Horizontal well geosteering method

Abstract

This invention relates to the field of oil and gas drilling exploration and development technology, and in particular to a horizontal well geological steering method. The method includes the following steps: 1) Calculating the dip angle θ based on two adjacent cross-layer points on the horizontal well trajectory, where dip angle θ = arctan(ΔH / ΔL), and ΔH and ΔL are the vertical depth difference and horizontal projection distance between the two adjacent cross-layer points, respectively; 2) Comparing the dip angle θ with the apparent dip angle range α of the formation in the target section of the horizontal well. min -α max The initial value of the apparent dip range of the strata was obtained from seismic data; 3) Adjust the drilling angle; when α min ≤θ≤α max If the previous cross-layer point is located at the top / bottom of the reservoir, then proceed with descending / increasing inclination drilling; when θ < α min Or θ > α max If the previous cross-section point is located at the top of the reservoir, drilling is initiated with increased inclination; if the previous cross-section point is located at the bottom of the reservoir, drilling is initiated with decreased inclination. This invention effectively solves the technical problem that the drill bit position cannot be determined from logging data during drilling in formations with similar top and bottom conditions.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil and gas drilling exploration and development, and particularly relates to a horizontal well geosteering method. BACKGROUND

[0002] A horizontal well refers to a well with a hole inclination angle reaching or approaching 90°, and a well bore drilled along a horizontal direction for a certain length. Generally, a horizontal well is suitable for thin oil and gas layers or fractured oil and gas reservoirs, and aims to increase the length of a well trajectory in an oil and gas reservoir, increase the oil discharge area, and improve oil and gas production.

[0003] In an ideal state, after entering a window (entering a reservoir), the hole inclination angle of a horizontal well is appropriately increased, and when the hole inclination angle is parallel to the stratum, stable inclination drilling is performed, so as to ensure that the well trajectory passes through the reservoir. In fact, due to the complexity of underground geological conditions, it is difficult for a geologist to provide a completely accurate apparent dip angle of the stratum, and the instability of drilling machinery also has an adverse effect on stable inclination drilling, and the drill bit may drill out of the reservoir.

[0004] In different target layer sections of top and bottom plate geological conditions, based on the different conditions of the top plate and the bottom plate of the target layer section, in order to enable the drill bit to drill out of the reservoir and then enter the window again in time, a commonly used method is to use the while-drilling GR curve and the element logging characteristic curve, to perform fine stratum comparison with the target layer section of the pilot hole, to determine whether the drill bit is located in the upper stratum or the lower stratum of the target layer section according to the geological conditions, and to adjust the hole inclination angle to enter the window again. However, in a continental sand and mud interbedded stratum, the top and bottom plate conditions of the reservoir are mostly similar, and the while-drilling GR and element characteristics are difficult to distinguish the upper and lower strata of the reservoir. SUMMARY

[0005] The present application aims to provide a horizontal well geosteering method, to solve the problem that in the process of drilling a horizontal well, the similar top and bottom plate conditions of the stratum cannot be used to determine the position of the drill bit through while-drilling GR, element logging and other data.

[0006] In order to solve the above problem, the horizontal well geosteering method of the present application adopts the following technical scheme: the horizontal well geosteering method comprises the following steps:

[0007] 1) calculating an inclination angle θ according to two adjacent layer-penetrating points of the horizontal well trajectory, the inclination angle θ = arctan (ΔH / ΔL), wherein ΔH is the vertical depth difference of the two adjacent layer-penetrating points, and ΔL is the horizontal plane projection distance of the two adjacent layer-penetrating points;

[0008] 2) comparing the inclination angle θ with the apparent dip angle range α of the target section of the horizontal well min -α max , and the initial value of the apparent dip angle range is obtained through seismic data;

[0009] 3) adjusting the drilling angle; when α min ≤ θ ≤ α max , if the previous layer-penetrating point is at the top of the reservoir, then the drilling angle is decreased, and if the previous layer-penetrating point is at the bottom of the reservoir, then the drilling angle is increased; when θ < α min or θ > α max , if the previous layer-penetrating point is at the top of the reservoir, then the drilling angle is increased, and if the previous layer-penetrating point is at the bottom of the reservoir, then the drilling angle is decreased.

[0010] Beneficial effects: the present application calculates the dip angle through the layer-penetrating point in the drilling process, and judges the layer-penetrating position of the drilling through the comparison between the dip angle and the apparent dip angle of the stratum, so that the judgment of the layer-penetrating position of the drill bit does not have to rely on the difference of the top and bottom plate geological conditions of the reservoir, the apparent dip angle of the stratum exists in any stratum, and can be obtained through geological data, and when the method of the present application is implemented, the drill bit position can be quickly judged through the comparison between the simple calculation of the while-drilling inclination data and the geological design depth profile, the drilling is guided, and the problem that the position of the drill bit cannot be judged through the while-drilling GR, element logging and other data in the stratum with similar top and bottom plate conditions in the horizontal well drilling process is solved.

[0011] Further, the range of the apparent dip angle of the stratum is adjusted to obtain a subsequent range of the apparent dip angle of the stratum, and the subsequent range of the apparent dip angle is obtained through the following method: the dip angle of the line segment between two layer-penetrating points on the same side of the reservoir is calculated according to the horizontal well trajectory adjacent to the two layer-penetrating points, the apparent dip angle of the top or bottom surface of the reservoir is determined according to the dip angle, and the subsequent range of the apparent dip angle is calculated according to the apparent dip angle, specifically, the apparent dip angle plus m is α max , and the apparent dip angle minus n is α min , and the m and n are empirical values, and the range of m and n is 0-1.5.

[0012] Further, on the basis of the combination of the initial value of the range of the apparent dip angle of the stratum and the subsequent range of the apparent dip angle, in step 2), the initial value of the range of the apparent dip angle of the stratum is obtained through the seismic data, and the method is as follows: at least two of the three seismic marker layers of the wave peak, zero phase and wave trough corresponding to the seismic event of the well trajectory are continuously tracked according to the seismic profile, the apparent dip angle of the stratum corresponding thereto is calculated, the maximum value plus m is α max , and the minimum value minus n is α min . Here, the value of m is 1, and further, the value of n is 1.

[0013] Further, in step 2), the initial value of the range of the apparent dip angle of the stratum is obtained through the method of the seismic data, and the method is as follows: at least two of the three seismic marker layers of the wave peak, zero phase and wave trough corresponding to the seismic event of the well trajectory are continuously tracked according to the seismic profile, the apparent dip angle of the stratum corresponding thereto is calculated, the maximum value plus m is α max, where the minimum value of the above equation is taken as a min , where m and n are experience values, and the range of m and n is 0-1.5. For a layered formation, the seismic event has good isochronous property, and simply speaking, the seismic event form and the formation occurrence are basically consistent. However, due to the influence of factors such as seismic data quality, thin reservoir seismic response characteristics, and well-seismic calibration accuracy, the occurrence of the target layer and the seismic event cannot be completely consistent. The occurrence of the upper and lower multiple seismic marker layers can reflect the real formation occurrence with a high probability. Therefore, the purpose of this is mainly to ensure that the obtained apparent dip of the formation is as close as possible to the real formation occurrence. Here, the value of m is 1, and the value of n is 1.

[0014] Further, in step 2), the range of the apparent dip of the formation of the target section of the horizontal well is obtained min -α max When, first, the target section of the horizontal well is divided into different stable sections according to the formation occurrence stability, and the range of the apparent dip of the formation of each section is calculated.

[0015] Further, the division method of different stable sections is as follows: on the seismic profile, the target layer corresponding to the well trajectory is located between the wave peak and the zero phase of the seismic event, and according to the variation trend of the apparent dip of the corresponding formation, the target layer section is divided into different stable sections. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is the flow chart of the method of the present application;

[0017] Figure 2 is the apparent dip diagram of adjacent crossing points;

[0018] Figure 3 is the seismic profile diagram of the depth domain of the designed well horizontal section;

[0019] Figure 4 is the first relationship diagram between the continuous multiple window-out points and the reservoir top and bottom positions;

[0020] Figure 5 is the second relationship diagram between the continuous multiple window-out points and the reservoir top and bottom positions;

[0021] Figure 6 is the schematic diagram of the real drilling guide profile. DETAILED DESCRIPTION

[0022] In order to make the objectives, technical solutions and advantages of the present application clearer, further detailed description will be made to the present application in combination with the accompanying drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and are not used to limit the present application, i.e., the described examples are only a part of the examples of the present application, but not all the examples. The components of the embodiments of the present application generally described and shown in the accompanying drawings can be arranged and designed in various different configurations.

[0023] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without making creative efforts are within the scope of protection of the present application.

[0024] As shown in Figure 1 , the method of the present application comprises the following steps: 1) calculating the dip angle θ according to two adjacent layer-penetrating points of the horizontal well trajectory, the dip angle θ = arctan(ΔH / ΔL), wherein ΔH is the vertical depth difference of the two adjacent layer-penetrating points, and ΔL is the horizontal plane projection distance of the two adjacent layer-penetrating points;

[0025] 2) comparing the dip angle θ with the range of the apparent dip angle α of the target section of the horizontal well min -α max , the initial value of the range of the apparent dip angle is obtained by seismic data;

[0026] 3) adjusting the drilling angle; when α min ≤θ≤α max , if the previous layer-penetrating point is located at the top of the reservoir, the angle is decreased, and if the previous layer-penetrating point is located at the bottom of the reservoir, the angle is increased; when θ < α min or θ > α max , if the previous layer-penetrating point is located at the top of the reservoir, the angle is increased, and if the previous layer-penetrating point is located at the bottom of the reservoir, the angle is decreased.

[0027] The algorithm of the dip angle θ in step 1) is shown in Figure 2 , the layer-penetrating points of the horizontal well are defined as a i , and the next adjacent layer-penetrating point is defined as a i+1 , the first layer-penetrating point (reservoir window entry point) a0 is defined, and it is obvious that a0 is the top of the reservoir, the second layer-penetrating point (window exit point) a1 is defined, the depth difference of the line segment a0a1 is ΔH, and the horizontal plane projection distance is ΔL. The dip angle θ of the line segment a0a1 is calculated as arctan(ΔH / ΔL). In this step, the coordinates of a0 and a1 are obtained by the while-drilling inclination data, and the calculation result is θ = 25°.

[0028] As shown in Figure 3As shown, in step 2), the apparent dip angle range α of the target section of the horizontal well is obtained through seismic data. min -α max The process is as follows: Based on the depth-domain seismic data provided by the geologists, the horizontal section of the designed well is divided into three stable sections, S1, S2, and S3, according to the trend of attitude change.

[0029] Based on the seismic profile, the three marker layers corresponding to the seismic phase axis where the well trajectory is located—the crest layer, the zero-phase layer, and the trough layer—are traced separately. The apparent dip angles of the three marker layers in each segment are calculated based on the longitudinal and transverse coordinate values ​​of the seismic profile. Figure 3 As shown, the algorithm for each marker layer in the three marker segments all uses the coordinate height difference between the upper and lower ends of the segment. Figure 3 The vertical coordinate (in the diagram) and the projected distances of the upper and lower ends onto the horizontal plane (in the diagram) Figure 3 The range of apparent dip angles of the strata is calculated from the x-coordinate in the graph, and this range is the initial range.

[0030] In this embodiment, the apparent dip angles of the three strata in segment S1 are 15°, 17°, and 16.5°, respectively. To minimize human error in determining these values, based on experience, the range of apparent dip angles for each segment is broadened by m and n from the maximum and minimum values ​​of the three values. Here, m and n are both set to 1. m and n are empirical values, and their respective ranges can also be 0-1.5. Therefore, the apparent dip angle range of segment S1 is 14°-18°, which is α for segment S1. min =14, α of segment S1 max =18. Similarly, the apparent dip angles of the three strata in segment S2 are 26°, 27°, and 26.4°, respectively. The apparent dip angle range of segment S2 is 25°-28°, i.e., α of segment S2... min =25, α of segment S2 max =28; The apparent dip angles of the three strata in segment S3 are 13°, 13.7°, and 14°, respectively. The apparent dip angle of the strata in segment S3 ranges from 12° to 15°, that is, the α of segment S3. min =12, α of segment S3 max =15. For example... Figure 6 As shown, based on the definitions of the three marker layers, it can be seen that the apparent dip angle range of each stratum fluctuates relatively little.

[0031] The method for adjusting the drilling angle in step 3) is as follows: Define the range of apparent dip angles between two adjacent reservoir points as α. i -α i+1 Compare the dip angle θ and the apparent dip range α of the corresponding stable stratigraphic segment. i -α i+1 This allows for the decision to either increase or decrease the drilling inclination, as detailed below:

[0032] First time going out the window:

[0033] As Figure 4 and Figure 5 shown, the angle θ of the line segment a0a1 is 25°, which is obviously greater than the range 14°-18° of the stratigraphic dip of S1 segment, because the first layer-penetrating point a0 of the well trajectory is the reservoir top, so it can be determined that the second layer-penetrating point a1 is not the reservoir top, thus the apparent dip of a0a1 exceeds the range 14°-18°, indicating that the drill bit is drilled out from below the reservoir, that is, it is judged as Figure 5 the mode, and the angle should be increased at this time. After a period of strata, the drill bit enters the reservoir again at a2 point.

[0034] During the continuous drilling process, the drill bit exits the window again at a3 point.

[0035] Second exit from the window:

[0036] According to the formula for calculating the angle of the two adjacent layer-penetrating points of the horizontal well, the angle θ of the line segment a1a2 is 17°, and the angle θ of the line segment a2a3 is 11°, as shown in Figure 5 the angle θ of the line segment a1a2 can determine that the apparent dip of the reservoir bottom is 17°, and then the range of the subsequent apparent dip of the strata of this segment is determined to be 16°-18° according to the experience of appropriately widening the fluctuation range of the apparent dip (the actual strata are not ideal, and the apparent dip will have a certain fluctuation range). Comparing the angle θ value 11° of the line segment a2a3, which obviously deviates from the actual apparent dip 16°-18° of the strata of S1 segment, it is determined that the layer-penetrating points a3 and a2 are located on different sides of the reservoir, and it is further determined that the layer-penetrating point a3 exits the window from the top of the reservoir, at which time the angle is decreased, and the drill bit enters the reservoir again after penetrating a period of strata.

[0037] In this way, according to this method, the well is adjusted in time after exiting the window multiple times during the drilling process, which greatly improves the reservoir drilling rate. This technology relies on the while-drilling inclination data, is accurate, timely and efficient, and has strong applicability.

[0038] In the above embodiment, the apparent dip range α min -α max of the target segment of the horizontal well is obtained through seismic data, and the peak layer, the zero-phase layer, and the trough layer corresponding to the seismic event of the well trajectory are used for tracking, respectively. In other embodiments, only one of the above marker layers can be used according to the needs. In this case, after obtaining the apparent dip of the corresponding marker layer, the apparent dip of the strata can be expanded according to experience, for example, floating 0-1.5 up and down; or it is also feasible to use two of the above marker layers.

[0039] In the above embodiment, the designed horizontal segment of the well is divided into three segments S1, S2, and S3 according to the trend of the change, and in other embodiments, the segments can also not be divided according to the actual situation.

Claims

1. A method of geosteering a horizontal well, characterized in that, The method comprises the following steps: 1) calculating the dip angle θ according to two adjacent crossing layer points of the horizontal well trajectory, wherein the dip angle θ = arctan(ΔH / ΔL), ΔH is the vertical depth difference of the two adjacent crossing layer points, and ΔL is the horizontal projection distance of the two adjacent crossing layer points; 2) the contrast angle θ and the range of apparent dip angle α of the target section of the horizontal well min -α max The initial value of the range of apparent dip angle is obtained from seismic data, and the method is as follows: according to the seismic profile, at least two of the three seismic marker layers of wave peak, zero phase and wave trough corresponding to the seismic event of the well track are continuously tracked, the corresponding apparent dip angle is calculated, and the maximum value plus m is α max The minimum value minus n is α min m and n are empirical values, and the range of m and n is 0-1.

5. 3) adjusting the drilling angle; when α min ≤ θ ≤ α max , if the previous crossing point is at the top of the reservoir, then the drilling angle is decreased, if the previous crossing point is at the bottom of the reservoir, then the drilling angle is increased; when θ < α min or θ > α max , if the previous crossing point is at the top of the reservoir, then the drilling angle is increased, if the previous crossing point is at the bottom of the reservoir, then the drilling angle is decreased; The range of the apparent dip angle of the formation is adjusted by drilling to obtain a subsequent range of the apparent dip angle of the formation, and the subsequent range of the apparent dip angle is obtained by: calculating the dip angle of a line segment between two cross-layer points on the same side of the reservoir according to a horizontal well trajectory adjacent two cross-layer point dip angle calculation formula, determining the apparent dip angle of the bottom surface or the top surface of the reservoir according to the dip angle, and calculating the subsequent range of the apparent dip angle according to the apparent dip angle, specifically, taking the apparent dip angle plus m as α max , and taking the apparent dip angle minus n as α min , wherein m and n are empirical values, and the ranges of m and n are both 0-1.

5.

2. The method of geosteering a horizontal well according to claim 1, characterized in that, The value of m is 1.

3. The method of geosteering a horizontal well of claim 1, wherein, The value of n is 1.

4. The method for geosteering a horizontal well according to claim 1, characterized in that, In step 2), the range of apparent dip angle α of the target section of the horizontal well is obtained min -α max First, the target section of the horizontal well is divided into different stable sections according to the stability of the formation occurrence, and the range of apparent dip angle of each section is calculated.

5. The method for geosteering a horizontal well according to claim 2, wherein, In step 2), the range of apparent dip angle α of the target section of the horizontal well is obtained min -α max First, the target section of the horizontal well is divided into different stable sections according to the stability of the formation occurrence, and the range of apparent dip angle of each section is calculated.

6. The method for geosteering a horizontal well according to claim 3, wherein, In step 2), the range of apparent dip angle α of the target section of the horizontal well is obtained min -α max First, the target section of the horizontal well is divided into different stable sections according to the stability of the formation occurrence, and the range of apparent dip angle of each section is calculated.

7. The method for geosteering a horizontal well according to any of claims 4-6, characterized in that, The different stable segments are divided as follows: on the seismic profile, the target layer corresponding to the well trajectory is located between the wave peak and zero phase of the seismic phase axis, and the target layer is divided into different stable segments according to the variation trend of the apparent dip angle of the stratum corresponding to the phase axis.

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