Multi-mode fluid compression optimized negative pressure gas production device

Abstract

The invention belongs to the technical field of gas collection and compression, and particularly relates to a multi-mode fluid compression optimized negative pressure gas collection device which comprises a gas collection module, a fluid compression module and a gas storage and transmission module. The gas collection module is used for enabling formation gas to flow to a collection pipeline under the action of negative pressure and transmitting the formation gas to the fluid compression module; the fluid compression module comprises a plurality of cascaded compressors, a dynamic pressure optimization control module and a sensor module; the dynamic pressure optimization control module conveys compressed gas to the gas storage and transmission module through gas parameters obtained by the sensor module and environmental parameters during underground gas collection; and the gas storage and transmission module is used for storing the compressed gas and transmitting the compressed gas to a far end. According to the invention, the gas recovery efficiency is improved, the compression energy consumption is reduced, and the problems of unstable shaft pressure, overload of the compressor and the like are effectively avoided.

Description

Technical Field

[0001] The present invention belongs to the technical field of gas collection and compression, and in particular relates to a negative pressure gas collection device for multi-modal fluid compression optimization. Background Art

[0002] With the increasing depth and difficulty of oil and gas resource exploitation, traditional conventional oil and gas fields have gradually entered a stage of declining production, and unconventional resources such as shale gas, coalbed methane, and tight sandstone gas have gradually become the main growth points of current oil and gas exploration and development. However, these unconventional reservoirs often have the characteristics of deep burial, low porosity, and poor permeability, which leads to limited natural flow of gas between the wellbore and the formation. Conventional positive pressure gas production methods are difficult to fully utilize the production capacity of these reservoirs. In order to cope with this problem, the industry has successively proposed a variety of advanced methods such as negative pressure gas production, staged fracturing, and horizontal well technology. Among them, negative pressure gas production has attracted much attention because it can maintain a lower pressure in the wellbore, thereby amplifying the pressure difference between the formation and the wellbore and significantly improving the driving force of gas flow.

[0003] In the published technical literature or patents, negative pressure gas production is more often applied to unconventional gas reservoirs such as low permeability gas reservoirs and shale gas reservoirs, and the research focuses on the intensity, duration and formation stability of downhole negative pressure control. For example, some existing technologies install vacuum pumps or negative pressure devices at the wellhead to reduce the wellhead pressure, so that the formation gas is more easily gathered into the wellbore to achieve the purpose of increasing production; there are also studies that propose a series of improvement measures for downhole packers and multiphase flow conditions to reduce the wellbore annulus pressure and stabilize gas production. However, the above-mentioned negative pressure gas production methods often rely on a single manual experience or simple negative pressure pumping control, lack of comprehensive optimization of multiple parameters such as gas flow, pressure and temperature, and are often difficult to finely control when facing different depths and different permeability sections. In addition, these methods rarely systematically discuss the coupling problem between negative pressure gas production and subsequent ground multi-stage compression systems, resulting in the overall efficiency from formation gas production to ground gathering and transportation still has room for improvement.

[0004] On the other hand, multi-stage compression technology has been relatively maturely applied in the field of conventional natural gas production and transportation. Traditional multi-stage compressor systems usually use a fixed compression ratio or a single variable efficiency determined according to empirical data, which has limited adaptability to fluctuations in the inlet gas and changes in composition. When the gas inlet pressure and composition change significantly, it is necessary to manually adjust the operating parameters of each stage of the compressor frequently, which is not only complicated to operate, but also often difficult to achieve the optimal balance between energy utilization and gas production capacity. Some existing patents and literatures propose to improve efficiency by increasing interstage cooling and accurately controlling the compressor speed, but most studies still remain in the context of normal pressure or positive pressure gas production, and fail to fully consider the impact of wellbore negative pressure on the inlet pressure, so it is difficult to directly apply to unconventional situations such as negative pressure gas production. Under negative pressure conditions, the gas pressure in the wellbore is often much lower than the level during conventional production, resulting in more significant changes in the volume and viscosity of the gas during the process of entering the compressor. In addition, if the formation permeability is low and the pressure is uneven, the gas production will often fluctuate, which will have a significant impact on the inlet parameters of the multi-stage compressor, making it difficult for traditional fixed ratio or approximate compression strategies to maintain high-efficiency operation. Summary of the invention

[0005] In view of this, the main purpose of the present invention is to provide a negative pressure gas production device optimized by multi-modal fluid compression, enhance the gas production capacity of low permeability gas reservoirs through negative pressure gas production, and use the intelligent control strategy of multi-stage compression to overcome the problem that the traditional fixed compression ratio mode is difficult to adapt to gas flow fluctuations, and ensure that the system can maintain efficient operation under different working conditions. Compared with the prior art, the present invention establishes a collaborative optimization model of negative pressure gas production and multi-stage compression, improves gas recovery rate, reduces compression energy consumption, and effectively avoids problems such as unstable wellbore pressure and compressor overload, providing a safer, more economical and more intelligent solution for the efficient exploitation of unconventional gas reservoirs and low permeability gas reservoirs.

[0006] The technical solution adopted by the present invention is as follows: A negative pressure gas extraction device with multimodal fluid compression optimization, the device comprising: a gas collection module, a fluid compression module and a gas storage and transmission module; the gas collection module is used to make the formation gas flow to the collection pipeline and transmit it to the fluid compression module through the action of negative pressure; the fluid compression module comprises a plurality of cascaded compressors, a dynamic pressure optimization control module and a sensor module; the dynamic pressure optimization control module adjusts the working mode and pressure output of each stage of the compressor in real time according to the gas parameters obtained by the sensor module and the environmental parameters during underground gas collection, and transmits the compressed gas to the gas storage and transmission module; the gas storage and transmission module is used to store the compressed gas and transmit the compressed gas to the remote end in response to the control command from the remote end.

[0007] Furthermore, the execution process of the dynamic pressure optimization control module specifically includes: establishing a flow model of gas in porous media under negative pressure conditions according to environmental parameters and gas parameters, and calculating the formation gas production; adjusting the intake pressure of the first-stage compressor to a safe intake pressure according to the formation gas production and in combination with the gas parameters, and adjusting the inlet pressure, outlet pressure, inlet temperature, outlet temperature, compression power of each stage of the compressor and the inter-stage cooling temperature drop between adjacent stages of compressors according to the safe intake pressure and the required final discharge pressure.

[0008] Furthermore, environmental parameters include: absolute permeability of the formation , the value range is 1 to 100, the unit is mD; formation pressure , unit is Pa; formation temperature , unit is K; wellbore perforation area , in m²; formation porosity ; Formation hydraulic pressure , unit is Pa; uniaxial compressive strength of formation , unit is MPa; Poisson's ratio of formation ; The gas parameters include: gas dynamic viscosity , unit is Pa·s; gas molecular weight , in g / mol; critical pressure of gas , unit is MPa; gas critical temperature , unit is K; gas adiabatic index ; Gas real-time temperature , unit is K; gas specific heat capacity , unit is kg·K; real-time gas pressure , unit is Pa.

[0009] Furthermore, the flow model is used to calculate the formation gas production: in, is the formation gas production, in kg / s; is the flow rate of gas in porous media, in m / s; is the gas density in kg / m³.

[0010] Furthermore, the gas flow rate in the porous medium Use the following formula to calculate: in, is the standard reference pressure, which is 101325Pa; is the standard reference temperature, which is 293.15K; gas density Use the following formula to calculate: in, is the universal gas constant, which is 8.314 J / (mol·K); is the gas compressibility factor, which is calculated using the following formula: .

[0011] Furthermore, the safe intake pressure is calculated by the following formula: in, is the critical pressure of formation collapse; To ensure safe intake pressure, adjust the intake pressure of the first stage compressor to ; is the safety margin, the value range is 50 to 100, the unit is kPa; is the cross-sectional area of ​​the air intake duct, in m²; For the The inlet pressure of the compressor is is the inlet pressure of the first stage compressor ,for It is the outlet pressure of the previous stage minus the pipeline pressure drop.

[0012] Furthermore, the outlet pressure of each compressor stage is adjusted by the following formula: in, For the Gas compression factor of the compressor stage; is the gas compression factor of the first stage compressor; For the final discharge pressure; is the total number of compressor stages; For the The outlet pressure of the compressor.

[0013] Furthermore, the inlet temperature, outlet temperature and inter-stage cooling temperature drop of each stage compressor are adjusted by the following formula: in, For the Stage compressor inlet temperature; is the negative pressure adiabatic cooling amount; For the Stage compressor outlet temperature; It is the interstage cooling temperature drop; is the minimum outlet temperature of the cooler; is the gas adiabatic index; For the Stage compressor outlet temperature; For the Stage compressor outlet pressure; For the Variable efficiency of the compressor stage; For the The gas compression factor at the outlet of the first-stage compressor.

[0014] Furthermore, the following formula is used to calculate Variable efficiency of stage compressor: in, Design flow for compressor; The design pressure ratio of the compressor ranges from 1.5 to 4.0.

[0015] Furthermore, the compression power of each stage of the compressor is adjusted by the following formula: in, For the The compression power of the compressor; For the The gas compression factor at the inlet of the first-stage compressor.

[0016] By adopting the above technical scheme, the present invention produces the following beneficial effects: in the system disclosed by the present invention, the relationship between the formation gas production and the wellbore negative pressure is no longer just a passive relationship, but through real-time monitoring and mathematical model calculation, the comprehensive scheduling of key parameters such as negative pressure intensity, compressor intake pressure and outlet pressure is realized. This collaborative optimization allows the wellbore and formation to not bear additional risks due to the pursuit of extreme negative pressure, and also allows subsequent multi-stage compressors to avoid rapid loss of efficiency in the case of large flow fluctuations or sudden changes in pressure ratio. Through the explanation of strategies such as safe intake pressure, step-by-step distribution of outlet pressure, and inter-stage cooling in the embodiment, it can be seen that the present invention, by establishing an adaptive compression process, ensures that the compressor group can maintain a relatively stable thermodynamic state and pressure increase when dealing with different scales of gas production. Such an adaptive mechanism greatly alleviates the dependence of multi-stage compression on wellhead conditions, enabling it to continue to work in a dynamically changing negative pressure gas production environment, and also stably output high-quality airflow in different production capacity fluctuation cycles. With this dynamic matching of the entire process, the potential production capacity in the formation can be more fully utilized. Compared with traditional positive pressure gas production, the pressure gradient under negative pressure conditions is enlarged, making it easier for low permeability pores to release stored gas, greatly increasing the instantaneous gas production rate and delaying the decline of production capacity. In the conventional negative pressure gas production mode, if there is a lack of intelligent compression means, the compression equipment will be overloaded or frequently started and stopped with the gas production peak, wasting energy and accelerating equipment wear. The improvement of the present invention in this regard enables the coordination of negative pressure enhancement and multi-stage compression to form a smooth and adjustable "production-transmission-use" chain from the wellbore to the gas storage and transmission links. As a result, while meeting the high-yield gas production needs, the system can also control the compression energy consumption to the lowest possible level through interstage cooling, precise pressure ratio distribution and real-time power regulation, thereby achieving the dual benefits of high production and high efficiency. Furthermore, by calculating and correcting parameters such as gas compression factor, critical pressure and critical temperature, the system can cope with potential complex effects such as gas volume expansion, density change and even phase change caused by a significant reduction in wellbore pressure. Traditional gas production compression methods often accumulate errors when the gas deviates from the ideal state, resulting in inaccurate gas production efficiency assessment and deviation in compressor selection. Once entering an unconventional formation environment, it is even more impossible to accurately control. In the multimodal fluid compression optimization framework proposed in this invention, these correction formulas enable formation production prediction, negative pressure scheduling, and compression ratio division to closely follow the actual gas behavior, providing an accurate basis for the setting of inlet and outlet temperatures and pressures of compressors at all levels, and also preventing unnecessary heat accumulation and energy loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A schematic diagram of the device structure of a negative pressure gas extraction device with multi-modal fluid compression optimization provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0018] All features disclosed in this specification, or steps in all methods or processes disclosed, except mutually exclusive features and / or steps, can be combined in any manner.

[0019] Any feature disclosed in this specification (including any additional claims and abstract), unless otherwise stated, may be replaced by other alternative features that are equivalent or have similar purposes. That is, unless otherwise stated, each feature is only an example of a series of equivalent or similar features.

[0020] Example 1: Reference Figure 1 , a negative pressure gas extraction device with multi-modal fluid compression optimization, the device comprising: a gas collection module, a fluid compression module and a gas storage and transmission module; the gas collection module is used to make the formation gas flow to the collection pipeline and transmit it to the fluid compression module through the action of negative pressure; the fluid compression module comprises a plurality of cascaded compressors, a dynamic pressure optimization control module and a sensor module; the dynamic pressure optimization control module adjusts the working mode and pressure output of each stage of the compressor in real time according to the gas parameters obtained by the sensor module and the environmental parameters during underground gas collection, and transmits the compressed gas to the gas storage and transmission module; the gas storage and transmission module is used to store the compressed gas and transmit the compressed gas to the remote end in response to the control command from the remote end.

[0021] Specifically, during the negative pressure gas production process, the pressure in the wellbore is reduced to a level less than the original pressure of the formation, thereby forming a large pressure gradient between the formation and the wellbore, and this pressure gradient becomes the main power source for driving gas flow. The movement of gas in the pores of the formation is affected by many factors, including permeability, porosity, gas viscosity, pressure gradient, etc. In porous media, the seepage velocity of gas is not only constrained by Darcy's law, but also affected by gas compressibility and temperature changes. The present invention introduces environmental parameters and gas parameters into the calculation by establishing a multimodal fluid seepage model to accurately predict the flow behavior of formation gas, and makes real-time adjustments under different pressure conditions to ensure the stability of the gas flow rate. Since the gas is affected by the combined effects of viscous force and inertial force during the seepage process, nonlinear flow phenomenon may occur under high pressure difference conditions. The gas collection module of the present invention is combined with a dynamic pressure optimization control module to perform real-time regulation of the negative pressure intensity to avoid excessive negative pressure causing formation structure damage or gas production channel blockage, while ensuring sufficient pressure gradient to maintain continuous gas flow.

[0022] In addition, the gas collection module of the present invention monitors key parameters such as formation pressure, gas density, flow rate, permeability, etc. in real time through the sensor module, and establishes a dynamic feedback system in combination with environmental parameters to achieve intelligent control. In particular, when the formation pressure is low or the permeability is low, the system can optimize the gas collection efficiency by adjusting the negative pressure level to avoid reservoir damage caused by excessive negative pressure. During the negative pressure gas production process, after the gas enters the collection pipeline, its pressure and temperature will change. As the gas enters the low-pressure zone from the formation, the expansion effect will cause the temperature to drop, which may affect the fluidity of the gas and even induce hydrate formation or gas condensation. Therefore, the present invention combines the gas state equation and thermodynamic model to make real-time corrections to the temperature changes of the gas inside the wellbore, and adopts appropriate temperature compensation strategies as needed, such as using a heating device or heat recovery technology to prevent the adverse effects of low temperature effects on gas flow.

[0023] The fluid compression module plays a vital role in the multi-modal fluid compression optimized negative pressure gas extraction device of the present invention. It not only gradually increases the low-pressure airflow from the gas collection module to the required final discharge pressure, but also must take into account multiple factors such as energy consumption, equipment operation safety and gas property changes in this process to ensure the efficiency and stability of the overall system. A multi-stage series compressor is set inside the module. Each stage of the compressor will dynamically adjust the working mode, inlet and outlet pressures and operating speed according to the real-time data collected by the sensor module during operation. The purpose is to make the compression ratio of each stage work within the optimal range, thereby minimizing the energy waste and mechanical wear risks caused by over-compression or under-compression. Because under negative pressure gas extraction conditions, the gas from the formation often has a large pressure difference and temperature gradient, and the temperature of the underground formation and the ambient temperature at the compressor inlet will also be significantly different, so it is necessary to monitor and control the parameters such as gas pressure, temperature, density and flow rate in real time during the multi-stage compression process. To this end, the fluid compression module is equipped with a special dynamic pressure optimization control module, which will determine the range of inlet pressure and outlet pressure of each stage based on the gas composition, formation gas production rate, gas pressure and temperature information provided by the sensor, combined with the design parameters and load capacity of each stage of the compressor, and comprehensively manage the heat generated during the compression process.

[0024] In order to reduce the problem of excessive temperature rise of gas under high pressure, which leads to decreased equipment efficiency or adverse changes in gas properties, the module often sets an intermediate cooling device between adjacent compressors, so as to cool the gas after completing the first or second stage compression, so that it can maintain a relatively suitable temperature range when entering the next compression stage, avoiding material stress concentration and extra energy consumption caused by high temperature. At the same time, the fluid compression module will determine the most suitable variable compression strategy based on information such as the adiabatic index, molecular weight and real-time temperature of the gas, and dynamically update the compression ratio and flow distribution of each stage, so that the overall power consumption can be maintained at a low level under the premise of achieving a given discharge pressure. This process relies on the multimodal fluid optimization model proposed in the present invention. After the formation gas is calculated for seepage and the gas production is predicted, the model will match the calculated gas production rate with the intake requirements of each level of compressors, and then combine the key data such as the gas compression factor, flow parameters and compressor speed obtained by real-time monitoring to generate a set of optimal control instructions after continuous iteration, so that the compressors at all levels can complete the boosting task with higher efficiency under the negative pressure gas production environment. Through this adaptive, multi-parameter coupled algorithm, the present invention can ensure appropriate intake pressure when the formation pressure is low, prevent excessive gas from being sucked in and overloading the compressor, and can also timely increase the flow and pressure ratio of each level of compressor when the formation gas supply is sufficient, thereby maximizing the gas production efficiency. It is worth mentioning that the fluid compression module and the gas acquisition module do not operate in isolation, but are closely linked through pressure detection, temperature detection, and flow detection: when the acquisition module detects that the formation production capacity is insufficient or the wellbore pressure fluctuates, the compression module will correspondingly reduce the intake pressure or reduce the compression ratio to avoid causing excessive pressure difference to the formation; conversely, when the formation shows high production capacity or the gas viscosity is significantly reduced, the compression module can increase the working power and operating speed of each level of compressor, so that the gas can be pumped to the subsequent gas storage and transmission module with higher efficiency. In addition, the present invention also pays special attention to the detection of gas composition during the compression process, because natural gas and other formation gases may condense or precipitate heavy components when the pressure and temperature change. The fluid compression module will work together with the sensor module. Once a condensation trend or the possibility of hydrate formation is detected in the gas, the liquid phase will be avoided by adjusting the intermediate cooling temperature, increasing the outlet temperature of a certain stage, or adding external additives, thereby ensuring the smooth operation of the compression system.

[0025] Compared with the existing technology that simply relies on a fixed compression ratio or manual adjustment, the fluid compression module of the present invention can realize adaptive multi-level pressure distribution and temperature management, significantly reducing the energy consumption and loss risk of the system under different gas production conditions, while taking into account the complexity of the gas components, and using the inherent advantages of negative pressure gas production to more thoroughly collect the underground low permeability gas resources. Under such an overall design concept, the fluid compression module not only has the ability of efficient pressurization, but also forms a closely coordinated organic whole with the gas collection module and the gas storage and transmission module, greatly improving the production capacity and controllability of the entire negative pressure gas production system, and also providing accurate and flexible operating space for subsequent remote monitoring and intelligent scheduling. Since the real-time status of the gas is always paid attention to during this process and various parameters are dynamically adjusted in combination with the characteristics of the equipment, the module successfully overcomes the problems that the traditional compression method is easily affected by negative pressure fluctuations, the energy consumption cannot be precisely controlled, and the gas properties are difficult to correct in time after nonlinear changes, so that the present invention can play the advantages of high efficiency, stability and flexibility in the actual exploitation of low permeability formations.

[0026] In the process of negative pressure gas production, due to the limited mobility of formation gas, the gas production rate often has a large uncertainty, and may fluctuate significantly due to changes in formation permeability, fluctuations in wellbore pressure, or adjustments in gas production intensity. Therefore, the gas storage and transmission module must have a certain buffering capacity to cope with possible uneven gas supply problems and ensure the stability of subsequent transportation links. At the same time, since the operating state of the compressor is affected by the real-time gas source flow, the existence of the gas storage system can also provide a temporary pressure regulation function when the gas production rate fluctuates violently, avoiding the unstable operation of the compressor due to too low intake pressure or the overpressure of the storage unit due to excessive gas supply in a short time. In order to achieve this goal, the gas storage and transmission module of the present invention adopts a storage and transportation strategy based on dynamic regulation, monitors the gas pressure entering the storage unit in real time through an intelligent pressure management system, and dynamically adjusts the storage pressure in combination with factors such as gas physical properties, ambient temperature, and downstream demand, so that it always remains within the optimal working range. Compared with the traditional fixed pressure gas storage system, the gas storage and transmission module of the present invention can adaptively adjust the gas storage state according to the actual working conditions, improve the system's adaptability to different load conditions, and significantly reduce the energy loss caused by storage pressure fluctuations. After the gas enters the storage unit, in order to prevent the influence of temperature and pressure changes on the physical state of the gas, the module also adopts a precise thermal management system. By monitoring the temperature changes of the storage environment, the gas pressure control strategy is adjusted in time to prevent the gas from liquefying due to temperature drop or the gas density from decreasing due to temperature rise, which affects the transmission efficiency.

[0027] When it is necessary to transport gas to the far end, the system will perform intelligent scheduling based on downstream demand, and determine the optimal transportation time and pressure parameters in combination with the far-end pressure level, the flow resistance of the transportation pipeline and the remaining capacity of the storage unit to ensure the efficiency and stability of the transportation process. In addition, the gas storage and transmission module of the present invention is also optimized specifically for the pressure loss and pipeline friction loss that may occur during the transportation process. By optimizing the gas transportation path, reducing the roughness of the inner wall of the pipeline and adopting a segmented pressurization strategy, the energy loss during the transportation process is effectively reduced, and the final gas transportation efficiency is improved. It is worth noting that since the long-distance transmission of the transportation pipeline may be interfered by external environmental factors, such as the gas may undergo thermal expansion or contraction due to changes in external temperature during long-distance transportation, resulting in unstable transportation pressure, and may even cause pipeline blockage due to hydrate formation in a low-temperature environment, the gas storage and transmission module of the present invention tracks the state of the transported gas in real time through an online monitoring system, and adjusts the pressure and temperature parameters in the pipeline when necessary to ensure the safety and reliability of the transportation process. Compared with traditional storage and transportation methods.

[0028] Embodiment 2: The execution process of the dynamic pressure optimization control module specifically includes: establishing a flow model of gas in a porous medium under negative pressure conditions according to environmental parameters and gas parameters, and calculating the formation gas production; adjusting the intake pressure of the first-stage compressor to a safe intake pressure according to the formation gas production and in combination with the gas parameters, and adjusting the inlet pressure, outlet pressure, inlet temperature, outlet temperature, compression power of each stage of the compressor and the inter-stage cooling temperature drop between compressors of adjacent stages according to the safe intake pressure and the required final discharge pressure.

[0029] Specifically, in the execution process of the dynamic pressure optimization control module, it is necessary to first establish a flow model of gas in porous media under negative pressure conditions, which is the theoretical basis for ensuring that the gas production device can operate stably. The flow of formation gas is affected by multiple factors such as permeability, porosity, pressure gradient, temperature change, and physical parameters of the gas itself. Therefore, it is difficult to accurately describe the flow behavior of gas by simply using the classic Darcy's law. The model adopted by the present invention not only considers the influence of permeability on gas flow rate, but also introduces gas viscosity, temperature, compression factor and gas molecular motion characteristics to more accurately characterize the flow characteristics of gas in the formation. The flow model can calculate the formation gas production in real time, and combine the data collected by the sensor to determine whether the current gas supply capacity is sufficient to support the established compression load. Once the formation gas production is determined, the dynamic pressure optimization control module will combine the gas parameters to accurately control the intake pressure of the first-stage compressor to ensure that its intake pressure remains within a safe range. Determination of safe intake pressure is one of the key factors for stable operation of the system. If the intake pressure is too low, the compressor may not be able to absorb enough gas, reducing the processing capacity of the overall system; if the intake pressure is too high, it may impose too much pressure drop on the formation, thereby causing the risk of formation structure damage or even collapse. Therefore, the present invention calculates the optimal safe intake pressure through mathematical modeling method, combined with gas state equation and formation stress analysis, and makes real-time adjustments during dynamic control to adapt to the fluctuation of formation pressure and changes in gas production rate.

[0030] After determining the safe intake pressure of the first-stage compressor, the system will further optimize the calculation of the inlet pressure, outlet pressure, temperature change and compression power of each stage of the compressor according to the requirements of the final discharge pressure. Since the gas will experience a significant temperature rise during the stage-by-stage compression process, and high temperature may cause the compressor efficiency to decrease, the gas composition to change, and even material fatigue damage, the present invention introduces a cooling optimization strategy between the compressor stages, and through the reasonable design of the interstage cooling temperature drop, the inlet temperature of each stage of the compressor is always kept within an appropriate range. When calculating the outlet pressure of each stage, the control module not only considers the theoretical isentropic compression ratio, but also combines the gas compression factor, temperature change and the variable efficiency of the compressor to ensure that the compressor can maintain a high compression efficiency under different working conditions. In addition, the control module will also adjust the compression power according to the real-time operating status to ensure that the energy transfer between the compressors at all levels remains stable and minimizes energy loss. Overall, the dynamic pressure optimization control module of the present invention realizes intelligent control of the entire process from formation gas production to multi-stage compression through precise modeling and real-time optimization and regulation, so that the flow of gas in the entire system can always be in the optimal state. Compared with traditional fixed-parameter compression systems, this module can adaptively adjust the operating status of the compressor, showing higher adaptability and energy efficiency advantages when facing challenges such as unstable formation gas supply, changes in gas properties, and fluctuating environmental conditions.

[0031] Example 3: Environmental parameters include: absolute permeability of the formation , the value range is 1 to 100, the unit is mD; formation pressure , unit is Pa; formation temperature , unit is K; wellbore perforation area , in m²; formation porosity ; Formation hydraulic pressure , unit is Pa; uniaxial compressive strength of formation , unit is MPa; Poisson's ratio of formation ; The gas parameters include: gas dynamic viscosity , unit is Pa·s; gas molecular weight , in g / mol; critical pressure of gas , unit is MPa; gas critical temperature , unit is K; gas adiabatic index ; Gas real-time temperature , unit is K; gas specific heat capacity , unit is kg·K; real-time gas pressure , unit is Pa.

[0032] Specifically, the primary variable of environmental parameters is the absolute permeability of the formation, which is an important indicator that describes the ability of gas to flow in the pore structure of the formation. Its value range is between 1 and 100mD, where mD (millidarcy) is the standard unit for measuring permeability. When the permeability is high, the gas flows more easily into the wellbore and the recovery rate is high; when the permeability is low, the gas flow is restricted and the role of negative pressure gas production is more significant. Therefore, in practical applications, the system needs to dynamically adjust the negative pressure intensity according to the permeability of the formation to ensure an appropriate pressure gradient so that the formation gas can flow smoothly into the collection pipeline. Another important parameter closely related to permeability is the formation pressure, which is the original pressure of the gas in the formation and determines the driving force for the gas to flow into the wellbore. During negative pressure gas production, the pressure in the wellbore is usually reduced to a level below the formation pressure, thereby forming a sufficient pressure gradient to drive the gas to flow into the collection pipeline. However, if the formation pressure is too low, the system needs to adopt a more precise pressure control strategy to avoid damage to the formation structure or stagnation of gas flow caused by excessive pressure reduction.

[0033] The primary variable of environmental parameters is the absolute permeability of the formation, which is an important indicator that describes the ability of gas to flow in the pore structure of the formation. Its value range is between 1 and 100mD, where mD (millidarcy) is the standard unit for measuring permeability. When the permeability is high, the gas flows more easily into the wellbore and the recovery rate is high; when the permeability is low, the gas flow is restricted and the role of negative pressure gas production is more significant. Therefore, in practical applications, the system needs to dynamically adjust the negative pressure intensity according to the permeability of the formation to ensure an appropriate pressure gradient so that the formation gas can flow smoothly into the collection pipeline. Another important parameter closely related to permeability is the formation pressure, which is the original pressure of the gas in the formation and determines the driving force for the gas to flow into the wellbore. During negative pressure gas production, the pressure in the wellbore is usually reduced to a level below the formation pressure, thereby forming a sufficient pressure gradient to drive the gas to flow into the collection pipeline. However, if the formation pressure is too low, the system needs to adopt a more precise pressure control strategy to avoid damage to the formation structure or stagnation of gas flow caused by excessive pressure reduction.

[0034] Formation porosity is another key factor that affects gas reserves and flow capacity. It determines the amount of storage space for gas in the formation. Higher porosity means that the formation can hold more gas and that gas flow is less restricted, while lower porosity indicates that the gas storage space is limited and the flow is poor. Therefore, during the system optimization process, the system needs to comprehensively consider parameters such as porosity, permeability, and pressure to determine the most appropriate gas production strategy. The formation hydraulic pressure and the uniaxial compressive strength of the formation jointly determine the stability of the formation and its ability to withstand pressure changes. During negative pressure gas production, if the wellbore pressure drops too quickly or too low, it may cause formation collapse or well wall damage. Therefore, the system needs to monitor these two parameters in real time and calculate the formation stress in combination with the Poisson's ratio to ensure that the gas production process is carried out within a safe range.

[0035] In addition to environmental parameters, the present invention also monitors and optimizes gas parameters in detail to ensure that the state of the gas during collection, compression and transportation is always at the optimal level. The dynamic viscosity of the gas is one of the key parameters that affect the flow resistance of the gas. Higher viscosity means greater flow resistance. Therefore, in a high-viscosity gas environment, the system may need to increase the negative pressure intensity or adjust the gas collection rhythm to ensure that the gas can flow smoothly. The molecular weight of the gas affects the density and flow rate of the gas. A larger molecular weight usually means a higher density, and the change in density directly determines the workload of the compressor. Therefore, when the system performs pressure optimization calculations, the influence of the molecular weight of the gas must be considered. The critical pressure and critical temperature of the gas are basic parameters for measuring the change in the state of the gas. When approaching the critical state, the physical properties of the gas will change dramatically. Therefore, the system needs to monitor the pressure and temperature of the gas in real time to avoid the gas entering the critical zone and affecting the compression efficiency. The adiabatic index of the gas determines the thermodynamic behavior of the gas during the compression process. It affects the degree of temperature increase of the gas during the compression process. Therefore, in the compressor optimization process, this parameter is used to calculate the temperature adjustment strategy of each level of compressor. In addition, the real-time temperature and specific heat capacity of the gas determine the heat capacity and heat exchange capacity of the gas. During the interstage cooling process, these parameters are used to calculate the optimal cooling temperature drop to ensure that the gas maintains a suitable temperature when entering the next stage compressor. Finally, the real-time pressure of the gas is one of the core parameters for the operation of the entire system. It not only affects the flow rate of the gas and the working state of the compressor, but also directly determines the final delivery pressure and storage conditions. Therefore, the dynamic pressure optimization control module of the present invention will continuously monitor the gas pressure, and dynamically adjust the operating state of the system in combination with all environmental and gas parameters to achieve optimal gas collection, compression and delivery efficiency.

[0036] Example 4: Calculating formation gas production using a flow model: in, is the formation gas production, in kg / s; is the flow rate of gas in porous media, in m / s; is the gas density in kg / m³.

[0037] Specifically, gas density is an important factor in determining gas production, which is affected by formation pressure, temperature, gas molecular weight and compression factor. Since the negative pressure gas production device enhances the fluidity of formation gas by reducing the pressure in the wellbore, the gas pressure inside the wellbore is usually much lower than the formation pressure, which causes the gas to experience a large pressure change during the flow process, and the density of the gas changes with the change of pressure. Under low pressure, the volume of the gas expands and the density decreases, while under high pressure, the gas density increases, thereby affecting the mass content per unit volume. The present invention uses the gas state equation to calculate the density, ensuring that the mass of the gas flowing into the wellbore can be accurately calculated on the basis of real-time monitoring of the gas pressure and temperature. Secondly, the flow rate of the gas in the formation determines the efficiency of the gas flowing into the wellbore. In the negative pressure gas production mode, the pressure in the wellbore is much lower than the formation pressure, forming a pressure gradient converging to the wellbore, and this gradient becomes the main driving force for driving the gas flow. However, the gas does not flow freely in the formation, but is affected by the formation permeability, pore structure and flow resistance, so its flow rate is constrained by multiple factors. The present invention adopts the modified Darcy's law to describe the seepage behavior of gas in porous media, and makes corrections for the compressibility and temperature change of gas to ensure the accuracy of flow rate calculation. Since the permeability of the formation determines the fluidity of the gas, the flow rate is low in low permeability gas reservoirs, while the flow rate is high in high permeability formations. In order to optimize the effect of negative pressure gas production, the present invention dynamically adjusts the negative pressure intensity in the wellbore by real-time monitoring of parameters such as formation pressure, permeability and gas viscosity, so that the gas flow rate is kept within an optimal range, which can ensure sufficient gas production rate and avoid formation damage or pore structure changes caused by excessive flow rate. In addition to the influence of flow rate and density, the wellbore perforation area is also a key factor in determining gas production. Wellbore perforation is the main channel for gas to enter the collection pipeline, and its size directly determines the gas flow rate that can pass through per unit time. If the perforation area is too small, even if the pressure gradient of the formation gas is large, the restricted flow will still lead to a decrease in the gas production rate, and if the perforation area is too large, it may cause excessive local negative pressure, causing instability of the formation structure. The present invention adopts precise optimization design of perforation area, so that the perforation of the wellbore can be optimally distributed according to the formation characteristics, and combined with a dynamic control system, the negative pressure level is adjusted in time during the gas production process to match the flow characteristics of the perforation area, ensuring smooth and efficient gas flow. Finally, the formation porosity determines the storage capacity of gas in the formation. It reflects the proportion of effective gas space inside the porous medium, which in turn affects the release rate of gas under negative pressure drive. Higher porosity generally means larger gas reserves and faster flow rate, while lower porosity may lead to limited gas production process.In traditional gas production calculation methods, it is often assumed that the formation porosity is a fixed value. The present invention combines formation structure analysis with real-time monitoring data to establish a dynamic porosity adjustment mechanism, which enables the system to adaptively adjust the rate of negative pressure gas production according to the actual conditions of the formation around the wellbore, thereby preventing formation pore closure or flow channel blockage due to excessive extraction.

[0038] Example 5: Gas flow rate in porous media Use the following formula to calculate: in, is the standard reference pressure, which is 101325Pa; is the standard reference temperature, which is 293.15K; gas density Use the following formula to calculate: in, is the universal gas constant, which is 8.314 J / (mol·K); is the gas compressibility factor, which is calculated using the following formula: .

[0039] Specifically, let's first look at the formula that describes the gas flow rate. The most basic part is , here Represents the formation permeability. The higher the value, the better the interconnection of pores in the porous medium of the formation, and the more freely the gas can pass through it. is the viscosity of the gas, which reflects the magnitude of the internal friction of the gas when it flows. When it is too large, the molecular forces between gases are more significant, and the flow resistance increases accordingly, resulting in a decrease in the gas seepage velocity. At this time, the negative pressure gas production device may need to maintain a higher pressure gradient to ensure the established gas production rate. The negative sign indicates the pressure gradient, and the negative sign indicates that the gas flows in the direction of decreasing pressure, which is the main "driving force" for gas seepage. The principle of negative pressure gas production is to apply a lower pressure than the formation in the wellbore to amplify the pressure. The value of , so that the gas has enough power to flow into the wellbore, thereby improving the gas recovery efficiency. However, if the pressure gradient is too large, the formation may face the risk of collapse or particle migration. Therefore, the dynamic pressure optimization control module of the present invention needs to continuously monitor and regulate the negative pressure intensity to achieve a balance between high recovery rate and formation safety.

[0040] besides, The purpose of the standard reference pressure is to correct for differences in the compressibility of gases at different absolute pressures. The value is usually 101325Pa (i.e. one standard atmospheric pressure), and is the actual pressure in the well or in the local formation. When the pressure in the wellbore is significantly lower than the formation pressure, the value of this correction factor may be large, which reflects the characteristic that the gas volume expands rapidly with pressure changes under low pressure, and also reveals that when When the pressure is further reduced, the actual contribution of negative pressure gas production to the increase of gas flow rate will become more obvious. The value of will decrease, indicating that the gas no longer has a large volume expansion space relative to the standard state. At this time, negative pressure gas production needs to be combined with other strategies (such as adjusting formation permeability or wellbore perforation parameters) to maintain a stable gas production. This part is the temperature correction factor, which is used to reflect the change in the gas molecule movement rate as the temperature increases or decreases. For an ideal gas, an increase in temperature means an increase in the molecular kinetic energy, and thus the seepage rate will increase accordingly. If the formation temperature is significantly lower than the reference temperature, (Generally, the value is 293.15K), the thermal motion of gas molecules weakens, and the flow performance also decreases. Through real-time monitoring and appropriate calculation simulation, the present invention can take insulation or heating compensation measures in advance under low temperature conditions to prevent the flow rate attenuation caused by temperature reduction from having an adverse effect on gas production efficiency.

[0041] Once the flow rate of the gas in the formation is known, its density needs to be further calculated, because in the negative pressure gas extraction device, the mass of gas that can be obtained per unit time depends on the product of the flow rate and density. The calculation formula for gas density is: , which is derived from the expanded form of the ideal gas state equation, combined with a correction for the real gas compressibility factor. Here is still the pressure of the environment in which the gas is located, and the flow rate in the calculation Mutually reinforcing: When the pressure is higher, the number of gas molecules contained in the same volume increases, and the density increases, while negative pressure gas production makes the wellbore at a lower pressure, so the gas density in this area is relatively low. However, if the original formation pressure is extremely high, even if the wellbore is negative pressure, it will not affect the high-density characteristics when it flows to the wellbore. It is the molecular weight of the gas, which is used to distinguish natural gas or mixed gas with different components. For example, gas containing more heavy components often has a larger molecular weight, which will directly lead to an increase in density. The present invention will refresh the gas composition information collected regularly. The value of the compressor can be used to calculate the density more accurately and guide the intake parameter control of the compressor. is the universal gas constant, a fixed value used in physics that provides a link between dimensions such as pressure, volume, temperature, and molecular weight. It indicates the real-time temperature of the gas. When the temperature rises, the molecular motion intensifies, resulting in volume expansion and density decrease. However, the impact on gas production still needs to be comprehensively evaluated in combination with factors such as flow rate. Sometimes the increase in temperature causes the gas viscosity to decrease and the flow rate to increase, which may compensate for the production loss caused by the decrease in density.

[0042] Compression Factor It is the key to correct the deviation of real gas from the ideal gas characteristics under high pressure or special temperature conditions. If it is ignored and the gas is simply treated as an ideal gas, significant errors may occur in the high pressure section, resulting in a large difference between the predicted value and the actual gas production situation, thus misleading the control strategy of the negative pressure gas production device. The core idea of ​​the formula is that when the current pressure of the gas and temperature When approaching or exceeding the critical point, the intermolecular forces will cause the gas to exhibit obvious non-ideal properties. The value of usually deviates from 1, and the degree of this deviation is related to the critical pressure of the gas. and critical temperature If the ratio of system pressure to critical pressure is large, and the ratio of current temperature to critical temperature is small, then This part will become more obvious, making it possible for the gas compression factor to become smaller (often less than 1), thereby further amplifying the density calculation, which corresponds to the fact that the mutual attraction between gas molecules is enhanced and the volume shrinks under high pressure. For this reason, when controlling the pressure difference between the formation and the wellbore, the negative pressure gas production device needs to pay special attention to this non-ideal effect to avoid the formation of local condensation or phase change in the formation pores due to excessive extraction in the high-pressure area, which will have an adverse effect on gas production efficiency and reservoir integrity.

[0043] Embodiment 6: Calculate the safe intake pressure by the following formula: in, is the critical pressure of formation collapse; To ensure safe intake pressure, adjust the intake pressure of the first stage compressor to ; is the safety margin, the value range is 50 to 100, the unit is kPa; is the cross-sectional area of ​​the air intake duct, in m²; For the The inlet pressure of the compressor is is the inlet pressure of the first stage compressor ,for It is the outlet pressure of the previous stage minus the pipeline pressure drop.

[0044] Specifically, in the multi-modal fluid compression optimized negative pressure gas production device of the present invention, in order to ensure that the formation can maintain a high gas flow efficiency during the gas production process, and will not cause safety hazards such as collapse, sand migration or well wall instability due to excessive negative pressure, it is necessary to finely control the intake pressure of the first-stage compressor and set a reasonable pressure safety boundary accordingly. To this end, this embodiment provides a set of formulas that include dual constraints of formation mechanics and fluid dynamics for the safe intake pressure, so as to achieve the best compromise between formation pressure and negative pressure gas production. The formula first calculates the critical pressure of formation collapse To evaluate the stability of the wellbore under negative pressure, the formation hydraulic pressure minus This means that the uniaxial compressive strength of the formation is further considered on the basis of hydraulic pressure. Poisson's ratio When the effective stress applied externally exceeds this threshold, the stratum is very likely to undergo irreversible deformation or even collapse. Poisson's ratio represents the ratio of the lateral deformation to the longitudinal deformation of the stratum material under compression. If the pressure is larger, the formation is more likely to expand or deform laterally when compressed, which makes the critical collapse pressure relatively low, and vice versa. Since negative pressure gas production requires maintaining a lower pressure in the wellbore than in the formation to enhance gas flow, this requires us to estimate Finally, leave a certain safety margin for the system , thereby preventing the formation from working near the critical limit for a long time and causing safety risks. Based on this, the sum of the critical pressure of formation collapse and the safety margin is The first candidate inlet pressure is considered. On the other hand, the gas supply capacity itself must also be considered, that is, the gas production capacity of the formation Molecular weight of bound gas , Real-time temperature and the universal gas constant Calculate the minimum pressure required to maintain a specific flow rate. If the negative pressure is too large, although it can increase the flow rate, it will also increase the risk of formation instability; if the negative pressure is insufficient, the flow rate cannot meet the intake requirements of the subsequent compressor.

[0045] In the formula It comes from the analysis of gas flow and cross-sectional flux: when the gas mass flow rate When fixed, if you want to maintain a high flow rate, you need to ensure that the intake velocity and density are in a reasonable range, which is related to molecular weight, temperature, gas constant and the cross-sectional area of ​​the intake duct. The larger the item, the more Higher inlet pressure may be required to support sufficient transport capacity. At the same time, in order to correct the impact of the actual gas in the formation deviating from the ideal state, a compression factor is also introduced into the formula , which plays the role of correcting the compressibility of the real gas in the denominator: when When the gas is actually more compressible than the ideal gas, it is easy to show the mutual attraction effect of molecules in the high pressure area; This indicates that the molecular repulsion of the gas or other factors lead to differences from the ideal gas model. If these phenomena are not taken into account, large errors will occur in high pressure or high flow rate environments.

[0046] Finally, from the formula Select the higher of the two as the inlet pressure of the first stage compressor , thereby ensuring that even at the time of maximum gas production demand, the system will not pull the wellbore pressure too low, so as not to exceed the critical point of formation collapse. In this way, on the one hand, the formation can obtain a sufficiently large negative pressure driving force to accelerate gas seepage and improve the recovery rate; on the other hand, it provides a certain pressure redundancy for formation damage and reduces the potential threat to wellbore stability. For the compressors of subsequent stages, if there is a pipeline pressure drop, the outlet pressure of the previous stage minus the pipeline pressure drop is used as the inlet pressure of the next stage to ensure that the compressors of each stage can be connected in series on the overall flow plan at the beginning of the design. The dynamic pressure optimization control module of the present invention will be combined with real-time monitoring data of the formation, such as changes in porosity over time or gas production intensity, formation deformation monitoring, data provided by flow and pressure sensors, etc., to continuously correct rationality. Once it is detected that the formation pressure continues to decay or local loosening occurs, it is necessary to increase the wellbore pressure in time to avoid excessive negative pressure; if it is observed that the formation production capacity is still sufficient and the pore structure has not changed significantly, the wellbore pressure can be appropriately reduced to maintain a higher recovery rate. In this way, negative pressure gas production and formation safety can be taken into account under the balanced control of the overall system, providing a stable air intake source for the subsequent steady-state operation of the multi-stage compressor, and allowing the entire set of negative pressure gas production equipment to show more efficient and safe performance in complex geological environments such as low permeability gas reservoirs and shale gas reservoirs. It is worth mentioning that The value range is between 50 and 100 kPa, which not only takes into account the variable formation mechanical characteristics, but also provides sufficient operational adaptability for different types of compressors.

[0047] Embodiment 7: The outlet pressure of each compressor stage is adjusted by the following formula: in, For the Gas compression factor of the compressor stage; is the gas compression factor of the first stage compressor; For the final discharge pressure; is the total number of compressor stages; For the The outlet pressure of the compressor.

[0048] Specifically, in the formula we can see a The exponential term appears in the form of Represents the final discharge pressure, which is the target pressure that the system is to reach after completing all compression stages; is the intake pressure of the first-stage compressor, which is determined by the negative pressure gas collection strategy and the safe intake boundary. Reflects the division of the compression process into After the basic stage, The compression ratio share that the compressor should bear is: When the compression is just started, only the total compression ratio is obtained. power; when When , it means that all compression stages have been completed, and the exponential term in the formula becomes , and the final discharge pressure is reached without compromise. In an ideal situation, if the properties of the gas do not change significantly during the compression process at each stage, or can be approximately regarded as an ideal gas, then The overall compression ratio is distributed to each stage according to such an index, so that the compressor group can work under a relatively balanced load, avoiding a large increase in mechanical energy consumption, exhaust temperature or equipment wear due to excessive compression ratio of a single stage, and avoiding the waste of investment and system complexity that may be caused by splitting the compression ratio into many stages.

[0049] However, in actual working conditions, the degree to which the gas deviates from the ideal gas state is often not negligible, especially in the negative pressure gas production mode, where the inlet pressure in the wellbore is much lower than the normal conditions, and the target discharge pressure of the subsequent compression process may be quite high, resulting in a large difference in the pressure range of the compressor before and after the compressor, and the temperature change will also be quite drastic. In order to solve this problem, the present invention multiplies the end of the formula by ,in It is The gas compression factor of the compressor is represents the gas compression factor of the first stage. The physical meaning of this correction term is that if the first Compared with the gas processed by the first stage, the gas processed by the second stage shows more significant non-ideality (meaning ), then it is necessary to make appropriate adjustments in the compression ratio distribution so that The actual outlet pressure of the stage is slightly higher or lower to compensate for the impact of the gas deviating from the ideal state. Under high pressure or high temperature, real gas may behave significantly different from ideal gas. For example, the influence of intermolecular attraction or repulsion is more significant, which ultimately leads to gas compression ratio, exhaust temperature or specific volume and other parameters are very different from the ideal formula. If a simple geometric exponential allocation strategy is still used, then in the subsequent compression stages, the temperature rise or volume change of the gas may be far beyond expectations, which will not only cause energy waste, but also threaten the safe operation of the compression equipment. Therefore, the It is an adaptive correction that allows the actual outlet pressure of subsequent levels to be fine-tuned as the gas properties change, ensuring The stage can pressurize the gas just right and avoid the situation where the load of a certain stage suddenly increases or decreases.

[0050] In actual operation, the dynamic pressure optimization control module calculates the instantaneous compressibility factor of the gas based on the data collected by the sensor (including the temperature, pressure, flow rate of the gas at the inlet of each stage, and similar information at the outlet of each stage). If the system detects The gas composition or pressure state of the second-stage compressor is far different from that of the first stage. This may be because the temperature of the gas rises after several stages of compression and the interaction between molecules is enhanced, thus compared to There is a significant decrease, at this time it is necessary to automatically correct the first The outlet pressure of the first stage is slightly higher than the original proportional distribution value, so as to distribute more compression to avoid excessively pushing up the subsequent stages, resulting in a surge in energy consumption or a rise in temperature. On the contrary, if the compression factor in the subsequent stage is greater than the value in the first stage, it means that the non-ideality of the gas has weakened, or enough heat has been released in the intercooling process, and the gas is closer to the ideal state. In this case, the compression system can transfer the "extra" compression ratio to the subsequent stage, increase the compression of the middle and rear stages, and let the first The load of each stage is appropriately reduced, so that the entire system remains at the originally designed total energy input level. In addition, this corrective exponential distribution also allows a more balanced temperature gradient and pressure gradient to be formed between the first and last stages, without producing an obvious "bottleneck level" phenomenon, and also helps to disperse the compression heat to multiple interstage coolers for processing, thereby improving the overall thermal management efficiency.

[0051] In the past, in multi-stage compression, a very simple fixed compression ratio distribution principle was usually adopted, or the compression ratios of different stages were distributed based on empirical data, while the differences in the thermodynamic properties of the gas between different stages were ignored. This often led to overload of some stages or the working point of individual stages deviating too far from the optimal efficiency range. The formula of the present invention introduces The correction is made and adapted to the characteristic of low intake pressure during negative pressure gas extraction, thereby realizing real-time optimization of load distribution between compressor units. At the same time, since the present invention also monitors various operating indicators such as outlet temperature, flow rate, compression power consumption, etc. of each stage, the outlet pressure control formula and the overall energy optimization model can be coupled together. When it is detected that the energy utilization rate of a certain compression stage is low or the output temperature is too high, the outlet pressure target of the subsequent stage can be automatically adjusted through the control module to alleviate problems such as local heat load concentration and mechanical stress concentration, and ultimately improve the comprehensive performance of the entire compression system under different working conditions.

[0052] It is worth noting that in this formula It only describes the piecewise exponential relationship of the compression ratio, but It plays the role of a "correction factor" that takes into account the real gas properties. When the gas properties remain approximately unchanged or the intermolecular interactions are not significant, will be relatively close to 1, that is to say, the formula basically returns to the ideal geometric distribution model, making the pressure steps of each level of compressor increase in equal proportion. On the contrary, once the gas leaves the ideal range, This will cause a "slight tilt" in this proportional distribution, with some stages appropriately increasing the compression amount, while some stages relatively reducing the compression amount, ultimately meeting the accurate demand for total discharge pressure. Since the present invention is often adapted to complex working conditions such as low-permeability formations or unconventional natural gas, the gas is affected by temperature, composition, and permeability conditions in the formation, and may show a large deviation from the ideal state. Therefore, this correction term can well offset the uncertainty caused by the true characteristics of the gas, so that multi-stage compression can still maintain the expected efficiency range and avoid frequent human intervention.

[0053] Finally, under the premise of negative pressure gas production, the present invention embeds this formula into the dynamic pressure optimization control module, and forms a closed-loop regulation with formation pressure, wellbore negative pressure, real-time flow, interstage cooler temperature adjustment and other safety restrictions. Whenever the formation gas production fluctuates or the wellbore pressure level changes due to external factors, the outlet pressure of each level will be recalculated accordingly and updated at any time according to the gas state. In this process, the first The pressure output of the stage can meet the gas intake demand of the subsequent stage, and the compression load of the corresponding stage can be reduced when the gas production volume decreases, thereby reducing the overall energy consumption of the system. In this way, the coupled operation of negative pressure gas production and multi-stage compression no longer relies on artificially set fixed ratio control, but becomes more flexible and adaptable, greatly improving the overall efficiency of natural gas production and subsequent processing, and also providing an advanced solution for the development and utilization of unconventional oil and gas resources that can maintain high efficiency in complex geological and operating environments.

[0054] Embodiment 8: The inlet temperature, outlet temperature and inter-stage cooling temperature drop of each stage compressor are adjusted by the following formula: in, For the Stage compressor inlet temperature; is the negative pressure adiabatic cooling amount; For the Stage compressor outlet temperature; It is the interstage cooling temperature drop; is the minimum outlet temperature of the cooler; is the gas adiabatic index; For the Stage compressor outlet temperature; For the Stage compressor outlet pressure; For the Variable efficiency of the compressor stage; For the The gas compression factor at the outlet of the first-stage compressor.

[0055] Specifically, in the multimodal fluid compression optimized negative pressure gas extraction device of the present invention, in order to give full play to the working efficiency of the multi-stage compressor in different pressure sections and ensure that the gas can maintain a suitable temperature range during the coupling process of negative pressure gas extraction and multi-stage compression, it is necessary to accurately control the inlet and outlet temperatures of each stage of the compressor. Based on this, the present invention proposes a set of formulas for dynamically adjusting the temperature and cooling strategy, so as to effectively control the compression heat accumulation and the resulting energy loss and material load while maintaining the compression efficiency. In these formulas, the first thing to pay attention to is the inlet temperature of each stage of the compressor. For the first stage compressor, considering the negative pressure adiabatic cooling phenomenon in the wellbore or pipeline, the original gas temperature is Subtract one item , which reflects the adiabatic cooling effect of gas expansion in a negative pressure environment. As the negative pressure increases, the adiabatic expansion of the gas becomes more obvious, and the temperature drop increases accordingly. It is obtained by estimating the relationship between the gas adiabatic index, formation pressure and wellbore negative pressure, so that the gas temperature entering the first-stage compressor is closer to the actual working conditions. For any compressor of the previous stage, the inlet temperature is derived from the outlet temperature of the previous compressor. , minus one more , in order to represent the result after the interstage cooler releases heat to the gas. The first-stage gas can be cooled before entering the compressor, reducing the load on the compressor and reducing the accumulation of additional heat when the gas is further compressed.

[0056] In the formula, This term is used to describe the interstage cooling temperature drop between different compression stages, and its size depends on the gas outlet temperature of the previous stage. , Cooler minimum outlet temperature As the gas cools, Down to The adiabatic expansion effect is as follows: Cool down to the point where the device can output stably , combined with the gas adiabatic index during expansion Thermodynamic constraints, This part is subtracted to represent the additional heat released when expanding from a higher pressure to a lower pressure, which further corrects the cooling. The reason for this design is that after each stage of compression, if the temperature is too high, the viscosity and density of the gas will change adversely with the increase in temperature, and the material will also face more stress and fatigue risks under high temperature conditions, so it is necessary to efficiently remove some of the heat through the intercooler. However, if the cooling is excessive, it may also cause condensation or hydrate formation, which will affect the gas flow or the safe operation of the equipment. This formula can be used in practice to appropriately compromise the current pressure difference, gas properties and equipment cooling capacity, so that the gas can avoid thermal damage without being overcooled and affecting subsequent flow.

[0057] When calculating the outlet temperature of a compressor at a certain stage When the adiabatic index of the gas is introduced into the formula , variable efficiency And the pressure ratio , and there is also a , which is used to correct the deviation between real gas and ideal gas. When the compressor performs adiabatic compression, if the energy loss in the compression process is ignored, the gas can be regarded as being subjected to However, in actual working conditions, various irreversible factors will reduce the efficiency of the compressor, so the present invention uses variable efficiency Characterize the actual deviations in these thermodynamic processes to more accurately predict the gas temperature rise. The higher the variable efficiency, the smaller the temperature rise of the compressor at the same pressure ratio and the more efficient the energy utilization; if the efficiency is low, the same pressure ratio will lead to a significant increase in gas temperature. At the same time, It is further shown that when the gas deviates from the ideal gas model, its temperature rise during compression will also differ from the ideal calculated value. The gas deviation at the exit of the first stage is more serious than that of the first stage, for example, the gas has been compressed and heated by the previous stages. compared to There will be a significant reduction, indicating that the intermolecular interaction increases and the gas compressibility increases, so the actual temperature rise may be more drastic than the "ideal state". Through this part of the correction, when the sum of the multi-stage compression remains fixed, adaptive space can be left for the specific thermodynamic changes of each compression process, and the dynamic pressure optimization control module can fine-tune the outlet temperature target at any time according to the change of gas state.

[0058] In this formula It is called the gas adiabatic index, which is an important parameter to measure the relationship between the pressure and volume change of a gas in a reversible adiabatic process. For common natural gas media, Most of them are between 1.25 and 1.4, and the specific value depends on the composition and temperature and pressure conditions. The value may deviate slightly, thus affecting the temperature rise law during compression. , and The coupling of multiple factors makes the temperature control of multi-stage compression more flexible and adaptable. In this way, if an abnormal temperature rise or pressure ratio imbalance occurs in a certain stage, the system can respond in time to maintain the outlet temperature of that stage within a safe and controllable range, and to a certain extent alleviate the energy consumption imbalance and material aging caused by excessive local temperature.

[0059] As for It represents the negative pressure adiabatic cooling amount. Its calculation idea is that when the formation gas is pumped into the wellbore, since the wellbore pressure is significantly lower than the formation pressure, a significant pressure drop is generated between the formation and the wellbore, and the gas expansion potential energy is released, which will cause the gas temperature to drop. Control, but also depends on the initial formation temperature, pressure and the actual negative pressure level in the wellbore. If the formation pressure is very high and the wellbore is kept at a very low pressure, the cooling effect of the gas diffusing from the high pressure to the low pressure area will be more significant. In this case, the inlet temperature of the first stage compressor will drop more significantly. However, if the difference between the wellbore and formation pressure is limited, or the negative pressure gas production intensity is relatively weak, the gas expansion is not sufficient, The present invention introduces it into the setting of the inlet temperature of the first-stage compressor, which can avoid overestimating the inlet temperature, thereby making the operation and energy consumption analysis of the compressor more realistic.

[0060] The application background of the above series of temperature adjustment formulas is that the strata faced by the present invention often have a low permeability, and negative pressure gas production is required to strengthen gas flow, while multi-stage compression is required to raise the relatively low-pressure gas flow in the wellbore to a higher pressure in order to meet the transportation needs or subsequent processing requirements. Multi-stage compression inevitably brings about heat accumulation, and if reasonable inter-stage cooling is not performed, the gas temperature will increase layer by layer, resulting in extremely high temperature at the final stage outlet, which not only wastes energy but also keeps the equipment in a high-temperature load state for a long time, accelerates component wear and even endangers production safety. On the contrary, through the dynamic temperature control strategy of the present invention, not only can the excess heat be removed as much as possible in the inter-stage cooler, but also the compressors at each stage can work in a relatively ideal temperature range, maximizing the compression efficiency and reducing energy consumption. At the same time, these formulas also fully consider the initial impact of negative pressure gas production on the temperature on the gas inlet side, including the adiabatic cooling caused by the formation pressure reduction, so that the final multi-stage compression process can be carried out at a lower temperature from the beginning, laying the foundation for reducing subsequent heat loads.

[0061] Embodiment 9: Calculate the following formula: Variable efficiency of stage compressor: in, Design flow for compressor; The design pressure ratio of the compressor ranges from 1.5 to 4.0.

[0062] Specifically, this formula gives Variable efficiency of the compressor The relationship between the gas flow rate and the pressure ratio deviation is shown in Figure 1. The base efficiency value is 0.85, which reflects the variable efficiency limit that can be achieved when the machine is running ideally under the design conditions. The more the actual conditions deviate from the design parameters, the lower the efficiency will be. It refers to the "nominal flow rate" targeted by the compressor during the design phase. It is usually the optimal operating range determined by a large amount of experimental data or equipment specifications under certain pressure, temperature and gas composition conditions. If the flow rate exceeds the design value for a long time, it means that the total amount of gas that the compressor has to handle has increased significantly, which may easily lead to increased energy consumption, additional friction loss or increased heat load inside the compressor, so the efficiency will be reduced. When the gas output is lower than the design value, although the small flow rate will not directly cause serious overload, the compressor often cannot maintain the ideal working point in the low flow area, and will also lose some efficiency due to the mismatch of internal fluid dynamics, so it will also lead to corresponding deductions.

[0063] In addition to the flow deviation affecting the variable efficiency, is the actual value of the pressure ratio close to the design pressure ratio? In the negative pressure gas extraction device of the present invention, since the pressure in the wellbore is often lower than the normal working condition, and the gas needs to be raised to a certain discharge pressure later, If the actual pressure ratio of the compressor is too different from the preset design pressure ratio, the internal impeller flow path, seal design and thermodynamic characteristics may not work within the optimal range, resulting in a significant decrease in efficiency. The system will add a proportional deduction item to the pressure ratio deviation, which will introduce the influence of pressure ratio deviation into the calculation of variable efficiency. When the system detects that the larger the ratio is, the farther the actual pressure ratio of the compressor is from the ideal design point. More efficiency deductions will be added to reflect the poor operation of the equipment and the increase in energy loss. For example, if the design pressure ratio is around 2.5, and the pressure ratio is 2.5 under negative pressure gas production conditions, the system will add a proportional deduction item to the pressure ratio deviation. The inlet pressure of the first stage is lower than originally thought, or the outlet pressure is pulled higher to meet the pressure increase demand of the next stage, so that the actual pressure ratio reaches 3.2 or even greater. Such a deviation exceeds the design range, and it is very likely to cause excessive power consumption or thermal management imbalance when matching gas flow, speed and temperature, and ultimately reduce the actual efficiency of the compression process. Based on the same principle, when the actual pressure ratio is too much lower than the design value, the efficiency will also be reduced because the impeller and diffuser structure do not fully utilize the hard-earned pressure head.

[0064] The coefficient of 0.05 used in the formula actually represents the "penalty intensity" of flow deviation and pressure ratio deviation on variable efficiency, and is an empirical value range determined by the present invention based on a large number of numerical simulations and experimental verifications. If these deviations are very significant, the efficiency may drop further from 0.85, and the final result may even fall below 0.7. This urges the system to minimize the deviation from the design point during real-time regulation, or to dispatch other parallel compressors to share excessive flow when necessary, to avoid a single device operating in a non-design range for a long time. At the same time, the design pressure ratio It is usually set between 1.5 and 4.0, which is a range established based on the compressor model and the transportation needs of the oil and gas field. It must not only meet the ability to deliver the gas to the required pressure in the middle and late stages, but also take into account the limitations of the compressor impeller structure, drive shaft power and safety margin. If the intake pressure generated during the negative pressure gas production process is extremely low, or the discharge pressure requirement is much higher than the common value, the system will share the overall pressure ratio through multiple stages or parallel connections, so that each compressor can match its relatively optimal design pressure ratio; if a single compressor is forced to bear an excessively high pressure ratio, it will receive a large deduction in this efficiency calculation, thereby prompting the control module to make corresponding strategic adjustments, such as adding interstage cooling, changing the speed, or introducing additional compensation measures to alleviate the excessive load of a single device.

[0065] The reason why the present invention adopts such a formula to express the variable efficiency and deducts it from the basic value of 0.85 is mainly to provide an approximate estimate that is easy to calculate in real time and can reflect the fluctuations in actual working conditions under negative pressure gas production environment. For each stage of the compressor, if the actual gas production it processes is exactly consistent with the design flow rate and the pressure ratio does not deviate from the pre-conceived assumption, then the compressor can be relatively close to the efficiency upper limit of 0.85; on the contrary, if the current working condition deviates significantly in flow rate or pressure ratio, it means that it is moving away from the optimal working point and the efficiency is correspondingly reduced. The present invention uses automated monitoring and control algorithms to constantly check Once the efficiency of individual levels is found to be continuously decreasing or fluctuating too much, we will try to adjust the wellbore negative pressure, the outlet pressure of the downstream compression stage, and the inlet flow distribution of the compressor, so that the overall system can achieve the maximum gas production with the minimum energy consumption. In unconventional formations or low permeability conditions, with the change of the formation gas supply capacity and the increase or decrease of the negative pressure intensity, it is very likely that each stage of the compressor will experience different degrees of deviation. Therefore, by combining this formula to continuously update the variable efficiency, it can provide a more accurate basis for subsequent thermal management, power distribution and cooling control, so that the entire device can always maintain steady-state and efficient operation.

[0066] Embodiment 10: The compression power of each stage compressor is adjusted by the following formula: in, For the The compression power of the compressor; For the The gas compression factor at the inlet of the first-stage compressor.

[0067] Specifically, we can see in the formula Such an item comprehensively describes the most basic energy input required for gas compression from aspects such as mass flow rate, gas molecular weight, universal gas constant, inlet temperature and compressor variable efficiency. Its meaning is that if the actual gas production of the formation is is much higher than the design value, then under the same inlet and outlet pressure, The compressor must process a larger mass flow rate of gas, and the power consumption will naturally increase; if the gas output is small, even if the pressure ratio remains unchanged, the energy consumption of this part will be reduced accordingly. The larger the value, the more mass the gas contains per unit volume or per unit flow rate. The compressor needs to do more work on the molecules to achieve the same pressure ratio, which leads to an increase in power. The pressure, temperature, volume and molecular weight are unified in one equation, so that the calculation can be applied to different types of natural gas or mixed gas. When the compressor is It will affect the average kinetic energy and specific volume of gas molecules. When the temperature is high, the molecular motion is more intense. Although the density may be slightly reduced, the input work required by the compressor will still increase within a certain range. This part is also closely related to the mechanical characteristics and heat dissipation capacity of the compressor itself. , which describes the loss caused by irreversible factors in the actual operation of the compressor of this level. If the compression process is far away from the ideal isentropic or isothermal curve, or the equipment operating conditions are not in the optimal range, such as the flow rate and pressure ratio deviate greatly from the design value, it will lead to a decrease in efficiency, thereby increasing the power required for the unit mass of gas to be compressed. Combined with the existing multi-variable efficiency calculation model in the present invention, this part can be quantitatively estimated, and the energy consumption caused by the deviation of flow rate and pressure ratio can be reflected in the power calculation, so as to make corrections in subsequent optimization decisions.

[0068] There is another term in the formula , which is part of the thermodynamics of the energy consumption of adiabatic or polytropic compression of a gas. If the gas is theoretically reversibly adiabatically compressed, the gas temperature rises without dissipating heat to the outside world, then the required work can be written as a similar expression, using As an adiabatic index, it reflects the influence of gas molecular freedom and heat capacity ratio. When the pressure is increased, the gas is compressed more tightly, and the work required will increase significantly. When the gas flows between multi-stage compressors, it will also go through inter-stage cooling and thermal management, which will have an additional impact on the final temperature and phase state. However, the work provided by the compressor itself mainly depends on the pressure change and the adiabatic index. A larger value indicates that the gas is closer to the adiabatic properties of an ideal monatomic or diatomic molecule, and the temperature rises faster when compressed, and the power consumption is more significant. is too small, indicating that the molecular vibration mode or heat capacity characteristics of the gas are different, and the temperature rise is not so drastic. This directly reflects the relative magnitude of the work required by the gas under ideal conditions without considering additional losses after a certain pressure ratio occurs. The coefficient adjustment is to quantify the enthalpy change of the compression process. If we consider that the gas produced by some low permeability or unconventional formations contains heavy hydrocarbons or impurities, or the inlet and outlet pressures and the formation negative pressure fluctuate frequently, The dynamic correction of and the linkage of the aforementioned mass flow term are reflected.

[0069] In order to make the formula adaptive in negative pressure gas collection and multi-stage compression environment, the dynamic pressure optimization control module of the present invention continuously collects data such as gas flow, temperature, inlet and outlet pressure, compressor speed, working power, etc., and calculates the pressure of each stage in real time. Value and . Once it is found that the pressure ratio increases due to an increase in gas production or a decrease in wellbore pressure, the corresponding power increase will be triggered. If it is detected that the power of a certain stage of the compressor continues to rise and approaches the safety upper limit of the equipment, the system will disperse the pressure burden by adjusting the inter-stage cooling amount, adjusting the next stage pressure ratio, or changing the opening of the intake regulating valve to avoid overloading the single-stage compressor. In the case of attenuation of formation gas supply or weakening of wellbore negative pressure, the formula will automatically derive a lower power requirement, thereby preventing the compressor from doing extra work under low load conditions and achieving energy saving. In addition, due to It often changes slightly with changes in temperature, gas composition and pressure, especially in high temperature and high pressure conditions or natural gas environments containing multiple components. By measuring the compression factor and specific heat capacity of the gas in real time, it can be dynamically updated to keep the formula accurately depicting the energy consumption. When the negative pressure in the wellbore is very strong, the formation gas flows into the wellbore with a large pressure gradient, and at the same time, it undergoes a significant pressure increase process in the multi-stage compressor. This large-scale temperature and pressure change can easily cause the compression process at each stage to deviate from the ideal model. At this time, the present invention can make the variable efficiency and gas heat capacity ratio in the formula accurately reflect the actual state through continuous monitoring and feedback correction, ensuring that the calculation of the entire compression power has sufficient timeliness and accuracy.

[0070] Although the specific embodiments of the present invention are described above, it should be understood by those skilled in the art that these specific embodiments are only illustrative, and those skilled in the art may omit, replace, and change the details of the above methods and systems in various ways without departing from the principles and essence of the present invention. For example, merging the above method steps so as to perform substantially the same functions in substantially the same manner to achieve substantially the same results is within the scope of the present invention. Therefore, the scope of the present invention is limited only by the appended claims.

Claims

1. A negative pressure gas extraction device with multi-modal fluid compression optimization, characterized in that: It includes a gas collection module, a fluid compression module and a gas storage and transmission module; the gas collection module is used to make the formation gas flow to the collection pipeline through negative pressure, and transmit it to the fluid compression module; The fluid compression module includes a plurality of cascaded compressors, a dynamic pressure optimization control module and a sensor module; The dynamic pressure optimization control module adjusts the working mode and pressure output of each compressor in real time based on the gas parameters obtained by the sensor module and the environmental parameters during underground gas collection, and delivers the compressed gas to the gas storage and transmission module; The gas storage and transmission module is used to store compressed gas and transmit the compressed gas to the remote end in response to a control instruction from the remote end.

2. The multi-modal fluid compression optimized negative pressure gas extraction device according to claim 1, characterized in that: The execution process of the dynamic pressure optimization control module specifically includes: establishing a flow model of gas in porous media under negative pressure conditions according to environmental parameters and gas parameters, and calculating the gas production of the formation; adjusting the intake pressure of the first-stage compressor to a safe intake pressure in combination with the gas parameters according to the formation gas production, and adjusting the inlet pressure, outlet pressure, inlet temperature, outlet temperature, compression power of each stage of the compressor and the inter-stage cooling temperature drop between compressors of adjacent stages according to the safe intake pressure and the required final discharge pressure.

3. The multi-modal fluid compression optimized negative pressure gas extraction device according to claim 2, characterized in that: Environmental parameters include absolute formation permeability , the value range is 1 to 100, the unit is mD; formation pressure , unit is Pa; formation temperature , unit is K; wellbore perforation area , in m²; formation porosity ; Formation hydraulic pressure , unit is Pa; uniaxial compressive strength of formation , unit is MPa; Poisson's ratio of formation ; The gas parameters include gas dynamic viscosity , unit is Pa·s; gas molecular weight , in g / mol; critical pressure of gas , unit is MPa; gas critical temperature , unit is K; gas adiabatic index ; Gas real-time temperature , unit is K; gas specific heat capacity , unit is kg·K; real-time gas pressure , unit is Pa.

4. The multi-modal fluid compression optimized negative pressure gas extraction device according to claim 3, characterized in that: The flow model is used to calculate the formation gas production: in, is the formation gas production, in kg / s; is the flow rate of gas in porous media, in m / s; is the gas density in kg / m³.

5. The multi-modal fluid compression optimized negative pressure gas extraction device according to claim 4, characterized in that: Gas flow rate in porous media Use the following formula to calculate: in, is the standard reference pressure, which is 101325Pa; is the standard reference temperature, which is 293.15K; is the pressure gradient; is the formation permeability; gas density Use the following formula to calculate: in, is the universal gas constant, which is 8.314 J / (mol·K); is the gas compressibility factor, which is calculated using the following formula: 。 6. The multi-modal fluid compression optimized negative pressure gas extraction device according to claim 5, characterized in that: Calculate the safe intake pressure using the following formula: in, is the critical pressure of formation collapse; To ensure safe intake pressure, adjust the intake pressure of the first stage compressor to ; is the safety margin, ranging from 50 to 100, in kPa; is the cross-sectional area of ​​the air intake duct, in m²; For the The inlet pressure of the compressor is is the inlet pressure of the first stage compressor ,for It is the outlet pressure of the previous stage minus the pipeline pressure drop.

7. The multi-modal fluid compression optimized negative pressure gas extraction device according to claim 6, characterized in that: The outlet pressure of each compressor stage is adjusted by the following formula: in, For the Gas compression factor of the compressor stage; is the gas compression factor of the first stage compressor; For the final discharge pressure; is the total number of compressor stages; For the The outlet pressure of the compressor.

8. The multi-modal fluid compression optimized negative pressure gas extraction device according to claim 7, characterized in that: The inlet temperature, outlet temperature and inter-stage cooling temperature drop of each stage compressor are adjusted by the following formula: in, For the Stage compressor inlet temperature; is the negative pressure adiabatic cooling amount; For the Stage compressor outlet temperature; It is the interstage cooling temperature drop; is the minimum outlet temperature of the cooler; is the gas adiabatic index; For the Stage compressor outlet temperature; For the Stage compressor outlet pressure; For the Variable efficiency of the compressor stage; For the The gas compression factor at the outlet of the first-stage compressor.

9. The multi-modal fluid compression optimized negative pressure gas extraction device according to claim 8, characterized in that: Calculate the first Variable efficiency of stage compressor: in, Design flow for compressor; The design pressure ratio of the compressor ranges from 1.5 to 4.

0.

10. The multi-modal fluid compression optimized negative pressure gas extraction device according to claim 9, characterized in that: The compression power of each compressor stage is adjusted by the following formula: in, For the The compression power of the compressor; For the The gas compression factor at the inlet of the first-stage compressor.

Images