A method and related device for calculating formation pressure of an ultra-low permeability reservoir
By constructing a cumulative advance water injection-formation pressure relationship model in ultra-low permeability reservoirs, the problem of the inability of traditional methods to accurately calculate formation pressure has been solved, thereby improving the accuracy of formation pressure calculation and the effectiveness of oilfield development.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- PETROCHINA CO LTD
- Filing Date
- 2024-11-28
- Publication Date
- 2026-05-29
Smart Images
Figure CN122113706A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of oilfield development technology, and specifically relates to a method and related apparatus for calculating formation pressure in ultra-low permeability reservoirs. Background Technology
[0002] Pre-injection water is a technique used in oil reservoirs with low formation pressure and insufficient natural energy. Water is injected into the formation before the reservoir is put into production to raise the formation pressure and thus increase the pressure gradient between wells. During pre-injection water injection, water is injected but not extracted, increasing the formation pressure to a level higher than the original formation pressure and establishing an effective displacement system, thereby increasing oil well production. After pre-injection water injection, determining the formation pressure level is crucial to ensuring oilfield production.
[0003] Currently, the traditional method for calculating formation pressure through pre-injection water is based on the material balance method. This method establishes a linear equilibrium equation between the pre-injection water volume, reservoir parameters, well pattern parameters, and formation pressure changes, and then directly calculates the formation pressure rise from the pre-injection water volume. However, this method considers relatively few parameters and is mostly used for conventional reservoirs. When dealing with ultra-low permeability reservoirs, the porous media in ultra-low permeability reservoirs have small throats, complex pore structures, and strong stress sensitivity and initiation pressure gradient characteristics. This leads to a significant nonlinearity in fluid flow in ultra-low permeability reservoirs, resulting in the calculated pressure rise value failing to accurately reflect the actual pressure changes in the formation. Consequently, this affects the determination of pre-injection water schemes in the oilfield. Summary of the Invention
[0004] To address the technical problems existing in the prior art, this invention provides a method and related apparatus for calculating formation pressure in ultra-low permeability reservoirs, in order to solve the technical problem that the pressure rise value calculated by the traditional advanced water injection formation pressure calculation method cannot truly reflect the actual pressure changes in the formation when facing ultra-low permeability reservoirs.
[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: This invention provides a method for calculating formation pressure in ultra-low permeability reservoirs, comprising: Obtain the cumulative advance water injection volume of the formation to be calculated at the current time step; The cumulative advance water injection volume of the formation to be calculated at the current time step is substituted into the pre-constructed cumulative advance water injection volume-formation pressure relationship model to calculate the formation pressure of the formation to be calculated at the current time step. Specifically, the pre-constructed cumulative advance water injection volume-formation pressure relationship model is: a relationship model between the increase in formation water volume and the cumulative advance water injection volume by introducing the continuous seepage motion equation, the permeability stress sensitivity equation and the rock state equation. The continuous seepage motion equation includes the initiation pressure gradient influence parameter and the nonlinear seepage influence parameter.
[0006] Furthermore, the construction process of the pre-constructed cumulative advance water injection volume-formation pressure relationship model is as follows: Based on the principle of material balance, a model is established to show the relationship between the increase in water volume in the formation and the cumulative advance water injection. By introducing a continuous seepage motion equation into the relationship model between the increase in water volume in the formation and the cumulative advance water injection, a nonlinear equation containing the cumulative advance water injection and formation pressure is obtained. By incorporating the permeability stress-sensitive equation and the rock state equation into the nonlinear equation containing the cumulative advance water injection volume and formation pressure, the pre-constructed cumulative advance water injection volume-formation pressure model is obtained.
[0007] Furthermore, based on the principle of material balance, the process of constructing a model relating the increase in formation water volume to the cumulative advance water injection is as follows: Determine the relationship between the increase in formation water volume at any time step and the injection flow rate of the injection well; Based on the principle of material balance, the relationship between the increase in formation water volume and the injection flow rate of injection wells at any time step is accumulated to obtain a model relating the increase in formation water volume to the cumulative advance injection volume.
[0008] Furthermore, the relationship model between the increase in water volume in the formation and the cumulative advance water injection volume is as follows:
[0009] in, Porosity under the current formation pressure; The volume of the stratum to be calculated; This represents the water saturation level under the current formation pressure. This is the water volume coefficient under the current formation pressure; Porosity at the initial formation pressure; The initial water saturation level under formation pressure; The water volume coefficient under the initial formation pressure; For the first Cumulative advance water injection volume over time steps; For the first Time step water injection well water injection flow rate; For the first Time step.
[0010] Furthermore, the continuous seepage motion equation is specifically as follows:
[0011] in, The seepage velocity; Formation permeability; Viscosity; To initiate the pressure gradient; These are parameters affecting nonlinear seepage. To determine the parameters affecting the pressure gradient.
[0012] Furthermore, the permeability stress-sensitive equation is specifically as follows:
[0013] in, The initial formation permeability; This is the stress sensitivity coefficient; This represents the original formation pressure; This represents the current formation pressure.
[0014] Furthermore, the rock state equation is specifically as follows:
[0015] in, is the rock compressibility coefficient.
[0016] This invention also provides a formation pressure calculation system for ultra-low permeability reservoirs, comprising: The data acquisition module is used to obtain the cumulative advance water injection volume of the formation to be calculated at the current time step; The calculation module is used to substitute the cumulative advance water injection volume of the formation to be calculated at the current time step into the pre-constructed cumulative advance water injection volume-formation pressure relationship model to calculate the formation pressure calculation result of the formation to be calculated at the current time step. Specifically, the pre-constructed cumulative advance water injection volume-formation pressure relationship model is: a relationship model between the increase in formation water volume and the cumulative advance water injection volume by introducing the continuous seepage motion equation, the permeability stress sensitivity equation and the rock state equation. The continuous seepage motion equation includes the initiation pressure gradient influence parameter and the nonlinear seepage influence parameter.
[0017] This invention also provides a formation pressure calculation device for ultra-low permeability reservoirs, comprising: Memory, used to store computer programs; A processor is used to implement the formation pressure calculation method for ultra-low permeability reservoirs when executing the computer program.
[0018] The present invention also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the method for calculating formation pressure in ultra-low permeability reservoirs.
[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: The formation pressure calculation method for ultra-low permeability reservoirs provided by this invention introduces the continuous seepage motion equation, permeability stress sensitivity equation, and rock state equation into the relationship model between the increase in formation water volume and the cumulative advance water injection volume. This allows for full consideration of the influence of permeability stress sensitivity, starting pressure gradient, and nonlinear seepage parameters during the advance water injection pressure calculation process, accurately describing the relationship between the cumulative advance water injection volume and formation pressure. This ensures that the formation pressure calculation results can truly reflect the actual pressure changes in the formation, providing a theoretical basis for formulating reasonable advance water injection schemes for ultra-low permeability reservoirs. At the same time, it can quickly guide the optimization of advance water injection schemes in the field, effectively improving the oilfield development effect.
[0020] The formation pressure calculation system, equipment, and computer-readable storage medium for ultra-low permeability reservoirs provided by this invention possess all the advantages of the aforementioned formation pressure calculation methods for ultra-low permeability reservoirs. Attached Figure Description
[0021] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0022] Figure 1 A flowchart illustrating the formation pressure calculation method for ultra-low permeability reservoirs provided in Example 1; Figure 2 This is a schematic diagram of the five-point horizontal well network in Example 1; Figure 3 This is a structural block diagram of the formation pressure calculation system for ultra-low permeability reservoirs provided in Example 2; Figure 4 This is a structural block diagram of the formation pressure calculation device for ultra-low permeability reservoirs provided in Example 3. Detailed Implementation
[0023] To make the technical problems, technical solutions, and beneficial effects solved by this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.
[0024] Example 1 As attached Figure 1 As shown in Example 1, this method for calculating formation pressure in ultra-low permeability reservoirs includes the following steps: Step 1: Construct a cumulative advance water injection volume-formation pressure relationship model to obtain a pre-constructed cumulative advance water injection volume-formation pressure relationship model; wherein, the pre-constructed cumulative advance water injection volume-formation pressure relationship model is specifically: a relationship model between the increase in formation water volume and the cumulative advance water injection volume by introducing the continuous seepage motion equation, the permeability stress sensitivity equation and the rock state equation, wherein the continuous seepage motion equation includes the initiation pressure gradient influence parameter and the nonlinear seepage influence parameter.
[0025] Specifically, the process of constructing the cumulative advance water injection volume-formation pressure relationship model involves the following steps: Step 11: Based on the principle of material balance, establish a relationship model between the increase in formation water volume and the cumulative advance water injection. Specifically, the implementation steps for establishing this relationship model are as follows: Step 111: Determine the relationship between the increase in formation water volume at any time step and the injection flow rate of the injection well; wherein, the increase in formation water volume at any time step is equal to the product of the injection flow rate of the injection well and the corresponding time step; specifically, the relationship between the increase in formation water volume at any time step and the injection flow rate of the injection well is as follows: (1) in, For the first The increase in water volume in the formation at time step, in m 3 ; For the first Water volume in formation at time step, m 3 ; For the first Water volume in formation at time step, m 3 ; For the first Time step water injection well water injection flow rate, m 3 / d; For the first Time step, d.
[0026] Step 112: Based on the principle of material balance, the relationship between the increase in formation water volume and the injection flow rate of the injection well at any time step is accumulated to obtain a relationship model between the increase in formation water volume and the cumulative advance injection volume; specifically, the relationship between the first time step and the second time step is accumulated. The relationship between the increase in formation water volume and the injection flow rate of the injection well is obtained by summing both sides of the equation. This yields a model showing the relationship between the increase in formation water volume and the cumulative advance injection volume.
[0027] The relationship model between the increase in water volume in the formation and the cumulative advance water injection volume is as follows: (2) in, Let m be the initial volume of water in the formation. 3 ; For the first Time step water injection well water injection flow rate, m 3 / d; For the first Time step, d.
[0028] use For formula (2) By making the substitution, formula (2) can be rewritten as: (3) in, For the first Cumulative advance water injection volume under time step, m 3 .
[0029] Based on the relationship between water volume in any formation and formation porosity, water saturation in the formation, water volume factor, and the volume of the formation to be calculated, formula (3) can be rewritten as: (4) in, Porosity under the current formation pressure; Let m be the volume of the formation to be calculated. 3 ; This represents the water saturation level under the current formation pressure. Let m be the water volume factor under the current formation pressure. 3 / m 3 ; Porosity at the initial formation pressure; The initial water saturation level under formation pressure; Let m be the water volume factor under the initial formation pressure. 3 / m 3 ; For the first Cumulative advance water injection volume under time step, m 3 .
[0030] According to the definition of formation oil saturation, formation water saturation is: (5) (6) in, This represents the water saturation level under the current formation pressure. This represents the oil saturation under the current formation pressure. Let m be the total volume of oil in the current formation. 3 ; This represents the initial oil saturation of the formation. The volume factor of formation oil is m. 3 / m 3 ; m is the volume factor of the initial formation oil. 3 / m 3 .
[0031] Due to the current formation oil volume factor Regarding formation pressure If the function is: (7) in, Let m be the oil volume factor under the current formation pressure. 3 / m 3 .
[0032] Step 12: Introduce the continuous seepage motion equation into the relationship model between the increase in water volume in the formation and the cumulative advance water injection volume to obtain a nonlinear equation containing the cumulative advance water injection volume and formation pressure.
[0033] Specifically, the process of obtaining the nonlinear equations containing the cumulative advance water injection volume and formation pressure is as follows: Substituting the continuous seepage motion equation into Darcy's formula, we obtain the first equation containing the continuous seepage motion equation. Time step water injection well water injection flow rate The first equation containing the continuous seepage motion equation Time step water injection well water injection flow rate The process of substituting the values into the relationship model between the increase in water volume and the cumulative advance water injection in the formation yields a nonlinear equation containing the cumulative advance water injection and formation pressure.
[0034] Darcy's formula is: (8) in, The seepage flow rate per unit time; Permeability, mD; This is the cross-sectional area for seepage. To initiate the pressure gradient; The viscosity of groundwater is given in mPa·s. The length of the seepage path is in meters (m). The seepage velocity is given.
[0035] The equation for continuous seepage flow is: (9) in, This refers to the nonlinear seepage influence parameter, specifically the shape factor that affects the low-velocity nonlinear seepage curve segment. ; To activate the pressure gradient influence parameters, activate the pressure gradient influence parameters. The reciprocal of this is equal to the pseudo-initiating pressure gradient in the quasi-linear seepage model; it should be noted that the nonlinear seepage influence parameters... And the parameters affected by the starting pressure gradient All were determined through experiments.
[0036] The first one containing the continuous seepage motion equation Time step water injection well water injection flow rate The expression is: (10) in, Inject pressure into the injection well; The current average formation pressure is in MPa. The length of the stratum to be calculated.
[0037] Step 13: Add the permeability stress sensitivity equation and the rock state equation to the nonlinear equation containing the cumulative advance water injection volume and formation pressure, and the pre-constructed cumulative advance water injection volume-formation pressure model is obtained.
[0038] The permeability stress-sensitive equation is specifically as follows: (11) in, The initial formation permeability; This is the stress sensitivity coefficient; This represents the original formation pressure; This represents the current formation pressure.
[0039] The rock state equation is as follows: (12) in, is the rock compressibility coefficient.
[0040] Specifically, by substituting equations (7), (10), (11), and (12) into equation (4) and rearranging, the pre-constructed cumulative advance water injection volume-formation pressure model can be obtained; wherein, the pre-constructed cumulative advance water injection volume-formation pressure model is specifically as follows: (13) It should be noted that equation (13) is the pre-constructed cumulative advance water injection volume-formation pressure model; where, the water volume coefficient under the current formation pressure is... And the oil volume factor under current formation pressure All are related to formation pressure The function is obtained by fitting data from on-site crude oil and formation water physical property tests to obtain a function of volume coefficient with respect to pressure.
[0041] Step 2: Obtain the cumulative advance water injection volume for the current time step of the formation to be calculated. Specifically, by consulting field data from the oilfield, obtain the cumulative advance water injection volume for the current time step of the formation to be calculated, which will be used for calculating the formation pressure at the current time step.
[0042] Step 3: Substitute the cumulative advance water injection volume of the formation to be calculated at the current time step into the pre-constructed cumulative advance water injection volume-formation pressure relationship model to calculate the formation pressure calculation result of the formation to be calculated at the current time step.
[0043] It should be noted that the original formation pressure in Example 1 of this embodiment... Rock compressibility coefficient Porosity under initial formation pressure Initial oil saturation of the formation Water saturation under initial formation pressure Groundwater viscosity and initial formation permeability All data were obtained from oilfield geological data; stress sensitivity coefficient Volume factor of initial formation oil Water volume coefficient under initial formation pressure Water volume coefficient under current formation pressure Oil volume coefficient under current formation pressure Parameters affected by nonlinear seepage Influence parameters of starting pressure gradient and start pressure gradient All data were obtained from experimental testing; injection pressure of water injection wells. Volume of the stratum to be calculated Length of the stratum to be calculated seepage cross-sectional area The cumulative advance water injection volume of the formation at the current time step to be calculated was obtained from field data of the oilfield.
[0044] Example explanation: Taking a five-point horizontal well network in Block A of an ultra-low permeability reservoir as an example; the basic reservoir parameters of Block A are shown in Table 1 below, and the distribution structure of the five-point horizontal well network is shown in the attached figure. Figure 2 As shown.
[0045] Using the formation pressure calculation method for ultra-low permeability reservoirs described in Example 1 above, the formation pressure changes in Block A of the ultra-low permeability reservoir under different advance water injection volumes were calculated, and the results are shown in Table 2 below.
[0046] Table 1. Basic reservoir parameters of Block A, an ultra-low permeability reservoir.
[0047] Table 2. Formation pressure variations under different advance water injection volumes.
[0048] Analysis of the formation pressure changes under different advance water injection volumes in Table 2 shows that, comparing the development effects of Block A of the ultra-low permeability reservoir before and after adopting the above formation pressure calculation method, the single-well production of horizontal wells put into production in the later stage was 4.2-4.7 t / d, which is 0.2-0.5 t / d higher than that of the block put into production in 2020, and the development effect was significantly improved.
[0049] It should also be noted that the formation pressure calculation results obtained by using the formation pressure calculation method described in Example 1 under different advance water injection volumes can be applied to guide the optimization of advance water injection schemes on site. When applied to an ultra-low permeability full water injection development block with an annual output of 1.2 million tons, the initial daily oil production per well is increased by 0.2 tons, and the initial oil production rate is increased by 0.1%, which has significant economic and applicability value.
[0050] The formation pressure calculation method for ultra-low permeability reservoirs described in Example 1 addresses the issue that fluid flow in ultra-low permeability reservoirs is often influenced by the initiation pressure gradient, exhibiting non-Darcy flow characteristics. By considering seepage stress sensitivity, initiation pressure gradient, and nonlinear seepage parameters, the method can more accurately describe the fluid movement in ultra-low permeability reservoirs. Secondly, the permeability of ultra-low permeability reservoirs is typically stress-sensitive, meaning that permeability changes with formation stress. Introducing a permeability stress sensitivity equation can more accurately reflect the impact of formation stress changes on permeability, thereby improving the accuracy of formation pressure calculation. Furthermore, the rock state equation describes the relationship between the physical state of rocks and pressure conditions. Considering the rock state equation in the formation pressure calculation of ultra-low permeability reservoirs can more comprehensively reflect the influence of formation conditions on formation pressure. Therefore, the method described in Example 1 can ensure the accuracy of the pre-injection pressure calculation results, enabling rapid guidance for on-site optimization of pre-injection schemes and effectively improving development results.
[0051] Example 2 As attached Figure 3 As shown in the figure, this embodiment 2 provides a formation pressure calculation system for ultra-low permeability reservoirs, including a relational model construction module, a data acquisition module, and a substitution calculation module.
[0052] The relationship model construction module is used to construct a cumulative advance water injection volume-formation pressure relationship model to obtain a pre-constructed cumulative advance water injection volume-formation pressure relationship model. Specifically, the pre-constructed cumulative advance water injection volume-formation pressure relationship model is a relationship model between the increase in formation water volume and the cumulative advance water injection volume, incorporating the continuous seepage motion equation, the permeability stress sensitivity equation, and the rock state equation. The continuous seepage motion equation includes parameters related to the initiation pressure gradient and nonlinear seepage. The data acquisition module is used to acquire the cumulative advance water injection volume of the formation at the current time step. The substitution calculation module is used to substitute the cumulative advance water injection volume of the formation at the current time step into the pre-constructed cumulative advance water injection volume-formation pressure relationship model to calculate the formation pressure at the current time step.
[0053] In this Example 2, the process of constructing the cumulative advance water injection volume-formation pressure relationship model is as follows: Based on the principle of material balance, a relationship model is established between the increase in water volume in the formation and the cumulative advance water injection. A continuous seepage motion equation is introduced into this model to obtain a nonlinear equation containing the cumulative advance water injection and formation pressure. Finally, a permeability stress sensitivity equation and a rock state equation are added to this nonlinear equation to obtain the pre-constructed cumulative advance water injection-formation pressure model.
[0054] Example 3 As attached Figure 4 As shown, this embodiment 3 provides a formation pressure calculation device for ultra-low permeability reservoirs, including: a processor, a memory, and a computer program stored in the memory and executable on the processor, such as a formation pressure calculation method program for ultra-low permeability reservoirs. (The attached text is incomplete and requires further context.) Figure 4 The communication interface is used to connect to external devices to obtain data.
[0055] When the processor executes the computer program, it implements the steps of the above-mentioned method for calculating formation pressure in ultra-low permeability reservoirs, such as: constructing a cumulative advance water injection volume-formation pressure relationship model to obtain a pre-constructed cumulative advance water injection volume-formation pressure relationship model; wherein, the pre-constructed cumulative advance water injection volume-formation pressure relationship model specifically includes: introducing a relationship model between the increase in formation water volume and the cumulative advance water injection volume based on the continuous seepage motion equation, the permeability stress sensitivity equation, and the rock state equation, wherein the continuous seepage motion equation includes the initiation pressure gradient influence parameter and the nonlinear seepage influence parameter; obtaining the cumulative advance water injection volume of the formation to be calculated at the current time step; substituting the cumulative advance water injection volume of the formation to be calculated at the current time step into the pre-constructed cumulative advance water injection volume-formation pressure relationship model to calculate the formation pressure calculation result of the formation to be calculated at the current time step.
[0056] Alternatively, when the processor executes the computer program, it implements the functions of each module in the above system, such as: a relational model construction module, used to construct a cumulative advance water injection volume-formation pressure relationship model to obtain a pre-constructed cumulative advance water injection volume-formation pressure relationship model; wherein, the pre-constructed cumulative advance water injection volume-formation pressure relationship model specifically includes: a relationship model between the increase in formation water volume and the cumulative advance water injection volume by introducing the continuous seepage motion equation, the permeability stress sensitivity equation, and the rock state equation, wherein the continuous seepage motion equation includes the initiation pressure gradient influence parameter and the nonlinear seepage influence parameter; a data acquisition module, used to acquire the cumulative advance water injection volume of the formation to be calculated at the current time step; and a substitution calculation module, used to substitute the cumulative advance water injection volume of the formation to be calculated at the current time step into the pre-constructed cumulative advance water injection volume-formation pressure relationship model to calculate the formation pressure calculation result of the formation to be calculated at the current time step.
[0057] For example, the computer program can be divided into one or more modules / units, which are stored in the memory and executed by the processor to complete this embodiment. The one or more modules / units can be a series of computer program instruction segments capable of performing specific functions, which describe the execution process of the computer program in the formation pressure calculation device for ultra-low permeability reservoirs.
[0058] For example, the computer program can be divided into a relational model construction module, a data acquisition module, and a substitution calculation module. The specific functions of each module are as follows: The relational model construction module is used to construct a cumulative advance water injection volume-formation pressure relationship model to obtain a pre-constructed cumulative advance water injection volume-formation pressure relationship model; wherein, the pre-constructed cumulative advance water injection volume-formation pressure relationship model is specifically: a relationship model between the increase in formation water volume and the cumulative advance water injection volume by introducing the continuous seepage motion equation, the permeability stress sensitivity equation, and the rock state equation, wherein the continuous seepage motion equation includes the initiation pressure gradient influence parameter and the nonlinear seepage influence parameter; The data acquisition module is used to acquire the cumulative advance water injection volume of the formation to be calculated at the current time step; The substitution calculation module is used to substitute the cumulative advance water injection volume of the formation to be calculated at the current time step into the pre-constructed cumulative advance water injection volume-formation pressure relationship model to calculate the formation pressure calculation result of the formation to be calculated at the current time step.
[0059] The formation pressure calculation device for the ultra-low permeability reservoir can be a desktop computer, laptop, handheld computer, or cloud server, etc. The formation pressure calculation device for the ultra-low permeability reservoir may include, but is not limited to, a processor and memory. Those skilled in the art will understand that the appended... Figure 4 The schematic diagram is merely an example of a formation pressure calculation device for ultra-low permeability reservoirs and does not constitute a limitation on such a device. It may include more or fewer components than those shown in the diagram, or combine certain components, or use different components. For example, the formation pressure calculation device for ultra-low permeability reservoirs may also include input / output devices, network access devices, buses, etc.
[0060] The processor can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor or any conventional processor. This processor is the control center of the formation pressure calculation equipment for the ultra-low permeability reservoir, connecting all parts of the equipment via various interfaces and lines.
[0061] The memory can be used to store the computer program and / or modules. The processor realizes various functions of the formation pressure calculation device for the ultra-low permeability reservoir by running or executing the computer program and / or modules stored in the memory and calling the data stored in the memory.
[0062] The memory may primarily include a program storage area and a data storage area. The program storage area may store the operating system and at least one application program required for a function (such as sound playback, image playback, etc.); the data storage area may store data created based on the use of the mobile phone (such as audio data, phonebook, etc.). Furthermore, the memory may include high-speed random access memory, and may also include non-volatile memory, such as hard disks, RAM, plug-in hard disks, SmartMediaCards (SMC), Secure Digital (SD) cards, FlashCards, at least one disk storage device, flash memory device, or other volatile solid-state storage devices.
[0063] Example 4 This embodiment 4 also provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the steps of the method for calculating formation pressure in an ultra-low permeability reservoir.
[0064] When the processor executes the computer program, it implements the steps of the above-described method for calculating formation pressure in ultra-low permeability reservoirs, for example: A cumulative advance water injection volume-formation pressure relationship model is constructed to obtain a pre-constructed cumulative advance water injection volume-formation pressure relationship model. Specifically, the pre-constructed cumulative advance water injection volume-formation pressure relationship model is as follows: a relationship model between the increase in formation water volume and the cumulative advance water injection volume is introduced by incorporating the continuous seepage motion equation, the permeability stress sensitivity equation, and the rock state equation. The continuous seepage motion equation includes the initiation pressure gradient influence parameter and the nonlinear seepage influence parameter. The cumulative advance water injection volume of the formation to be calculated at the current time step is obtained. The cumulative advance water injection volume of the formation to be calculated at the current time step is substituted into the pre-constructed cumulative advance water injection volume-formation pressure relationship model to calculate the formation pressure of the formation to be calculated at the current time step.
[0065] If the modules / units integrated by the formation pressure calculation equipment for ultra-low permeability reservoirs are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium.
[0066] Based on this understanding, the implementation of all or part of the above-described methods in Embodiment 4 can also be accomplished by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium. When executed by a processor, the computer program can implement the steps of the above-described method for calculating formation pressure in ultra-low permeability reservoirs. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms.
[0067] The computer-readable medium may include: any entity or device capable of carrying the computer program code, recording media, USB flash drive, portable hard drive, magnetic disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signal, telecommunication signal, and software distribution medium, etc.
[0068] It should be noted that the content contained in the computer-readable medium may be appropriately added to or subtracted from the content as required by the legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, the computer-readable medium may not include electrical carrier signals and telecommunication signals.
[0069] The formation pressure calculation method for ultra-low permeability reservoirs described in this invention, based on the material balance method, introduces the continuous seepage motion equation, the permeability stress sensitivity equation, and the rock state equation to accurately reflect the initiation pressure gradient phenomenon and low-velocity nonlinear seepage characteristics exhibited by fluid seepage in low-permeability media. By establishing a cumulative advance water injection volume-formation pressure relationship model, the accuracy of the advance water injection pressure calculation results provides a theoretical basis for formulating reasonable advance water injection schemes for ultra-low permeability reservoirs, and achieves the purpose of quickly guiding the optimization of advance water injection schemes in the field.
[0070] It should be clarified that ultra-low permeability reservoirs typically refer to oil and gas reservoirs with extremely low permeability; the permeability of ultra-low permeability reservoirs is generally less than 1×10⁻⁶. -3 Ultra-low permeability reservoirs, with a diameter of μm² or 1mD, are characterized by low porosity, low permeability, small throats, poor fluid permeability, and low production capacity.
[0071] The above embodiments are merely one of the implementation methods for achieving the technical solution of the present invention. The scope of protection claimed by the present invention is not limited to this embodiment, but also includes any variations, substitutions and other implementation methods that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention.
Claims
1. A method for calculating formation pressure in ultra-low permeability reservoirs, characterized in that, include: Obtain the cumulative advance water injection volume of the formation to be calculated at the current time step; The cumulative advance water injection volume of the formation to be calculated at the current time step is substituted into the pre-constructed cumulative advance water injection volume-formation pressure relationship model to calculate the formation pressure of the formation to be calculated at the current time step. Specifically, the pre-constructed cumulative advance water injection volume-formation pressure relationship model is: a relationship model between the increase in formation water volume and the cumulative advance water injection volume by introducing the continuous seepage motion equation, the permeability stress sensitivity equation and the rock state equation. The continuous seepage motion equation includes the initiation pressure gradient influence parameter and the nonlinear seepage influence parameter.
2. The method for calculating formation pressure in ultra-low permeability reservoirs according to claim 1, characterized in that, The construction process of the pre-constructed cumulative advance water injection volume-formation pressure relationship model is as follows: Based on the principle of material balance, a model is established to show the relationship between the increase in water volume in the formation and the cumulative advance water injection. By introducing a continuous seepage motion equation into the relationship model between the increase in water volume in the formation and the cumulative advance water injection, a nonlinear equation containing the cumulative advance water injection and formation pressure is obtained. By incorporating the permeability stress-sensitive equation and the rock state equation into the nonlinear equation containing the cumulative advance water injection volume and formation pressure, the pre-constructed cumulative advance water injection volume-formation pressure model is obtained.
3. The method for calculating formation pressure in ultra-low permeability reservoirs according to claim 2, characterized in that, The process of constructing a model relating the increase in formation water volume to the cumulative advance water injection volume, based on the principle of material balance, is as follows: Determine the relationship between the increase in formation water volume at any time step and the injection flow rate of the injection well; Based on the principle of material balance, the relationship between the increase in formation water volume and the injection flow rate of injection wells at any time step is accumulated to obtain a model relating the increase in formation water volume to the cumulative advance injection volume.
4. The method for calculating formation pressure in ultra-low permeability reservoirs according to claim 2, characterized in that, The relationship model between the increase in water volume in the formation and the cumulative advance water injection is as follows: in, Porosity under the current formation pressure; The volume of the stratum to be calculated; This represents the water saturation level under the current formation pressure. This is the water volume coefficient under the current formation pressure; Porosity at the initial formation pressure; The initial water saturation level under formation pressure; The water volume coefficient under the initial formation pressure; For the first Cumulative advance water injection volume over time steps; For the first Time step water injection well water injection flow rate; For the first Time step.
5. The method for calculating formation pressure in ultra-low permeability reservoirs according to claim 1, characterized in that, The equation for continuous seepage motion is as follows: in, The seepage velocity; Formation permeability; Viscosity; To initiate the pressure gradient; These are parameters affecting nonlinear seepage. To determine the parameters affecting the pressure gradient.
6. The method for calculating formation pressure in ultra-low permeability reservoirs according to claim 1, characterized in that, The permeability stress-sensitive equation is as follows: in, The initial formation permeability; This is the stress sensitivity coefficient; This represents the original formation pressure; This represents the current formation pressure.
7. The method for calculating formation pressure in ultra-low permeability reservoirs according to claim 1, characterized in that, The rock state equation is as follows: in, is the rock compressibility coefficient.
8. A formation pressure calculation system for ultra-low permeability oil reservoirs, characterized in that, include: The data acquisition module is used to obtain the cumulative advance water injection volume of the formation to be calculated at the current time step; The calculation module is used to substitute the cumulative advance water injection volume of the formation to be calculated at the current time step into the pre-constructed cumulative advance water injection volume-formation pressure relationship model to calculate the formation pressure calculation result of the formation to be calculated at the current time step. Specifically, the pre-constructed cumulative advance water injection volume-formation pressure relationship model is: a relationship model between the increase in formation water volume and the cumulative advance water injection volume by introducing the continuous seepage motion equation, the permeability stress sensitivity equation and the rock state equation. The continuous seepage motion equation includes the initiation pressure gradient influence parameter and the nonlinear seepage influence parameter.
9. A formation pressure calculation device for ultra-low permeability oil reservoirs, characterized in that, include: Memory, used to store computer programs; A processor, configured to execute the computer program to implement the steps of the formation pressure calculation method for ultra-low permeability reservoirs as described in any one of claims 1-6.
10. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it implements the steps of the formation pressure calculation method for ultra-low permeability reservoirs as described in any one of claims 1-6.