A method for measuring permeability tensor of shale reservoirs
Patent Information
- Application Number
- CN202311348180.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-10-16
- Publication Date
- 2026-11-03
- Estimated Expiration
- 2043-10-16
AI Technical Summary
Existing permeability tensor measurement methods are difficult to implement with multiple core sampling in the laboratory, and nuclear magnetic resonance methods have large errors when core pairing is poor. Formation permeability measurement methods can only determine the strength and cannot accurately measure the permeability anisotropy of shale reservoirs.
By determining measurement points and conducting axial and radial permeability tests, and combining borehole camera exploration and planar flow theory, a permeability tensor model is established, and a permeability tensor cloud map is drawn to intuitively understand the changes in reservoir permeability.
It reduces experimental steps, improves the accuracy and reliability of measurements, and provides a direct understanding of the anisotropy of shale reservoir permeability.
Smart Images
Figure CN117388147B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of formation permeability characteristics technology, specifically relating to a method for measuring the permeability tensor of shale reservoirs. Background Technology
[0002] The directional arrangement of rock particles during deposition and compaction results in a layered structure, leading to significant anisotropy. Permeability, as a non-free vector, is related to the seepage path. Some studies indicate that permeability is highest parallel to the bedding plane and lowest perpendicular to it. Therefore, a permeability tensor is introduced to describe the permeability variation at a point. Permeability anisotropy is a crucial parameter for evaluating oil and gas reservoirs, making permeability tensor-related research essential.
[0003] Currently available methods for measuring permeability tensors include laboratory testing methods, nuclear magnetic resonance (NMR) measurement methods, and formation permeability measurement methods, among which:
[0004] Laboratory testing methods: Permeability is obtained by taking core samples from different directions at the measurement points and measuring the permeability in different directions. Common laboratory permeability measurement methods include steady-state measurement, pulse decay method, and periodic oscillation method. The seepage medium can be liquid or gas. The steady-state method is suitable for cores with good permeability. For some denser cores, the pulse decay method and periodic oscillation method are more suitable. The steady-state method is based on Darcy's theory. When the flow rate is stable, the fluid is also in a stable state when passing through the sample. The permeability of the sample is calculated by the stable flow rate upstream or downstream. The pulse decay method applies a pressure pulse to one end of the sample, causing one-dimensional seepage inside the sample. The pressure difference between the two ends is recorded over time, and the permeability of the rock sample is calculated using theoretical formulas. The periodic oscillation method is based on the measurement of thermal diffusivity. A specific oscillating pressure is applied upstream of the core, exhibiting sinusoidal oscillation. A corresponding pressure feedback occurs downstream of the sample. The phase delay and amplitude decay of the downstream pressure are used to calculate the permeability using theoretical formulas. Laboratory measurements of the key points are intuitive and accurate, but multiple core samples need to be taken from the same point to measure permeability in different directions, which is difficult to achieve in engineering fields, increasing the difficulty of permeability tensor measurement.
[0005] Nuclear magnetic resonance (NMR) measurement method: Traditional NMR measurement of core permeability anisotropy involves taking horizontal and vertical cylindrical samples and using the SDR model combined with porosity and the logarithm of T2 to calculate the horizontal and vertical permeability of the core. Building upon this, researchers have used NMR to measure permeability in different directions on cylindrical cores, using pulse gradient field spatial resolution to determine the distribution of porosity and pore size at the thin-layer level. Then, the SDR model is used to calculate the core permeability from the average of porosity and the logarithm of T2. However, NMR measurement of core permeability is relatively accurate when the core samples are well-matched, but becomes problematic when the matching is poor, resulting in significant errors. Therefore, the method for measuring core permeability using NMR needs further improvement.
[0006] Formation permeability measurement methods: In traditional engineering, methods such as cable formation logging and sonic logging are commonly used to measure formation permeability anisotropy. Cable formation logging can obtain dynamic characteristics data of the oil reservoir, and the formation permeability anisotropy can be determined based on the recorded pressure information. For single-probe formation logging, the larger the ratio of horizontal to vertical permeability, the greater the pressure at the probe and the faster the formation fluid flows. For multi-probe cable formation logging, the stronger the formation anisotropy, the greater the time delay of the pressure signal. In sonic logging, the propagation speed of sound waves differs along the vertical periodic thin layer direction and the horizontal direction. However, since the wave velocity is the same in all directions within the horizontal thin layer plane, this method provides better results for permeability anisotropy measurement in a plane perpendicular to the horizontal plane and can only be used to determine the strength of formation permeability anisotropy.
[0007] To address the aforementioned shortcomings, we need to propose a method for measuring the permeability tensor of shale reservoirs. Summary of the Invention
[0008] The purpose of this invention is to provide a method for measuring the permeability tensor of shale reservoirs, which eliminates the need for multiple core permeability measurements. By determining the permeability tensor, reservoir evaluation can be performed more intuitively, thereby solving the problems mentioned in the background art.
[0009] To achieve the above objectives, the present invention adopts the following technical solution:
[0010] A method for measuring the permeability tensor of shale reservoirs includes the following steps:
[0011] S1. Determine the measurement points of the shale reservoir, drill cores, and then conduct axial and radial permeability tests to summarize the permeability patterns;
[0012] S2. After selecting the measurement points, conduct borehole video surveys to analyze the bedding direction and dominant attitude of the points;
[0013] S3. Based on a large number of permeability tests, summarize the permeability law and establish a shale permeability tensor model by combining the plane flow theory and the equivalent displacement theory.
[0014] S4. Based on the axial and radial permeability results of the measurement points, and combined with the bedding direction of the points, determine the permeability values in the two vertical directions below the point. Then, combine the shale permeability tensor model to back-calculate the magnitude and direction of the permeability extremum at the point. Finally, back-calculate the permeability values in all directions at the point and draw the permeability tensor cloud map of the shale reservoir measurement points.
[0015] Preferably, in step S1, when determining the shale reservoir measurement points, the target shale reservoir is first identified, then the measurement points are selected, then core samples are taken, and finally axial and radial permeability tests are performed.
[0016] Preferably, before conducting the permeability test, the on-site construction personnel first use drilling equipment to drill to the test point at a depth of Depth, then take core samples from the target measurement point of the shale gas well, process the core samples into ring-shaped cores and cylindrical cores, and finally use a permeability testing device to conduct permeability tests on the processed core samples.
[0017] Preferably, the permeability testing device includes a core holder for holding a core sample. The sidewall of the core holder is connected to a ring pressure pump via a pipeline. The inlet end of the core holder is provided with an inlet pipeline, and the outlet end is provided with an outlet pipeline. An inlet pressure sensor, an air inlet valve, a pressure regulating valve, and a cylinder are sequentially provided in the inlet pipeline. An outlet pressure sensor and a vent valve are sequentially provided in the outlet pipeline.
[0018] Preferably, an inlet buffer container is provided in the inlet pipeline, located between the inlet end of the core holder and the inlet pressure sensor, connected by a first pipe; and an outlet buffer container is provided in the outlet pipeline, located between the outlet end of the core holder and the outlet pressure sensor, connected by a second pipe.
[0019] Preferably, in step S2, during borehole imaging exploration, the borehole imaging equipment is used to conduct borehole imaging exploration of shale gas well models, analyze the borehole images of the measurement points, and calculate the bedding trend and dominant occurrence of the borehole images at the measurement points.
[0020] Preferably, the drilling camera device comprises a probe, a depth pulse generator, a winch, an image card, and a computer system. The reflector in the probe is made into a conical shape and truncated. A hole is drilled in the center of the conical reflector. The surface of the north needle of the compass in the probe is coated with a non-reflective material, and the surface of the south needle of the compass is coated with a reflective material. The panoramic image and the compass orientation image are merged and transmitted to the computer via a cable.
[0021] Preferably, in step S3, the process for establishing the shale permeability tensor model is as follows:
[0022] As a non-free vector, the magnitude of permeability at the same point is related to the direction of the seepage path. Therefore, a tensor is introduced to describe permeability.
[0023]
[0024] Shale permeability tests show that when the permeation direction is parallel to the bedding plane, the permeability is equal, i.e., k. x =k y =k xy ON represents the pressure gradient. Direction, A is the direction of... Vertical seepage cross-sectional area; The displacement effect on the fluid is equivalent to its components in the OM and z directions within the OMN plane. The combined displacement effect of the fluid, represented by Q. n Indicates in The flow rate Q of the fluid passing through section A under the action of the action. OM Q z The fluids are respectively in The flow rate through section A along the OM and z directions under the action can be obtained from the principle of equivalent displacement;
[0025] Q n =Q OM +Q z ;
[0026] Because of k x =k y =k xy 'i.e., k x =k OM So Q OM =Q x ;
[0027] According to Darcy's law for planes:
[0028]
[0029] Derivation and establishment of a rock permeability calculation model in the xoz plane:
[0030] k n =k x cos 2 α+k z sin 2 α.
[0031] Preferably, based on the rock permeability calculation model, considering that the pressure gradient direction and the seepage velocity direction are not necessarily parallel during the seepage process in anisotropic rocks, the seepage velocity component perpendicular to the pressure gradient direction should be considered, and the original model should be modified accordingly:
[0032]
[0033] To more accurately describe the variation of permeability N at measurement points in the reservoir, a spherical coordinate system is introduced to represent the permeability variation at point N. Directional permeability k N The quantitative description uses a rectangular coordinate system xyz to describe the spatial position of point N in the reservoir. The xoy plane is parallel to the bedding plane; the horizontal polar axis coincides with the bedding plane, and the vertical polar axis is perpendicular to the bedding plane.
[0034] Point N is at The permeability calculation model in the direction is as follows:
[0035]
[0036] in The permeability value within the plane containing the horizontal polar axis. This represents the permeation value along the vertical polar axis.
[0037] The shale reservoir permeability tensor measurement method proposed in this invention has the following advantages compared with the prior art:
[0038] 1. The method of this invention involves fewer experimental steps. It only requires processing core samples from selected formation measurement points into cylindrical / ring-shaped specimens, and then using a permeability measuring device to test the axial and radial permeability to obtain permeability values in two vertical directions.
[0039] 2. The method of this invention combines borehole wall images, ensuring reliable data. Borehole photography is used to survey the measurement points, and the bedding strike and dominant attitude of the measurement points are statistically analyzed using the borehole images.
[0040] 3. The method of this invention establishes a permeability tensor calculation model through theoretical derivation. By summarizing permeability patterns through numerous permeability experiments and combining planar seepage theory and equivalent displacement theory, a permeability tensor calculation model is established.
[0041] 4. The method of this invention combines laboratory measurements, borehole photography exploration, and theoretical derivation calculations to establish a permeability tensor model for the measurement point. Permeability values in two orthogonal directions are obtained through two laboratory measurements. The bedding trend at that point is determined through borehole images. Combined with theoretical calculations, permeability values in each direction at that point are plotted, and a permeability tensor cloud map is drawn to intuitively understand the permeability changes at the reservoir measurement point. Attached Figure Description
[0042] Figure 1 This is a flowchart of the present invention;
[0043] Figure 2 This is a flowchart illustrating the axial and radial permeability testing process for this invention.
[0044] Figure 3 This is a schematic diagram of the process for conducting penetration testing according to the present invention;
[0045] Figure 4 This is a schematic diagram illustrating the principle of borehole camera exploration in this invention;
[0046] Figure 5 These are unfolded and three-dimensional views of the borehole images of this invention;
[0047] Figure 6 This invention incorporates an equivalent displacement principle diagram;
[0048] Figure 7 This is a schematic diagram of the permeability of point O in the ON direction according to the present invention;
[0049] Figure 8 This is a graph showing the results of the shale reservoir permeability tensor test according to the present invention. Detailed Implementation
[0050] 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 specific embodiments described herein are merely used to explain the present invention and are not intended to limit the present invention. 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.
[0051] This invention provides, for example Figure 1 The method for measuring the permeability tensor of a shale reservoir, as shown, includes the following steps:
[0052] S1. Determine the measurement points of the shale reservoir, drill cores, and then conduct axial and radial permeability tests to summarize the permeability patterns;
[0053] like Figure 2 As shown, when determining the measurement points for the shale reservoir, the target shale reservoir is first identified, then the measurement points are selected, core samples are taken, and finally axial and radial permeability tests are performed.
[0054] Before conducting penetration testing, such as Figure 3As shown, the on-site construction personnel first used drilling equipment to drill to the test point at a depth of Depth, then took core samples from the target measurement point of the shale gas well, processed the cores into ring-shaped cores and cylindrical cores, and finally used a permeability testing device to test the permeability of the processed cores.
[0055] The permeability testing device includes a core holder for holding a core sample. The sidewall of the core holder is connected to a ring pressure pump via a pipeline. The core holder has an inlet pipeline at its inlet end and an outlet pipeline at its outlet end. An inlet pressure sensor, an air inlet valve, a pressure regulating valve, and a cylinder are sequentially arranged in the inlet pipeline. An outlet pressure sensor and a vent valve are sequentially arranged in the outlet pipeline.
[0056] An inlet buffer container is provided in the inlet pipeline, located between the inlet end of the core holder and the inlet pressure sensor, connected by a first pipe. An outlet buffer container is provided in the outlet pipeline, located between the outlet end of the core holder and the outlet pressure sensor, connected by a second pipe.
[0057] S2. After selecting the measurement points, conduct borehole video surveys to analyze the bedding direction and dominant attitude of the points;
[0058] like Figure 4 As shown, during borehole video exploration, borehole images of shale gas wells are analyzed using borehole video equipment. The bedding strike and dominant orientation of the borehole images at each measurement point are then calculated. Figure 5 The images shown are the unfolded and 3D views of the borehole image.
[0059] The drilling camera device includes a device consisting of a probe, a depth pulse generator, a winch, an image card, and a computer system. The reflector in the probe is made into a conical shape and truncated. A hole is drilled in the center of the conical reflector. The surface of the north needle of the compass in the probe is coated with a non-reflective material, and the surface of the south needle of the compass is coated with a reflective material. The panoramic image and the compass orientation image are merged and sent to the computer via a cable.
[0060] S3. Based on a large number of permeability tests, summarize the permeability law and establish a shale permeability tensor model by combining the plane flow theory and the equivalent displacement theory.
[0061] The process for establishing the shale permeability tensor model is as follows:
[0062] As a non-free vector, the magnitude of permeability at the same point is related to the direction of the seepage path. Therefore, a tensor is introduced to describe permeability.
[0063]
[0064] Shale permeability tests show that when the permeation direction is parallel to the bedding plane, the permeability is equal, i.e., k. x =k y =k xy Combining the principle of equivalent displacement, such as Figure 6 As shown, the permeability of point O in the ON direction is as follows: Figure 7 As shown, ON represents the pressure gradient. Direction, A is the direction of... Vertical seepage cross-sectional area; The displacement effect on the fluid is equivalent to its components in the OM and z directions within the OMN plane. The combined displacement effect of the fluid, represented by Q. n Indicates in The flow rate Q of the fluid passing through section A under the action of the action. OM Q z The fluids are respectively in The flow rate through section A along the OM and z directions under the action can be obtained from the principle of equivalent displacement;
[0065] Q n =Q OM +Q z ;
[0066] Because of k x =k y =k xy , i.e., k x =k OM Therefore, Q OM =Q x ;
[0067] According to Darcy's law for planes:
[0068]
[0069] Derivation and establishment of a rock permeability calculation model in the xoz plane:
[0070] k n =k x cos 2 α+k z sin 2 α.
[0071] Based on the aforementioned rock permeability calculation model, considering that the pressure gradient direction and the seepage velocity direction are not necessarily parallel during anisotropic rock seepage, the seepage velocity component perpendicular to the pressure gradient direction needs to be considered, thus modifying the original model:
[0072]
[0073] To more accurately describe the variation of permeability N at measurement points in the reservoir, a spherical coordinate system is introduced to represent the permeability variation at point N. Directional permeability k N The quantitative description is that the rectangular coordinate system xyz describes the spatial position of point N in the reservoir, and the xoy plane is parallel to the bedding plane. Figure 7 The horizontal polar axis coincides with the bedding plane, and the vertical polar axis is perpendicular to the bedding plane;
[0074] Point N is at The permeability calculation model in the direction is as follows:
[0075]
[0076] in The permeability value within the plane containing the horizontal polar axis. This represents the permeation value along the vertical polar axis.
[0077] S4. Based on the axial and radial permeability results at the measurement points, and considering the bedding strike at the points, determine the permeability values in the two vertical directions below the point. Then, using the shale permeability tensor model, calculate the magnitude and direction of the permeability extrema at the point. Finally, calculate the permeability values in all directions at the point and plot the permeability tensor cloud map of the shale reservoir measurement points. Figure 8 The figure shown is a graph of the permeability tensor test results for shale reservoirs.
[0078] In summary, this invention requires only core samples from selected formation measurement points, which are then processed into cylindrical / ring-shaped specimens. A permeability measuring device is used to test the axial and radial permeability of the processed core samples, obtaining permeability values in two perpendicular directions. This minimizes experimental steps. Furthermore, borehole imaging is conducted at the measurement points. The borehole images are used to statistically analyze the bedding direction and dominant orientation of the measurement points. Combined with borehole wall image analysis, the data is reliable. Extensive permeability tests are used to summarize permeability patterns. A permeability tensor calculation model is established using plane flow theory and equivalent displacement theory. This model combines laboratory measurements, borehole imaging, and theoretical derivation to create a permeability tensor model for the measurement points. Permeability values in two orthogonal directions are obtained from two laboratory measurements. The bedding direction at the point is determined from the borehole images. Combined with theoretical calculations, permeability values in each direction at the point are generated, and a permeability tensor cloud map is plotted, providing a direct understanding of permeability variations at the reservoir measurement points.
[0079] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A method for measuring the permeability tensor of shale reservoirs, characterized in that: Includes the following steps: S1. Determine the measurement points of the shale reservoir, drill cores, and then conduct axial and radial permeability tests to summarize the permeability patterns; S2. After selecting the measurement points, conduct borehole video surveys to analyze the bedding direction and dominant attitude of the points; S3. Based on a large number of permeability tests, summarize the permeability law and establish a shale permeability tensor model by combining the plane flow theory and the equivalent displacement theory. The process for establishing the shale permeability tensor model is as follows: As a non-free vector, the magnitude of permeability at the same point is related to the direction of the seepage path. Therefore, a tensor is introduced to describe permeability. Shale permeability tests show that when the permeation direction is parallel to the bedding plane, the permeability is equal in magnitude. , Pressure gradient direction, To and Vertical seepage cross-sectional area; The displacement effect on the fluid is equivalent to its effect on... in plane and Components in direction , The combined displacement effect of the fluid, using Indicates in Fluid passing through the cross section under action Traffic, , The fluids are respectively in , lower edge of action and Direction through cross section The flow rate can be obtained from the principle of equivalent displacement; ； because ,Right now ,so ; According to Darcy's law for planes: Derivation and establishment In-plane rock permeability calculation model: ； S4. Based on the axial and radial permeability results of the measurement points, and combined with the bedding direction of the points, determine the permeability values in the two vertical directions below the points. Then, combine the shale permeability tensor model to back-calculate the magnitude and direction of the extreme permeability values at the points. Finally, back-calculate the permeability values in all directions at the points and draw the permeability tensor cloud map of the shale reservoir measurement points. Based on the aforementioned rock permeability calculation model, considering that the pressure gradient direction and the seepage velocity direction are not necessarily parallel during anisotropic rock seepage, the seepage velocity component perpendicular to the pressure gradient direction needs to be considered, thus modifying the original model: To more accurately describe the measurement points in the reservoir The permeability variation pattern is analyzed using a spherical coordinate system. Dot at Directional permeability Quantitative description, rectangular coordinate system describe The spatial location of the point in the reservoir. The plane is parallel to the bedding plane; the horizontal polar axis coincides with the bedding plane, and the vertical polar axis is perpendicular to the bedding plane; Dot at The permeability calculation model in the direction is as follows: in The permeability value within the plane containing the horizontal polar axis. This represents the permeation value along the vertical polar axis.
2. The method for measuring the permeability tensor of shale reservoirs according to claim 1, characterized in that: In step S1, when determining the measurement points of the shale reservoir, the target shale reservoir is first identified, then the measurement points are selected, then core samples are taken, and finally axial and radial permeability tests are performed.
3. The method for measuring the permeability tensor of shale reservoirs according to claim 2, characterized in that: Before conducting the permeability test, the on-site construction personnel first used drilling equipment to drill to the test point at a depth of Depth, then took core samples from the target measurement point of the shale gas well, processed the cores into ring-shaped cores and cylindrical cores, and finally used a permeability testing device to conduct permeability tests on the processed cores.
4. The method for measuring the permeability tensor of a shale reservoir according to claim 3, characterized in that: The permeability testing device includes a core holder for holding a core sample. The sidewall of the core holder is connected to a ring pressure pump via a pipeline. The inlet end of the core holder is provided with an inlet pipeline, and the outlet end is provided with an outlet pipeline. An inlet pressure sensor, an air inlet valve, a pressure regulating valve, and a cylinder are sequentially provided in the inlet pipeline. An outlet pressure sensor and a vent valve are sequentially provided in the outlet pipeline.
5. The method for measuring the permeability tensor of a shale reservoir according to claim 4, characterized in that: An inlet buffer container is provided in the inlet pipeline, located between the inlet end of the core holder and the inlet pressure sensor, connected by a first pipe. An outlet buffer container is provided in the outlet pipeline, located between the outlet end of the core holder and the outlet pressure sensor, connected by a second pipe.
6. The method for measuring the permeability tensor of a shale reservoir according to claim 5, characterized in that: In step S2, during borehole imaging exploration, the borehole imaging equipment is used to conduct borehole imaging exploration of shale gas well models, analyze the borehole images at the measurement points, and calculate the bedding trend and dominant occurrence of the borehole images at the measurement points.
7. The method for measuring the permeability tensor of a shale reservoir according to claim 6, characterized in that: The drilling camera device includes a device consisting of a probe, a depth pulse generator, a winch, an image card, and a computer system. The reflector in the probe is made into a conical shape and truncated. A hole is drilled in the center of the conical reflector. The surface of the north needle of the compass in the probe is coated with a non-reflective material, and the surface of the south needle of the compass is coated with a reflective material. The panoramic image and the compass orientation image are merged and sent to the computer via a cable.