Device, system and method for evaluating influence degree of fluid scaling on core porosity

Abstract

The invention discloses a device, system and method for evaluating the influence degree of fluid scaling on core porosity, the device comprises a sleeve, a middle cavity of the sleeve is used for containing and clamping a core, one end of the sleeve is provided with a fluid inlet connected with a displacement device, and the other end of the sleeve is provided with a fluid outlet connected with a collecting device; the fluid inlet, the fluid outlet and the rock core are communicated to form a displacement flow channel; the inner wall of the sleeve and the outer wall of the core are provided with a confining through channel for confining pressure liquid to flow in to conduct confining pressure on the core; when the influence degree of fluid scaling on the porosity of the rock core is evaluated, the rock core is placed in the sleeve, confining pressure liquid is injected into the surrounding channel to provide confining pressure, and the displacement flow channel is used for performing displacement operation on the rock core, so that the porosity before scaling and the porosity after scaling of the rock core before and after the displacement operation are measured, and the influence degree of fluid scaling on the porosity of the rock core is evaluated. The evaluation of the influence degree of the fluid scaling on the core porosity is realized; the device can effectively simulate a near wellbore zone reservoir pressure drop scaling environment, and ensures a reliable and accurate evaluation result.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of oil and gas production engineering, and particularly relates to a device, system and method for evaluating the influence degree of fluid scaling on core porosity. BACKGROUND

[0002] The influence of scaling on core porosity is significant. After water injection and formation water breakthrough, if the injected water / formation water containing CO3 2- , SO4 2- ions is not compatible with the formation water containing Ca 2+ , Ba 2+ , or scaling occurs in the near wellbore zone with the change of temperature and pressure during production; such scaling will block the formation pore throat, resulting in a significant decrease in porosity. When a small amount of scale is generated in the core, the porosity will decrease rapidly. With the increase of the displacement pore volume multiple, the amount of scaling in the core increases, further leading to the decrease of the core porosity. Therefore, scaling will lead to the decrease of core porosity, which brings huge economic losses to oil production.

[0003] Currently, the research on scaling in China mainly focuses on the scaling amount and scaling trend of water injection wells. For example, the Chinese patent with the patent application number CN201910098986.3 provides a wellbore scaling trend prediction method and device, which can determine the scaling trend of the well to be measured according to the corresponding phase segment of the reservoir of the well to be measured; the Chinese patent with the patent application number CN202110034699.3 provides an oilfield dynamic scaling and scale inhibition evaluation device and method, which simulates the changes of differential pressure and permeability under the conditions of different flow patterns, flow rates and different flow conditions at the site temperature and pressure, so as to quickly determine the scaling induction period time and provide technical basis for the on-site water injection scheme. However, the above-mentioned technical solutions provided in the patents ignore the influence of scaling in the near wellbore zone reservoir caused by pressure drop in the production process of high-pressure oil and gas wells on the porosity of the reservoir.

[0004] As can be seen from the above, in the research on scaling in the production process of high-pressure oil and gas wells, the existing evaluation measures cannot evaluate the influence of scaling in the near wellbore zone reservoir caused by pressure drop on the porosity of the reservoir, which leads to the lack of evaluation results and the inability to establish corresponding reservoir protection measures, thereby increasing the damage of scaling to the reservoir. SUMMARY

[0005] The present application provides a device and method for evaluating the influence degree of fluid scaling on core porosity, to solve the technical problem that the existing evaluation measures cannot evaluate the influence of scaling in the near wellbore zone reservoir caused by pressure drop on the porosity of the reservoir, which leads to the lack of evaluation results and the inability to establish corresponding reservoir protection measures, thereby increasing the damage of scaling to the reservoir.

[0006] In order to achieve the above object, the present application adopts the following technical contents:

[0007] A device for evaluating the influence degree of fluid fouling on core porosity, comprising a sleeve;

[0008] The sleeve is provided with a fluid inlet at one end and a fluid outlet at the other end, and a middle cavity for containing and clamping the core; the fluid inlet, the fluid outlet and the core are in communication to form a displacement flow channel;

[0009] The inner wall of the sleeve and the outer wall of the core are provided with a surrounding passage, which is used for flowing in the confining pressure liquid to provide confining pressure to the core.

[0010] Further, the core is externally sleeved with a rubber, which is used to realize the confining pressure sealing of the core.

[0011] Further, the sleeve is provided with a confining pressure inlet in communication with the surrounding passage, which is used for injecting confining pressure liquid into the surrounding passage.

[0012] Further, the connection parts of the fluid inlet, the fluid outlet and the core are respectively provided with sealing rings.

[0013] A system for evaluating the influence degree of fluid fouling on core porosity, comprising the above-mentioned device for evaluating the influence degree of fluid fouling on core porosity, and further comprising:

[0014] A displacement device connected to the fluid inlet end of the device for evaluating the influence degree of fluid fouling on core porosity, used for water displacement operation on the core;

[0015] A pressurizing device in communication with the confining pressure passage of the device for evaluating the influence degree of fluid fouling on core porosity, used for establishing an initial formation water saturation environment and applying confining pressure to the core in the initial formation water saturation environment;

[0016] A collection device connected to the fluid outlet end of the device for evaluating the influence degree of fluid fouling on core porosity, used for collecting the liquid flowing out of the core during the test;

[0017] A data acquisition device arranged between the pressurizing device and the fluid inlet end, the collection device and the fluid outlet end, and the pressurizing device and the confining pressure passage, used for monitoring the fluid inlet pressure, the fluid outlet pressure and the confining pressure.

[0018] Further, the displacement device comprises a plurality of displacement fluid containers, each of which is connected with a uniform flow pump; the plurality of displacement fluid containers are in communication with the fluid inlet end through a multi-way valve.

[0019] Further, the collecting device comprises a collecting bottle connected with the fluid outlet end, and a drying tube and a gas flow meter are sequentially connected with an air outlet pipeline of the collecting bottle.

[0020] A method for evaluating the influence degree of fluid fouling on core porosity based on the device for evaluating the influence degree of fluid fouling on core porosity or the system for evaluating the influence degree of fluid fouling on core porosity comprises the following steps:

[0021] Step one: establishing an initial formation water saturation environment and measuring the pre-fouling porosity of the core;

[0022] Step two: under the initial formation water saturation environment, applying confining pressure to the core and performing displacement operation on the core at a preset displacement flow rate until a threshold value is reached to end the displacement operation;

[0023] Step three: measuring the post-fouling porosity of the core after the displacement operation;

[0024] Step four: obtaining the porosity loss rate according to the pre-fouling porosity and the post-fouling porosity, and completing the evaluation of the influence degree of fluid fouling on core porosity according to the porosity loss rate.

[0025] Further, in step one, the specific steps for establishing the initial formation water saturation environment comprise:

[0026] Performing a test test on the prepared core;

[0027] Performing vacuum extraction and pressure operation on the core that passes the test test, or performing oil and gas fluid injection and formation water injection operation on the core that passes the test test, to establish the initial formation water saturation environment.

[0028] Further, in step two, the displacement flow rate is determined based on the liquid production rate per second, the pay zone area and the cross-sectional area of the core, and the specific formula is as follows:

[0029] ν=A2×Q l / A1

[0030] Wherein, ν represents the displacement flow rate; Q l represents the liquid production rate; A1 represents the pay zone area; and A2 represents the cross-sectional area of the core.

[0031] Compared with the prior art, the present application has the following beneficial effects:

[0032] The application provides a device for evaluating the influence degree of fluid scaling on core porosity, which comprises a sleeve, a middle cavity of the sleeve is used for containing and clamping a core, a fluid inlet connected with a displacement device is arranged at one end of the sleeve, a fluid outlet connected with a collection device is arranged at the other end of the sleeve, the fluid inlet, the fluid outlet and the core are communicated to form a displacement flow channel; a confining channel for flowing in confining liquid to provide confining pressure on the core is arranged between the inner wall of the sleeve and the outer wall of the core; when the influence degree of fluid scaling on core porosity is evaluated, the core is placed in the sleeve, the confining liquid is injected into the confining channel to provide confining pressure, and the core is subjected to displacement operation by using the displacement flow channel, so that the pre-scaling porosity and the post-scaling porosity of the core before and after the displacement operation are determined, and the evaluation of the influence degree of fluid scaling on core porosity is realized; the device has simple structure and principle, can effectively simulate the reservoir pressure drop scaling environment in the near wellbore zone, improves the accuracy and reliability of the test, and ensures reliable and accurate evaluation results.

[0033] Preferably, in the application, a rubber is sleeved outside the core, preferably a pressure-resistant elastic rubber, the setting of the rubber effectively realizes the confining pressure sealing of the core, prevents the leakage of the confining liquid, and ensures the smooth progress and accuracy of the test.

[0034] Preferably, in the application, the confining inlet is arranged on the sleeve, which facilitates the injection of the confining liquid and makes the application of the confining pressure more convenient and flexible, and improves the convenience of the test operation.

[0035] Preferably, in the application, a sealing ring is arranged at the connection between the fluid inlet, the fluid outlet and the core, which further enhances the sealing property of the device, prevents the leakage of the fluid during the displacement process, and improves the accuracy and reliability of the test.

[0036] The application also provides a system for evaluating the influence degree of fluid scaling on core porosity, which comprises the device for evaluating the influence degree of fluid scaling on core porosity, the system further comprises a displacement device used for water displacement operation, a pressurizing device used for establishing an initial formation water saturation environment and applying confining pressure on the core in the initial formation water saturation environment, a data acquisition device used for collecting the liquid flowed out of the core during the test and used for monitoring the fluid inlet pressure, the fluid outlet pressure and the confining pressure; the system can comprehensively simulate the actual formation conditions, monitor and record various parameters in the test process in real time, and adjust according to the monitored parameters to meet the test requirements, thereby providing comprehensive and accurate data support for the evaluation of the influence degree of fluid scaling on core porosity; the system can effectively evaluate the influence of the pressure drop scaling in the near wellbore zone reservoir on the reservoir porosity, so that corresponding reservoir protection measures are established according to the evaluation results to reduce the damage of scaling to the reservoir.

[0037] Preferably, in the present application, the displacement device adopts a combination of multiple displacement fluid containers and a uniform flow pump, and the switching of different fluids is realized through a multi-way valve, so that the test process is more flexible, the scaling under various fluid environments can be simulated, and the diversity and practicability of the test are improved.

[0038] Preferably, in the present application, the collection device includes a drying tube and a gas flow meter, which can accurately collect and measure the liquid and gas flowing out of the core during the test, and further improve the accuracy and integrity of the test data.

[0039] The present application also provides a method for evaluating the influence degree of fluid scaling on core porosity, which measures the porosity change of the core before and after scaling, calculates the porosity loss rate, and thus accurately evaluates the influence degree of fluid scaling on core porosity, providing a scientific basis for scale prevention and removal in oil and gas field development.

[0040] Preferably, in the present application, the specific steps for establishing an initial formation water saturation environment include test compression, vacuum extraction, pressure increase, or injection of oil and gas fluid and re-injection of formation water, which ensures the accuracy and repeatability of the test conditions and improves the reliability of the test results.

[0041] Preferably, in the present application, a calculation formula of displacement flow rate is provided, which determines the displacement flow rate based on the liquid production rate, the producing layer area and the core cross-sectional area, so that the displacement operation in the test process is more scientific and reasonable, and the fluid flow in the actual formation can be more accurately simulated. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 A structural schematic diagram of a device for evaluating the influence degree of fluid scaling on core porosity provided by the present application;

[0043] Figure 2 A structural schematic diagram of a system for evaluating the influence degree of fluid scaling on core porosity provided by the present application;

[0044] Figure 3 A pressure drop funnel curve graph of the near-wellbore zone of DK1 well provided by the present application;

[0045] Figure 4 A nuclear magnetic resonance T2 spectrum distribution graph provided by the present application;

[0046] Figure 5 A nuclear magnetic resonance T2 decay curve graph provided by the present application.

[0047] REFERENCE NUMERALS:

[0048] Core clamping device-1, uniform flow pump-2, multi-way valve-3, pressure increasing device-4, back pressure valve-5, produced liquid-6, drying tube-7, gas flow meter-8;

[0049] Sleeve-101; Fluid inlet end-102; Fluid outlet end-103; Confining pressure channel-104; Confining pressure liquid-105; Rubber-106; Core-107; Sealing ring-108. Detailed Implementation

[0050] To make the technical problems solved by the present invention, the technical solutions, and the beneficial effects clearer, the following specific embodiments provide a further detailed description of the present invention. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of the invention.

[0051] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0052] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0053] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0054] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper," "lower," "horizontal," or "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. Furthermore, terms such as "first" and "second" are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0055] Furthermore, the use of the term "horizontal" does not imply that the component must be absolutely horizontal, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0056] In the description of the embodiments of the present invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

[0057] The present invention will now be described in further detail with reference to the accompanying drawings:

[0058] Example 1

[0059] As described in the background section, current research on scaling has neglected the impact of scaling on reservoir porosity caused by pressure drop in the near-wellbore area during the production process of high-pressure oil and gas wells. This lack of evaluation results makes it impossible to establish corresponding reservoir protection measures, thereby increasing the damage of scaling to the reservoir.

[0060] To address the aforementioned issues, this embodiment provides a device for evaluating the impact of fluid scaling on core porosity. This device can effectively simulate the test environment before and after core scaling, thereby effectively evaluating the impact of fluid scaling on core porosity. Based on the evaluation results, corresponding reservoir protection measures can be established to minimize reservoir damage and improve reservoir development efficiency.

[0061] like Figure 1 As shown, this embodiment provides a device for evaluating the impact of fluid scaling on core porosity, used to accurately assess the influence of fluid scaling on changes in core material porosity. Since the main body of this device is used to hold and clamp the core, it can also be called a core clamping device 1, specifically including:

[0062] The device is cylindrical in shape, and its core component is a carefully designed sleeve 101. The sleeve 101 is preferably a pressure-resistant metal sleeve. The sleeve 101 not only supports the core of the experiment—the rock core 107, but also simulates the fluid flow and pressure environment in the formation through its unique structural design. The specific design is as follows:

[0063] The sleeve 101 has a fluid inlet and a fluid outlet at its two ends, namely the fluid inlet end 102 and the fluid outlet end 103 of the sleeve 101; together they form a displacement channel that runs through the center of the sleeve 101 and is directly connected to the core 107. This design allows the experimental fluid to enter through the inlet, flow through the interior of the core 101, and finally exit from the fluid outlet, simulating the natural flow process of fluids in the formation.

[0064] In order to be more close to the actual formation pressure conditions, a surrounding passage 104 is ingeniously arranged between the inner wall of the sleeve 101 and the outer wall of the core 107; the surrounding passage 104 serves as a transmission path for the confining pressure liquid, and when the confining pressure liquid 105 is injected through the confining pressure inlet, it can be uniformly and stably applied to the outside of the core, simulating the confining pressure effect of the formation on the core.

[0065] In addition, in order to ensure the tightness of the confining pressure seal, the outside of the core 107 is further sleeved with a layer of rubber material 106, preferably pressure-resistant elastic rubber; this layer of rubber not only provides the necessary elasticity and sealing performance, but also effectively prevents leakage of the confining pressure liquid, ensuring the stability and controllability of the pressure environment during the experiment.

[0066] In terms of detailed design, the device also considers the sealing performance of fluid flow, and a sealing ring 108 is installed at the connection between the fluid inlet, the fluid outlet and the core 107; the sealing ring 108 further enhances the sealing performance of the entire flow channel system, avoiding unnecessary leakage of the experimental fluid during flow, thereby ensuring the accuracy and reliability of the experimental data.

[0067] The embodiment provides a device for evaluating the influence degree of fluid scaling on core porosity, and the specific working principle is as follows:

[0068] The fluid inlet end 102 of the device is connected with an oil and gas displacement system, and the fluid in the container is injected into the core 107 according to the actual production through a pump; first, oil and gas fluid is injected, and then formation water is injected; when the amount of injected water is equal to the amount of produced water, the displacement is ended, and the initial saturation of the oil and gas reservoir is established; here, the initial formation water can also be saturated by vacuum according to the Chinese Petroleum and Natural Gas Industry Standard SY / T 5358-2010 “Evaluation Method for Reservoir Sensitivity Flow Experiment”; after the initial formation water is saturated, the core is taken out, and the porosity of the core before scaling is measured by a nuclear magnetic resonance measuring instrument.

[0069] After the test is completed, the core 107 is again loaded into the core device; according to the pressure drop funnel pressure difference of the near wellbore at the bottom of the wellbore, the pressure values of the two ends of the core clamping device 1 are set; after the valve is opened, the fluid flows in the core; because the pressure difference between the two sides is large, scaling exists in the core 107; by simulating the phenomenon that fluid scaling is caused by the decrease of temperature and pressure after water breakthrough in the oil and gas well in the near wellbore, after the flow is completed, the core 107 is taken out, and the porosity of the core after scaling is measured by a nuclear magnetic resonance measuring instrument, so as to determine the influence degree of scaling on the porosity of the reservoir after pressure drop.

[0070] In the embodiment, the core 107 used can be a real core taken from the target layer of the block, or an outcrop core of the same structure, or a simulated artificial core.

[0071] Therefore, the device successfully constructs an experimental device that can simulate the actual formation fluid flow and pressure environment and accurately evaluate the degree of influence of fluid scaling on core porosity through ingenious structural design and careful material selection.

[0072] Embodiment 2

[0073] As Figure 2 shown, the present embodiment provides a system for evaluating the degree of influence of fluid scaling on core porosity, which includes the device for evaluating the degree of influence of fluid scaling on core porosity mentioned in Embodiment 1 (i.e., core clamping device 1). The present system aims to evaluate the degree of influence of fluid scaling on core porosity, and not only integrates the core evaluation device, but also is equipped with multiple auxiliary devices to ensure accurate control of the experimental process and accurate collection of data. The specific structure includes:

[0074] Firstly, the system contains a displacement device, which realizes water displacement operation on the core 107 through the fluid inlet end 102 connected to the core clamping device 1. The displacement device contains multiple displacement fluid containers, each of which is equipped with a uniform flow pump 2 to ensure that the fluid enters the core at a stable and controllable flow rate. The displacement fluid containers are flexibly connected to the fluid inlet end through the multi-way valve 3, providing diversified fluid selection for the experiment.

[0075] Next, in order to simulate the pressure environment in the actual formation, the present system is equipped with a pressurizing device 4. The pressurizing device 4 is connected to the confining pressure channel 104 of the core clamping device 1, which can establish an initial formation water saturation environment before the experiment starts, and apply confining pressure to the core on this basis. This design ensures that the pressure conditions experienced by the core during the experiment are highly similar to the actual formation environment.

[0076] In order to collect and analyze the liquid flowing out of the core during the experiment, the system is also equipped with a collection device. The collection device is connected to the fluid outlet end 103 of the core clamping device 1, which can effectively collect the liquid samples flowing out. The collection bottle is the core component of the collection device, and a drying tube 7 and a gas flow meter 8 are installed on the gas outlet pipeline of the collection bottle in turn. The drying tube 7 is used to remove water from the gas, and the gas flow meter 8 is used to accurately measure the volume of the outflowing gas, which is crucial for subsequent experimental analysis.

[0077] In addition, the present system also integrates a data acquisition device, which is cleverly arranged between the pressurizing device 4 and the fluid inlet end 102, the collection device and the fluid outlet end 103, and the pressurizing device 4 and the confining pressure channel 104. It is mainly used for real-time monitoring and recording of key parameters such as fluid inlet pressure, fluid outlet pressure and confining pressure, which can accurately collect the above parameters to provide a strong guarantee for the reliability and accuracy of the experimental results.

[0078] Therefore, the system integrates multiple functional modules such as the displacement device, the pressurizing device 4, the collecting device, and the data acquisition device, and builds a comprehensive and efficient system for accurately evaluating the influence of fluid scaling on the porosity of the core.

[0079] The embodiment also provides a method for evaluating the influence of fluid scaling on the porosity of a core, and the specific steps are as follows:

[0080] Step one: establish an initial formation water saturation environment, and measure the porosity of the core 107 before scaling.

[0081] Step two: under the initial formation water saturation environment, apply confining pressure to the core 107, and perform displacement operation on the core 107 at a preset displacement flow rate until the threshold is reached to end the displacement operation.

[0082] Step three: measure the porosity of the core 107 after the displacement operation.

[0083] Step four: obtain the porosity loss rate according to the porosity before scaling and the porosity after scaling, and complete the evaluation of the influence of fluid scaling on the porosity of the core according to the porosity loss rate.

[0084] In the embodiment, more specific steps include:

[0085] (1) Core production: drill a real core / outcrop core or process a quartz sand to obtain a core sample.

[0086] (2) Connect the test system according to the above device connection, test the pressure according to the highest displacement pressure, stabilize the pressure for 5 minutes, and the pressure drop ≤0.5 MPa is qualified.

[0087] (3) Put the core sample into the pressurized saturation device container, vacuumize for more than 8 hours, and pressurize and saturate the simulated formation water for more than 24 hours; or put it into the core clamping device 1 in the system, and inject the fluid in the displacement fluid container into the core 107 according to the actual production through the horizontal flow pump 2, first inject the oil and gas fluid, and then inject the formation water, until the injected water amount is equal to the produced water amount, end the displacement, and establish the initial saturation of the oil and gas reservoir.

[0088] (4) After the initial formation water saturation, take out the core, measure the porosity of the core before scaling by the nuclear magnetic resonance measuring instrument, and record it as Φ1.

[0089] (5) Put the core 107 saturated with the simulated formation water into the core clamping device 1 again, and perform gas displacement of water according to the gas logging permeability direction to produce a bound water saturation sample.

[0090] (6) According to the near wellbore pressure drop funnel curve, the displacement pressure and the fluid outlet end 103 pressure are set, or the wellhead 0.5m-2.0m range pressure is directly selected as the displacement pressure, and the bottom hole flowing pressure is selected as the fluid outlet end 103 pressure.

[0091] (7) According to the displacement pressure, the appropriate formation water displacement flow rate is selected, and the displacement flow rate can be referred to as v=A2xQ l / A1, after adding the corresponding units of the parameters, the formula is transformed to: v=11.6xA2xQ l / A1, wherein v is the flow rate, unit: mL / min; Q l is the liquid production, unit: m 3 / d; A1 is the producing layer area, unit: cm 2 ; A2 is the core cross-sectional area, unit: cm 2 .

[0092] (8) The confining pressure is kept unchanged by using the pressurizing device 4, and the displacement is carried out in the forward direction. The threshold value here is that the displacement time is not less than 2h and greater than 10 pore volumes (PV). The PV number is calculated when the liquid flows out of the outlet end in the same direction as the nitrogen displacement. Until the above threshold condition is reached, the displacement operation is ended.

[0093] (9) After the displacement is ended, the core 107 is taken out, the porosity Φ2 of the core after scaling is measured by the nuclear magnetic resonance measuring instrument, and the influence degree of the scaling after pressure drop on the reservoir porosity is determined.

[0094] (10) The porosity loss rate (%)=(Φ1-Φ2) / Φ1x100. According to the porosity loss rate, the influence degree of the scaling after pressure drop on the reservoir in the development process of the near wellbore zone in different production periods can be evaluated.

[0095] Further, in the embodiment, the influence degree of the scaling caused by the pressure drop in the development process of the near wellbore zone in different production periods of the reservoir can be evaluated, and the influence degree of the scaling of the oil and gas well caused by the injection of different water qualities on the reservoir core porosity can be evaluated. The specific operation is as follows:

[0096] (11) The same block core or similar permeability simulation core is selected, and the flow rate, displacement pressure and other parameters are changed. The steps (2)-(9) are repeated, and the influence degree of the scaling caused by the pressure drop in the development process of the near wellbore zone in different production periods of the reservoir can be obtained.

[0097] (12) The formation water is established according to the steps (1)-(5), and the injection water of different water qualities is selected for displacement in the step (6). The steps (6)-(9) are repeated, and the influence degree of the scaling of the oil and gas well caused by the injection of different water qualities on the reservoir core porosity can be obtained.

[0098] Example 3

[0099] As Figure 3 shown, the devices, systems and methods mentioned in the above embodiments 1 and 2 are applied to the evaluation test of the degree of influence of the scaling on the reservoir porosity of the oil and gas well DK1, and the specific test process is as follows:

[0100] The oil and gas well DK1 has a production layer depth of 6435-6535m, a production layer thickness of 100m, and a reservoir of fractured and dense sandstone gas reservoir. The initial daily liquid production is 2.08t, and the daily gas production is 23.16 million square meters. Due to the continuous production and development, the single well water invasion high angle fracture, the daily liquid production is 321t, the daily oil production is 0t, the daily water production is 321t, the daily gas production is 6.44 million square meters, and the production capacity has a continuous downward trend.

[0101] The device for evaluating the degree of influence of the fluid scaling on the core porosity provided in the embodiment has one end connected with a gas and formation water displacement system. The fluid in the container is injected into the core according to the actual production by the pump. The pressure values at the two ends of the core device are set according to the pressure drop funnel differential value of the near wellbore zone at the bottom of the wellbore. After the valve is opened, the fluid flows in the core. Due to the large differential pressure value at the two sides, there is scaling in the core. After the flow ends, the core porosity change value is tested to determine the degree of influence of the scaling on the reservoir porosity after the pressure drop.

[0102] A method for evaluating the degree of influence of the scaling on the reservoir porosity after the pressure drop, comprising the following steps:

[0103] (1) The artificial core is processed by quartz sand, and the helium porosity is 3.24%.

[0104] (2) The sample is placed in the pressurized saturation device container, vacuumed for more than 8h, and pressurized and saturated with simulated formation water for more than 24h.

[0105] (3) After the initial formation water saturation, the core is taken out, and the core porosity before scaling is measured by a nuclear magnetic resonance measuring instrument, which is recorded as Φ1. The nuclear magnetic porosity (%) test value before scaling is 2.49%.

[0106] (4) The core saturated with simulated formation water is again loaded into the core clamping device 1, and the gas drives water according to the gas permeability direction to make a bound water saturation sample, and the gas displacement volume is 50PV.

[0107] (5) As Figure 3 shown, the displacement pressure and the outlet end pressure are set according to the near wellbore zone pressure drop funnel curve. The pressure in the wellhead 2.0m range is selected as the displacement pressure, and the bottom hole flowing pressure is selected as the outlet end pressure. The displacement pressure is set to 68MPa, and the outlet end pressure is set to 65MPa.

[0108] (6) The appropriate formation water displacement flow is selected according to the displacement pressure. The displacement flow rate can be referred to as v=11.6xA2xQ lA1, wherein v is flow rate, unit: mL / min; Q l is liquid production, unit: m 3 / d; A1 is producing layer area, unit: cm 2 ; A2 is core cross-sectional area, unit: cm 2 .

[0109] (7) Keep the confining pressure 70 MPa unchanged, and positively drive in, and displace 100 PV (in the same direction as nitrogen gas driving in, and the liquid starts to flow out from the outlet end to calculate the PV number).

[0110] (8) After the displacement ends, the core is taken out, and the porosity Φ2 after the core is scaled is measured by a nuclear magnetic resonance measuring instrument. The test value of the nuclear magnetic porosity (%) before scaling is 1.15%.

[0111] (9) The porosity loss rate (%) = (Φ1-Φ2) / Φ1×100 = 53.82%, according to the core porosity change, the influence degree of the scaling after the pressure drop on the reservoir can be evaluated.

[0112] Finally, after the above evaluation steps, the T2 test results obtained are shown in Table 1, and the specific nuclear magnetic resonance T2 spectrum distribution and the nuclear magnetic resonance T2 decay curve are shown in Figure 4 and Figure 5 It can be seen that the evaluation device, system and method provided in the embodiment can effectively evaluate the influence degree of the fluid scaling on the core porosity, and reliable and accurate evaluation results are obtained.

[0113] Table 1 is the T2 test results

[0114]

[0115] The above embodiment is only one of the implementation manners of the technical scheme of the present application, and the scope of the present application is not limited to the above embodiment, but also includes any changes, substitutions and other implementation manners easily thought by those skilled in the art within the technical range disclosed by the present application.

Claims

1. An apparatus for evaluating the degree to which fluid fouling affects the porosity of a core, comprising: Includes sleeve (101); The sleeve (101) has a fluid inlet at one end and a fluid outlet at the other end, with a hollow cavity in the middle for holding and clamping the core (107); the fluid inlet and the fluid outlet are connected to the core (107) to form a displacement channel; The inner wall of the sleeve (101) and the outer wall of the core (107) are provided with a confining channel (104), which is used to allow confining liquid (105) to flow in to provide confining pressure to the core (107).

2. The apparatus of claim 1, wherein, The core (107) is covered with a rubber (106), which is used to achieve a pressure seal for the core (107).

3. The apparatus of claim 1, wherein, The sleeve (101) has a confining pressure inlet that communicates with the confining channel (104) for injecting confining pressure liquid (105) into the confining channel (104).

4. The apparatus of any one of claims 1-3, wherein, Sealing rings (108) are respectively provided at the connection between the fluid inlet, the fluid outlet and the core (107).

5. A system for evaluating the degree of impact of fluid fouling on core porosity, the system comprising: The apparatus for evaluating the effect of fluid scaling on core porosity as described in any one of claims 1-4 further includes: The displacement device is connected to the fluid inlet end (102) of the device for evaluating the influence of fluid scaling on core porosity, and is used to perform water displacement operation on the core (107). The pressurization device (4) is connected to the confining pressure channel (104) of the device for evaluating the influence of fluid scaling on core porosity, and is used to establish an initial formation water saturation environment and apply confining pressure to the core (107) under the initial formation water saturation environment; A collection device, connected to the fluid outlet end (103) of the device for evaluating the influence of fluid scaling on core porosity, is used to collect the liquid flowing out of the core (107) during the test; A data acquisition device is installed between the pressurizing device (4) and the fluid inlet end (102), the collecting device and the fluid outlet end (103), and the pressurizing device (4) and the confining pressure channel (104) to monitor the fluid inlet pressure, the fluid outlet pressure and the confining pressure.

6. The system for evaluating the degree of impact of fluid fouling on core porosity according to claim 5, wherein, The displacement device includes multiple displacement fluid containers, each of which is connected to a horizontal flow pump (2); the multiple displacement fluid containers are connected to the fluid inlet (102) through a multi-way valve (3).

7. The system for evaluating the degree of impact of fluid fouling on core porosity according to claim 5, wherein, The collection device includes a collection bottle connected to the fluid outlet end (103), and a drying tube (7) and a gas flow meter (8) are connected in sequence on the gas outlet pipe of the collection bottle.

8. A method of evaluating the extent to which fluid fouling affects the porosity of a core, characterized by, The apparatus for evaluating the influence of fluid scaling on core porosity according to any one of claims 1-4, or the system for evaluating the influence of fluid scaling on core porosity according to any one of claims 5-7, comprises: Step 1: Establish the initial formation water-saturated environment and measure the porosity of the core (107) before scaling; Step 2: Under the initial formation water saturation environment, apply confining pressure to the core (107) and simultaneously perform displacement operation on the core (107) at a preset displacement flow rate until the threshold is reached to end the displacement operation. Step 3: Measure the porosity of the core (107) after scaling following the displacement operation; Step 4: Obtain the porosity loss rate based on the porosity before and after scaling, and evaluate the degree of influence of fluid scaling on core porosity based on the porosity loss rate.

9. The method for evaluating the influence of fluid scaling on core porosity according to claim 8, characterized in that, Step one, the specific steps for establishing the initial formation water-saturated environment include: The prepared core (107) was subjected to a pressure test; For the cores (107) that passed the pressure test, vacuuming and pressurization operations were carried out in sequence, or oil and gas fluids were injected and then formation water was injected in sequence to establish an initial formation water saturated environment.

10. The method for evaluating the influence of fluid scaling on core porosity according to claim 8, characterized in that, In step two, the displacement velocity is determined based on the production rate per second, the producing layer area, and the core cross-sectional area, using the following formula: v = A2 x Q l / A1 wherein v represents the displacement flow rate; Q l represents the fluid production rate; A1represents the producing layer area; A2represents the core cross-sectional area.

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