CN115407052A - Method for testing influence of wax content on phase state of high-wax-content condensate oil gas system - Google Patents
Method for testing influence of wax content on phase state of high-wax-content condensate oil gas system Download PDFInfo
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Abstract
The invention discloses a method for testing influence of wax content on phase state of a high-wax-content condensate oil gas system, and solves the technical problems that a test method about influence of wax on phase state change is not established in the prior art, and research about influence of wax content on condensate gas reservoir phase state change rule is not performed. It comprises the following steps: s1, sampling and checking a field separator; s2, determining the wax content of the condensate oil, and extracting pure wax and light oil; s3, adjusting and calculating the wax content of the condensate oil and calculating a sample preparation; s4, preparing formation fluid from the dead oil samples with different wax contents; s5, preparing formation fluid by using the live oil samples with different wax contents; and S6, carrying out PVT experiments on formation fluids with different wax contents to obtain experimental data of the influence of the wax contents on the phase state of the high-wax-content condensate oil-gas system. Under the condition of not changing gas-oil ratio and wax components, the invention is difficult to prepare the condensate gas with different wax contents, and the experimental analysis test of the influence of the wax content on the phase state can be completed only by preparing the corresponding condensate oil gas by adopting the wax of the well.
Description
Technical Field
The invention relates to the field of high-wax-content condensate gas reservoir development, in particular to a method for testing influence of wax content on phase state of a high-wax-content condensate oil gas system.
Background
With the expansion of the natural gas exploration field and the improvement of the technology, the conventional condensate gas reservoir research cannot completely meet the development and production requirements of oil and gas fields. The high-wax condensate gas reservoir which is found in a certain oil field of Tarim wood in Xinjiang and is different from a conventional condensate gas reservoir has the problems of serious condensation and wax deposition in the development process, and the wax deposition in a shaft causes shaft blockage, so that the oil gas yield is greatly reduced, and even the production is stopped. The well wax is seriously deposited, so that the on-site wax removal and prevention operation is frequent, the stable operation of production is seriously influenced, and the exploitation cost of an oil and gas reservoir is greatly improved. Meanwhile, the influence of the wax content on the dew point pressure, the reverse condensate amount and the recovery ratio of the high-wax-content condensate gas field is not clear. Therefore, in order to prevent the problem of wax precipitation caused by the condensate gas from the stratum to the wellhead, experimental research needs to be carried out on the influence of the wax content of the high-wax-content condensate gas reservoir on the condensate gas phase change.
The condensate gas reservoir has the characteristics of both an oil reservoir and a gas reservoir, and the complex phase change of the condensate gas reservoir is accompanied with the whole process of field development, so that great difficulty and challenge are brought to high-efficiency development. Especially in the later development period, the retrograde damage becomes more and more serious due to the continuous reduction of the reservoir pressure. The main characteristic of the reverse condensation phenomenon is that when the formation pressure is reduced below the dew point pressure, reverse condensation is generated in the reservoir and is continuously accumulated, so that the gas phase permeability is sharply reduced, and the yield is greatly reduced. However, the wax content in the gas reservoir affects the composition of well fluid, and thus affects the condensate dew point pressure, the retrograde condensate amount, the condensate recovery ratio and the like. The different components have different degrees of influence on the fluid dew point pressure, wherein C 3 ,C 4 ,H 2 The influence of components such as S is obvious. The dew point pressure is an important criterion for determining the saturation degree and fluid characteristics of the condensate gas reservoir. Therefore, the research on the influence of different wax contents on the condensate gas phase state has certain field guiding significance for formulating a reasonable development mode and continuously improving the development level of a condensate gas field.
The research on the condensate gas phase characteristics is always the most basic and the most critical ring in the related research work, the phase characteristics and other aspects of the conventional natural gas reservoir containing wax are researched by the predecessors, but the related research is not complete aiming at the problem that the wax content in the condensate gas affects the phase, and how to effectively develop the condensate gas reservoir becomes a research hotspot along with the increase of the development proportion of the gas reservoir. Therefore, for the influence of the wax content of the high-wax condensate gas reservoir on the phase change, the related experimental method is not perfect, and the following problems exist:
ungerer et al pioneered the study of phase change in condensate reservoirs in 1995, and used an experimental method of mixing reservoir fluid and artificial fluid in a high-pressure vessel to study gas-liquid, gas-solid, gas-liquid-solid phase diagrams. The Nichia establishes a paraffin deposition model in the condensate gas through a dynamic method and is used for comparing different points of the paraffin deposition law of the condensate gas reservoir and the oil reservoir. Leontaritis found paraffin deposits in condensate reservoirs when studying the analysis of condensate production and analyzed the condensate reservoirs using near infrared equipment.
At present, the wax testing method mainly focuses on wax precipitation points, wax deposition and the like, a testing method about the influence of wax on phase change is not established, and the influence of wax content on the phase change rule of a condensate gas reservoir is not researched. Under the condition of not changing gas-oil ratio and wax components, it is difficult to prepare condensate gas with different wax contents, and the experimental analysis test of the influence of the wax content on the phase state can be completed only by preparing corresponding condensate oil gas by using the wax of the well.
In the prior art, wax testing methods mainly focus on wax precipitation points, wax deposition and the like, and no testing method about the influence of wax on phase change is established, and no research about the influence of wax content on the phase change rule of a condensate gas reservoir is carried out.
Disclosure of Invention
The invention aims to provide a method for testing the influence of wax content on the phase state of a high-wax-content condensate oil gas system, and aims to solve the technical problems that no test method about the influence of wax on the phase state change is established in the prior art, and no research about the influence of wax content on the phase state change rule of a condensate gas reservoir is carried out.
In order to achieve the purpose, the invention provides the following technical scheme:
the method for testing the influence of the wax content on the phase state of the high-wax-content condensate oil-gas system comprises the following steps:
s1, sampling and checking of field separator
Separating hydrocarbon fluid in an oil-gas reservoir through an on-site oil-gas separator to obtain a gas sample and an oil sample; and inspecting the obtained gas sample and oil sample; obtaining liquid hydrocarbon under the atmospheric condition after degassing hydrocarbon fluid of the oil-gas reservoir once to obtain a dead oil sample, and inspecting the obtained dead oil sample;
s2, determining the wax content of the condensate oil, and extracting pure wax and light oil
Fractionating the condensate oil extracted by the oil-gas separator, and separating a light component from a heavy component and a wax component by using the difference of the volatility of each component in an oil sample; obtaining pure wax and light oil;
s3, adjusting and calculating the wax content of the condensate oil and calculating a sample preparation;
s4, preparing formation fluid by using dead oil samples with different wax contents
The condensate oil sample is mixed with light oil and pure wax extracted from the same well to change the wax content of the condensate oil, and then the condensate oil samples with different wax contents are compounded with the separator gas samples under the condition of ensuring that the gas-oil ratio of production is not changed to obtain well streams with different wax contents;
s5, preparing formation fluid by using the live oil samples with different wax contents;
and S6, carrying out PVT experiments on formation fluids with different wax contents to obtain experimental data of the influence of the wax contents on the phase state of the high-wax-content condensate oil-gas system.
Further, in step S1, the gas sample check includes:
1) Placing a gas sample bottle containing a gas sample in an air box, vertically heating to the temperature of the separator, and keeping the temperature constant for more than 4 hours; the valve of the gas sample bottle is connected with a pressure gauge, and the reading of the pressure gauge is the gas sample pressure; the deviation between the pressure of the gas sample and the pressure of the on-site oil-gas separator is less than 5 percent, and the product is qualified;
2) And analyzing the composition of the components of the gas sample according to the GB/T13610 standard.
Further, in step S1, the oil sample inspection includes:
s11, checking the pressure of the oil bubble point of the separator
Pressurizing the separator oil sample to above the formation pressure at the formation temperature, and fully shaking to make the oil sample into a single phase; recording the reading and the pressure value of the pressure pump stably; fully shaking the sample after reducing the pressure by 1-2 Mpa each time until the pressure is stable, and recording the corresponding pressure value and the pump reading; plotting the measurement result on an arithmetic coordinate, wherein the inflection point of the curve is the pressure of the oil bubble point; the deviation between the separator oil bubble point pressure and the field separator pressure is less than 5 percent, namely the separator oil bubble point pressure is qualified;
s12, single degassing experiment of separator oil sample
Pressurizing the oil sample to a pressure above saturation pressure at the formation temperature and stirring sufficiently to make it a single phase; then transferring the monophase formation fluid sample into a PVT container; maintaining the pressure by using a metering pump, slowly and uniformly discharging a certain volume of formation fluid sample, and then measuring the oil-gas composition, the gas-oil ratio, the volume coefficient and the density of the oil layer of the separator;
s13, measuring the oil gas composition of the separator oil sample by using a Roche SY/T5779-1995;
s14, calculating the volume coefficient and the gas-oil ratio of oil in the separator
Oil in an oil tank: after being separated by an oil-gas separator, hydrocarbon fluid in the oil-gas reservoir enters an oil storage tank and is in a liquid hydrocarbon state in a balanced state with oil tank gas under the atmospheric condition;
the S14 includes the following substeps:
s141, calculating the oil volume of the oil tank:
in the formula:
V ot : volume of oil in tank, cm 3 ；
m ot Oil quality of the oil tank, g;
ρ ot : oil density of oil tank, g/cm 3 ；
S142, calculating the volume coefficient of the separator oil:
in the formula:
B os separator oil volume factor;
V os separator oil volume, cm 3 ；
S143, calculating oil sample gas of the separatorOil ratio:
in the formula:
GOR t gas-oil ratio of separator, cm 3 /cm 3 ；
T o : standard temperature, K;
P 1 day atmospheric pressure, mpa;
V 1 volume, cm, of gas emitted at room temperature and atmospheric pressure 3 ；
P o : standard pressure, mpa;
T 1 room temperature, K.
Further, in step S1, the dead oil sample inspection includes: dead oil density, average molecular weight and dead oil composition were determined as SH/T0604, SH/T0619 and SY/T5779-1995.
Further, the step S3 specifically includes the following sub-steps:
s31, adjusting and calculating the wax content of the condensate oil,
measuring the wax content of the light oil obtained in the step S2 to obtain the light oil component with the wax content of 0; from this, a wax content reduction formula can be obtained:
in the formula:
c 1 : the condensate oil contains wax content concentration, mol/ml;
v 1 : condensate volume, ml;
c 2 : after wax reduction, the wax content concentration of the oil sample is mol/ml;
v 2 : volume of light oil, ml;
according to the mass conservation law, a wax content increase formula can be obtained:
in the formula:
c 3 after wax increasing, the wax content concentration of an oil sample is mol/ml;
c 1 : the condensate oil contains wax content concentration, mol/ml;
v 3 : adding pure wax to the mixture, and then adding the volume of the mixture in the conical flask, namely ml;
m: extracting pure wax by mass g;
m: pure wax molar mass, g/mol;
condensate oil samples with different wax contents can be obtained through the above formula, and then the condensate oil samples and the separator gas sample are compounded to obtain a well fluid sample;
s32, sample preparation calculation, wherein the step S32 comprises the following substeps:
s321, correcting and calculating a gas-oil ratio;
s322, calculating the sample preparation amount;
wherein the step S321 includes the following substeps:
s3211, correcting the gas-oil ratio in field:
in the formula:
GOR c : correcting gas-oil ratio, m 3 /m 3 ；
COR f : in situ gas to oil ratio, m 3 /m 3 ；
d f : calculating the relative density of natural gas used for gas quantity on site;
Z f : calculating a natural gas deviation coefficient for gas quantity on site;
d L : the relative density of natural gas measured in a laboratory;
d L : natural gas deviation coefficient under the condition of a separator measured in a laboratory;
s3212, calculating the gas-oil ratio of the primary separator:
in the formula: GOR s : gas-oil ratio of first-stage separator, m 3 /m 3
The step S322 includes the following substeps:
s3221, preparation xcm 3 Calculating the oil quantity of the volume condensate gas flow sample:
in the formula: v op Amount of oil used under a sample dispensing member, cm 3 。
S3222, calculating gas amount of sample preparation
(1) Gas deviation coefficient under matched sample piece:
in the formula:
Z p : gas deviation coefficient under matched sample
P p : sample preparation pressure, mpa
V p Volume of high pressure gas, cm 3 ；
T p : sample preparation temperature, K;
Z 1 : the gas deviation coefficient at room temperature and atmospheric pressure is generally approximately 1;
(2) Calculating the air quantity under the matched sample piece:
in the formula:
V sg : gas consumption under matched sample, cm 3 ；
Z o : the gas deviation coefficient under standard conditions is generally considered to be approximately 1.
Further, the step S4 specifically includes the following substeps:
s41, preparing dead oil samples with different wax contents;
s42, preparing formation fluid from dead oil samples with different wax contents;
s43, transferring samples of the PVT container;
wherein the step S41 includes the following substeps:
s411, determining the wax content of dead oil according to the step S31, and then calculating according to a formula to obtain the light oil required by condensate oil with different wax contents or the amount of pure wax extracted from the same well;
s412, fully mixing the condensate oil with the light oil or the extracted pure wax of the same well, heating to 50 ℃, and continuously stirring until the mixed condensate oil is transparent and has no precipitate;
s413, determining the wax content percentage of the mixed condensate oil samples with different wax contents according to the step S31, and determining that the deviation of the wax content percentage is less than 5% compared with the theoretical calculation, namely the condensate oil samples are qualified;
the step S42 includes the following substeps:
s421, transferring the gas sample at the temperature of the separator into a piston type high-pressure container by adopting a gas booster pump method or a freezing method, and boosting the gas sample to a sample preparation pressure;
s422, cleaning the sample preparation container, and connecting;
s423, heating the two constant temperature baths to the sample preparation temperature, then evacuating the sample preparation container by using a vacuum pump until the sample preparation container reaches 133pa, and then evacuating for 30min;
s424, transferring an oil sample, calculating the required dead oil amount according to the produced gas-oil ratio, and transferring the required dead oil amount to a sample preparation container by using a double-pump method; calculating the required gas quantity and oil quantity according to the constant production gas-oil ratio in sample transfer, and then selecting dead oil with different wax contents to participate in sample transfer to obtain formation fluids with different wax contents;
s425, converting gas samples, replacing oil bottles in the two constant-temperature baths with gas bottles, keeping a constant production gas-oil ratio, calculating the required gas volume of a separator, and then converting the required gas volume of the separator into a sample preparation container by using a double-pump method;
the step S43 includes the following substeps:
s431, connecting the PVT containers;
s432, heating the sample storage device and the PVT container to the formation temperature, vacuumizing the PVT container by using a vacuum pump until 133pa is reached, and then vacuumizing for 30min;
and S433, pressurizing to the formation pressure by using a metering pump, fully stirring to enable the formation pressure to be a single phase, slowly opening valves at the sample end of the sample storage device and the PVT container end under the condition of constant formation pressure, and transferring the required sample amount into a PVT container.
Further, in the step S5, preparing formation fluids with different wax-containing live oils includes the following sub-steps:
s51, preparing live oil samples with different wax contents;
s52, preparing formation fluid by using live oil samples with different wax contents;
s53, transferring samples of the PVT container;
wherein the step S51 includes the following substeps:
s511, determining the wax content of the live oil according to the step S31, and then determining the mole fraction of the live oil component according to the step S12 to calculate the oil amount and the gas amount in a 100ml live oil sample; calculating the amount of light oil or pure wax extracted from the same well required by the live oil with different wax contents by taking the oil amount as the volume of the condensate oil;
s512, reducing the wax content of the live oil, after determining the required light oil quantity, filling the light oil into an intermediate container, connecting the intermediate container which is transferred into the live oil in advance by using a pipeline, and pressing the required light oil quantity into the live oil intermediate container by using a metering pump;
s513, increasing the wax content of the live oil, after determining the pure wax content extracted from the needed live oil, filling the needed pure wax into an intermediate container, connecting the pure wax with a vacuum pump, evacuating to 133pa, connecting a pipeline with the intermediate container which is transferred into the live oil in advance, and pressing the needed live oil into the intermediate container filled with the pure wax by a metering pump;
s514, measuring the wax content percentage of the mixed live oil samples with different wax contents according to the step S31, and determining that the deviation of the wax content percentage of the mixed live oil samples with different wax contents from the theoretical calculation is less than 5 percent to be qualified;
the step S52 includes the following sub-steps:
s521, transferring the gas sample at the temperature of the separator into a piston type high-pressure container by adopting a gas booster pump method, a freezing method or other methods, and boosting the gas sample to a sample preparation pressure;
s522, cleaning the sample preparation container and connecting;
s523, heating the two constant temperature baths to the sample preparation temperature, then evacuating the sample preparation container by using a vacuum pump until the sample preparation container reaches 133pa, and then evacuating for 30min;
s524, transferring an oil sample, calculating the required oil amount according to the produced gas-oil ratio, transferring the required oil amount into a sample preparation container by using a double-pump method, calculating the required gas amount and oil amount according to the constant produced gas-oil ratio in the sample transfer, and selecting the live oil with different wax contents to participate in the sample transfer to obtain the stratum fluids with different wax contents;
s525, transferring a gas sample, replacing oil bottles in the two constant-temperature baths with gas bottles, keeping a constant production gas-oil ratio to calculate the required gas volume of the separator, and transferring the required gas volume of the separator into a sample preparation container by a double-pump method;
the step S53 includes the following substeps:
s531, connecting the PVT containers;
s532, heating the sample storage device and the PVT container to the formation temperature, vacuumizing the PVT container for 133pa by using a vacuum pump, and then vacuumizing for 30min;
s533, pressurizing to the formation pressure by using a metering pump, and fully stirring to enable the formation pressure to be a single phase; the sample end of the sample storage device and the valve of the PVT container end are opened slowly under the condition that the formation pressure is constant, and the required sample amount is transferred into the PVT container.
Further, in step S6, the PVT experiment of formation fluids with different wax contents includes:
s61, testing a flash evaporation experiment;
s62, performing a constant volume failure experiment;
s63, testing constant mass expansion;
wherein the step S61 includes the following substeps:
s611, mixing the obtained oil gas samples with different wax contents according to the gas-oil ratio of a separator or the gas-oil ratio of on-site production, compounding well fluid by adopting a double-pump method, and stabilizing for 12 hours at the formation temperature and the formation pressure;
s612, opening a valve, flashing the well flow to a normal temperature and pressure condition, respectively measuring oil and gas products to obtain a gas-oil ratio, and then carrying out chromatographic analysis on the oil and the gas to obtain well flow components;
the step S62 includes the following substeps:
s621, transferring well flow with different wax contents into a PVT cylinder under pressure maintaining, pumping to discharge 1/5 of gas under formation pressure, metering the discharge volume and separated gas and liquid, and taking oil and gas samples to analyze the composition;
s622, reducing the pressure to saturation pressure, recording the reading of the pump after balancing for 2 hours, wherein the volume occupied by the gas in the container is equal volume;
s623, withdrawing the pump, reducing the pressure in stages, generally dividing the pressure into 6-8 stages, reducing the pressure of each stage by about 3MPa, shaking the sample for 2 hours after reducing the pressure, standing for 0.5 hour, and recording the pressure and the pump reading; opening a top valve to exhaust, simultaneously keeping pressure entering a pump, discharging to a reading of a constant volume pump, and recording gas quantity and oil quantity after the exhaust is finished, and taking an oil gas sample to analyze composition and a reverse condensate quantity;
the step S63 includes the following substeps:
s631, transferring different well fluid into the PVT cylinder in a pressure maintaining mode, changing the pressure in the PVT cylinder in a pump withdrawing mode, observing the phase change of the well fluid, and when liquid drops or white mist occur, determining the pressure as the dew point pressure;
s632, after the dew point pressure is obtained, balancing for 1h, and recording the down pressure and the pump reading; withdrawing the pump to reduce the pressure by 2MPa of pressure reduction, shaking the sample for 2 hours under each stage of pressure, and standing for 0.5 hour to read the pressure, the pump reading and the condensate amount; until the sample volume is expanded by a factor of 3.
Based on the technical scheme, the embodiment of the invention can at least produce the following technical effects:
(1) A set of method for testing the wax content to the high-wax-content condensate oil gas phase state is established, the reverse condensate amount and the condensate gas dew point pressure change rule of a condensate oil gas system under different wax contents are determined, and preparation is made for further researching the relation between the wax content and the phase state change of the high-wax-content condensate gas reservoir;
(2) The experimental method can quantitatively change the wax content of the condensate oil gas system under the condition of keeping the well flow components constant, and provides a more scientific test method for researching the influence of the wax content of the high-wax-content condensate gas reservoir on the condensate gas phase state change;
(3) The experimental method can provide a corresponding experimental test means for the paraffin solid phase deposition problem in a shaft, a gathering and transportation pipeline and a stratum in the process of exploiting the oil and gas field, and has certain guiding significance for formulating a reasonable development mode of the condensate gas reservoir and improving the recovery ratio.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the structures shown in the drawings without creative efforts.
FIG. 1 is a flow diagram of a separator gas take-off according to an embodiment of the present invention;
FIG. 2 is a flow chart of formation fluid sampling according to an embodiment of the present invention;
FIG. 3 is a sample transfer flow diagram of an embodiment of the invention;
FIG. 4 is a comparison of phase diagrams of different wax contents of a well;
FIG. 5 is a plot of wax content versus dew point pressure for a well;
FIG. 6 shows the amount of retrograde oil condensate for different wax concentrations in a well.
In the drawings, the names of the parts corresponding to the reference numerals are as follows:
1: a gas valve; 2: a pressure-resistant pipeline; 3: a three-way valve; 4: a valve is arranged on the sampling bottle; 5: sampling a bottle; 6: a lower valve of the sampling bottle; 7. 8: a high pressure metering pump; 9: a separator oil (or gas) sample storage bottle; 10: a sample preparation container; 11. 12: constant temperature bathing; 13: a valve; 14: a sample storage device; 15: a PVT container.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention. In addition, the technical solutions in the embodiments may be combined with each other, but must be based on the realization of the technical solutions by those skilled in the art, and when the technical solutions are contradictory or cannot be realized, the technical solutions should be considered that the combination does not exist, and the technical solutions are not within the protection scope of the present invention.
Example (b):
the invention provides a method for testing the influence of wax content on the phase state of a high-wax-content condensate oil-gas system, which comprises the following steps:
s1, sampling and checking of field separator
Separating hydrocarbon fluid of an oil-gas reservoir by an on-site oil-gas separator to obtain a gas sample and an oil sample; and checking the obtained gas sample and oil sample; obtaining liquid hydrocarbon under the atmospheric condition after degassing hydrocarbon fluid of the oil-gas reservoir once to obtain a dead oil sample, and inspecting the obtained dead oil sample;
s11, gas sample detection comprises the following steps:
s111, placing a gas sample bottle containing a gas sample in a bellows, vertically heating to the temperature of the separator, and keeping the temperature for more than 4 hours; the valve of the gas sample bottle is connected with a pressure gauge, and the reading of the pressure gauge is the gas sample pressure; the deviation between the gas sample pressure and the pressure of the on-site oil-gas separator is less than 5 percent, namely the product is qualified;
and S112, analyzing the composition of the components of the gas sample according to the GB/T13610 standard.
S21, the oil sample detection comprises the following steps:
s211, checking the pressure of the oil bubble point of the separator
Pressurizing the separator oil sample to above the formation pressure at the formation temperature, and fully shaking to make the oil sample into a single phase; recording the reading and pressure value of the pressure pump to be stable; fully shaking the sample after reducing the pressure by 1-2 Mpa each time until the pressure is stable, and recording the corresponding pressure value and the pump reading; plotting the measurement result on an arithmetic coordinate, wherein the inflection point of the curve is the pressure of the oil bubble point; the deviation between the separator oil bubble point pressure and the field separator pressure is less than 5 percent, namely the separator oil bubble point pressure is qualified;
s212, single degassing experiment of separator oil sample
Pressurizing the oil sample to a pressure above saturation pressure at the formation temperature and stirring sufficiently to make it a single phase; then transferring the monophase formation fluid sample into a PVT container; maintaining the pressure by using a metering pump, slowly and uniformly discharging a certain volume of formation fluid sample, and then measuring the oil-gas composition, the gas-oil ratio and the volume coefficient of the formation oil density of the separator;
s213, measuring the oil gas composition of the separator oil sample by using a Roche SY/T5779-1995;
s214, calculating the volume coefficient and the gas-oil ratio of the separator oil
Oil in an oil tank: after being separated by an oil-gas separator, hydrocarbon fluid in the oil-gas reservoir enters an oil storage tank and is in a liquid hydrocarbon state in a balanced state with oil tank gas under the atmospheric condition;
s2141, oil volume of the oil tank:
in the formula:
V ot : volume of oil in tank, cm 3 ；
m ot Oil quality of the oil tank, g;
ρ ot : oil density of oil tank, g/cm 3 ；
S2142, separator oil volume coefficient:
in the formula:
B os separator oil volume factor;
V os separator oil volume, cm 3 ；
S2143, gas-oil ratio of the separator oil sample:
in the formula:
GOR t gas-oil ratio of separator, cm 3 /cm 3 ；
T o : the temperature of the sample is measured at a standard temperature,K；
P 1 day atmospheric pressure, mpa;
V 1 volume of gas discharged at room temperature and atmospheric pressure, cm 3 ；
P o : standard pressure, mpa;
T 1 room temperature, K;
s13, inspection of dead oil sample
The method comprises the following steps: dead oil density, average molecular weight and dead oil composition were determined as SH/T0604, SH/T0619 and SY/T5779-1995.
S2, determining the wax content of the condensate oil, and extracting pure wax and light oil
Fractionating the condensate oil taken from the separator, and separating the light components from the heavy components and the wax components by using the difference of the volatility of each component in an oil sample; obtaining pure wax and light oil;
s3, adjusting and calculating the wax content of the condensate oil and calculating a sample preparation; the method specifically comprises the following substeps:
s31, adjusting and calculating wax content of condensate oil
Measuring the wax content of the light oil obtained in the step S2 to obtain the light oil component with the wax content of 0; from this, a wax content reduction formula can be obtained:
in the formula:
c 1 : the condensate oil contains wax content concentration, mol/ml;
v 1 : condensate volume, ml;
c 2 : after wax reduction, the wax content concentration of the oil sample is mol/ml;
v 2 : light oil volume, ml.
According to the mass conservation law, a wax content increase formula can be obtained:
in the formula:
c 3 after wax increasing, the wax content concentration of the oil sample is mol/ml;
c 1 : the condensate oil contains wax content concentration, mol/ml;
v 3 : adding pure wax to the mixture, and then adding the volume of the mixture in the conical flask, namely ml;
m: extracting pure wax mass g;
m: pure wax molar mass, g/mol.
Condensate oil samples with different wax contents can be obtained through the above formula, and then the condensate oil samples and the separator gas sample are compounded to obtain a well fluid sample;
s32, sample preparation calculation
S321, gas-oil ratio correction calculation
S3211, correcting the on-site produced gas-oil ratio:
in the formula:
GOR c : correcting gas-oil ratio, m 3 /m 3 ；
GOR f : in situ gas to oil ratio, m 3 /m 3 ；
d f : calculating the relative density of natural gas used for gas quantity on site;
Z f : calculating a natural gas deviation coefficient for gas quantity on site;
d L : the relative density of natural gas measured in a laboratory;
d L : natural gas deviation coefficient under the condition of a separator measured in a laboratory;
s3212, calculating the gas-oil ratio of the primary separator:
in the formula:
GOR s : gas-oil ratio of first-stage separator, m 3 /m 3
S322, calculating sample preparation amount
S3221, preparation xcm 3 Volume condensate flow sample oil mass calculation
In the formula:
V op oil consumption under sample preparation condition, cm 3 。
S3222, calculating gas amount of sample preparation
(1) Gas deviation coefficient under matched sample:
in the formula:
Z p : gas deviation coefficient under matched sample
P p : sample preparation pressure, mpa
V p Volume of high pressure gas, cm 3 ；
T p : sample preparation temperature, K;
Z 1 : the coefficient of deviation of gas at room temperature and atmospheric pressure (generally considered to be approximately 1).
(2) Calculating the gas quantity under the matched sample piece:
in the formula:
V sg : gas consumption under matched sample, cm 3 ；
Z o : the gas deviation coefficient under standard conditions is generally considered to be approximately 1.
S4, preparing formation fluid from dead oil samples with different wax contents
The condensate oil sample is mixed with light oil and pure wax extracted from the same well to change the wax content of the condensate oil, and then the condensate oil samples with different wax contents are compounded with the separator gas sample under the condition of ensuring that the gas-oil ratio of production is unchanged to obtain well streams with different wax contents; the method specifically comprises the following substeps:
s41, preparation of dead oil samples with different wax contents
S411, determining the wax content of dead oil according to the step S31, and then calculating according to a formula to obtain the light oil required by condensate oil with different wax contents or the amount of pure wax extracted from the same well;
s412, fully mixing the condensate oil with the light oil or the extracted pure wax of the same well, heating to 50 ℃, and continuously stirring until the mixed condensate oil is transparent and has no precipitate;
s413, determining the wax content percentage of the mixed condensate oil samples with different wax contents according to the step S31, and determining that the deviation of the wax content percentage is less than 5% compared with the theoretical calculation, namely the condensate oil samples are qualified;
s42, preparing formation fluid by using dead oil samples with different wax contents
S421, transferring the gas sample at the temperature of the separator into a piston type high-pressure container by adopting a gas booster pump method or a freezing method, and boosting the gas sample to a sample preparation pressure;
s422, cleaning the sample preparation container, and connecting according to the figure 1;
s423, heating the two constant temperature baths to the sample preparation temperature, then evacuating the sample preparation container by using a vacuum pump until the sample preparation container reaches 133pa, and then evacuating for 30min;
s424, transferring an oil sample, calculating the required dead oil amount according to the produced gas-oil ratio, and transferring the required dead oil amount to a sample preparation container by using a double-pump method; calculating the required gas quantity and oil quantity according to the constant production gas-oil ratio in sample transfer, and then selecting dead oil with different wax contents to participate in sample transfer to obtain formation fluids with different wax contents;
s425, converting gas samples, replacing oil bottles in the two constant-temperature baths with gas bottles, keeping a constant production gas-oil ratio, calculating the required gas volume of a separator, and then converting the required gas volume of the separator into a sample preparation container by using a double-pump method;
s43, PVT container transfer
S431, connecting the PVT containers according to the graph 3;
s432, heating the sample storage device and the PVT container to the formation temperature, vacuumizing the PVT container by using a vacuum pump until 133pa is reached, and then vacuumizing for 30min;
and S433, pressurizing to the formation pressure by using a metering pump, fully stirring to enable the formation pressure to be a single phase, slowly opening valves at the sample end of the sample storage device and the PVT container end under the condition of constant formation pressure, and transferring the required sample amount into the PVT container.
S5, preparing formation fluid by using live oil samples with different wax contents; the method specifically comprises the following substeps:
s51, preparation of live oil samples with different wax contents
S511, determining the wax content of the live oil according to the step S31, and then determining the mole fraction of the live oil component according to the step S12 to calculate the oil amount and the gas amount in a 100ml live oil sample; calculating the amount of light oil or pure wax extracted from the same well required by the live oil with different wax contents by taking the oil amount as the volume of the condensate oil;
s512, reducing the wax content of the live oil, after determining the required light oil quantity, filling the light oil into an intermediate container, connecting the intermediate container which is transferred into the live oil in advance by using a pipeline, and pressing the required light oil quantity into the live oil intermediate container by using a metering pump;
s513, increasing the wax content of the live oil, after determining the pure wax content extracted from the needed live oil, filling the needed pure wax into an intermediate container, connecting the intermediate container with a vacuum pump to pump out 133pa of the pure wax, connecting a pipeline with the intermediate container which is shifted into the live oil in advance, and pressing the needed live oil into the intermediate container filled with the pure wax by using a metering pump;
s514, measuring the wax content percentage of the mixed live oil samples with different wax contents according to the step S31, and determining that the deviation of the wax content percentage of the mixed live oil samples with different wax contents from the theoretical calculation is less than 5 percent to be qualified;
s52, preparing formation fluid by using live oil samples with different wax contents
S521, transferring the gas sample at the temperature of the separator into a piston type high-pressure container by adopting a gas booster pump method, a freezing method or other methods, and boosting the gas sample to a sample preparation pressure;
s522, cleaning the sample preparation container, and connecting according to the figure 2;
s523, heating the two constant temperature baths to the sample preparation temperature, then evacuating the sample preparation container by using a vacuum pump until the sample preparation temperature reaches 133pa, and then pumping for 30min;
s524, transferring an oil sample, calculating the required oil amount according to the produced gas-oil ratio, transferring the required oil amount into a sample preparation container by using a double-pump method, calculating the required gas amount and oil amount according to the constant produced gas-oil ratio in the sample transfer, and selecting the oil with different wax contents to participate in the sample transfer to obtain the stratum fluids with different wax contents;
s525, converting gas samples, replacing oil bottles in the two constant temperature baths with gas bottles, keeping constant production gas-oil ratio, calculating the required gas flow of the separator, and then converting the required gas flow of the separator into a sample preparation container by a double-pump method;
s53, sample transfer of PVT container
S531, connecting the PVT containers according to the graph 3;
s532, heating the sample storage device and the PVT container to the formation temperature, vacuumizing the PVT container by using a vacuum pump until 133pa is reached, and then vacuumizing for 30min;
s533, pressurizing to the formation pressure by using a metering pump, and fully stirring to form a single phase; and slowly opening the valves at the sample end of the sample storage device and the PVT container end under the condition of constant formation pressure, and transferring the required sample amount into the PVT container.
S6, carrying out PVT experiments on formation fluids with different wax contents to obtain experimental data of the influence of the wax contents on the phase state of the high-wax-content condensate oil-gas system; the PVT experiment specifically included:
s61, flash evaporation experiment test
S611, mixing the obtained oil gas samples with different wax contents according to the gas-oil ratio of a separator or the gas-oil ratio of on-site production, compounding well fluid by adopting a double-pump method, and stabilizing for 12 hours at the formation temperature and the formation pressure;
s612, opening a valve, flashing the well fluid to the normal temperature and pressure, respectively measuring oil and gas products to obtain a gas-oil ratio, and then carrying out chromatographic analysis on the oil and gas to obtain well fluid components;
s62, constant volume exhaustion experiment
S621, transferring well flow with different wax contents into a PVT cylinder under pressure maintaining, pumping to discharge 1/5 of gas under formation pressure, metering the discharge volume and separated gas and liquid, and taking oil and gas samples to analyze the composition;
s622, reducing the pressure to saturation pressure, recording the reading of the pump after balancing for 2 hours, wherein the volume occupied by the gas in the container is equal volume;
s623, withdrawing the pump, reducing the pressure in stages, generally dividing the pressure into 6-8 stages, reducing the pressure of each stage by about 3MPa, shaking the sample for 2 hours after reducing the pressure, standing for 0.5 hour, and recording the pressure and the pump reading; opening a top valve to exhaust, simultaneously keeping the pressure in a pump, discharging to a reading of a constant volume pump, and recording the gas quantity and the oil quantity after the exhaust is finished, and taking an oil-gas sample to analyze the composition and the quantity of the reverse condensate;
s63, constant Mass expansion test
S631, pressure maintaining of different well fluids is transferred to the PVT cylinder, the pressure in the PVT cylinder is changed in a pump withdrawing mode, phase state change of the well fluids is observed, and when liquid drops or white mist appears, the pressure is the dew point pressure;
s632, after the dew point pressure is obtained, balancing for 1h, and recording the down pressure and the pump reading; withdrawing the pump to reduce the pressure by 2MPa of pressure reduction, shaking the sample for 2 hours under each stage of pressure, and standing for 0.5 hour to read the pressure, the pump reading and the condensate amount; until the sample volume is expanded by a factor of 3.
AX well oil samples were prepared by the method of example 1 at constant gas-oil ratio using condensate oil samples of different wax contents and separator gas samples to obtain well fluid samples of 7.43%, 5.84%, 3.68% and 1.84% wax contents, and the experiments were carried out according to GB/T26981-2020 standard.
1. Flash evaporation experiment
And (3) rapidly reducing the pressure of the compounded well fluid samples with different wax contents to normal pressure, measuring the gas-oil ratio, and analyzing oil-gas components. The results are shown in table 1 below:
TABLE 1 analysis data of the composition of the stream from different wells containing wax
2. Constant mass expansion experiment
The pressure in the PVT cylinder is changed in a pump withdrawing mode in the PVT cylinder, so that the dew point pressure of well flow with different wax contents is observed, and high-pressure physical parameters such as a deviation factor, a volume coefficient, density, a compression coefficient and the like of natural gas are obtained. As shown in fig. 4 and 5, it is found through a large amount of experimental data that the lower the wax content, the lower the dew point pressure.
3. Constant volume exhaustion test
The purpose of the constant volume failure experiment is to simulate parameters such as the change of condensate saturation and the condensate extraction degree in the failure development process. And changing the pressure in the PVT cylinder in a pump withdrawing mode in the PVT cylinder, and discharging gas after each stage of pressure drop to obtain parameters such as the change of condensate saturation in the failure development process, the well fluid composition and the condensate extraction degree in the extraction process. It was found by experimental tests that the higher the wax content, the higher the retrograde condensate saturation as shown in fig. 6.
The foregoing shows and describes the general principles and broad features of the present invention and advantages thereof. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.
Claims (8)
1. The method for testing the influence of the wax content on the phase state of the high-wax-content condensate oil-gas system is characterized by comprising the following steps of:
s1, sampling and checking of field separator
Separating hydrocarbon fluid in an oil-gas reservoir through an on-site oil-gas separator to obtain a gas sample and an oil sample; and inspecting the obtained gas sample and oil sample; obtaining liquid hydrocarbon under the atmospheric condition after degassing hydrocarbon fluid of the oil-gas reservoir once to obtain a dead oil sample, and inspecting the obtained dead oil sample;
s2, determining the wax content of the condensate oil, and extracting pure wax and light oil
Fractionating the condensate oil extracted by the oil-gas separator, and separating light components from heavy components and wax components by using the volatility difference of each component in an oil sample; obtaining pure wax and light oil;
s3, adjusting and calculating the wax content of the condensate oil and calculating a sample preparation;
s4, preparing formation fluid from dead oil samples with different wax contents
The condensate oil sample is mixed with light oil and pure wax extracted from the same well to change the wax content of the condensate oil, and then the condensate oil samples with different wax contents are compounded with the separator gas sample under the condition of ensuring that the gas-oil ratio of production is unchanged to obtain well streams with different wax contents;
s5, preparing formation fluid by using the live oil samples with different wax contents;
and S6, carrying out PVT experiments on formation fluids with different wax contents to obtain experimental data of the influence of the wax contents on the phase state of the high-wax-content condensate oil-gas system.
2. The method for testing the influence of the wax content on the phase state of the high-wax-content condensate oil-gas system according to claim 1, wherein the gas sample inspection in the step S1 comprises:
1) Placing a gas sample bottle containing a gas sample in an air box, vertically heating to the temperature of the separator, and keeping the temperature constant for more than 4 hours; the valve of the gas sample bottle is connected with a pressure gauge, and the reading of the pressure gauge is the gas sample pressure; the deviation between the gas sample pressure and the pressure of the on-site oil-gas separator is less than 5 percent, namely the product is qualified;
2) And analyzing the composition of the components of the gas sample according to the GB/T13610 standard.
3. The method for testing the influence of the wax content on the phase state of the high-wax-content condensate oil-gas system according to claim 1, wherein the step S1 of checking the oil sample comprises the following steps:
s11, checking the pressure of the oil bubble point of the separator
Pressurizing the separator oil sample to above the formation pressure at the formation temperature, and fully shaking to make the oil sample into a single phase; recording the reading and pressure value of the pressure pump to be stable; fully shaking the sample after reducing the pressure by 1-2 Mpa each time until the pressure is stable, and recording the corresponding pressure value and the pump reading; plotting the measurement result on an arithmetic coordinate, wherein the inflection point of the curve is the pressure of the oil bubble point; the deviation between the separator oil bubble point pressure and the field separator pressure is less than 5 percent, namely the separator oil bubble point pressure is qualified;
s12 single degassing experiment of separator oil sample
Pressurizing the oil sample to above saturation pressure and stirring sufficiently at the formation temperature to make it a single phase; then transferring the monophase formation fluid sample into a PVT container; maintaining the pressure by using a metering pump, slowly and uniformly discharging a certain volume of formation fluid sample, and then measuring the oil-gas composition, the gas-oil ratio, the volume coefficient and the density of the oil layer of the separator;
s13, measuring the oil gas composition of the separator oil sample by using a Roche SY/T5779-1995;
s14, calculating the volume coefficient and the gas-oil ratio of the separator oil
Oil in an oil tank: after being separated by an oil-gas separator, hydrocarbon fluid in the oil-gas reservoir enters an oil storage tank and is in a liquid hydrocarbon state in a balanced state with oil tank gas under the atmospheric condition;
the S14 includes the following substeps:
s141, calculating the oil volume of the oil tank:
in the formula:
V ot : oil volume, cm, of the tank 3 ；
m ot : oil quality of the oil tank, g;
ρ ot : oil density of oil tank, g/cm 3 ；
S142, calculating the volume coefficient of the separator oil:
in the formula:
B os : separator oil volume factor;
V os : separator oil volume, cm 3 ；
S143, calculating the gas-oil ratio of the separator oil sample:
in the formula:
GOR t : gas-oil ratio, cm, of the separator 3 /cm 3 ；
T o : standard temperature, K;
P 1 : day atmospheric pressure, mpa;
V 1 : volume of gas evolved at room temperature and atmospheric pressure, cm 3 ；
P o : standard pressure, mpa;
T 1 : room temperature, K.
4. The method for testing the influence of the wax content on the phase state of the high-wax-content condensate oil and gas system according to claim 1, wherein in the step S1, the dead oil sample inspection comprises the following steps: dead oil density, average molecular weight and dead oil composition were determined as SH/T0604, SH/T0619 and SY/T5779-1995.
5. The method for testing the influence of the wax content on the phase state of the high-wax-content condensate oil-gas system according to claim 1, wherein the step S3 specifically comprises the following substeps:
s31, adjusting and calculating the wax content of the condensate oil,
measuring the wax content of the light oil obtained in the step S2 to obtain the light oil component with the wax content of 0; from this, the wax content reduction formula can be obtained:
in the formula:
c 1 : the condensate oil contains wax content concentration, mol/ml;
v 1 : condensate volume, ml;
c 2 : after wax reduction, the wax content concentration of the oil sample is mol/ml;
v 2 : volume of light oil, ml;
according to the mass conservation law, a wax content increase formula can be obtained:
in the formula:
c 3 : after wax is increased, the wax content concentration of the oil sample is mol/ml;
c 1 : the condensate oil contains wax content concentration, mol/ml;
v 3 : adding pure wax to the mixture, and then adding the volume of the mixture in the conical flask, namely ml;
m: extracting pure wax mass g;
m: pure wax molar mass, g/mol;
condensate oil samples with different wax contents can be obtained through the above formula, and then the condensate oil samples and the separator gas sample are compounded to obtain a well fluid sample;
s32, sample preparation calculation, wherein the step S32 comprises the following substeps:
s321, correcting and calculating a gas-oil ratio;
s322, calculating the sample preparation amount;
wherein the step S321 includes the following substeps:
s3211, correcting the on-site produced gas-oil ratio:
in the formula:
GOR c : correcting gas-oil ratio, m 3 /m 3 ；
GOR f : on-site gas-oil ratio, m 3 /m 3 ；
d f : calculating the relative density of natural gas used for gas quantity on site;
Z f : calculating a natural gas deviation coefficient for gas quantity on site;
d L : measuring the relative density of natural gas in a laboratory;
d L : natural gas deviation coefficient under the condition of a separator measured in a laboratory;
s3212, calculating the gas-oil ratio of the primary separator:
in the formula: GOR s : gas-oil ratio of the first separator, m 3 /m 3
The step S322 includes the following substeps:
s3221, preparation xcm 3 Calculating the oil quantity of the volume condensate gas flow sample:
in the formula: v op : amount of oil used in cm under a sample fitting 3 。
S3222, calculating gas amount of sample preparation
(1) Gas deviation coefficient under matched sample piece:
in the formula:
Z p : gas deviation coefficient under matched sample
P p : sample preparation pressure, mpa
V p : volume of high pressure gas, cm 3 ；
T p : sample preparation temperature, K;
Z 1 : the gas deviation coefficient at room temperature and atmospheric pressure is generally approximately 1;
(2) Calculating the gas quantity under the matched sample piece:
in the formula:
V sg : gas consumption in cm under matched sample 3 ；
Z o : the gas deviation coefficient under standard conditions is generally considered to be approximately 1.
6. The method for testing the influence of the wax content on the phase state of the high-wax-content condensate oil-gas system according to claim 1, wherein the step S4 specifically comprises the following substeps:
s41, preparing dead oil samples with different wax contents;
s42, preparing formation fluid from the dead oil samples with different wax contents;
s43, transferring samples of the PVT container;
wherein the step S41 includes the following substeps:
s411, determining the wax content of dead oil according to the step S31, and then calculating according to a formula to obtain the light oil required by condensate oil with different wax contents or the amount of pure wax extracted from the same well;
s412, fully mixing the condensate oil with the light oil or the extracted pure wax of the same well, heating to 50 ℃, and continuously stirring until the mixed condensate oil is transparent and has no precipitate;
s413, determining the wax content percentage of the mixed condensate oil samples with different wax contents according to the step S31, and determining that the deviation of the wax content percentage is less than 5% compared with the theoretical calculation, namely the condensate oil samples are qualified;
the step S42 includes the following substeps:
s421, transferring the gas sample at the temperature of the separator into a piston type high-pressure container by adopting a gas booster pump method or a freezing method, and boosting the gas sample to a sample preparation pressure;
s422, cleaning the sample preparation container, and connecting;
s423, heating the two constant temperature baths to the sample preparation temperature, then pumping out the sample preparation container by using a vacuum pump for 30min after 133 pa;
s424, transferring an oil sample, calculating the required dead oil amount according to the produced gas-oil ratio, and transferring the required dead oil amount into a sample preparation container by using a double-pump method; calculating the required gas quantity and oil quantity according to the constant gas-oil ratio in sample transfer, and then selecting dead oil with different wax contents to participate in sample transfer to obtain formation fluids with different wax contents;
s425, converting gas samples, replacing oil bottles in the two constant-temperature baths with gas bottles, keeping a constant production gas-oil ratio, calculating the required gas volume of a separator, and then converting the required gas volume of the separator into a sample preparation container by using a double-pump method;
the step S43 includes the following substeps:
s431, connecting the PVT containers;
s432, heating the sample storage device and the PVT container to the formation temperature, vacuumizing the PVT container by using a vacuum pump until 133pa is reached, and then vacuumizing for 30min;
and S433, pressurizing to the formation pressure by using a metering pump, fully stirring to enable the formation pressure to be a single phase, slowly opening valves at the sample end of the sample storage device and the PVT container end under the condition of constant formation pressure, and transferring the required sample amount into a PVT container.
7. The method for testing the influence of wax content on the phase state of a high wax content condensate oil and gas system according to claim 1, wherein the step S5 of preparing formation fluid by using different wax content live oil comprises the following substeps:
s51, preparing live oil samples with different wax contents;
s52, preparing formation fluid by using the live oil samples with different wax contents;
s53, transferring samples of the PVT container;
wherein the step S51 includes the following substeps:
s511, determining the wax content of the live oil according to the step S31, and then determining the mole fraction of the live oil component according to the step S12 to calculate the oil content and the gas content in a 100ml live oil sample; calculating the amount of light oil or pure wax extracted from the same well required by the live oil with different wax contents by taking the oil amount as the volume of the condensate oil;
s512, reducing the wax content of the live oil, after determining the required light oil quantity, filling the light oil into an intermediate container, connecting the intermediate container which is shifted into the live oil in advance by using a pipeline, and pressing the required light oil quantity into the live oil intermediate container by using a metering pump;
s513, increasing the wax content of the live oil, after determining the pure wax content extracted from the needed live oil, filling the needed pure wax into an intermediate container, connecting the pure wax with a vacuum pump, evacuating to 133pa, connecting a pipeline with the intermediate container which is transferred into the live oil in advance, and pressing the needed live oil into the intermediate container filled with the pure wax by a metering pump;
s514, measuring the wax content percentage of the mixed live oil samples with different wax contents according to the step S31, and determining that the wax content percentage deviation is less than 5% from the theoretical wax content percentage deviation, namely the wax content is qualified;
the step S52 includes the following substeps:
s521, transferring the gas sample at the temperature of the separator into a piston type high-pressure container by adopting a gas booster pump method, a freezing method or other methods, and boosting the gas sample to a sample preparation pressure;
s522, cleaning the sample preparation container and connecting;
s523, heating the two constant temperature baths to the sample preparation temperature, then evacuating the sample preparation container by using a vacuum pump until the sample preparation container reaches 133pa, and then evacuating for 30min;
s524, transferring an oil sample, calculating the required oil amount according to the produced gas-oil ratio, transferring the required oil amount into a sample preparation container by using a double-pump method, calculating the required gas amount and oil amount according to the constant produced gas-oil ratio in the sample transfer, and selecting the oil with different wax contents to participate in the sample transfer to obtain the stratum fluids with different wax contents;
s525, transferring a gas sample, replacing oil bottles in the two constant-temperature baths with gas bottles, keeping a constant production gas-oil ratio to calculate the required gas volume of the separator, and transferring the required gas volume of the separator into a sample preparation container by a double-pump method;
the step S53 includes the following substeps:
s531, connecting PVT containers;
s532, heating the sample storage device and the PVT container to the formation temperature, vacuumizing the PVT container by using a vacuum pump until 133pa is reached, and then vacuumizing for 30min;
s533, pressurizing to the formation pressure by using a metering pump, and fully stirring to enable the formation pressure to be a single phase; and slowly opening the valves at the sample end of the sample storage device and the PVT container end under the condition of constant formation pressure, and transferring the required sample amount into the PVT container.
8. The method for testing the influence of the wax content on the phase state of the high-wax-content condensate oil-gas system according to claim 1, wherein in the step S6, the PVT experiment of the formation fluids with different wax contents comprises the following steps:
s61, testing a flash evaporation experiment;
s62, performing a constant volume failure experiment;
s63, testing constant mass expansion;
wherein the step S61 includes the following substeps:
s611, preparing the obtained oil-gas samples with different wax contents according to the gas-oil ratio of a separator or the gas-oil ratio of on-site production, compounding well flow materials by adopting a double-pump method, and stabilizing for 12 hours at the formation temperature and the formation pressure;
s612, opening a valve, flashing the well flow to a normal temperature and pressure condition, respectively measuring oil and gas products to obtain a gas-oil ratio, and then carrying out chromatographic analysis on the oil and the gas to obtain well flow components;
the step S62 includes the following substeps:
s621, transferring well flow with different wax contents into a PVT cylinder under pressure maintaining, pumping to discharge 1/5 of gas under formation pressure, metering the discharge volume and separated gas and liquid, and taking oil and gas samples to analyze the composition;
s622, reducing the pressure to saturation pressure, recording the reading of the pump after balancing for 2 hours, wherein the volume occupied by the gas in the container is equal volume;
s623, withdrawing the pump, reducing the pressure in stages, generally dividing the pressure into 6-8 stages, reducing the pressure of each stage by about 3MPa, shaking the sample for 2 hours after reducing the pressure, standing for 0.5 hour, and recording the pressure and the pump reading; opening a top valve to exhaust, simultaneously keeping the pressure in a pump, discharging to a reading of a constant volume pump, and recording the gas quantity and the oil quantity after the exhaust is finished, and taking an oil-gas sample to analyze the composition and the quantity of the reverse condensate;
the step S63 includes the following substeps:
s631, transferring different well fluid into the PVT cylinder in a pressure maintaining mode, changing the pressure in the PVT cylinder in a pump withdrawing mode, observing the phase change of the well fluid, and when liquid drops or white mist occur, determining the pressure as the dew point pressure;
s632, after the dew point pressure is obtained, balancing for 1h, and recording the down pressure and the pump reading; withdrawing the pump to reduce the pressure by 2MPa of pressure reduction, shaking the sample for 2 hours under each stage of pressure, and standing for 0.5 hour to read the pressure, the pump reading and the condensate amount; until the sample volume is expanded by a factor of 3.
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