Effect evaluation device and method for flow guarantee additive of high-pressure oil-water system

Abstract

The invention discloses a device and a method for evaluating the effect of a high-pressure oil-water system flow guarantee additive, which are used for evaluating the paraffin control effect and / or hydrate inhibition effect of the additive at the same time, and the device comprises a high-pressure kettle which is transversely arranged and is used for filling an oil-water emulsion containing the additive, and the high-pressure kettle does periodic swinging motion in the test process, a cold finger unit for providing a carrier for wax deposition and a temperature sensor for measuring the temperature in real time are arranged in the high-pressure kettle; at least one end of the autoclave is detachably and hermetically connected; the control unit is used for controlling the liquid temperature and the gas pressure in the autoclave; and the data acquisition and processing unit is used for acquiring the mass of sediments on the wall surface of the cold finger, the wax content of the initial oil phase in the sediments and the oil-water emulsion, and the induction time data of the wax-containing system hydrate, and calculating the comprehensive action index of the flow guarantee additive. According to the invention, the paraffin inhibition effect and hydrate generation inhibition effect of the additive can be jointly evaluated in one set of device; meanwhile, the flowing state of an actual pipeline can be better simulated, and the additive effect characterization is more scientific and visual.

Description

Technical Field

[0001] The invention relates to the technical field of oil and natural gas production, and in particular to a device and method for evaluating the effect of a flow assurance additive in a high-pressure oil-water system. Background Art

[0002] In submarine oil-gas-water multiphase pipelines, due to the presence of natural emulsifiers and frequent pump shear, the water phase is mainly dispersed in the crude oil in the form of droplets. In actual pipeline transportation, there are problems such as wax deposition and hydrate formation in pipeline flow safety assurance. When the crude oil temperature is lower than the wax precipitation point, wax crystals will precipitate and migrate under the action of concentration gradient and deposit on the inner wall of the pipeline to form sediments. Wax deposition will reduce the inner diameter of the pipeline and increase the pipeline pressure drop. If it is not removed in time, it will cause safety problems such as pipeline shutdown. At the same time, oil-gas-water multiphase pipelines in a low-temperature environment are at risk of hydrate formation under high pressure and disturbance conditions. Hydrate formation will cause solid ice particles to appear in the fluid, which will block the pipeline in severe cases and cause safety accidents.

[0003] The common wax deposition solutions in oilfield production are mainly mechanical cleaning and the use of wax inhibitors. Wax inhibitors can directly act on the prevention or removal of wax deposition, making the operation more convenient. At the same time, in order to inhibit the formation of hydrates, hydrate inhibitors such as methanol and ethylene glycol are widely used in multiphase mixed pipelines. Hydrate inhibitors can prolong the time for hydrates to appear, allowing the fluid in the pipeline to be safely transported to the processing or storage equipment. Therefore, the use of wax inhibitors and hydrate inhibitors has received widespread attention at engineering sites.

[0004] At present, the effect of paraffin inhibitors is mainly evaluated by atmospheric pressure cold finger devices and loop devices. Hydrate inhibitors are mainly evaluated with the help of high-pressure reactors and hydrate loops. Atmospheric pressure cold finger is mainly used for the determination of the quality of wax deposits in crude oil or oil-water emulsion systems and the calculation of deposition rate in atmospheric pressure environments. Cold finger devices and high-pressure stirred reactors can simulate cold walls, have low construction and operating costs, and are simple to operate. However, the disturbance environment imposed by the impeller makes the flow pattern of the fluid different from that of the actual pipeline, and the wax deposition rate and induction period data obtained are difficult to correspond to the engineering site. The loop device can simulate the actual pipe flow more realistically, but its high cost, large footprint, and high operating costs limit its large-scale promotion.

[0005] Currently, the effect of paraffin inhibitors is evaluated by the quality and wax content of the sediments. Excellent paraffin inhibitors can reduce the quality and wax content of the sediments. The effect of hydrate inhibitors is characterized by the induction period or generation time. Excellent inhibitors can prolong the hydrate generation time. However, there is no unified definition of the induction period. Paraffin inhibitors and hydrate inhibitors are commonly used additives in the field of pipeline flow safety. They are currently used and evaluated independently, and a joint evaluation method has not yet been established.

[0006] Therefore, the development of low-cost, effective, and suitable paraffin inhibitors for high-pressure environments is a widely-concerned issue in the field of pipeline safety. Considering that the flow assurance of high-pressure multiphase mixed crude oil pipelines involves multiple aspects such as wax deposition and hydrates, additives that have both the effects of paraffin prevention and hydrate formation inhibition are currently available. At the same time, the feasibility and cost of the device should be comprehensively considered to establish a high-pressure evaluation device that can analyze the effects of paraffin inhibitors and / or hydrate inhibitors, and further propose an evaluation operation process and effect characterization method.

[0007] Therefore, there is an urgent need for an effect evaluation device and method for flow assurance additives in high-pressure oil-water systems, which can jointly evaluate the anti-wax effect and hydrate formation inhibition effect of the additive in one set of equipment; at the same time, it can better simulate the flow state of the actual pipeline, and the characterization of the additive effect is more scientific and intuitive.

[0008] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention and should not be regarded as an acknowledgment or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the invention

[0009] The purpose of the present invention is to provide a device and method for evaluating the effect of flow assurance additives in a high-pressure oil-water system, which can jointly evaluate the anti-wax effect and the hydrate formation inhibition effect of the additive in a set of devices; at the same time, it can better simulate the flow state of the actual pipeline, and the characterization of the additive effect is more scientific and intuitive.

[0010] To achieve the above-mentioned purpose, according to the first aspect of the present invention, there is provided a device for evaluating the effect of flow assurance additives in a high-pressure oil-water system, which is used to simultaneously evaluate the anti-wax effect and / or hydrate inhibition effect of the additives, and comprises: an autoclave, which is arranged horizontally and is used to load an oil-water emulsion containing the additive, and the autoclave performs periodic swinging motion during the test, and a cold finger unit for providing a carrier for wax deposition and a temperature sensor for real-time temperature measurement are provided in the autoclave; at least one end of the autoclave is detachably sealed; a control unit is used to control the liquid temperature and gas pressure in the autoclave; a data acquisition and processing unit is used to collect data on the mass of the deposits on the cold finger wall, the wax content of the initial oil phase in the deposits and in the oil-water emulsion, and the hydrate induction time of the wax-containing system, and calculate the comprehensive effect index of the flow assurance additive.

[0011] Furthermore, in the above technical solution, the additive may be a wax inhibitor and a hydrate inhibitor, or a wax inhibitor having a hydrate inhibitory effect.

[0012] Furthermore, in the above technical solution, the cold finger unit may include a first cold finger and a second cold finger for providing different cold finger temperatures and / or wall areas.

[0013] Furthermore, in the above technical solution, the autoclave may use a stainless steel chamber, with a detachable end cover provided at one end of the chamber and a blind plate provided at the other end.

[0014] Furthermore, in the above technical solution, a swing portion may be provided at the bottom of the autoclave, and the bottom surface of the swing portion is an arc surface, which is used to provide a swing angle of 0 to 45 degrees; the swing portion is driven by a motor.

[0015] Furthermore, in the above technical solution, the control unit may include: a temperature control subunit, which controls the temperature of the autoclave through an autoclave water bath and a water bath sleeve wrapped around the outer wall of the autoclave; and performs auxiliary temperature control through a cold finger water bath; a pressure control subunit, which provides test gas to the autoclave through a gas cylinder and a valve and pressurizes it to a required pressure, and a gas flow meter is provided on the gas supply pipeline.

[0016] Furthermore, in the above technical solution, the mass of the deposit on the cold finger wall and the wax content in the deposit are collected by exhausting the gas in the autoclave, taking out the cold finger and measuring the mass of the deposit and the wax content on the cold finger wall.

[0017] Furthermore, in the above technical solution, the data acquisition and processing unit can calculate the wax precipitation deposition rate by collecting the mass of deposits on the cold finger wall, the wax content in the deposits and the initial oil phase in the oil-water emulsion, and the deposition time, thereby determining the anti-wax effect of the additive.

[0018] Furthermore, in the above technical solution, the data acquisition and processing unit can calculate the hydrate induction time data of the wax-containing system through the collected hydrate formation time data and the time data corresponding to the wax precipitation point, so as to determine the hydrate inhibition effect.

[0019] Furthermore, in the above technical solution, the value of the comprehensive effect index of the flow assurance additive can be used to comprehensively evaluate the anti-wax effect and hydrate inhibition effect of the additive.

[0020] Furthermore, in the above technical solution, the evaluation device may also include: a liquid filling and discharging unit, which includes a liquid filling valve and a liquid discharging valve, and is used for filling and draining the oil-water emulsion containing additives in the autoclave.

[0021] Furthermore, in the above technical solution, the test gas in the gas cylinder may be methane gas, carbon dioxide gas or natural gas, etc.

[0022] According to a second aspect of the present invention, the present invention provides a method for evaluating the effect of a flow assurance additive in a high-pressure oil-water system, which is used to simultaneously evaluate the anti-wax effect and / or hydrate inhibition effect of the additive, and comprises the following steps: A, determining the initial oil phase wax precipitation point temperature and wax content in the oil-water emulsion to be loaded; setting the autoclave water bath and the cold finger water bath to the wax deposition test temperature, and injecting the oil-water emulsion containing the flow assurance additive into the autoclave chamber after the temperature stabilizes; B, after pressurizing and maintaining the pressure constant, driving the autoclave to perform periodic swinging motion, and performing a wax deposition test so that wax crystals are precipitated and deposited on the cold finger wall under the temperature difference between the autoclave water bath and the cold finger water bath; C, after the wax deposition test, stopping pressurization and discharging the gas in the autoclave, taking out the cold finger and determining the mass and wax content of the cold finger wall sediment, and calculating the wax precipitation sediment. The accumulation rate is used to evaluate the anti-wax effect of the additive; D. Clean the cold finger wall and reinstall it into the autoclave chamber, adjust the temperature of the autoclave water bath and the cold finger water bath to be consistent, re-pressurize to the pressure required for the hydrate reaction, and simultaneously reduce the temperature of the autoclave water bath and the cold finger water bath to the hydrate test temperature and maintain constant; E. During the test, when the temperature in the autoclave increases sharply, it means that hydrates begin to form. The hydrate induction time of the wax-containing system is calculated by the time of the sudden increase in the temperature in the autoclave and the corresponding time of the wax precipitation point temperature, and then the hydrate inhibition effect of the additive is evaluated; F. The comprehensive action index of the flow assurance additive is calculated based on the mass of the cold finger wall sediment, the wax content of the initial oil phase in the sediment and the oil-water emulsion, and the hydrate induction time data of the wax-containing system, and then the anti-wax effect and hydrate inhibition effect of the additive are comprehensively evaluated.

[0023] Furthermore, in the above technical solution, the calculation of the wax precipitation and deposition rate can be specifically carried out in the following manner:

[0024]

[0025] Among them, D w is the wax precipitation and deposition rate; w d and w o are the wax contents of the cold finger wall deposits and the initial oil phase, respectively; M is the mass of the cold finger wall deposits; t is the deposition time.

[0026] Furthermore, in the above technical solution, the calculation of the hydrate induction time of the wax-containing system can be carried out in the following manner:

[0027] t=t f -t w ;

[0028] Where t is the hydrate induction time of the wax-containing system, t f is the hydrate formation time, t w It is the time corresponding to the wax precipitation point of the oil-water emulsion.

[0029] Furthermore, in the above technical solution, the comprehensive effect index F of the flow assurance additive is i The calculation of can be done as follows:

[0030]

[0031] Wherein, t is the hydrate induction time of the wax-containing system, i is the relevant parameter when no additive is added to the system, and n is the relevant parameter when the additive is added to the system.

[0032] Furthermore, in the above technical solution, F i When it is a negative value, it means that the additive has the dual effects of anti-wax and inhibiting hydrate formation, and the larger the absolute value, the better the comprehensive effect; when the calculation result is 0, it means that the additive only has an anti-wax effect; when the calculation result is a positive value, it means that the additive only has an anti-wax effect, but is not conducive to hydrate inhibition.

[0033] Furthermore, in the above technical solution, the initial oil phase wax precipitation point temperature and wax content can be measured by differential scanning calorimetry.

[0034] Furthermore, in the above technical solution, the temperature difference between the autoclave water bath and the cold finger water bath in step B means that the temperature of the cold finger water bath is lower than the temperature of the autoclave water bath.

[0035] Furthermore, in the above technical solution, before determining the mass and wax content of the cold finger wall deposits in step C, the method may further include: suspending the cold finger above the autoclave for 10 to 30 minutes to allow the condensed oil on the cold finger wall to separate under the action of gravity.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] 1) The evaluation device and method of the present invention can be used to evaluate the anti-wax effect of flow assurance additives in a high-pressure oil-gas-water coexistence environment, and can also be used to evaluate the hydrate inhibition effect of flow assurance additives, thus having dual uses. When the evaluation device of the present invention is used to evaluate the anti-wax effect alone, the wax content of the initial oil phase in the oil-water emulsion is fully considered, making the evaluation result more accurate; when evaluating the hydrate inhibition effect, the effects of wax crystal precipitation and wax deposition on hydrate formation are considered, and the hydrate induction time data of the wax-containing system is used for consideration, making the evaluation result more objective; in addition to the individual evaluation, the present invention introduces the indicator of the comprehensive effect index of flow assurance additives, which can provide a feasible method for evaluating the comprehensive effect of additives in the process of anti-wax and inhibition of hydrate formation. This indicator can be used not only to characterize the anti-wax effect of the additive, but also to further evaluate whether the additive has an effect on hydrate inhibition;

[0038] 2) The cold finger unit of the present invention can adopt a single cold finger or a double cold finger, that is, it includes a first cold finger and a second cold finger for providing different cold finger temperatures and / or wall areas. In the anti-wax effect evaluation test, the cold finger can realize the cold wall surface and provide a carrier for wax deposition. The design of the double cold finger can simultaneously explore the effects of different cold finger temperatures, liquid phase temperature, liquid level and wall area on the wax deposition rate through one evaluation experiment; in the hydrate inhibition effect evaluation test, the first cold finger and the second cold finger can assist the system temperature control and increase the heating and cooling rates of the liquid.

[0039] 3) The evaluation device of the present invention can make the autoclave perform periodic swinging motion during the test process through the design of the swinging part. Compared with the existing high-pressure stirring autoclave test equipment, it can better simulate the fluid state of the actual pipeline; the reciprocating operation of the fluid in the autoclave can simulate the periodic flushing effect of the oil-water system on the wall wax deposition; the swinging part can adjust the swing amplitude through the curvature of the bottom, and dynamically adjust the contact area between the cold finger wall and the liquid. At the same time, the device provided by the present invention has low construction and operation costs, small footprint, and simple operation;

[0040] 4) The evaluation method of the present invention can evaluate the anti-wax effect and hydrate inhibition effect of the flow assurance additive separately, and can also rely on the same set of evaluation devices to comprehensively evaluate the anti-wax effect and hydrate inhibition effect at the same time; the wax precipitation deposition rate proposed in the present invention can comprehensively consider the wax deposition mass, the wax content in the sediment and the initial oil phase to characterize the anti-wax effect of the additive, which is more comprehensive and reasonable. Among them, the smaller the wax precipitation deposition rate, the better the anti-wax agent effect; the hydrate inhibition effect of the additive is mainly characterized by the induction period. During the calculation process, the prior art generally takes the moment when the system enters the equilibrium state as the starting point for the induction period calculation. However, for a wax-containing system, the hydrate inhibition effect of the additive should take into account the influence of wax crystal precipitation. Therefore, the present invention proposes to take the time corresponding to the wax precipitation point of the oil phase as the starting point for the induction time calculation. The calculation result can take into account the hydrate inhibition effect of the additive when wax crystals exist. The longer the hydrate induction time of the wax-containing system, the better the hydrate inhibition effect of the additive. In addition, the present invention creatively introduces the evaluation index of the comprehensive effect index of the flow assurance additive. Through the positive and negative values ​​of this index, the anti-wax effect and hydrate inhibition effect of the additive can be intuitively and comprehensively evaluated.

[0041] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, and to make the above and other purposes, technical features and advantages of the present invention easier to understand, one or more preferred embodiments are listed below and described in detail with the accompanying drawings as follows. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1It is a structural schematic diagram of a device for evaluating the effect of flow assurance additives for a high-pressure oil-water system according to the present invention.

[0043] Figure 2 It is a schematic cross-sectional view of a cold finger in the evaluation device of the present invention.

[0044] Description of main reference numerals:

[0045] 1-computer; 2-data acquisition and processing unit; 3-flow regulating valve; 4-gas cylinder; 5-bolt; 6-autoclave chamber; 7-pressure gauge; 8-detachable end cover; 9-gas flow meter; 10-check valve; 11-temperature sensor; 12-drain valve; 13-pressure sensor; 14-liquid injection valve; 15-cold finger water inlet; 16-first cold finger; 17-second cold finger; 18-cold finger water outlet; 19-autoclave water bath sleeve; 20-water bath water inlet pipeline; 21-water bath water outlet pipeline; 22-first cold finger water bath; 23-second cold finger water bath; 24-autoclave water bath; 25-drain valve; 26-swinging part; 27-motor. DETAILED DESCRIPTION

[0046] The specific implementation modes of the present invention are described in detail below in conjunction with the accompanying drawings, but it should be understood that the protection scope of the present invention is not limited by the specific implementation modes.

[0047] Unless explicitly stated otherwise, throughout the specification and claims, the term “comprise” or variations such as “include” or “comprising”, etc., will be understood to include the stated elements or components but not to exclude other elements or components.

[0048] In this document, for the convenience of description, spatial relative terms such as "below", "below", "down", "above", "above", "upper", etc. may be used to describe the relationship between one element or feature and another element or feature in the accompanying drawings. It should be understood that the spatial relative terms are intended to include different orientations of the object in use or operation in addition to the orientation depicted in the figure. For example, if the object in the figure is turned over, the element described as being "below" or "below" other elements or features will be oriented "above" the element or feature. Therefore, the exemplary term "below" can include both below and above. Objects may also have other orientations (rotated 90 degrees or other orientations) and the spatial relative terms used in this document should be interpreted accordingly.

[0049] In this document, the terms "first", "second", etc. are used to distinguish two different elements or parts, and are not used to limit a specific position or relative relationship. In other words, in some embodiments, the terms "first", "second", etc. can also be interchangeable.

[0050] like Figure 1As shown, the present invention provides a device for evaluating the effect of flow assurance additives in a high-pressure oil-water system, which is used to simultaneously evaluate the anti-wax effect and / or hydrate inhibition effect of the additives. The flow assurance additives can be existing anti-wax agents and hydrate inhibitors, or anti-wax agents with hydrate inhibition effects, such as surfactants and nanoparticle anti-wax agents, such as nano-silicon dioxide particles, etc., and are obtained by modification of vacuum residue oil and deoiled asphalt. These anti-wax agents have both anti-wax effects and certain hydrate inhibition effects. The evaluation device of the present invention includes an autoclave, a control unit, and a data acquisition and processing unit 2. The autoclave is arranged horizontally and is used to load the oil-water emulsion containing the above-mentioned additives. During the test, the autoclave performs periodic swinging motion. A cold finger unit for providing a carrier for wax deposition and a temperature sensor for real-time temperature measurement are provided in the autoclave; at least one end of the autoclave is detachably sealed. The control unit is used to control the liquid temperature and gas pressure in the autoclave. The data acquisition and processing unit 2 is used to collect data on the mass of sediment on the cold finger wall, the wax content of the initial oil phase in the sediment and the oil-water emulsion, and the hydrate induction time of the wax-containing system, and calculate the comprehensive effect index of the flow assurance additive.

[0051] The evaluation device of the present invention can be used to evaluate the anti-wax effect of the flow assurance additive in a high-pressure oil-gas-water coexistence environment, and can also be used to evaluate the hydrate inhibition effect of the flow assurance additive, and has dual uses. When the evaluation device of the present invention is used, when evaluating the anti-wax effect alone, the wax content of the initial oil phase in the oil-water emulsion is fully considered, so that the evaluation result is more accurate; when evaluating the hydrate inhibition effect alone, the influence of wax crystal precipitation and wax deposition on hydrate formation is considered, and the hydrate induction time data of the wax-containing system is used for consideration, so that the evaluation result is more objective; in addition to the individual evaluation, the present invention introduces the comprehensive effect index of the flow assurance additive, which can provide a feasible method for evaluating the comprehensive effect of the additive in the process of anti-wax and inhibition of hydrate formation. Through this indicator, it can not only be used to characterize the anti-wax effect of the additive, but also can further evaluate whether the additive has an effect on hydrate inhibition.

[0052] Further Figure 1As shown, the autoclave chamber 6 can be made of a stainless steel chamber, preferably 316L stainless steel, which can withstand a pressure of 10MPa. The diameter of the autoclave chamber 6 can be designed to be 140mm and the length is 200mm. A removable end cover 8 is provided at one end of the chamber 6, and the removable end cover 8 can be sealed by a bolt 5 for rapid liquid inlet, liquid discharge and cleaning, and a blind plate is provided at the other end. The cold finger unit may further include a first cold finger 16 and a second cold finger 17 for providing different cold finger temperatures and / or wall areas. The inner diameter of the first cold finger 16 and the second cold finger 17 can be designed to be 18mm, and the length deep into the autoclave chamber 6 can be 80mm. During the wax deposition test, the first cold finger 16 and the second cold finger 17 can provide a cold wall surface. In the hydrate evaluation test, the first cold finger 16 and the second cold finger 17 can assist the system in temperature control and increase the heating and cooling rates of the liquid. The bottom of the autoclave is provided with a swinging portion 26, the bottom surface of which can be designed as an arc surface to provide a swinging angle of 0 to 45 degrees; the swinging portion 26 can be driven by a motor 27. Through the design of the swinging portion, the autoclave of the present invention can perform periodic swinging motion during the test process, and can better simulate the fluid state of the actual pipeline compared to the existing high-pressure stirring autoclave test equipment.

[0053] Further Figure 1 As shown, the control unit of the present invention further includes a temperature control subunit and a pressure control subunit. Among them, the temperature control subunit can control the temperature of the autoclave through the autoclave water bath 24 and the water bath sleeve 19 wrapped around the outer wall of the autoclave, and can also perform auxiliary temperature control through the cold finger water bath (i.e., the first cold finger water bath 22 and the second cold finger water bath 23). Specifically, the circulating water enters the cold finger from the cold finger water inlet 15 through the water bath outlet pipeline 21, and then flows into the constant temperature water bath from the cold finger outlet 18 through the water bath inlet pipeline 20 to realize the temperature control operation. The first cold finger water bath 22 and the second cold finger water bath 23 can control the wall temperature of the first cold finger 16 and the second cold finger 17 respectively, thereby providing a cold wall surface for the wax deposition process. For easy disassembly, the first cold finger 16 and the second cold finger 17 can be connected to the autoclave chamber 6 through a threaded seal (reference Figure 2 ). The temperature control range of the autoclave water bath 24, the first cold finger water bath 22 and the second cold finger water bath 23 is preferably -15 to 50°C. The pressure control subunit can provide test gas to the autoclave through the gas cylinder 4 and the valve and pressurize it to the required pressure. The gas supply pipeline is provided with a pressure gauge 7, a flow regulating valve 3, a gas flow meter 9 and a check valve 10 in sequence, which can be connected to the gas cylinder 4 to provide the autoclave with the high-pressure environment required for the test. The test gas in the gas cylinder 4 can be methane gas, carbon dioxide gas or natural gas, etc.

[0054] Further Figure 1As shown, the evaluation device of the present invention further comprises a liquid inlet and outlet unit, which further comprises a liquid injection valve 14 and a liquid discharge valve 25, and can be used for filling and draining the oil-water emulsion containing additives in the autoclave.

[0055] Further Figure 1 As shown, the data acquisition and processing unit 2 of the present invention not only collects and records data from the gas flow meter 9, the temperature sensor 11 (used to monitor the system temperature in the fluid in the autoclave) and the pressure sensor 13 (connected to the evacuation pipeline to monitor the system pressure in the autoclave), but more importantly, collects or calculates other relevant parameters during the test. Specifically, the method of collecting the mass of the deposit on the wall of the cold finger and the wax content in the deposit is: exhaust the gas in the autoclave, take out the cold finger and measure the mass of the deposit and the wax content on the wall of the cold finger. Preferably, but not restrictively, the data acquisition and processing unit 2 of the present invention calculates the wax precipitation deposition rate by the collected mass of the deposit on the wall of the cold finger, the wax content of the initial oil phase in the deposit and the oil-water emulsion, and the deposition time, so as to judge the anti-wax effect of the additive; the data acquisition and processing unit 2 can also calculate the hydrate induction time data of the wax-containing system by the collected hydrate generation time data and the time data corresponding to the wax precipitation point, so as to judge the hydrate inhibition effect. Further, the value of the comprehensive action index of the flow assurance additive obtained by calculation in the present invention can be used to comprehensively evaluate the anti-wax effect and hydrate inhibition effect of the additive.

[0056] The present invention also provides a method for evaluating the effect of a flow assurance additive in a high-pressure oil-water system, which can be used to simultaneously evaluate the anti-wax effect and / or hydrate inhibition effect of the additive, comprising the following steps:

[0057] Step S101, using light oil and petroleum ether to sequentially clean the autoclave cavity 6, the detachable end cover 8, the first cold finger 16 and the second cold finger 17, installing the various parts of the evaluation device of the present invention, measuring the initial oil phase wax precipitation point temperature and wax content in the oil-water emulsion to be filled (i.e., filled through the injection valve 14), and the oil phase wax precipitation point temperature and wax content are measured by an existing differential scanning calorimeter;

[0058] Step S102, the autoclave water bath 24, the first cold finger water bath 22 and / or the second cold finger water bath 23 are set to the wax deposition test temperature, and after the temperature is stabilized, the oil-water emulsion containing the additive is injected into the autoclave chamber through the injection valve 14. The cold finger water bath temperature can be lower than the autoclave water bath temperature, which can better provide a cold wall surface for wax deposition during the wax deposition test;

[0059] Step S103, start the pressure control subunit to raise the pressure in the autoclave to a set value, and maintain the system pressure constant through the flow control valve 9 during the test;

[0060] Step S104, turning on the motor 27 to make the autoclave perform periodic reciprocating swinging motion under the action of the swinging part 26, so as to realize the flow of the liquid in the autoclave, making it closer to the fluid state in the actual pipeline;

[0061] Step S105, maintaining the temperature, pressure, swing amplitude and frequency unchanged, and performing a wax deposition test for a certain period of time so that wax crystals are precipitated and deposited on the cold finger wall surface under the action of the temperature difference;

[0062] Step S106, after the wax deposition evaluation test is completed, the pressure control subunit is stopped from pressurizing and the drain valve 12 is opened to discharge the gas in the kettle, the cold finger is slowly taken out, the mass and wax content of the cold finger wall deposits are measured, and the wax precipitation deposition rate is calculated, thereby evaluating the anti-wax effect of the additive;

[0063] Preferably, but not limiting, the calculation of the wax precipitation deposition rate can be specifically carried out in the following manner:

[0064]

[0065] Among them, D w is the wax precipitation and deposition rate; w d and w o are the wax contents of the cold finger wall deposits and the initial oil phase, respectively; M is the mass of the cold finger wall deposits; t is the deposition time.

[0066] The calculation of the wax precipitation and deposition rate in this step takes into account the wax content in the initial oil phase. Compared with the prior art which only considers the wax content in the sediment, the evaluation of the anti-wax effect of the additive is more accurate and objective.

[0067] Furthermore, in order to make the determination results of the mass and wax content of the cold finger wall deposits more accurate, preferably but not restrictively, the present invention can hang the cold finger above the autoclave for 10 to 30 minutes before determining the mass and wax content of the cold finger wall deposits to allow the surface condensed oil to separate under the action of gravity.

[0068] Step S107, wipe off the deposits on the surface of the cold finger and reinstall it into the autoclave chamber 6, and adjust the temperature of the autoclave water bath 24, the first cold finger water bath 22 and / or the second cold finger water bath 23 to be consistent;

[0069] Step S108, turning on the pressure control subunit to raise the pressure in the autoclave to a set value (i.e., the pressure required for the hydrate reaction), and synchronously cooling the autoclave water bath 24, the first cold finger water bath 22, and / or the second cold finger water bath 23 to the hydrate test temperature and maintaining it constant. During the cooling process, the flow control valve 9 is used to maintain the system pressure constant;

[0070] Step S109, when the temperature in the kettle increases sharply during the test, it indicates that hydrates begin to form. At this time, the gas cylinder 4 and the flow regulating valve 9 are closed, and the hydrate induction time of the wax-containing system is calculated by the time when the temperature in the kettle increases sharply (that is, the time when the water bath starts to heat up) and the corresponding time of the wax precipitation point temperature (that is, the corresponding time, that is, the wax precipitation point temperature is first reached during the cooling process in step S108, and the corresponding time is the corresponding time of the wax precipitation point temperature, and then the temperature continues to cool to the hydrate formation temperature), so as to evaluate the hydrate inhibition effect of the additive;

[0071] The calculation of hydrate induction time of wax-containing system can be done as follows:

[0072] t=t f -t w ; Formula (2)

[0073] Where t is the hydrate induction time of the wax-containing system, t f is the hydrate formation time, t w The time corresponding to the wax precipitation point of the oil-water emulsion can be effectively evaluated by calculating this formula to evaluate the hydrate inhibition effect of the additive on the wax-containing system.

[0074] Step S110, by measuring the mass of the cold finger wall sediment collected in the aforementioned step S106, the wax content in the sediment collected in the aforementioned step S106, the wax content in the initial oil phase in the oil-water emulsion collected in the aforementioned step S101, and the hydrate induction time data of the wax-containing system calculated and obtained in the aforementioned step S109, calculate the comprehensive effect index of the flow assurance additive of the present invention, and then comprehensively evaluate the anti-wax effect and hydrate inhibition effect of the additive. The calculation of this step is performed by the data acquisition processing unit 2, and the comprehensive effect index F of the flow assurance additive is calculated. i The calculation of can be done as follows:

[0075]

[0076] Wherein, t is the hydrate induction time of the wax-containing system, i is the relevant parameter when no additive is added to the system, and n is the relevant parameter when the additive is added to the system. The relevant parameters in this formula (3) are all the parameters in the aforementioned formulas (1) and (2).

[0077] The F calculated by formula (3) i When it is a negative value, it means that the additive has the dual effects of anti-wax and inhibiting hydrate formation, and the larger the absolute value, the better the comprehensive effect; when the calculation result is 0, it means that the additive only has an anti-wax effect; when the calculation result is a positive value, it means that the additive only has an anti-wax effect, but is not conducive to hydrate inhibition.

[0078] The evaluation method of the present invention uses the aforementioned evaluation device to conduct experiments. The method can evaluate the anti-wax effect and hydrate inhibition effect of the flow assurance additive separately, and can also rely on the same set of evaluation devices to comprehensively evaluate the anti-wax effect and hydrate inhibition effect at the same time; the existing wax deposition inhibition (i.e., anti-wax) effect is mainly calculated by the deposition mass. The deposition rate is analyzed by only measuring the wax content in the sediment, and the wax content in the initial oil phase is missing. The wax precipitation deposition rate proposed in the present invention can comprehensively consider the wax deposition mass, the sediment and the wax content in the initial oil phase to characterize the anti-wax effect of the additive, which is more comprehensive and reasonable. Among them, the smaller the wax precipitation deposition rate, the better the anti-wax agent effect; the hydrate inhibition effect of the additive is mainly characterized by the induction period. In the calculation process, the prior art generally takes the time when the system enters the equilibrium state as the starting point for the induction period calculation. However, for a wax-containing system, the hydrate inhibition effect of the additive should take into account the influence of wax crystal precipitation. Therefore, the present invention proposes to take the time corresponding to the wax precipitation point of the oil phase as the starting point for the induction time calculation. The calculation result can consider the hydrate inhibition effect of the additive when wax crystals exist. The longer the hydrate induction time of the wax-containing system, the better the hydrate inhibition effect of the additive. In addition, the present invention creatively introduces the evaluation index of the comprehensive effect index of the flow assurance additive. Through the positive and negative values ​​of this index, the anti-wax effect and hydrate inhibition effect of the additive can be intuitively and comprehensively evaluated.

[0079] Example 1

[0080] This embodiment uses the aforementioned evaluation device and the steps of the aforementioned evaluation method to evaluate the effect of the wax inhibitor with hydrate inhibition effect (i.e., the flow assurance additive with dual effect). The evaluation process of this embodiment is specifically as follows:

[0081] (1) The autoclave cavity, the removable end cover and the first cold finger were cleaned in sequence with diesel and petroleum ether, and the various parts of the device were installed, wherein the second cold finger was not installed, and the removable end cover was sealed with a seal. The initial oil phase wax precipitation point temperature was measured to be 15.23°C and the wax content was 4.89%.

[0082] (2) The first cold finger water bath was set to the wax deposition test temperature of 0.5°C, and the autoclave water bath temperature was set to 5.0°C. The two water baths were gradually lowered from 20°C to the set temperature and maintained stable. 2000 mL of an oil-water emulsion with a water content of 10% and a certain mass of anti-wax agent were injected into the autoclave chamber through the injection valve.

[0083] (3) Open the pressure control subunit to raise the pressure in the autoclave to 1.0 MPa. During the test, the flow control valve is used to maintain the system pressure constant.

[0084] (4) Turn on the motor to make the autoclave perform periodic reciprocating swinging motion under the action of the swinging part, with a swinging amplitude of 45°, so as to realize the flow of liquid in the autoclave.

[0085] (5) Keeping the temperature, pressure, swing amplitude and frequency constant, a wax deposition test was conducted for 12 hours to allow wax crystals to precipitate and deposit on the cold finger wall under the action of temperature difference.

[0086] (6) After the wax deposition evaluation test is completed, the pressure control subunit is stopped from pressurizing and the drain valve is opened to discharge the gas in the kettle. The cold finger is slowly removed, the mass of the cold finger wall deposits and the wax content are measured, and the wax precipitation deposition rate is calculated by the aforementioned formula (1), thereby evaluating the anti-wax effect of the additive.

[0087] (7) After wiping off the deposits on the surface of the cold finger, reinstall it into the autoclave chamber and set the temperature of the autoclave water bath and the first cold finger water bath to 2.5°C.

[0088] (8) Open the pressure control subunit to raise the pressure in the autoclave to 3.0 MPa, and simultaneously cool the autoclave water bath and the first cold finger water bath from 20°C to 2.5°C and maintain constant. During the cooling process, the flow control valve is used to maintain the system pressure constant.

[0089] (9) When the temperature sensor reading suddenly rises, it indicates that hydrates begin to form. At this time, the gas cylinder and the flow control valve are closed, and the hydrate induction time of the wax-containing system is calculated by the time when the water bath starts to heat up and the corresponding time of the wax precipitation point temperature (calculated using the above formula (2)).

[0090] (10) The comprehensive effect index of the flow assurance additive of the present invention is calculated (calculated using the above formula (3)) based on the mass of the cold finger wall deposits collected by the above measurement, the wax content in the deposits collected by the above measurement, the wax content in the initial oil phase in the oil-water emulsion collected by the above measurement, and the hydrate induction time data of the wax-containing system obtained by the above calculation, and then the anti-wax effect and hydrate inhibition effect of the additive are comprehensively evaluated.

[0091] (11) When the temperature stabilizes, turn off the motor and data acquisition and processing unit, open the drain valve to drain the liquid in the kettle, and clean the test device.

[0092] The foregoing description of specific exemplary embodiments of the present invention is for the purpose of illustration and demonstration. These descriptions are not intended to limit the present invention to the precise form disclosed, and it is clear that many changes and variations can be made based on the above teachings. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the present invention and its practical application, so that those skilled in the art can realize and utilize various different exemplary embodiments of the present invention and various different selections and changes. Any simple modifications, equivalent changes and modifications made to the above exemplary embodiments should fall within the scope of protection of the present invention.

Claims

1. A device for evaluating the effect of flow assurance additives in a high-pressure oil-water system, characterized in that: Used to evaluate the anti-wax effect and / or hydrate inhibition effect of additives simultaneously, including: An autoclave is arranged horizontally and is used to load an oil-water emulsion containing additives. During the test, the autoclave performs periodic swinging motion. A cold finger unit for providing a carrier for wax deposition and a temperature sensor for real-time temperature measurement are provided in the autoclave. At least one end of the autoclave is a detachable sealed connection. A control unit, which is used to control the liquid temperature and gas pressure in the autoclave; The data acquisition and processing unit is used to collect data on the mass of the deposits on the cold finger wall, the wax content of the initial oil phase in the deposits and the oil-water emulsion, and the hydrate induction time of the wax-containing system, and calculate the comprehensive action index of the flow assurance additive.

2. The high-pressure oil-water system flow assurance additive effect evaluation device according to claim 1, characterized in that: The additives are a wax inhibitor and a hydrate inhibitor, or a wax inhibitor having a hydrate inhibitory effect.

3. The device for evaluating the effect of flow assurance additives for a high-pressure oil-water system according to claim 1, characterized in that: The cold finger unit comprises a first cold finger and a second cold finger for providing different cold finger temperatures and / or wall areas.

4. The high-pressure oil-water system flow assurance additive effect evaluation device according to claim 1, characterized in that: The autoclave is a stainless steel chamber, with a detachable end cover at one end and a blind plate at the other end.

5. The device for evaluating the effect of flow assurance additives for a high-pressure oil-water system according to claim 4, characterized in that: The bottom of the autoclave is provided with a swinging part, the bottom surface of which is an arc surface, for providing a swinging angle of 0 to 45 degrees; the swinging part is driven by a motor.

6. The device for evaluating the effect of flow assurance additives for a high-pressure oil-water system according to claim 1, characterized in that: The control unit comprises: A temperature control subunit controls the temperature of the autoclave through an autoclave water bath and a water bath jacket wrapped around the outer wall of the autoclave; and performs auxiliary temperature control through a cold finger water bath; The pressure control subunit supplies test gas to the autoclave through a gas cylinder and a valve and pressurizes it to the required pressure. A gas flow meter is provided on the gas supply pipeline.

7. The device for evaluating the effect of flow assurance additives for a high-pressure oil-water system according to claim 1, characterized in that: The mass of the deposit on the cold finger wall and the wax content in the deposit are collected by exhausting the gas in the autoclave, taking out the cold finger and measuring the mass of the deposit and the wax content on the cold finger wall.

8. The device for evaluating the effect of flow assurance additives for a high-pressure oil-water system according to claim 1, characterized in that: The data acquisition and processing unit calculates the wax precipitation and deposition rate by collecting the mass of the deposit on the cold finger wall, the wax content in the deposit and the initial oil phase in the oil-water emulsion, and the deposition time, so as to determine the anti-wax effect of the additive.

9. The device for evaluating the effect of flow assurance additives for a high-pressure oil-water system according to claim 8, characterized in that: The data acquisition and processing unit calculates the hydrate induction time data of the wax-containing system through the collected hydrate generation time data and the time data corresponding to the wax precipitation point, so as to determine the hydrate inhibition effect.

10. The device for evaluating the effect of flow assurance additives for a high-pressure oil-water system according to claim 9, characterized in that: The value of the comprehensive effect index of the flow assurance additive is used to comprehensively evaluate the anti-wax effect and hydrate inhibition effect of the additive.

11. The device for evaluating the effect of flow assurance additives for a high-pressure oil-water system according to claim 1, characterized in that: The evaluation device also includes: The liquid inlet and outlet unit comprises a liquid injection valve and a liquid discharge valve, and is used for filling and draining the oil-water emulsion containing additives in the autoclave.

12. The device for evaluating the effect of flow assurance additives for a high-pressure oil-water system according to claim 6, characterized in that: The test gas in the gas cylinder is methane gas, carbon dioxide gas or natural gas.

13. A method for evaluating the effect of flow assurance additives in a high-pressure oil-water system, characterized in that: The method is used to simultaneously evaluate the anti-wax effect and / or hydrate inhibition effect of an additive, comprising the following steps: A. Determine the initial oil phase wax precipitation point temperature and wax content in the oil-water emulsion to be loaded; set the autoclave water bath and the cold finger water bath to the wax deposition test temperature, and inject the oil-water emulsion containing the flow assurance additive into the autoclave chamber after the temperature stabilizes; B. After increasing the pressure and maintaining the pressure constant, the autoclave is driven to perform periodic swinging motion, and a wax deposition test is performed to allow wax crystals to precipitate and deposit on the cold finger wall under the temperature difference between the autoclave water bath and the cold finger water bath; C. After the wax deposition test, stop pressurizing and exhaust the gas in the kettle, take out the cold finger and measure the mass and wax content of the cold finger wall sediment, and calculate the wax precipitation and deposition rate, so as to evaluate the anti-wax effect of the additive; D. Clean the wall surface of the cold finger and reinstall it into the autoclave chamber, adjust the temperature of the autoclave water bath and the cold finger water bath to be consistent, re-pressurize to the pressure required for the hydrate reaction, and simultaneously reduce the temperature of the autoclave water bath and the cold finger water bath to the hydrate test temperature and maintain it constant; E. During the test, when the temperature in the kettle increases sharply, it means that hydrates begin to form. The hydrate induction time of the wax-containing system is calculated by the time of the sharp increase in the temperature in the kettle and the corresponding time of the wax precipitation point temperature, and then the hydrate inhibition effect of the additive is evaluated; F. Calculate the comprehensive effect index of the flow assurance additive based on the mass of the cold finger wall deposit, the wax content in the deposit and the initial oil phase in the oil-water emulsion, and the hydrate induction time data of the wax-containing system, and then comprehensively evaluate the anti-wax effect and hydrate inhibition effect of the additive.

14. The method for evaluating the effect of flow assurance additives in a high-pressure oil-water system according to claim 13, characterized in that: The wax precipitation and deposition rate is calculated specifically in the following manner: Among them, D w is the wax precipitation and deposition rate; w d and w o are the wax contents of the cold finger wall deposits and the initial oil phase, respectively; M is the mass of the cold finger wall deposits; t is the deposition time.

15. The method for evaluating the effect of flow assurance additives in a high pressure oil-water system according to claim 13, characterized in that: The hydrate induction time of the wax-containing system is calculated as follows: t=t f -t w ; Where t is the hydrate induction time of the wax-containing system, t f is the hydrate formation time, t w It is the time corresponding to the wax precipitation point of the oil-water emulsion.

16. The method for evaluating the effect of flow assurance additives in a high-pressure oil-water system according to claim 13, characterized in that: The comprehensive effect index F of the flow assurance additive i The calculation of is as follows: Wherein, t is the hydrate induction time of the wax-containing system, i is the relevant parameter when no additive is added to the system, and n is the relevant parameter when the additive is added to the system.

17. The method for evaluating the effect of flow assurance additives in a high-pressure oil-water system according to claim 16, characterized in that: The F i When it is a negative value, it means that the additive has the dual effects of anti-wax and inhibiting hydrate formation, and the larger the absolute value, the better the comprehensive effect; when the calculation result is 0, it means that the additive only has an anti-wax effect; when the calculation result is a positive value, it means that the additive only has an anti-wax effect, but is not conducive to hydrate inhibition.

18. The method for evaluating the effect of flow assurance additives in a high pressure oil-water system according to claim 13, characterized in that: The initial oil phase wax precipitation point temperature and wax content are measured by differential scanning calorimetry.

19. The method for evaluating the effect of flow assurance additives in a high pressure oil-water system according to claim 13, characterized in that: The temperature difference between the autoclave water bath and the cold finger water bath in step B means that the temperature of the cold finger water bath is lower than the temperature of the autoclave water bath.

20. The method for evaluating the effect of flow assurance additives in a high pressure oil-water system according to claim 13, characterized in that: Before determining the mass and wax content of the cold finger wall sediment in step C, the method further includes: hanging the cold finger above the autoclave for 10 to 30 minutes to allow the condensed oil on the cold finger wall to separate under the action of gravity.

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