;

[0082] Specifically, the multivariate fitting method is used to target the collapsed section curves. First, the curves affected by wellbore collapse with a rate less than 5% are subjected to multivariate fitting and correction.

[0083] The acoustic time difference curve is corrected using the following formula:

[0084] P_AC=125.878-0.472*(GR)-0.0914*(RT) Formula ①

[0085] Where, P_AC is the acoustic time difference, unit is μs / m;

[0086] For the density curve, correction is performed using the following formula:

[0087] DEN=2.655+0.00027*(GR)-0.00195*(RT) Formula②

[0088] Where: DEN is density, unit is g / cm 3 ; RT is resistivity, unit is Ω·m; GR is natural gamma, unit is API;

[0089] S2. Interpretation of small-layer structures under high-precision sequence stratigraphic constraints

[0090] Select m interfaces with the most obvious velocity changes as marker layers, conduct well-seismic joint analysis, and complete the structural interpretation of the marker layers in the entire area; for the sweet spots that cannot be identified by seismic, use the method of linear tracing of sequence stratigraphy under the constraint of marker layers to establish a small layer stratigraphic model, and use the residual between the interpreted layer and the well logging layer to correct the initial interpreted layer to ensure the consistency of well-seismic analysis and obtain high-precision interpreted layers; m ≥ 4;

[0091] In practice, technicians select interfaces with obvious velocity changes from the collected data charts as marker layers according to their needs. In this embodiment, m=6, and in the microstructural implementation of a shale oil field in the Junggar Basin, Xinjiang, P3wt, P2l2 1 、P2l2 2 -3 、P2l2 2-4 、P2l1 2-2 、P2l1 2-7 The six interfaces with obvious velocity changes at the bottom are used as the marker layers of the entire area;

[0092] S3, high-precision and rapid field construction with combined well-seismic and

[0093] S31, complete the velocity field construction of the middle and deep layers and the shallow surface layer;

[0094] S32, fusion of shallow surface velocity field and mid-deep velocity field;

[0095] S4, iterative correction of the marker layer inverted triangle layer-by-layer approximation method

[0096] Based on the high-precision velocity field initially obtained and according to subsequent horizontal well data, the marker layer inverted triangle layer-by-layer approximation method is adopted to correct the velocity body in real time and continuously improve the accuracy of the structural model.

[0097] In the above process, step S2 is performed in the following order:

[0098] S21. Establish a high-precision sequence stratigraphic framework that is unified with well and seismic data.

[0099] According to the principle that "well logging curves show abrupt interfaces, and seismic data show strong amplitude and continuous reflection characteristics", 6 marker layers were selected from 14 small layers. Through the joint comparison of well and seismic data, the structural interpretation of the marker layers in the entire area was completed, and a high-precision sequence stratigraphic framework unified by well and seismic data was established.

[0100] S22. Linear tracing of small layers under sequence stratigraphic constraints

[0101] Currently, the dominant frequency of newly acquired and processed seismic data is around 40 Hz. Based on the Widess criterion (resolution = λ / 8), only a 12.5 m reservoir can be identified. The shale oil sweet spot is relatively thin, with the minimum thickness of a single sweet spot being only 2-5 m. Seismic data cannot effectively identify small layers within the sweet spot, making manual interpretation of these layers unrealistic.

[0102] This embodiment uses the marker layer of structural interpretation as the basis and applies the small layer linear tracing method under the constraint of sequence stratigraphy to realize the intelligent interpretation of small layers;

[0103] S23, Well Seismic Residual Correction

[0104] There is a certain difference in resolution between well logging curves and seismic data. Even based on the detailed interpretation of well logging curves, there are still certain errors. Therefore, according to the errors in the interpreted horizons and layers, this step specifically corrects them through the following process:

[0105] S231, gridding the interpretation horizon, extracting the interpretation horizon value at the well point, subtracting the layer time value at the well point from the interpretation horizon time value to obtain the well-seismic error;

[0106] S232, gridding the obtained well seismic errors on each well to obtain a well seismic error trend surface;

[0107] S233, gridding the interpreted horizon and adding the resulting error trend surface to obtain a corrected horizon surface;

[0108] S234. Convert the corrected horizon surface into horizon data for subsequent velocity field framework establishment and timely depth conversion.

[0109] The sweet spot in the application area of ​​this embodiment is relatively thin and has well-developed micro-amplitude structures. It is necessary to fully exploit the lateral stability advantage of seismic data and the vertical high-resolution advantage of well logging data, so the information of seismic data and well logging data are effectively integrated.

[0110] Specifically, the deep velocity field building in step S31 is performed in the following order:

[0111] S311, converting the acoustic time difference curve corrected in step S1 into an instantaneous velocity curve using formula ③

[0112] V=1000000 / P_AC formula ③

[0113] Where, V is the longitudinal wave velocity, in m / s; P_AC is the acoustic wave time difference, in us / m;

[0114] The instantaneous velocity curve and the density curve corrected in step S1 are calculated using formula ④ to generate the longitudinal wave impedance curve.

[0115] Longitudinal wave impedance = velocity × density (Formula ④);

[0116] S312, establishing a stratigraphic framework model using the high-precision interpretation horizon obtained in step S2;

[0117] S313, obtain the P-wave impedance body through waveform phase-controlled geostatistical inversion;

[0118] S314. Using the longitudinal wave impedance body as a constraint, conduct seismic waveform phase-controlled geostatistical simulation of the velocity curve to obtain a velocity simulation body constrained by seismic data. While ensuring the stability of the lateral trend, take into account the vertical resolution, obtain the mid-deep velocity body, and complete the mid-deep velocity field establishment.

[0119] Since there are few wells drilled from the surface, the velocity field obtained in the first step loses velocity information in the shallow layer, resulting in abnormal shallow layer velocity data. Therefore, it is necessary to merge the shallow layer velocity using the velocity information of the velocity spectrum.

[0120] Specifically, step S31 shallow surface velocity field construction is performed in the following order:

[0121] P311. Convert the velocity spectrum into a reference surface for measurement, and correct any abnormal points in the velocity spectrum to obtain a corrected velocity spectrum.

[0122] P312, using the Dix formula, convert the corrected velocity spectrum into the average velocity field;

[0123] P313, use existing drilling information to correct the average velocity field;

[0124] P314. Select the marker layer of the shallow layer. In this embodiment, the work area selects the bottom boundary of the Paleogene as the marker layer, extracts the instantaneous velocity of the layer, and interpolates the instantaneous velocity vertically to obtain a velocity body with the same vertical velocity at each X and Y point and varying lateral velocity. This velocity body is regarded as the layer velocity body of the Paleogene, that is, the shallow layer velocity body. At this point, the shallow layer velocity field construction is completed.

[0125] In this embodiment, step S32 includes the following process:

[0126] For the same working area Ω, the speed x1∈Ω1, the speed x2∈Ω2, and the boundary between Ω1 and Ω2 Set the fusion width between speed x1 and speed x2 to Then, the fusion operator is

[0127] J(x1, x2)=λ(x)x1+(1-λ(x))x2 Formula ⑤

[0128]

[0129] Further, the total fusion operator is

[0130]

[0131] The mid-deep velocity body obtained in the mid-deep velocity field construction process and the shallow velocity body constructed in the shallow surface velocity field construction process are fused using the fusion operators of formulas ⑤⑥⑦.

[0132] Step S4 is performed in the following order:

[0133] S41, using the high-precision velocity field established in step S3, performing time-depth conversion to obtain a depth-domain seismic data volume;

[0134] S42. Design well trajectory before drilling based on deep-domain seismic data.

[0135] S43. During the real-time drilling process of the horizontal well, when a marker layer is encountered, the actual drilling layer data of the marker layer is input, the velocity field is corrected in real time, and the time-depth conversion is re-performed to obtain a corrected depth domain seismic data volume;

[0136] S44. Utilize the corrected depth-domain seismic data volume to optimize the remaining marker layers and predicted target depth, continuously iterate the correction, and improve the horizontal well target accuracy.

[0137] The method provided in this example was implemented in a shale oil microstructure in the Junggar Basin, Xinjiang. This area is a key area for oilfield capacity development. Established in 2019 as China's first shale oil demonstration area, it exemplifies shale oil in foreland saline lake basins. Due to the low porosity and permeability of the sweet spot, vertical well production is low. Horizontal well development is an effective means of increasing shale oil reserves and production. Due to the early use of conventional variable-speed drilling methods, the structural model accuracy was low. The average structural error at the target point for horizontal wells was 15 meters, with a maximum error of 23 meters. This resulted in premature landing of horizontal wells and an average sweet spot drilling rate of 68.4%, severely hindering the efficient development of shale oil in the area.

[0138] The method provided in this embodiment was applied to the oil field, effectively solving the problem of not being able to simultaneously take into account both the vertical velocity accuracy and the horizontal trend, improving the accuracy of structural implementation and reducing the structural error in the study area. The specific effects are as follows:

[0139] Using 6 verification wells to verify the accuracy of conventional methods and this method, it can be seen that the well interpolation field construction error is between 2.32m-11.78m, with an average error of 7.06m. The velocity spectrum Dix ​​formula field construction error is between 0.82m-10.84m, with an average error of 5.06m. The structural error of the well-seismic combined velocity field construction method based on this embodiment is between 0.29m-4.87m, with an average error of 2.78m, as shown in Table 1, and the microstructural details of the structural map compiled based on the present invention are more prominent, and the northeast-oriented en echelon strip features are obvious. From the verification results, the accuracy of the structural map using the results of the embodiment is more accurate. At the same time, through the verification of the horizontal wells drilled in 2020, the target point error is less than 5m, which reduces the frequency of horizontal well trajectory adjustment, improves drilling efficiency, and saves on-site costs, as shown in Table 2.

[0140] Table 1 P2l2 of verification wells in Ji 305 well area 2-1 Top boundary structural error analysis table

[0141]

[0142]

[0143] Table 2 Statistics of structural errors of horizontal wells drilled in 2020

[0144]

[0145] like Figure 2 The figure shows a cross-sectional diagram of the interval velocity body through the well constructed by using different velocity field construction methods in the embodiment. Figure 2 a is the interval velocity profile obtained by interpolating velocity field construction method based on multi-well time-depth relationship; 2b is the interval velocity profile obtained by numerical interpolation of velocity curves; Figure 2 c is the interval velocity profile obtained by the well-seismic combined velocity field construction method based on the embodiment. As can be seen from the figure, the well-seismic combined velocity field construction method not only takes into account the vertical velocity accuracy, but also has a reasonable horizontal trend and no abnormal shallow layer velocity, and the effect is significantly better than the previous two methods.

[0146] Figure 3 a is a target layer structural map drawn based on velocity field construction by interpolating time-depth relationship curves of multiple wells according to an embodiment of the present invention; Figure 3 b is a structural map of the target layer drawn based on the well-seismic combined velocity field construction according to an embodiment of the present invention. It can be seen from the figure that the structural map compiled based on the well-seismic combined velocity field construction has more prominent microstructural details and a distinct northeast-trending en echelon strip feature.

[0147] Relying on the method provided in this embodiment, the oil layer drilling rate of the recently drilled horizontal wells in the guarantee area is above 93%. After production, the average daily oil production of a single well is 43 tons, and the highest daily production is 62 tons. The production effect is better than that of the previous oil wells. The production situation is good, effectively supporting the efficient development of production capacity, and at the same time, filling the technical gap in high-precision and high-speed field construction of shale oil.

Claims

1. A high-precision velocity field construction method based on well-seismic integration for horizontal well development, characterized by: Follow these steps in order: S1, Curve environment correction The multivariate fitting method is used to carry out curve environment correction on the acoustic time difference curve and the density curve to obtain the corrected acoustic time difference curve and the corrected density curve; S2. Interpretation of small-layer structures under high-precision sequence stratigraphic constraints Select m interfaces with the most obvious velocity changes as marker layers, conduct well-seismic joint analysis, and complete the structural interpretation of the marker layers in the entire area; For sweet spots that cannot be identified by seismic analysis, a stratigraphic linear tracing method under the constraint of marker layers is used to establish a stratigraphic model of the small layers. The residual between the interpreted layers and the well logging layers is used to correct the initial interpreted layers to ensure the consistency between well and seismic data and obtain high-precision interpreted layers. m≥4； S3, high-precision and rapid field construction with combined well-seismic and S31, complete the velocity field construction of the middle and deep layers and the shallow surface layer; S32, fusion of shallow surface velocity field and mid-deep velocity field; S4, iterative correction of the marker layer inverted triangle layer-by-layer approximation method Based on the high-precision velocity field initially obtained and according to subsequent horizontal well data, the marker layer inverted triangle layer-by-layer approximation method is adopted to correct the velocity body in real time and continuously improve the accuracy of the structural model.

2. The method for high-precision velocity field construction based on well-seismic integration for horizontal well development according to claim 1 is characterized in that: In step S1, a multivariate fitting method is used to perform multivariate fitting and correction on the collapsed section curve, firstly on the curve with a wellbore collapse influence rate of less than 5%. The acoustic time difference curve is corrected using the following formula: P_AC=125.878-0.472*(GR)-0.0914*(RT) Formula ① Where, P_AC is the acoustic time difference, unit is μs / m; For the density curve, correction is performed using the following formula: DEN=2.655+0.00027*(GR)-0.00195*(RT) Formula② Where: DEN is density, unit is g / cm 3 ; RT is resistivity, unit is Ω·m; GR is natural gamma, unit is API.

3. The method for high-precision velocity field construction based on well-seismic integration for horizontal well development according to claim 1 is characterized in that: Step S2 is performed in the following order: S21. Establish a high-precision sequence stratigraphic framework that is unified with well and seismic data. Select n seismically traceable horizons from m well logging marker layers, complete the structural interpretation of the marker layers in the entire area through well-logging and seismic comparison, and establish a high-precision sequence stratigraphic framework unified by well logging and seismic analysis; n≤m; S22. Linear tracing of small layers under sequence stratigraphic constraints Based on the marker layers of structural interpretation, the linear tracing method of small layers under the constraints of sequence stratigraphy is applied to realize the intelligent interpretation of small layers. S23, Well Seismic Residual Correction S231, gridding the interpretation horizon, extracting the interpretation horizon value at the well point, subtracting the layer time value at the well point from the interpretation horizon time value to obtain the well-seismic error; S232, gridding the obtained well seismic errors on each well to obtain a well seismic error trend surface; S233, gridding the interpreted horizon and adding the resulting error trend surface to obtain a corrected horizon surface; S234. Convert the corrected horizon surface into horizon data for subsequent velocity field framework establishment and timely depth conversion.

4. The method for high-precision velocity field construction based on well-seismic integration for horizontal well development according to claim 1 is characterized in that: The deep velocity field building in step S31 is performed in the following order: S311, converting the acoustic time difference curve corrected in step S1 into an instantaneous velocity curve using formula ③ V=1000000 / P_AC formula ③ Where, V is the longitudinal wave velocity, in m / s; P_AC is the acoustic wave time difference, in us / m; The instantaneous velocity curve and the density curve corrected in step S1 are calculated using formula ④ to generate the longitudinal wave impedance curve. Longitudinal wave impedance = velocity × density (Formula ④); S312, establishing a stratigraphic framework model using the high-precision interpretation horizon obtained in step S2; S313, obtain the P-wave impedance body through waveform phase-controlled geostatistical inversion; S314. Using the longitudinal wave impedance body as a constraint, carry out seismic waveform phase-controlled geostatistical simulation of the velocity curve to obtain a velocity simulation body constrained by seismic data, obtain the mid-deep velocity body, and complete the mid-deep velocity field establishment.

5. The method for high-precision velocity field construction based on well-seismic integration for horizontal well development according to claim 1 is characterized in that: The shallow surface velocity field construction step S31 is performed in the following order: P311. Convert the velocity spectrum into a reference surface for measurement, and correct any abnormal points in the velocity spectrum to obtain a corrected velocity spectrum. P312, using the Dix formula, convert the corrected velocity spectrum into the average velocity field; P313, use existing drilling information to correct the average velocity field; P314. Select the marker layer of the shallow layer, extract the instantaneous velocity of this layer, and interpolate the instantaneous velocity longitudinally to obtain a velocity body with the same longitudinal velocity at each X and Y point and varying lateral velocity. Treat this velocity body as the shallow layer velocity body, and the shallow layer velocity field construction is completed.

6. The method for high-precision velocity field construction based on well-seismic integration for horizontal well development according to claim 1 is characterized in that: The step S32 includes the following process: For the same working area Ω, the speed x1∈Ω1, the speed x2∈Ω2, and the boundary between Ω1 and Ω2 Set the fusion width between speed x1 and speed x2 to Then, the fusion operator is J(x1, x2)=λ(x)x1+(1-λ(x))x2 Formula ⑤ Further, the total fusion operator is The mid-deep velocity body obtained in the mid-deep velocity field construction process and the shallow velocity body constructed in the shallow surface velocity field construction process are fused using the fusion operators of formulas ⑤⑥⑦.

7. The method for high-precision velocity field construction based on well-seismic integration for horizontal well development according to claim 1 is characterized in that: Step S4 is performed in the following order: S41, using the high-precision velocity field established in step S3, performing time-depth conversion to obtain a depth-domain seismic data volume; S42. Design well trajectory before drilling based on deep-domain seismic data. S43. During the real-time drilling process of the horizontal well, when a marker layer is encountered, the actual drilling layer data of the marker layer is input, the velocity field is corrected in real time, and the time-depth conversion is re-performed to obtain a corrected depth domain seismic data volume; S44. Utilize the corrected depth-domain seismic data volume to optimize the remaining marker layers and predicted target depth, continuously iterate the correction, and improve the horizontal well target accuracy.

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