Geologically Constrained Wellbore Trajectory Design Methods for Directional Wells

Abstract

This invention relates to a method for designing geologically constrained wellbore trajectories in directional wells, belonging to the field of drilling engineering design technology. The specific steps are as follows: For complex multi-target formations, 3D seismic technology is used to accurately locate each target body in space, precisely interpreting the target formation and fault spatial distribution, and then establishing a 3D model of the target formation and faults. For multi-target directional wells with immovable wellheads, a multi-target five-segment trajectories design is adopted. Based on the target point locations, constrained wellbore trajectory data is calculated using the five-segment wellbore trajectory model. 3D seismic data is fused with the drilling targets, spatially positioning the targets on the 3D seismic data volume. Multiple targets to be drilled are then designed using a top-down, multi-target, five-segment wellbore trajectory system. This method effectively avoids the precisely identified fault spatial morphology in 3D seismic data, setting wellbore trajectories for each target body and avoiding the influence of faults.

Description

Technical Field

[0001] This invention relates to a method for designing geologically constrained wellbore trajectories in directional wells, belonging to the field of drilling engineering design technology. Background Technology

[0002] Directional drilling is becoming an extremely important means of oilfield exploration and development. Wellbore trajectory measurement and control technology has undergone a development process from experience to science, and from qualitative to quantitative methods. Currently, directional drilling technology is developing rapidly, and measurement-while-drilling (MWD) technology is widely used. This provides a foundation for geologists to shift from qualitative to three-dimensional quantitative methods for determining the subsurface targets being drilled. In conventional fault-bounded formations, the wellbore trajectory design method involves the geologist providing the wellhead location and the location of the main subsurface geological targets to be drilled. Drilling engineers use analytical methods to design the wellbore trajectory. This design method has little impact under conditions of simple geological structures and a single target layer. However, when there are several target layers and the formation traverses complex fault strata, this method can easily lead to the loss of oil-bearing sections or difficulties in later reservoir stimulation due to proximity to faults. Summary of the Invention

[0003] To address the problems existing in the prior art, this invention discloses a geologically constrained wellbore trajectory design method for directional wells. First, based on determining the wellhead location on the surface, it innovatively introduces three-dimensional seismic data to guide the drilling location of the target body in different layers, thereby locating the target body to be drilled in a layered system and forming a geologically controlled drilling trajectory.

[0004] The technical solution adopted in this invention is a method for designing the trajectory of geologically constrained directional wells, and the specific steps are as follows:

[0005] Step 1: For complex multi-target strata, 3D seismic technology is used to mark the precise location of each target body in space, accurately interpret the target strata and fault spatial distribution, and then establish target strata and fault models in 3D space.

[0006] Step 2: For multi-target directional wells with immovable wellheads, a multi-target five-segment trajectory design is adopted;

[0007] Step 3: Based on the target point location, calculate the constrained wellbore trajectory data using a five-segment wellbore trajectory model. Then, fuse the three-dimensional seismic data with the drilling target to spatially locate the target on the three-dimensional seismic data volume. Design the multi-target five-segment wellbore trajectory for the multiple targets to be drilled from top to bottom.

[0008] Furthermore, in step one, the model is used to effectively avoid the fracture spatial morphology accurately identified in the three-dimensional seismic data during the well location design process, and the wellbore trajectory is reasonably set for each target body from the surface downwards, with the main layer as the primary focus.

[0009] Furthermore, step two, the multi-target five-segment trajectory design, specifically includes:

[0010] S1, the known vertical depth D of the target point or the starting point of the target segment. t Horizontal displacement S of the target point or the starting point of the target segment t Target segment length △D mm Target section well inclination angle α t Vertical depth D t Horizontal displacement S t and target segment length △D mm The unit is meters (m), and the target section well inclination angle α t The unit is °;

[0011] S2, Determine the vertical depth D of the inclined plane point. kop The unit is meters; the slope ratio K of the inclined section. z The unit is ° / 30m; the slope drop rate K of the descending section. n The unit is ° / 30m; the radius of curvature R is calculated according to formula (1), and the unit is m:

[0012] R = 30 / (K*π / 180) Formula (1)

[0013] Where K is the slope of any segment; when K = K z At that time, the radius of curvature R of the inclined section was obtained. Z When K = K n At that time, the radius of curvature R of the descending slope segment was obtained. n ;

[0014] S3, calculate D according to formula (2-4). e S e and R e ;

[0015] D e =D t -D kop +R n *sinα t ; Formula (2)

[0016] S e =S t +R n *(1-cosα t ); Formula (3)

[0017] R e =R z +R n ; Formula (4)

[0018] S4, Calculate key parameters: D from S3 e S e and Re Substitute into formula (5-6) to find

[0019] Destable inclined section well inclination angle α b Length of the stable inclined section △D mw ;

[0020]

[0021] α b =2*arctan[(D e -ΔD mw ) / (2*R e -S e )] Formula (6)

[0022] Furthermore, in step three, the wellbore trajectory data includes depth, inclination angle, azimuth angle, etc.

[0023] Furthermore, in step three, the wellbore trajectory design needs to comprehensively consider the drilling capacity and continuously adjust parameters such as the vertical depth of the build-up point, the build-up rate, and the descent rate to achieve a design trajectory that meets geological objectives and realizes wellbore trajectory design under geological constraints.

[0024] This invention discloses a geologically constrained wellbore trajectory design method for directional wells. Its advantages, compared to existing technologies, include breaking through the fixed pattern of traditional single-wellbore trajectory design. For complex multi-target formations, it utilizes 3D seismic technology to accurately locate multiple target bodies in space, effectively avoiding fault spatial morphologies precisely identified in 3D seismic data. Starting from the surface and focusing on the main stratigraphic layer, wellbore trajectories are set for each target body individually, avoiding the influence of faults. While meeting the drilling objectives, a simpler profile type should be selected as much as possible, striving for the minimum well deviation, which is beneficial for safe and rapid drilling and reducing drilling costs. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 The diagram shown is a schematic of the wellbore track design in Example 1;

[0027] Figure 2 The diagram shown is a schematic diagram of the geologically constrained wellbore trajectory in Example 1. Specific implementation methods

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] To further understand the invention, the following detailed description, in conjunction with specific embodiments, further illustrates the invention.

[0030] Example 1: As Figures 1-2 As shown, the geologically constrained wellbore trajectory design method for directional wells specifically includes:

[0031] Step 1: For complex multi-target strata, 3D seismic technology is used to accurately locate each target body in space, precisely interpret the target strata and fault spatial distribution, and then establish target strata and fault models in 3D space. Using the model, the fault spatial morphology accurately identified in the 3D seismic data is effectively avoided during well location design. Starting from the surface downwards, the main strata are the primary focus, and the wellbore trajectory is reasonably set for each target body.

[0032] Step two, for multi-target directional wells where the wellhead cannot be moved, adopts a multi-target five-segment trajectory design; specifically including:

[0033] S1, the known vertical depth D of the target point or the starting point of the target segment. t Horizontal displacement S of the target point or the starting point of the target segment t Target segment length △D mm Target section well inclination angle α t Vertical depth D t Horizontal displacement S t and target segment length △D mm The unit is meters (m), and the target section well inclination angle α t The unit is °;

[0034] S2, Determine the vertical depth D of the inclined plane point. kop The unit is meters; the slope ratio K of the inclined section. z The unit is ° / 30m; the slope drop rate K of the descending section. n The unit is ° / 30m; the radius of curvature R is calculated according to formula (1), and the unit is m:

[0035] R = 30 / (K*π / 180) Formula (1)

[0036] Where K is the slope of any segment; when K = K z At that time, the radius of curvature R of the inclined section was obtained. Z When K = K n At that time, the radius of curvature R of the descending slope segment was obtained. n ;

[0037] S3, calculate D according to formula (2-4). e S e and R e ;

[0038] D e =D t -D kop +R n *sinα t ; Formula (2)

[0039] S e =S t +R n *(1-cosα t ); Formula (3)

[0040] R e =R z +R n ; Formula (4)

[0041] S4, Calculate key parameters: D from S3 e S e and R e Substitute into formula (5-6) to find

[0042] Destable inclined section well inclination angle α b Length of the stable inclined section △D mw ;

[0043]

[0044] α b =2*arctan[(D e -ΔD mw ) / (2*R e -S e )] Formula (6)

[0045] Step 3: Based on the target point location, calculate the constrained wellbore trajectory data using a five-segment wellbore trajectory model. Table 1 shows the wellbore trajectory data, including depth, inclination angle, azimuth angle, ordinate, and abscissa. Fusion is performed using 3D seismic data and the drilling target, spatially positioning the target on the 3D seismic data volume. Multiple targets to be drilled are then designed using a multi-target five-segment wellbore trajectory from top to bottom. A geologically constrained wellbore trajectory diagram is then drawn. Figure 2Wellbore trajectory design requires comprehensive consideration of drilling capacity, continuously adjusting parameters such as vertical depth of the build-up point, build-up rate, and descent rate to achieve a design trajectory that meets geological objectives and fulfills wellbore trajectory design under geological constraints. Vertical depth refers to the distance from a point on the trajectory to the horizontal plane where the wellhead is located. Depth measurement refers to measuring the well depth, i.e., the wellbore length from the wellhead to the measurement point. Inclination angle refers to the angle between the tangent at a point on the wellbore axis and the perpendicular. Azimuth angle refers to the angle between the projection of the tangent at a point on the wellbore axis and the direction of true north.

[0046] This method breaks through the fixed pattern of traditional single-wellbore trajectory design. For complex multi-target formations, it uses 3D seismic technology to accurately locate multiple target bodies in space, effectively avoiding the fracture spatial morphology precisely identified in 3D seismic data. Starting from the surface and focusing on the main stratigraphic layer, wellbore trajectories are set for each target body individually, avoiding the influence of fractures. While meeting the drilling objectives, the simplest profile type should be selected as much as possible, striving for the minimum well deviation, which is conducive to safe and rapid drilling and reducing drilling costs.

[0047] Table 1: Wellbore Track Data

[0048]

[0049]

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for designing the trajectory of a geologically constrained directional well, characterized in that, The specific steps are as follows: Step 1: For complex multi-target strata, 3D seismic technology is used to mark the exact location of each target body in space, accurately interpret the target strata and fault spatial distribution, and then establish target strata and fault models in 3D space. The model is used to avoid the fault spatial morphology accurately identified in the 3D seismic data during well location design. Starting from the surface downwards, the main layer is the primary focus, and the wellbore trajectory is reasonably set for each target body. Step 2: For multi-target directional wells with immovable wellheads, a multi-target five-segment trajectory design is adopted; The multi-target five-segment orbit design specifically includes: S1, the known vertical depth D of the target point or the starting point of the target segment. t Horizontal displacement S of the target point or the starting point of the target segment t Target segment length △D mm Target section well inclination angle α t Vertical depth D t Horizontal displacement S t and target segment length △D mm The unit is meters (m), and the target section well inclination angle α t The unit is °; S2, Determine the vertical depth D of the inclined plane point. kop The unit is meters; the slope ratio K of the inclined section. z The unit is ° / 30m; the slope drop rate K of the descending section. n The unit is ° / 30m; the radius of curvature R is calculated according to formula (1), and the unit is m: R = 30 / (K*π / 180) Formula (1) Where K is the slope of any segment; when K = K z At that time, the radius of curvature R of the inclined section was obtained. Z When K = K n At that time, the radius of curvature R of the descending slope segment was obtained. n ; S3, calculate D according to formulas (2)-(4). e S e and R e ; D e =D t -D kop +R n *sinα t ; Formula (2) S e =S t +R n *(1-cosα t ); Formula (3) R e =R z +R n ; Formula (4) S4, Calculate key parameters: D from S3 e S e and R e Substituting into formulas (5)-(6), The inclination angle α of the stable section of the well is obtained. b Length of the stable inclined section △D mw ; α b = 2 * arctan[(D e - ΔD mw ) / (2 * R e - S e )] Formula (6); Step 3: Based on the target point location, calculate the constrained wellbore trajectory data using a five-segment wellbore trajectory model. Then, fuse the three-dimensional seismic data with the drilling target to spatially locate the target on the three-dimensional seismic data volume. Design the multi-target five-segment wellbore trajectory for the multiple targets to be drilled from top to bottom.

2. The directional well geological constraint wellbore trajectory design method according to claim 1, characterized in that, Step 3: Wellbore trajectory data includes depth, inclination angle, azimuth angle, x-axis, and y-axis.

3. The directional well geological constraint wellbore trajectory design method according to claim 1, characterized in that, Step 3: Wellbore trajectory design needs to comprehensively consider the parameters of vertical depth of the build-up point, build-up rate, and descent rate, and continuously adjust them, under the premise that the drilling capacity allows, to complete the design trajectory that meets the geological objectives and carry out wellbore trajectory design under geological constraints.

4. The directional well geological constraint wellbore trajectory design method according to claim 2, characterized in that, Depth measurement refers to the length of the wellbore from the wellhead to the measuring point.

5. The directional well geological constraint wellbore trajectory design method according to claim 2, characterized in that, The well inclination angle refers to the angle between the tangent and the perpendicular at a point on the well shaft axis.

6. The directional well geological constraint wellbore trajectory design method according to claim 2, characterized in that, Azimuth refers to the angle between the projection of the tangent at a point on the shaft axis and the due north direction.

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