CN114965140B - Method for correcting saturation of oil and water by airtight coring of active oil reservoir - Google Patents
Method for correcting saturation of oil and water by airtight coring of active oil reservoir Download PDFInfo
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- 239000011435 rock Substances 0.000 claims abstract description 135
- 238000012360 testing method Methods 0.000 claims abstract description 109
- 238000007872 degassing Methods 0.000 claims abstract description 48
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- 238000006073 displacement reaction Methods 0.000 claims abstract description 14
- 238000007667 floating Methods 0.000 claims abstract description 10
- 239000003921 oil Substances 0.000 claims description 84
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 20
- 229920006395 saturated elastomer Polymers 0.000 claims description 15
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- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 6
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Abstract
The invention provides a method for correcting the saturation of oil and water in a sealed coring process of a living oil reservoir. The method for correcting the saturation of the closed coring oil and water of the living oil reservoir comprises the following steps: selecting a test rock sample, and measuring the total volume V1 and the mass M1 of the test rock sample; calculating the porosity and the pore volume V2 of the rock sample according to the total volume V1, the mass M2 and the floating weight M3 of the test rock sample; taking out the test rock sample from the displacement device clamp and measuring the mass M4 and the volume V3 of the displaced brine; according to the mass M4 of the test rock sample and the volume V3 of the expelled brine, the oil saturation and the water saturation of the test rock sample are calculated respectively; placing the test rock sample into a clamp of a depressurization degasser, and calculating the gas-oil ratio of the test rock sample; and taking out the test rock sample from the clamp of the depressurization degasser, measuring the mass M5 of the clamp, and calculating the mass M7 of the residual moisture in the test rock sample. The invention solves the problem that the prior art does not have a method for simulating the influence of formation pressure on depressurization and degassing and carrying out a physical model experiment to correct.
Description
Technical Field
The invention relates to the technical field of petroleum and natural gas matching, in particular to a method for correcting the saturation of oil and water by airtight coring of a living oil reservoir.
Background
The oil and water saturation in the reservoir directly reflects the oil and water content in the effective reservoir space in the reservoir, is an important parameter of the oil and gas properties of the reservoir, and is also a basic parameter for estimating the oil reserves and judging the liquid production properties and flooding conditions of the reservoir. Therefore, the evaluation thereof is one of the important contents of exploration and development of oil and gas.
Typically, a live oil reservoir containing dissolved gas will have a reduced oil-water saturation when cored to the surface due to depressurization and degassing, such that the sum of the oil-water saturation is less than 100%. Therefore, it is necessary to perform the depressurization and the degassing correction. The conventional method has the defects that the influence of formation pressure (gas-oil ratio) on depressurization and degassing is not simulated, and an object model experiment is carried out to correct the influence, and the technology is deficient. Therefore, it is necessary to experimentally establish a closed coring oil-water saturation correction method for the depressurization and degassing process under the condition of simulating the formation pressure (gas-oil ratio) so as to accurately obtain the true fluid saturation value of the formation.
The prior art has the problem that no method for simulating the influence of formation pressure on depressurization and degassing and carrying out a physical model experiment to correct is available.
Disclosure of Invention
The invention mainly aims to provide a method for correcting the saturation of oil and water in a sealed coring mode of a living oil reservoir, which aims to solve the problem that the prior art does not have a method for simulating the influence of formation pressure on depressurization and degassing and carrying out a physical model experiment to correct.
In order to achieve the above object, according to one aspect of the present invention, there is provided a method for correcting the saturation of oil and water in a closed core of a living oil reservoir, comprising: selecting a test rock sample, and measuring the total volume V1 and the mass M1 of the test rock sample; vacuumizing the test rock sample and then saturating stratum brine; measuring the mass M2 and the floating weight M3 of a test rock sample after saturated stratum brine; calculating the porosity and the pore volume V2 of the rock sample according to the total volume V1, the mass M2 and the floating weight M3 of the test rock sample; placing the test rock sample after saturated stratum brine into a displacement device clamp holder, and displacing stratum crude oil; taking out the test rock sample from the displacement device clamp and measuring the mass M4 and the volume V3 of the displaced brine; according to the mass M4 of the test rock sample and the volume V3 of the expelled brine, the oil saturation and the water saturation of the test rock sample are calculated respectively; placing the test rock sample into a clamp of a depressurization degasser, and calculating the gas-oil ratio of the test rock sample; taking out the test rock sample, clamping the depressurization degasser, measuring the mass M5 of the clamp, and calculating the mass M7 of the residual moisture in the test rock sample; calculating the water saturation of the test rock sample after depressurization and degassing; calculating the oil saturation of the loss of the test rock sample after depressurization and degassing; calculating the oil saturation of the test rock sample after depressurization and degassing; and (5) establishing a correction model.
Further, after the test rock sample is removed from the displacement device holder, the surface of the test rock sample needs to be wiped dry.
Further, after the test rock sample is placed in the depressurization degasser holder, a test gas is introduced into the depressurization degasser holder.
Further, the test gas is methane.
Further, an over-pressure is added to the depressurization degasser prior to introducing the test gas to the depressurization degasser holder.
Further, after the test gas is introduced into the depressurization degasser holder, the depressurization degasser is pressurized to the pore pressure.
Further, when the pump volume reading of the depressurization degasser is unchanged, the coring barrel lifting process is simulated for the test rock sample.
Further, in the process of simulating the lifting process of the core barrel, the pressure is reduced under the condition of ensuring that the effective pressure and the temperature are unchanged.
Further, after obtaining the mass M5 of the test rock sample, mashing the test rock sample in a mortar, pouring absolute ethyl alcohol into the mortar, sealing the mortar, extracting water in the test rock sample, extracting an extract by a sample injector, injecting the extract into a micro-moisture tester, measuring the water mass, and calculating the residual water mass M7 of the rock sample.
By applying the technical scheme of the application, the method for correcting the closed coring oil-water saturation of the active oil reservoir comprises the following steps: selecting a test rock sample, and measuring the total volume V1 and the mass M1 of the test rock sample; vacuumizing the test rock sample and then saturating stratum brine; measuring the mass M2 and the floating weight M3 of a test rock sample after saturated stratum brine; calculating the porosity and the pore volume V2 of the rock sample according to the total volume V1, the mass M2 and the floating weight M3 of the test rock sample; placing the test rock sample after saturated stratum brine into a displacement device clamp holder, and displacing stratum crude oil; taking out the test rock sample from the displacement device clamp and measuring the mass M4 and the volume V3 of the displaced brine; according to the mass M4 of the test rock sample and the volume V3 of the expelled brine, the oil saturation and the water saturation of the test rock sample are calculated respectively; placing the test rock sample into a clamp of a depressurization degasser, and calculating the gas-oil ratio of the test rock sample; taking out the test rock sample, clamping the depressurization degasser, measuring the mass M5 of the clamp, and calculating the mass M7 of the residual moisture in the test rock sample; calculating the water saturation of the test rock sample after depressurization and degassing; calculating the oil saturation of the loss of the test rock sample after depressurization and degassing; calculating the oil saturation of the test rock sample after depressurization and degassing; and (5) establishing a correction model.
The method for correcting the oil-water saturation of the closed coring of the living oil reservoir can be used for selecting a batch of rock samples with different porosities for a certain oil reservoir, the process of lifting, reducing and degassing the coring barrel under different stratum pressure conditions is physically simulated by a laboratory, the change of the oil-water saturation and the water-saturation is experimentally measured in advance (before reducing and degassing) and after lifting (after reducing and degassing), and the statistical relationship between the change of the oil-water saturation and the water-saturation and the porosity, saturation and stratum pressure of the rock samples is established as a correction model of the oil-water saturation.
Drawings
The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the application. In the drawings:
FIG. 1 illustrates a flow chart of a method of live oil reservoir closed core oil-water saturation correction in accordance with one embodiment of the present invention;
FIG. 2 illustrates a chart of oil porosity versus oil saturation reduction in an embodiment of the present application;
FIG. 3 shows a plot of pore pressure versus oil saturation reduction for one of the oil porosities of the present application;
FIG. 4 shows a plot of pore pressure versus oil saturation reduction for another oil porosity of the present application;
FIG. 5 shows a plot of pore pressure versus oil saturation reduction for another oil porosity of the present application.
Detailed Description
It should be noted that, without conflict, the embodiments of the present application and features of the embodiments may be combined with each other. The application will be described in detail below with reference to the drawings in connection with embodiments.
It is noted that all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs unless otherwise indicated.
In the present invention, unless otherwise indicated, terms of orientation such as "upper, lower, top, bottom" are used generally with respect to the orientation shown in the drawings or with respect to the component itself in the vertical, upright or gravitational direction; also, for ease of understanding and description, "inner and outer" refers to inner and outer relative to the profile of each component itself, but the above-mentioned orientation terms are not intended to limit the present invention.
The application provides a method for correcting the closed coring oil-water saturation of a living oil reservoir, which aims to solve the problem that the prior art does not have a method for simulating the influence of formation pressure on depressurization and degasification and carrying out a physical model experiment to correct.
As shown in fig. 1, the method for correcting the closed coring oil-water saturation of the active oil reservoir comprises the following steps: selecting a test rock sample, and measuring the total volume V1 and the mass M1 of the test rock sample; vacuumizing the test rock sample and then saturating stratum brine; measuring the mass M2 and the floating weight M3 of a test rock sample after saturated stratum brine; calculating the porosity and the pore volume V2 of the rock sample according to the total volume V1, the mass M2 and the floating weight M3 of the test rock sample; placing the test rock sample after saturated stratum brine into a displacement device clamp holder, and displacing stratum crude oil; taking out the test rock sample from the displacement device clamp and measuring the mass M4 and the volume V3 of the displaced brine; according to the mass M4 of the test rock sample and the volume V3 of the expelled brine, the oil saturation and the water saturation of the test rock sample are calculated respectively; placing the test rock sample into a clamp of a depressurization degasser, and calculating the gas-oil ratio of the test rock sample; taking out the test rock sample, clamping the depressurization degasser, measuring the mass M5 of the clamp, and calculating the mass M7 of the residual moisture in the test rock sample; calculating the water saturation of the test rock sample after depressurization and degassing; calculating the oil saturation of the loss of the test rock sample after depressurization and degassing; calculating the oil saturation of the test rock sample after depressurization and degassing; and (5) establishing a correction model.
Wherein M2 is saturated water mass.
The method for correcting the oil-water saturation of the closed coring of the living oil reservoir can be used for selecting a batch of rock samples with different porosities for a certain oil reservoir, the process of lifting, reducing and degassing the coring barrel under different stratum pressure conditions is physically simulated by a laboratory, the change of the oil-water saturation and the water-saturation is experimentally measured in advance (before reducing and degassing) and after lifting (after reducing and degassing), and the statistical relationship between the change of the oil-water saturation and the water-saturation and the porosity, saturation and stratum pressure of the rock samples is established as a correction model of the oil-water saturation.
Specifically, after the test rock sample is removed from the displacement device holder, the surface of the test rock sample needs to be wiped dry. After the test rock sample is placed in the depressurization and degasser holder, a test gas is introduced into the depressurization and degasser holder.
In one embodiment of the application, the test gas is methane.
Specifically, the overpressure is added to the depressurization degasser before the test gas is introduced into the depressurization degasser holder. After the test gas is introduced into the depressurization degasser holder, the depressurization degasser is pressurized to pore pressure. And when the reading of the pump volume of the depressurization degasser is unchanged, simulating the lifting process of the coring barrel for the test rock sample. In the process of simulating the lifting process of the coring barrel, the pressure is reduced under the condition of ensuring that the effective pressure and the temperature are unchanged. And the test rock sample is vacuumized to saturate the formation brine.
In one embodiment of the application, the effective pressure is 5MPa and the effective temperature is 25 degrees celsius. And 50000mg/L of saline was added to saturated formation brine after evacuating the test rock sample.
Specifically, after obtaining the mass M5 of the test rock sample, mashing the test rock sample in a mortar, pouring absolute ethyl alcohol into the mortar, sealing the mortar, extracting water in the test rock sample, extracting an extract by a sample injector, injecting the extract into a micro-moisture tester, measuring the water mass, and calculating the residual water mass M7 of the rock sample.
In one embodiment of the application, by selecting reservoirs, a batch of rock samples of different porosities may be selected for testing separately.
After selecting a rock sample in a target area, firstly, drying the rock sample, measuring the total volume V 1 of the rock sample, weighing the mass m 1 of the dried rock sample by an electronic balance, vacuumizing saturated stratum brine, and weighing the mass m 2 of the rock sample and the floating weight m 3 of the saturated stratum brine. The rock sample porosity Φ is:
The pore volume of the rock sample is as follows:
Secondly, placing a saturated brine rock sample into a displacement device clamp holder, using stratum crude oil to displace for a certain time, taking out the rock sample, wiping the surface, weighing the mass m 4, and measuring the volume V 3 of the displaced brine, wherein the oil saturation S 01 of the sample is as follows:
the water saturation was:
S w＝1-So1 formula (4)
And thirdly, placing the rock sample into a clamp holder of a depressurization and degassing device, adding an overburden pressure, introducing methane gas into two ends of the clamp holder, pressurizing to a certain pore pressure, and standing for a period of time until the reading of the pump body is not changed any more, and considering that the methane gas is saturated and dissolved in crude oil to prepare the live oil core. The core barrel up-take process was then simulated and the effective pressure and temperature were maintained constant and slowly depressurized. Then, at this time, the gas-oil ratio R s in the sample is:
Wherein X T is the weight fraction of hydrocarbons in the crude oil; m T is the average molecular weight of hydrocarbons in crude oil; ρ 0 is the crude oil density; p is the gas pressure; k is the gas dissolution equilibrium constant; alpha is the secondary coefficient of action and is temperature dependent. Wherein, when the methane gas is at 25 ℃, lnk= -16.77, alpha= -0.0564.
The overburden pressure, pore pressure and differential effective pressure of a specific reservoir are determined according to the actual reservoir.
Also, as can be seen from the above equation, for a given crude oil, the gas-to-oil ratio of methane at a certain temperature is a function of pressure P, which is nearly linear, and pressure approximation can be used instead of gas-to-oil ratio in the absence of crude oil physical property data.
And then, wiping the surface of the rock sample taken out after depressurization and degassing, weighing the mass m 5, mashing the rock core by using a mortar, pouring absolute ethyl alcohol with the volume of V 4, sealing the mortar, and extracting for about 2 hours. The extract of volume V 5 was extracted by an injector and injected into a micro-moisture meter to measure moisture mass m 6. The mass m 7 of remaining moisture in the rock sample is:
The amount of V4 is based on the absolute ethyl alcohol fully submerging the core fragments, and V5 is the sample injection amount required by analysis of the micro-moisture meter.
The water saturation of the rock sample after depressurization and deaeration S w is:
The oil saturation Δs o of the rock sample loss after depressurization and degassing is:
the core oil saturation S o after depressurization and degassing is:
S o＝So1-ΔSo formula (9)
Finally, regression establishes the statistical relationship between the oil (water) saturation in advance (before depressurization and degassing) and the oil (water) saturation, porosity and formation pressure (gas-oil ratio) after the lifting (after depressurization and degassing) as a correction model of the oil-water saturation.
In one embodiment of the application, a method for correcting the saturation of a closed core oil water of a living oil reservoir comprises the following steps:
s1, selecting 20 rock samples of different reservoirs, and respectively measuring the porosity, permeability and dry weight of the rock samples after drying.
S2, vacuumizing the dried 20 rock samples, and then saturating 50000mg/L of saline.
S3, respectively placing rock samples of the saturated brine into a displacement experiment device to displace by using crude oil, recording the readings of the volume of the displaced water, and calculating the oil saturation.
S4, weighing 20 samples with an electronic balance, then respectively placing the samples into a clamp of a depressurization and degasification device, pressurizing to 35MPa, introducing methane gas into two ends of the clamp, and pressurizing to 30MPa pore pressure.
And S5, standing for a period of time until the volume reading of the pore pressure pump is not changed any more, and considering that methane gas is saturated and dissolved in crude oil. Then simulating the lifting process of the core barrel and keeping the effective pressure of 5MPa and the temperature of 25 ℃ unchanged, and slowly reducing the pressure. And wiping the surface of the rock sample taken out after depressurization and degassing, and weighing the mass of the rock sample. Repeating the steps, reducing the pressure and degassing all 20 samples to atmospheric pressure under the conditions of 20MPa, 25MPa, 30MPa, 35MPa of the overlying pressure and 15MPa, 20MPa, 25MPa and 30MPa of the pore pressure respectively, and recording the quality change.
S6, smashing the rock core by using a mortar, pouring absolute ethyl alcohol with the volume of 50ml, and standing for 2 hours to fully extract water in the rock core.
S7, extracting the extraction liquid with the volume V 3 by using a sample injector, injecting the extraction liquid into a micro-moisture tester, and measuring the moisture mass m 5.
S8, repeating the steps S6-S7, and measuring all 20 rock samples. The method provided by the invention is used for calculating the reduced fluid saturation of the rock sample after depressurization and degassing. Regression establishes a statistical relationship between the oil (water) saturation in advance of the upper run (before depressurization and degasification) and the oil (water) saturation after the upper run (after depressurization and degasification), the porosity, and the formation pressure (gas-oil ratio) as a correction model for the oil-water saturation.
The experimental measurement results are shown in table 1.
Table 1 experimental measurement results of this example
Analyzing the influence factors of the oil saturation reduction according to the data in the table 1, wherein the final oil porosity, pore pressure and oil saturation reduction have a better relationship, and fig. 2 is a chart showing the intersection of the oil porosity and oil saturation reduction; fig. 3 to 5 are graphs showing the intersection of pore pressure and the reduction in saturation of oil when the porosity of oil is similar.
From fig. 2 to 5, it is seen that the final oil porosity and pore pressure are all logarithmic with the reduction in oil saturation.
The following is obtained: the oil saturation reduction Δs o is:
Regression analysis: a=4.948, b=1.92, c=0.0348, d=1.538, r 2 = 0.8079.
Then, the initial oil saturation Δs o Initial initiation is:
From the above description, it can be seen that the technical effects achieved by the above embodiments of the present invention are: the process of lifting, depressurizing and degassing the coring barrel under different stratum pressure conditions is simulated physically in a laboratory, the changes of the oil saturation and the water saturation are measured experimentally in advance (before depressurizing and degassing) and after lifting (after depressurizing and degassing), and the statistical relationship between the changes of the oil saturation and the water saturation and the porosity, the saturation and the stratum pressure of a rock sample is established as a correction model of the oil saturation.
It will be apparent that the embodiments described above are merely some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present invention without making any inventive effort, shall fall within the scope of the present invention.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the present application. As used herein, the singular is also intended to include the plural unless the context clearly indicates otherwise, and furthermore, it is to be understood that the terms "comprises" and/or "comprising" when used in this specification are taken to specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof.
It should be noted that the terms "first," "second," and the like in the description and the claims of the present application and the above figures are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used may be interchanged where appropriate such that embodiments of the application described herein may be implemented in sequences other than those illustrated or otherwise described herein.
The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (4)
1. A method for correcting the saturation of oil and water in a closed coring process of a living oil reservoir, comprising the steps of:
Selecting a test rock sample, and measuring the total volume V1 and the mass M1 of the test rock sample;
vacuumizing the test rock sample to obtain saturated stratum brine;
Measuring the mass M2 and the floating weight M3 of the test rock sample after saturated stratum brine;
calculating the porosity and the pore volume V2 of the rock sample according to the total volume V1, the mass M2 and the floating weight M3 of the test rock sample;
placing the test rock sample after saturated stratum brine into a displacement device clamp holder, and displacing stratum crude oil;
taking the test rock sample out of the displacement device holder and measuring its mass M4 and the displaced brine volume V3;
according to the mass M4 of the test rock sample and the volume V3 of the expelled brine, respectively calculating the oil saturation and the water saturation of the test rock sample;
placing the test rock sample into a clamp holder of a depressurization degasser, and calculating the gas-oil ratio of the test rock sample;
Taking out the test rock sample from the pressure reducing and degassing device clamp holder, measuring the mass M5 of the clamp holder, and calculating the mass M7 of residual moisture in the test rock sample;
Calculating the water saturation of the test rock sample after depressurization and degassing;
Calculating the oil saturation of the test rock sample loss after depressurization and degassing;
Calculating the oil saturation of the test rock sample after depressurization and degassing;
Establishing a correction model;
After the test rock sample is placed in the pressure reducing and degassing device clamp holder, introducing test gas into the pressure reducing and degassing device clamp holder;
Before introducing test gas into the pressure reducing and degassing device clamp holder, adding an overlying pressure into the pressure reducing and degassing device;
After the test gas is introduced into the pressure reducing and degassing device clamp holder, the pressure reducing and degassing device is pressurized to pore pressure;
When the reading of the pump volume of the depressurization degasser is unchanged, simulating the lifting process of the coring barrel for the test rock sample;
In the process of simulating the lifting process of the coring barrel, the pressure is reduced under the condition of ensuring that the effective pressure and the temperature are unchanged.
2. The method of claim 1, wherein the surface of the test rock sample is required to be wiped dry after the test rock sample is removed from the displacement device holder.
3. The method for correcting the saturation of a closed core oil and water in a living oil reservoir according to claim 1, wherein the test gas is methane.
4. A method of correcting the water saturation of a closed core oil in a living oil reservoir according to any one of claims 1 to 3, wherein after obtaining the mass M5 of the test rock sample, the test rock sample is crushed in a mortar and poured into absolute ethyl alcohol, the mortar is sealed to extract water therein, and an extraction liquid is extracted by a sample injector and injected into a micro-moisture meter to measure the water mass, and the residual water mass M7 of the rock sample is calculated.
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