Oil and gas production increasing method, device and computer for releasing ground stress

Abstract

The present application provides a method, device, and computer for increasing oil and gas production by releasing ground stress. This method obtains the development location and development characteristics of natural fractures in the drilling area. The development characteristics include: fracture density, fracture aperture, and fracture occurrence. The fracture occurrence includes: fracture direction, fracture tendency, and fracture inclination. Based on the development location and the development characteristics, the wellbore trajectory is determined. The formation stress is then released on the wellbore trajectory. Finally, the oil and gas production in the natural fracture is determined based on a model of stress and fracture activity index. Starting from the optimized wellbore trajectory, this technical solution achieves a more accurate determination of reservoir oil and gas reserves, providing a basis for subsequent oil and gas production.

Description

Technical Field

[0001] The present application relates to the field of exploration and development technology, and in particular to a method, device and computer for increasing oil and gas production by releasing ground stress. Background Art

[0002] Deep oil and gas resources are the key focus area of ​​current oil and gas resource exploration and development. Their development is relatively difficult. In order to facilitate the development of deep oil and gas resources, technicians often need to determine the oil and gas production in the deep layer.

[0003] The main principle of determining oil and gas production in the existing technology is to use a ground fracturing vehicle group to inject a liquid of a certain viscosity (with acid, expanded clay, etc.) into the oil well along the wellbore at a sufficiently high pressure and a sufficiently large displacement to form large-scale artificial fractures. At the same time, proppant is used to maintain the fracture opening, thereby improving the seepage capacity to achieve the purpose of reservoir transformation, and then determine the reservoir oil and gas reserves.

[0004] However, the reservoir where the oil and gas resources are located is too deep, resulting in high safety risks and costs of the transformation project in existing technologies, and easily causing the risk of damage to the wellbore and reservoir. It is impossible to accurately determine the oil and gas reserves in the reservoir, resulting in a relative reduction in recoverable oil and gas. Summary of the Invention

[0005] The embodiments of the present application provide a method, device and computer for increasing oil and gas production by releasing ground stress, which are used to solve the problem that the existing technology cannot accurately determine the oil and gas reserves of the reservoir, resulting in a relative decrease in the recoverable oil and gas.

[0006] In a first aspect, an embodiment of the present application provides a method for increasing oil and gas production by releasing ground stress, comprising:

[0007] Obtaining the location and characteristics of natural fractures in the drilling area, wherein the characteristics include fracture density, fracture aperture, and fracture occurrence, wherein the fracture occurrence includes fracture direction, fracture tendency, and fracture dip;

[0008] determining a wellbore trajectory according to the development position and the development characteristics;

[0009] Releasing formation stress on the wellbore trajectory;

[0010] The oil and gas production in the natural fracture is determined based on the stress and fracture activity index model.

[0011] In a possible design of the first aspect, before obtaining the development location and development characteristics of natural fractures in the drilling area, the method further includes:

[0012] determining the mechanical activity of the natural fractures based on reservoir parameters within a preset area;

[0013] The area corresponding to the natural fracture where the mechanical activity is higher than the threshold is taken as a sweet spot;

[0014] The drilling area is determined based on the sweet spot.

[0015] In another possible design of the first aspect, determining the wellbore trajectory according to the development position and the development characteristics includes:

[0016] selecting a well type according to the development location and the development characteristics;

[0017] According to the well type, the wellbore trajectory is determined based on the principle of increasing the drilling rate of the natural fractures based on the orientation of the fracture surface normal.

[0018] In this possible design, the wellbore trajectory is determined according to the well type and based on the principle of increasing the drilling rate of the natural fracture based on the orientation of the fracture surface normal, including:

[0019] Establish and optimize multiple trajectory plans based on the orientation of the fracture surface normal line in order to increase the drilling rate of the natural fracture;

[0020] Based on the wellbore stability conditions corresponding to different trajectory schemes, the trajectory scheme with the best wellbore stability condition is selected as the wellbore trajectory.

[0021] Optionally, selecting a well type according to the development position and the development characteristics includes:

[0022] When low-angle horizontal fractures are developed in the drilling area, the well type selected is a vertical well;

[0023] When high-angle vertical fractures are developed in the drilling area, the well type selected is a highly deviated well or a horizontal well.

[0024] In another possible design of the first aspect, determining the oil and gas production in the natural fracture based on the stress and fracture activity index model includes:

[0025] determining a fracture activity index of the natural fracture according to a model of the stress and the fracture activity index;

[0026] The oil and gas production in the natural fracture is determined according to the fracture activity index of the natural fracture.

[0027] In this possible design, determining the fracture activity index of the natural fracture based on the model of the stress and the fracture activity index includes:

[0028] Determining the normal stress, shear force and critical opening pressure of the fracture surface of the natural fracture by tensor transformation of the stress;

[0029] Establishing a crack activity index equation based on the normal stress, the shear force, and the critical opening pressure;

[0030] According to the fracture activity index equation, the stress field and the stress state of the fracture surfaces of different natural fractures are determined, and the stress state indicates the fracture activity index.

[0031] In yet another possible design of the first aspect, the method further includes:

[0032] Determining the structure of the production string according to the oil and gas production and the natural fractures;

[0033] The oil and gas in the natural fractures are mined according to the production pipe of the production pipe string structure.

[0034] In a second aspect, an embodiment of the present application provides an oil and gas production increasing device, comprising:

[0035] An acquisition module is used to acquire the development location and development characteristics of natural fractures in the drilling area, wherein the development characteristics include: fracture density, fracture aperture and fracture occurrence, and the fracture occurrence includes: fracture direction, fracture tendency and fracture dip;

[0036] a determination module, configured to determine a wellbore trajectory according to the development position and the development characteristics, and perform formation stress release on the wellbore trajectory;

[0037] A calculation module is used to determine the oil and gas production in the natural fracture based on the model of stress and fracture activity index.

[0038] In a possible design of the second aspect, the determining module is further configured to:

[0039] determining the mechanical activity of the natural fractures based on reservoir parameters within a preset area;

[0040] The area corresponding to the natural fracture where the mechanical activity is higher than the threshold is taken as a sweet spot;

[0041] The drilling area is determined based on the sweet spot.

[0042] In another possible design of the second aspect, the determining module determines the wellbore trajectory according to the development position and the development characteristics, specifically for:

[0043] selecting a well type according to the development location and the development characteristics;

[0044] According to the well type, the wellbore trajectory is determined based on the principle of increasing the drilling rate of the natural fractures based on the orientation of the fracture surface normal.

[0045] In this possible design, the determination module determines the wellbore trajectory according to the well type and the principle of increasing the drilling rate of the natural fracture based on the orientation of the fracture surface normal, specifically for:

[0046] Establish and optimize multiple trajectory plans based on the orientation of the fracture surface normal line in order to increase the drilling rate of the natural fracture;

[0047] Based on the wellbore stability conditions corresponding to different trajectory schemes, the trajectory scheme with the best wellbore stability condition is selected as the wellbore trajectory.

[0048] Optionally, the determining module selects a well type according to the development position and the development characteristics, specifically for:

[0049] When low-angle horizontal fractures are developed in the drilling area, the well type selected is a vertical well;

[0050] When high-angle vertical fractures are developed in the drilling area, the well type selected is a highly deviated well or a horizontal well.

[0051] In yet another possible design of the second aspect, the computing module is specifically configured to:

[0052] determining a fracture activity index of the natural fracture according to a model of the stress and the fracture activity index;

[0053] The oil and gas production in the natural fracture is determined according to the fracture activity index of the natural fracture.

[0054] In this possible design, the calculation module determines the fracture activity index of the natural fracture based on the model of the stress and the fracture activity index, specifically for:

[0055] Determining the normal stress, shear force and critical opening pressure of the fracture surface of the natural fracture by tensor transformation of the stress;

[0056] Establishing a crack activity index equation based on the normal stress, the shear force, and the critical opening pressure;

[0057] According to the fracture activity index equation, the stress field and the stress state of the fracture surfaces of different natural fractures are determined, and the stress state indicates the fracture activity index.

[0058] In yet another possible design of the second aspect, the determining module is further configured to:

[0059] Determining the structure of the production string according to the oil and gas production and the natural fractures;

[0060] The oil and gas in the natural fractures are mined according to the production pipe of the production pipe string structure.

[0061] In a third aspect, an embodiment of the present application provides a computer comprising: a processor, a memory, and computer program instructions stored on the memory and executable on the processor, wherein when the processor executes the computer program instructions, the method for increasing oil and gas production by releasing ground stress as provided in the first aspect and various possible designs described above is implemented.

[0062] In a fourth aspect, an embodiment of the present application provides a computer-readable storage medium, in which computer execution instructions are stored. When the computer execution instructions are executed by a processor, they are used to implement the oil and gas production increase method of releasing ground stress as provided in the first aspect and various possible designs.

[0063] In a fifth aspect, an embodiment of the present application provides a computer program product, including a computer program, which, when executed by a processor, is used to implement the method for increasing oil and gas production by releasing ground stress as provided in the first aspect and various possible designs.

[0064] The embodiments of the present application provide a method, device, and computer for increasing oil and gas production by releasing ground stress. This method obtains the development location and development characteristics of natural fractures in the drilling area. The development characteristics include: fracture density, fracture aperture, and fracture occurrence. The fracture occurrence includes: fracture direction, fracture tendency, and fracture inclination. The wellbore trajectory is determined based on the development location and the development characteristics. The formation stress is then released on the wellbore trajectory. Finally, the oil and gas production in the natural fracture is determined based on a model of stress and fracture activity index. Starting from the optimized wellbore trajectory, this technical solution achieves a more accurate determination of the reservoir oil and gas reserves, providing a basis for subsequent oil and gas production. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present disclosure and, together with the description, serve to explain the principles of the present disclosure.

[0066] Figure 1 A schematic flow chart of Example 1 of a method for increasing oil and gas production by releasing geostress provided in an embodiment of the present application;

[0067] Figure 2 A schematic diagram of the decomposition of the vertical wellbore mechanics model provided in the embodiment of the present application;

[0068] Figure 3 A schematic diagram of the normal direction of the fracture surface of a natural fracture provided in an embodiment of the present application;

[0069] Figure 4 A schematic diagram of a decomposition of a wellbore mechanics model for a highly deviated well or horizontal well provided in an embodiment of the present application;

[0070] Figure 5 A schematic structural diagram of an oil and gas production-increasing device for releasing ground stress provided in an embodiment of the present application;

[0071] Figure 6 A schematic diagram of the structure of a computer provided in an embodiment of the present application.

[0072] The above drawings illustrate specific embodiments of the present disclosure, which will be described in more detail below. These drawings and textual descriptions are not intended to limit the scope of the present disclosure in any way, but rather to illustrate the concepts of the present disclosure to those skilled in the art by reference to specific embodiments. DETAILED DESCRIPTION

[0073] Exemplary embodiments will be described in detail herein, with examples illustrated in the accompanying drawings. In the following description, when referring to the drawings, identical numerals in different figures represent identical or similar elements, unless otherwise indicated. The embodiments described in the following exemplary embodiments are not intended to represent all possible embodiments consistent with the present disclosure. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the present disclosure, as detailed in the appended claims.

[0074] Before introducing the embodiments of the present application, the background technology of the present application is first explained:

[0075] Reservoir transformation is of great significance to the exploitation of oil and gas resources. In the existing technology, the methods of reservoir transformation include traditional hydraulic fracturing, acidizing, explosion, etc. In recent years, sand fracturing, acidizing fracturing, high-energy gas fracturing, hydraulic shock wave fracturing, vibration fracturing and other methods have been continuously developed. Sand fracturing is mainly used for sandstone and shale reservoirs, while acidizing fracturing is mainly used for carbonate reservoirs.

[0076] The current drilling technology mostly adopts balanced pressure drilling, that is, the pressure of the liquid column in the wellbore is kept equal to the formation pressure during drilling. After drilling is completed, the reservoir is transformed by the above-mentioned method. Regardless of the above-mentioned fracturing method, the main principle is to use a ground fracturing vehicle group to inject a liquid of a certain viscosity (with acid, ceramsite, etc.) into the well along the wellbore at a sufficiently high pressure and a sufficiently large displacement. Since the injection speed is much greater than the absorption speed of the oil and gas layer, the excess liquid will build up high pressure at the bottom of the well. When the pressure exceeds the tensile strength of the rock, the oil and gas layer will The cracks begin to break and form. After the cracks extend for a period of time, the mixed sand liquid carrying proppant is continuously injected to expand the extended cracks and fill the cracks with proppant. After the construction is completed, due to the supporting effect of the proppant, the cracks will not close or at least not close completely. Therefore, an artificial crack with sufficient length, width and height can be formed in the oil and gas layer, that is, a sand-filled crack. This crack has a high filtration capacity and expands the filtration area of ​​oil, gas and water. Therefore, oil and gas can flow freely into the well, and the injected water can smoothly enter the formation along the cracks, thereby achieving the purpose of increasing production and injection.

[0077] However, in actual applications, the use of the above-mentioned reservoir transformation technology based on hydraulic fracturing (including sand fracturing, acid fracturing, etc.) may cause the following problems:

[0078] 1. Extreme safety risks: Due to the high formation pressure and stress in ultra-deep reservoirs, the wellhead operating pressure during fracturing is high, generally exceeding 50MPa, and locally reaching over 120MPa. There are problems such as object impact, failure of wellhead equipment, and leakage of toxic and hazardous substances such as fracturing fluid.

[0079] 2. Not conducive to environmental protection: If fracturing gets out of control, the fracturing string breaks, or the high-pressure wellhead or pipeline leaks, it is very easy for fracturing fluid, toxic and harmful gases and crude oil to leak, polluting the atmosphere and surface water sources, land, etc., causing major ground pollution accidents.

[0080] 3. High site requirements: It is impossible to establish large well sites and water sources that meet the requirements of fracturing in complex surfaces such as mountains, sand-buried areas, and densely populated residential areas.

[0081] 4. Large-scale hydraulic fracturing is costly: According to incomplete statistics, the average fracturing cost of shale gas horizontal wells in a certain block in China is several tens of millions of yuan, accounting for 40%-50% of the total well construction cost. Fracturing has led to a sharp increase in oil and gas production costs, which does not meet the requirements for improving quality and efficiency.

[0082] 5. It may cause reservoir damage: During the fracturing process, the fracturing fluid invades the reservoir and causes water lock damage, clay expansion and migration damage, precipitation blockage damage, emulsification damage, cooling damage, adsorption and retention damage, wetting reversal damage, and fracturing fluid residue damage.

[0083] 6. Risk of communicating with water layers: The vertical and horizontal communication range of fracturing is large. For bottom water or edge water oil and gas reservoirs, there is a greater risk of communicating with water layers.

[0084] 7. There is a high probability of sand production in fracturing wells. On the one hand, it is due to the backflow of proppant, and on the other hand, the formation is severely crushed. The crushed formation particles are returned to the wellhead during mining, causing pipeline leakage, etc., affecting oil and gas production.

[0085] 8. It is difficult to maintain stable production in fracturing wells: Fracturing aims to achieve high oil and gas production in the early stages of transformation by connecting large formations. However, due to the secondary damage it causes to the reservoir and the above-mentioned reservoir pollution, it is difficult to maintain stable production in oil and gas wells.

[0086] The above problems will lead to errors in the prediction of oil and gas production from natural fractures.

[0087] In response to the above-mentioned technical problems, the inventors of this application have devised a technical concept as follows: during the drilling process, the formation pressure can be released to induce shear deformation of natural fractures, thereby achieving reservoir transformation, without the need for hydraulic fracturing implemented after drilling in the prior art. Therefore, there is no need to inject a large amount of liquid into the wellbore, return fracturing fluid to the outside of the well, and no need for high-quality completion tools, so as to determine the oil and gas production of natural fractures.

[0088] The technical solution of the present application is described in detail below through specific embodiments. It should be noted that the following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. The embodiments of the present application will be described below in conjunction with the accompanying drawings.

[0089] Figure 1 This is a flow chart of Example 1 of the oil and gas production increase method by releasing ground stress provided in the present application. Figure 1 As shown, the method for increasing oil and gas production by releasing the in-situ stress includes:

[0090] Step 11: Obtain the development location and development characteristics of natural fractures in the drilling area.

[0091] Among them, the development characteristics include: fracture density, fracture aperture and fracture occurrence, and the fracture occurrence includes: fracture direction, fracture tendency and fracture dip.

[0092] Before this, the drilling area needs to be determined, which can be achieved as follows:

[0093] Step 1: Determine the mechanical activity of natural fractures based on reservoir parameters within the preset area.

[0094] The geological data within the preset area for determining the oil and gas production is selected, and the preset area can be an area within any range.

[0095] Specifically, deep (>4500 meters) and ultra-deep (>6000 meters) oil and gas fields generally have very low reservoir matrix porosity and permeability. Natural fractures are a key factor in improving the permeability and conductivity of oil and gas reservoirs. The embodiments of this application utilize natural fractures to effectively connect the ultra-deep wellbore, the peri-well fracture network, and the three-dimensional oil and gas reservoir, thereby effectively increasing oil and gas well production and improving development efficiency. When implementing reservoir transformation, it is first necessary to determine the reservoir parameters and predict the development of natural fractures in the reservoir. The development here specifically refers to the location and characteristics of the natural fractures.

[0096] Specifically, based on the relationship between the three-dimensional stress field and natural fractures, the mechanical activity of natural fractures is predicted.

[0097] Step 2: The area corresponding to the natural cracks with mechanical activity higher than the threshold is regarded as the sweet spot.

[0098] Optionally, the natural fracture where the mechanical activity is higher than a threshold (or the area with the strongest mechanical activity) is taken as the sweet spot.

[0099] Step 3: Determine the drilling area based on the sweet spot.

[0100] Optionally, a drilling area is selected at the location of the sweet spot.

[0101] Step 12: Determine the wellbore trajectory based on the development location and development characteristics.

[0102] Specifically, the process may include the following steps:

[0103] Step 1: Select the well type based on the development location and development characteristics.

[0104] Among them, when low-angle-horizontal fractures develop in the drilling area, the selected well type is a vertical well; when high-angle-vertical fractures develop in the drilling area, the selected well type is a highly deviated well or a horizontal well.

[0105] Specifically, if low-angle horizontal fractures develop in the drilling area, vertical wells can penetrate more natural fractures to the greatest extent possible, so the well type selected is a vertical well; when high-angle vertical fractures develop in the drilling area, vertical wells often miss most natural fractures, while highly deviated wells or horizontal wells can penetrate more natural fractures to the greatest extent possible, so the well type selected is a highly deviated well or a horizontal well.

[0106] Step 2: Determine the wellbore trajectory based on the well type and the principle of increasing the drilling rate of natural fractures based on the orientation of the fracture surface normal.

[0107] Optionally, when designing the wellbore trajectory, it is an important consideration to pass through as many natural fractures of higher quality as possible. Based on the development location and development characteristics of the natural fractures in the selected drilling area, after selecting the well type, the wellbore trajectory should be further optimized to achieve a wellbore trajectory that can ensure a sufficiently high natural fracture encounter rate while ensuring safe drilling and avoiding complex drilling accidents.

[0108] Specifically, since the wellbore passes through the fracture surface, the natural fracture surface will be subjected to normal stress and shear stress. Considering that the shear slip of natural fractures under stress leads to damage to the wellbore wall and thus causes drilling complications such as collapse, after determining the well type, the wellbore trajectory with good wellbore stability during the drilling process should be further selected. Theory and practice show that when the wellbore is perpendicular to the natural fracture surface, the wellbore stability is the best, because the shear stress acting on the natural fracture surface is 0 at this time, and the possibility of shear slip is the lowest. Therefore, when designing the wellbore trajectory, the orientation that passes through as many natural fractures as vertically as possible (i.e., the orientation of the fracture surface normal) should be sought. This can not only ensure a higher fracture drilling rate, but also ensure safe drilling and avoid drilling complications. Based on this, a wellbore trajectory that best crosses the fracture is optimized.

[0109] Step 13: releasing formation stress on the wellbore trajectory;

[0110] In this step, drilling fluid is widely used in current drilling projects to balance formation pressure and stress to achieve drilling well wall stability. The method for reservoir transformation by releasing ground stress and inducing fracture activity provided by the present invention utilizes air drilling or underbalanced drilling methods to release formation stress, thereby activating natural fractures.

[0111] Furthermore, during air drilling or underbalanced drilling, the stress is in an underbalanced state, which can release the stress around the wellbore, thereby reducing the normal stress on the fracture surface of the natural fracture or increasing the shear force, which will cause small-scale fracture shear deformation. Even the slightest deformation may lead to the following three situations: expansion of the fracture aperture, increase of the fracture surface roughness and reduction of fracture cementation.

[0112] The above three situations will greatly increase the permeability of the reservoir around the well, forming a three-dimensional oil and gas reservoir that supplies fluid to the natural fracture network around the well. The natural fracture network then diverts fluid to the wellbore at high speed, similar to the benign seepage cycle of "streams converging into rivers, and rivers converging into the sea", so as to achieve effective production increase and improve development effect.

[0113] Since this solution can release formation pressure during the drilling process to induce shear deformation of natural fractures, thereby achieving reservoir transformation, without the need for hydraulic fracturing implemented after drilling in the existing technology, there is no need to inject a large amount of liquid into the wellbore, and no fracturing fluid is returned to the outside of the well, which can maximize water resource conservation and environmental protection. It also does not require high-quality completion tools, large amounts of fracturing fluid, proppants, etc., so the cost of increasing production is low, which can save a lot of money and improve the efficiency of ultra-deep oil and gas resource development.

[0114] Previously, when low-angle horizontal fractures developed in the drilling area, the well type selected was vertical well.

[0115] In one possible implementation, Figure 2 The schematic diagram of the decomposition of the vertical well wall mechanical model provided in the embodiment of the present application is as follows: Figure 2 As shown, when the wellbore trajectory is a vertical well, and the vertical well is a well with low-angle horizontal fractures developed in the drilling area, this step may include the following implementation process (in wellbore coordinates):

[0116] Step 1: Determine the effective stress of the minimum principal stress in the horizontal direction and the effective stress of the maximum principal stress in the horizontal direction of the wellbore trajectory based on the radial force, circumferential force, bottomhole pressure difference, polar angle and shear stress components of the wellbore trajectory.

[0117] Among them, 1. Radial force σ r Equal to the bottom hole pressure difference Δp of the wellbore trajectory;

[0118] Specifically, When R is the borehole radius and r is the polar coordinate radius, at the wellbore wall, that is, R = r, then, σ r =Δp.

[0119] 2. Circumferential force σ θ Equal to σ h +σ H +2(σ h -σ H )cos2θ-Δp;

[0120] Among them, σ H Effective stress of the maximum horizontal principal stress, σ h is the effective stress of the horizontal minimum principal stress.

[0121] Specifically, At the well wall, that is, R = r, then, σ θ =σ h +σ H +2(σ h -σ H )cos2θ-Δp.

[0122] Specifically, when θ = 90°, σ θ Take the maximum value, σ θmax =3σ H -σ h -Δp; σ when θ=0° θ Take the minimum value, σ θmax =3σ h -σ H =-Δp, so the axial stress is greatest at locations perpendicular to the direction of the maximum horizontal principal stress. This is where wellbore stress is concentrated and is most susceptible to wellbore collapse. For ease of study, the range of θ is 0° to 90°. As the angle θ changes, the stress around the wellbore follows a cosine function.

[0123] 3. The polar angle is θ;

[0124] 4. Component of shear stress τ rθ =τ θr =0.

[0125] Specifically, At the well wall, that is, R = r, then, τ rθ =τ θr =0.

[0126] Furthermore, when the range of θ is 0°~90°, as the angle θ changes, the stress around the wellbore changes in the cosine function. Figure 2 Point A is the critical position of wellbore collapse. At this time, the uniaxial compressive strength of the wellbore rock is equal to the wellbore peripheral stress.

[0127] Step 2: Determine the normal stress and shear force based on the effective stress of the minimum principal stress in the horizontal direction and the effective stress of the maximum principal stress in the horizontal direction.

[0128] Among them, according to the effective stress of the minimum principal stress in the horizontal direction and the effective stress of the maximum principal stress in the horizontal direction, the stresses in the three principal stresses of the natural fracture are determined from large to small, for example, σ1, σ2, and σ3. The geostress formula for most deep oil and gas reservoirs is:

[0129]

[0130] In addition, in the deep crust, the complex geostress field controls the development and seepage performance of natural fractures. This control is mainly manifested through the game relationship between normal stress and shear stress acting on the natural fracture surface. The principle of geostress-induced shear deformation activity in natural fractures is the Mohr-Coulomb criterion, that is:

[0131] Where, σ1=C0+σ3tan α 2 , C0 is the uniaxial compressive strength of rock, and α is the angle between the normal direction on the fault plane and the direction of the maximum principal stress.

[0132] Furthermore, the normal stress

[0133] Shear force is τ = n 11 n 12 σ1+n 12 n 22 σ2+n 13 n 23 σ3, where Figure 3 This is a schematic diagram of the normal direction of the crack surface of the natural crack provided in the embodiment of this application. Figure 3 As shown in the figure, n is the normal direction of the natural fracture surface, α, β, and γ are the angles between n and the axes (X, Y, and Z) of the spatial rectangular coordinate system, and ... and α, β, and γ are the angles between n and the axes ( 12 is the normal direction from the first axis to the second axis of the spatial rectangular coordinate system, n 23 is the normal direction from the second axis of the spatial rectangular coordinate system to the third axis, n 22 It is the normal direction of the plane where the second axis of the spatial rectangular coordinate system is located.

[0134] Step 3: Determine the critical opening pressure based on the normal stress and shear force of the ground stress.

[0135] Among them, the critical opening pressure μ is the ratio of σ1 to σ3 and the cross-section friction coefficient, that is,

[0136] Specifically, when the current ground stress field acts on the existing natural fracture surface, it will be decomposed into an effective normal stress σ perpendicular to the fracture surface. ne and a shear stress τ parallel to the fracture surface. These two forces are the main factors controlling the geomechanical response of natural fractures. When each fracture structure surface is in a critical sliding state, it satisfies the formula τ / σ. ne =μ.

[0137] Ratio of shear stress to normal stress τ / σ ne , which affects the sliding of natural fracture surfaces. It is not only a parameter that reflects the sliding of natural fracture surfaces, but also a parameter that characterizes the permeability and flow properties of fluids. The normal stress and shear stress borne on natural fracture surfaces of different occurrences and positions under specific stress environments, as well as the mechanical game between the two under the classical fracture criterion, are the best indices to characterize the geomechanical response of natural fractures in oil and gas reservoirs. There are two methods to calculate the normal stress and shear stress of structural surfaces such as cracks and faults in a determined stress environment. Among them, the tensor transformation method explains the relationship between the stress tensor and the geometric occurrence of the crack, and determines the normal stress and shear stress it is subjected to from the perspective of force analysis of the crack structural surface.

[0138] It can be seen that formation rupture mainly depends on the relationship between the maximum and minimum principal stresses, but is independent of the intermediate stress; after the formation ruptures, the friction properties of the rupture surface constrain the difference between the maximum and minimum principal stresses, thereby determining the current stress field state. When the vertical stress of the three principal stresses inside the reservoir (vertical stress σV, horizontal maximum principal stress σH, horizontal minimum principal stress σh) is at the maximum, intermediate, and minimum stress, respectively, its current stress state is potential normal fault type, strike-slip type, and reverse fault type stress state; from near the Earth's surface to a depth of 20 km deep in the crust, the stress state at any particle can be described by the magnitude and direction of a vertical stress and two orthogonal horizontal stresses.

[0139] Specifically, as an example, for the stress tensor formula σ in the positive coordinate system, the stress expression in the geographic coordinate system can be obtained through tensor transformation:

[0140]

[0141] Right now,

[0142] In the above formula, a is the orientation of σ1, b is the inclination of σ1, and c is the inclination of σ2. Then, the stress tensor on any natural fracture surface in the geographic coordinate system is calculated according to formula (21):

[0143]

[0144]

[0145] Where str is the direction of the natural fracture, dip is the inclination of the natural fracture, and the normal stress σ acting on the natural fracture surface is n and shear stress τ:

[0146] σ n =σ f (3, 3)

[0147] τ=σ r (3, 1)

[0148]

[0149]

[0150] where rake is the inclination of the slip vector in the rotated stress tensor, and the magnitude and direction of the in situ stress (the present maximum and minimum horizontal principal stresses) are obtained using the wellbore fracture trajectory inversion method.

[0151] In addition, when high-angle vertical fractures are developed in the drilling area, the well type selected is a highly deviated well or a horizontal well.

[0152] In one possible implementation, Figure 4 The schematic diagram of the decomposition of the wellbore mechanical model of the highly deviated well or horizontal well provided in the embodiment of the present application is combined with Figure 4 As shown, when the wellbore trajectory type is a highly deviated well or a horizontal well, and the highly deviated well or the horizontal well is a well with high-angle vertical fractures developed in the drilling area, this step may include the following implementation process:

[0153] Among them, the basic information also includes: well inclination and azimuth.

[0154] Step 1: Determine the tangential and axial forces of the wellbore trajectory based on the bottomhole pressure difference, well inclination, azimuth, and polar angle.

[0155] Optionally, in highly deviated or horizontal wells (in wellbore coordinates, on the well axis z):

[0156] 1. Radial force σ zz =σ 33 -2v(σ 11 -σ 22 )cos2θ-4vσ 12 sin2θ

[0157] Among them, σ 33 is the force on the surface where the radial force is located, σ 11 and σ 22 is the force on the other two sides, σ 12 is the force from the first surface to the second surface among the other two surfaces, and v is;

[0158] 2. Tangential force σ θθ =σ 11 +σ 22 -2(σ 11 -σ 22 )cos2θ-4vσ 12 sin2θ-Δp;

[0159] 3. Axial force τ θz =2(σ 23 cosθ-σ 13 sinθ);

[0160] Among them, σ 23 is the force of the second surface pointing to the surface where the radial force is located, and is the force of the first surface pointing to the surface where the radial force is located. 13 .

[0161] 4. Component of shear stress σ rr =Δp.

[0162] Where α is the well inclination angle, β is the azimuth angle, and σ 11 =cosα 2 (σH cosβ 2 +σ h sinβ 2 )+σ V sinβα 2 ,σ 22 =σ H sinβ 2 +σ h cosβ 2 ,σ 33 =sinα 2 (σ H cosβ 2 +σ h sinβ 2 )+σ V cosα 2 ,σ 12 =cosαcosβsinβ(σ H -σ h ), σ 23 =sinαcosβsinβ(σ H -σ h ).

[0163] Step 2: Determine the effective stress of the maximum principal stress and the effective stress of the minimum principal stress in the direction of the tangential plane of the wellbore trajectory based on the components of the radial force, tangential force, axial force and shear stress.

[0164] Effective principal stress of maximum principal stress

[0165] Effective principal stress of minimum principal stress

[0166] Step 3: Determine the normal stress and shear force based on the effective principal stress of the maximum principal stress and the effective stress of the minimum principal stress in the direction of the wellbore trajectory tangent plane.

[0167] Similar to the vertical well method mentioned above, normal stress and shear force can be obtained.

[0168] Step 4: Determine the critical opening pressure based on the normal stress and shear force of the ground stress.

[0169] Step 14: Determine the oil and gas production in the natural fractures based on the model of stress and fracture activity index.

[0170] Specifically, the implementation of this step can be divided into the following steps:

[0171] Step 1: Determine the fracture activity index of natural fractures based on the stress and fracture activity index model.

[0172] In this step, first, the normal stress, shear force and critical opening pressure of the fracture surface of the natural fracture are determined through tensor transformation of stress; secondly, the fracture activity index equation is established based on the normal stress, shear force and critical opening pressure; thirdly, based on the fracture activity index equation, the stress field and the stress state of the fracture surface of different natural fractures are determined, and the stress state indicates the fracture activity index.

[0173] Optional, activity index equation for natural fractures:

[0174]

[0175] Among them, σ nmax is the above σ tmax or σ H ,σ nmin is the above σ tmin or σ h ; For the above The maximum value of For the above The minimum value; W1 and W2 are the weights of natural fractures, and their sum is 1.

[0176] Step 2: Determine the oil and gas production in the natural fracture according to the fracture activity index of the natural fracture.

[0177] Optionally, the oil and gas production from natural fractures Q AOF =Aln(FGAI)+B, where A and B are experimentally measured values, i.e., the coefficient and constant term of ln(FGAI), for example, A is 189.36 and B is -722.67.

[0178] After step 25, the structure of the production string may be determined based on the oil and gas production and the natural fractures, and the oil and gas in the natural fractures may be mined using the production pipes of the production string structure.

[0179] In this step, after drilling the well using air drilling or underbalanced drilling, the fracture activity index of the natural fractures and the production are calculated, and then oil and gas production is carried out directly by using screen completion to avoid secondary disturbance of the oil and gas reservoir by subsequent operations such as cementing, thereby protecting the oil and gas reservoir to the greatest extent.

[0180] Optionally, the formation pressure, production layer fluid properties, etc. can be determined based on the normal stress, shear force, critical opening pressure, and the development location and development characteristics of natural fractures, and the screen can be designed based on the formation pressure and production layer fluid properties.

[0181] Optionally, the production string structure is determined based on the reservoir temperature, pressure, hydrogen sulfide content, and carbon dioxide content, and the production string is lowered after the packer, downhole safety valve, and oil pipe are pressure-tested and qualified.

[0182] Specifically, after the screen is reasonably designed, the production string is directly lowered into the well. Specifically, according to the temperature, pressure, hydrogen sulfide content, carbon dioxide content, etc. of the oil and gas reservoir, the safety production needs of oil and gas production and the production matching requirements of oil and gas wells are ensured to be met. The string force is checked and the appropriate string structure is determined. After the pressure tests of each packer, downhole safety valve, oil pipe, etc. are passed, the pipe is lowered into the wellbore.

[0183] Finally, after the well string is put into production and single-well oil and gas production is realized, a production increase and development plan with the best regional well location, well type, well trajectory and completion method can be formulated according to the stress release-induced fracture activity to achieve regional reservoir transformation.

[0184] Furthermore, by releasing the ground stress on the natural fracture surface, the natural fractures will produce shear dislocation, which will expand the fracture opening to a certain extent, increase the roughness of the fracture surface, reduce the degree of fracture cementation, and indirectly improve the permeability of the fracture network. This will form a three-dimensional oil and gas reservoir that supplies fluid to the fracture network around the well, and the fracture network will divert fluid to the wellbore at high speed, forming a benign seepage cycle of "streams converging into rivers, and rivers converging into the sea", thereby achieving an essential increase in gas reservoir production.

[0185] The method for increasing oil and gas production through geostress release provided in the embodiments of this application obtains the location and characteristics of natural fractures within the drilling area. These characteristics include fracture density, fracture aperture, and fracture occurrence, which includes fracture direction, fracture inclination, and fracture dip. Based on the location and characteristics, a wellbore trajectory is determined. Formation stress is then released on the wellbore trajectory. Finally, the oil and gas production within the natural fractures is determined based on a model of stress and fracture activity index. This technical solution, starting from the optimized wellbore trajectory, achieves a more accurate determination of reservoir oil and gas reserves, providing a foundation for subsequent oil and gas production.

[0186] Based on the above method embodiment, Figure 5 This is a schematic diagram of the structure of the oil and gas production enhancement device for releasing ground stress provided in the embodiment of the present application. Figure 5 As shown, the device includes:

[0187] An acquisition module 51 is used to acquire the location and characteristics of natural fractures in the drilling area. The characteristics include fracture density, fracture aperture, and fracture occurrence. The fracture occurrence includes fracture direction, fracture tendency, and fracture dip angle.

[0188] A determination module 52 is used to determine the wellbore trajectory according to the development position and development characteristics, and to release the formation stress on the wellbore trajectory;

[0189] The calculation module 53 is used to determine the oil and gas production in the natural fractures based on the model of stress and fracture activity index.

[0190] In a possible design of the embodiment of the present application, the determination module 52 is further configured to:

[0191] Determine the mechanical activity of natural fractures based on reservoir parameters within a pre-set area;

[0192] The area corresponding to the natural fracture with mechanical activity higher than the threshold is regarded as the sweet spot;

[0193] Based on the sweet spot, determine the drilling area.

[0194] In another possible design of the embodiment of the present application, the determination module 52 determines the wellbore trajectory according to the development position and development characteristics, specifically for:

[0195] Select the well type based on the development location and development characteristics;

[0196] According to the well type, the wellbore trajectory is determined based on the principle of increasing the drilling rate of natural fractures based on the orientation of the fracture surface normal.

[0197] In this possible design, the determination module 52 determines the wellbore trajectory according to the well type and the principle of increasing the drilling rate of natural fractures based on the orientation of the fracture surface normal line, specifically for:

[0198] Based on the orientation of the fracture surface normal line and the principle of increasing the drilling rate of natural fractures, multiple trajectory plans are established and optimized;

[0199] Based on the wellbore stability conditions corresponding to different trajectory schemes, the trajectory scheme with the best wellbore stability condition is selected as the wellbore trajectory.

[0200] Optionally, the determination module 52 selects a well type according to the development location and development characteristics, specifically for:

[0201] When the drilling area is developed with low-angle-horizontal fractures, the well type selected is vertical well;

[0202] When high-angle vertical fractures are developed in the drilling area, the well type selected is a highly deviated well or a horizontal well.

[0203] In another possible design of the embodiment of the present application, the calculation module 53 is specifically configured to:

[0204] Determine the fracture activity index of natural fractures based on the stress and fracture activity index model;

[0205] The oil and gas production in natural fractures is determined based on the fracture activity index of the natural fractures.

[0206] In this possible design, the calculation module 53 determines the fracture activity index of the natural fracture based on the stress and fracture activity index model, specifically for:

[0207] Through tensor transformation of stress, the normal stress, shear force and critical opening pressure of the fracture surface of natural fractures are determined;

[0208] Based on normal stress, shear force and critical opening pressure, the fracture activity index equation is established;

[0209] According to the fracture activity index equation, the stress field and the stress state of the fracture surface of different natural fractures are determined, and the stress state indicates the fracture activity index.

[0210] In another possible design of the embodiment of the present application, the determination module 52 is further configured to:

[0211] Determine the production string structure based on oil and gas production and natural fractures;

[0212] The oil and gas in the natural fractures are produced according to the production pipe of the production string structure.

[0213] The oil and gas production-increasing device for ground stress release provided in the embodiment of the present application can be used to implement the technical solution corresponding to the oil and gas production-increasing method for ground stress release in the above-mentioned embodiment. Its implementation principle and technical effects are similar and will not be repeated here.

[0214] It should be noted that it should be understood that the division of the various modules of the above device is merely a division of logical functions. In actual implementation, they can be fully or partially integrated into one physical entity, or they can be physically separated. Moreover, these modules can all be implemented in the form of software called by a processing element; they can also all be implemented in the form of hardware; some modules can also be implemented in the form of software called by a processing element, and some modules can be implemented in the form of hardware. In addition, these modules can be fully or partially integrated together or implemented independently. The processing element described here can be an integrated circuit with signal processing capabilities. During implementation, each step of the above method or each of the above modules can be completed by an integrated logic circuit in the hardware of the processor element or by instructions in the form of software.

[0215] Figure 6 This is a schematic diagram of the structure of the computer provided in the embodiment of the present application. Figure 6 As shown, the computer may include: a processor 60 , a memory 61 , and computer program instructions stored in the memory 61 and executable on the processor 60 .

[0216] The processor 60 executes the computer-executable instructions stored in the memory 61, so that the processor 60 implements the solution in the above embodiment. The processor 60 can be a general-purpose processor, including a central processing unit (CPU), a network processor (NP), etc.; it can also be a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components.

[0217] Optionally, the computer may further include a transceiver 62 .

[0218] The memory 61 and the transceiver 62 are connected to the processor 60 via a system bus and communicate with each other. The memory 61 is used to store computer program instructions.

[0219] Optionally, in hardware implementation, the above Figure 5 The acquisition module 51 in the illustrated embodiment corresponds to the transceiver 62 in this embodiment.

[0220] The system bus can be a Peripheral Component Interconnect (PCI) bus or an Extended Industry Standard Architecture (EISA) bus. System buses can be categorized as address buses, data buses, and control buses. For ease of illustration, the diagram uses a single thick line, but this does not imply a single bus or type of bus.

[0221] The computer provided in the embodiment of the present application can be used to execute the technical solution corresponding to the oil and gas production increase method by releasing ground stress in the above-mentioned embodiment. Its implementation principle and technical effect are similar and will not be repeated here.

[0222] An embodiment of the present application also provides a chip for running instructions, which is used to execute the technical solution of the oil and gas production increase method by releasing ground stress in the above-mentioned embodiment.

[0223] An embodiment of the present application also provides a computer-readable storage medium, which stores computer instructions. When the computer instructions are executed on a computer, the computer executes the technical solution of the oil and gas production increase method by ground stress release in the above-mentioned embodiment.

[0224] An embodiment of the present application further provides a computer program product, including a computer program, which, when executed by a processor, is used to execute the technical solution of the oil and gas production increase method by ground stress release in the above-mentioned embodiment.

[0225] The computer-readable storage medium can be implemented by any type of volatile or non-volatile storage computer or a combination thereof, such as static random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), magnetic storage, flash memory, magnetic disk, or optical disk. The computer-readable storage medium can be any available medium that can be accessed by a general-purpose or special-purpose computer.

[0226] It should be understood that the present disclosure is not limited to the exact structures that have been described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present disclosure is limited only by the appended claims.

Claims

1. A method for increasing oil and gas production by releasing ground stress, characterized in that: include: Obtaining the location and characteristics of natural fractures in the drilling area, wherein the characteristics include fracture density, fracture aperture, and fracture occurrence, wherein the fracture occurrence includes fracture direction, fracture tendency, and fracture dip; determining a wellbore trajectory according to the development position and the development characteristics; Using an air drill or an underbalanced drill to release formation stress on the wellbore trajectory; determining a fracture activity index of the natural fracture according to the stress and fracture activity index model; Based on the fitting relationship between the fracture activity index and the oil and gas production, the oil and gas production in the natural fracture is determined according to the fracture activity index of the natural fracture; Determining the structure of the production string according to the oil and gas production and the natural fractures; The oil and gas in the natural fractures are mined according to the production pipe of the production pipe string structure.

2. The method according to claim 1, characterized in that Before obtaining the development location and development characteristics of natural fractures in the drilling area, the method further includes: determining the mechanical activity of the natural fractures based on reservoir parameters within a preset area; The area corresponding to the natural fracture where the mechanical activity is higher than the threshold is taken as a sweet spot; The drilling area is determined based on the sweet spot.

3. The method according to claim 1 or 2, characterized in that Determining the wellbore trajectory according to the development position and the development characteristics includes: selecting a well type according to the development location and the development characteristics; According to the well type, the wellbore trajectory is determined based on the principle of increasing the drilling rate of the natural fractures based on the orientation of the fracture surface normal.

4. The method according to claim 3, characterized in that The method of determining the wellbore trajectory according to the well type and based on the principle of increasing the drilling rate of the natural fractures based on the orientation of the fracture surface normal line comprises: Establish and optimize multiple trajectory plans based on the orientation of the fracture surface normal line in order to increase the drilling rate of the natural fracture; Based on the wellbore stability conditions corresponding to different trajectory schemes, the trajectory scheme with the best wellbore stability condition is selected as the wellbore trajectory.

5. The method according to claim 4, characterized in that The selecting of a well type according to the development position and the development characteristics includes: When low-angle horizontal fractures are developed in the drilling area, the well type selected is a vertical well; When high-angle vertical fractures are developed in the drilling area, the well type selected is a highly deviated well or a horizontal well.

6. The method according to claim 1 or 2, characterized in that Determining the fracture activity index of the natural fracture based on the model of the stress and the fracture activity index includes: Determining the normal stress, shear force and critical opening pressure of the fracture surface of the natural fracture by tensor transformation of the stress; Establishing a crack activity index equation based on the normal stress, the shear force, and the critical opening pressure; According to the fracture activity index equation, the stress field and the stress state of the fracture surfaces of different natural fractures are determined, and the stress state indicates the fracture activity index.

7. An oil and gas production increasing device, characterized in that: include: An acquisition module is used to acquire the development location and development characteristics of natural fractures in the drilling area, wherein the development characteristics include: fracture density, fracture aperture and fracture occurrence, and the fracture occurrence includes: fracture direction, fracture tendency and fracture dip; a determination module, configured to determine a wellbore trajectory according to the development position and the development characteristics, and to release formation stress on the wellbore trajectory by using an air drill or an underbalanced drill; a calculation module for determining the fracture activity index of the natural fracture according to the stress and fracture activity index model; and determining the oil and gas production in the natural fracture according to the fracture activity index of the natural fracture based on a fitting relationship between the fracture activity index and the oil and gas production; The determination module is further configured to determine a production string structure based on the oil and gas production and the natural fractures; and to exploit the oil and gas in the natural fractures based on the production string structure of the production string.

8. A computer, characterized in that: include: A processor, a memory, and computer program instructions stored in the memory and executable on the processor, wherein when the processor executes the computer program instructions, the method for increasing oil and gas production by releasing ground stress as described in any one of claims 1 to 6 above is implemented.

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