Method and device for determining minimum miscibility pressure of oil and gas
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A technology of miscible pressure and determination method, applied in measuring devices, measuring fluid pressure, instruments, etc., can solve the problems of poor calculation stability, large difference in initial value, and change of minimum miscible pressure of oil and gas, and achieves strong theory and improved accuracy. , the effect of improving convergence and stability
Inactive Publication Date: 2021-01-12
CHINA UNIV OF PETROLEUM (BEIJING) +1
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But this criterion is not ideal
First, different oil samples F m The initial values are very different, possibly up to several orders of magnitude, and the F m The value tends to be extremely small as the judgment standard, resulting in poor calculation stability
Secondly, F m The value tends to be extremely small is only a theoretical ideal situation. If it is used as a judgment standard in practical applications, it is necessary to add more mole fractions of injected gas to achieve a miscible state, resulting in errors in calculation results.
At the same time, none of the above methods can consider the influence of the confinement effect of nanopores on the minimum miscible pressure of oil and gas, and can only be used to calculate the minimum miscible pressure of oil and gas in conventional reservoirs; due to the strong fluid adsorption and capillary force effects in nanopores, the Therefore, the conventional equation of state method cannot be used to calculate the EOR process of gas injection in unconventional reservoirs (tight / shale reservoirs). minimum miscible pressure of oil and gas in
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Embodiment 1
[0101] Step a, determine the basic characteristic parameter value, as follows:
[0102] A simulated oil system, temperature T = 344K, injected gas is CO 2 and CH 4 Mix gas in equal proportions, set the pore radius R p = 1 μm.
[0103] The simulated oil components and their properties are shown in Table 1:
[0104] Table 1 Crude oil components and component properties
[0105] components z i
T c / K
P c / MPa
ω MW x i
CO 2
0 304.21 7.384 0.2250 44.010 82.00 CH 4
0.25 190.58 4.604 0.0104 16.043 74.05 n-C 4 h 10
0.50 425.18 3.797 0.2010 58.123 193.90 n-C 10 h 22
0.25 617.65 2.115 0.4900 142.290 440.69
[0106] The interaction coefficients among the components are shown in Table 2:
[0107] Table 2 Interaction coefficients of crude oil components
[0108] components CO 2
CH 4
n-C 4 h 10
n-C 10 h 22
CO 2
0.0000 0.1000 0.1257 ...
Embodiment 2
[0119] Step a, according to the actual situation of the target reservoir, determine each parameter value, as follows:
[0120] In a shale reservoir, the temperature T=388.7K, and the pore radius is mostly about 50nm, set R p = 50nm.
[0121] Crude oil components and component properties are shown in Table 5:
[0122] Table 5 Crude oil components and component properties
[0123] components z i
P c / MPa
T c / K
MW Ω x i
CO 2
0.0 72.80 304.20 44.01 0.2250 78.0 CH 4
0.2506 45.40 190.60 16.04 0.0080 77.0 C 2 -C 4
0.22 42.54 363.30 42.82 0.1432 145.2 C 5 -C 7
0.20 33.76 511.56 83.74 0.2474 250.0 C 8 -C 9
0.13 30.91 579.34 105.91 0.2861 306.0 C 10+
0.1994 21.58 788.74 200.00 0.6869 686.3
[0124] The interaction coefficients among the components are shown in Table 6:
[0125] Table 6 Interaction coefficients between components of crude oil
[0126]...
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Abstract
The invention provides an oil-gas minimum miscible pressure determining method and device, and the method comprises the steps: determining the initial gas phase escape degree and initial liquid phaseescape degree of each component according to the molar composition, an initial gas-liquid equilibrium constant and an initial capillary pressure value, and the adsorption parameters of fluids in pores; updating the gas-liquid equilibrium constant of each component of a crude oil sample after gas injection; determining interfacial tension and capillary pressure of the gas-injected crude oil sampleaccording to the updated gas-liquid equilibrium constant of each component of the gas-injected crude oil sample; and determining the minimum miscible pressure of the initial crude oil sample and injected gas according to the interfacial tension and the capillary pressure. According to the method, fluid adsorption parameters in the pores are introduced in the calculation process, the influence of fluid adsorption in the pores is considered, and the method can be used for calculating the molar fractions of all components in the crude oil sample after gas injection under the nanopore condition during gas-liquid balance such that the method can be used for determining the minimum oil-gas miscible pressure of conventional oil reservoirs and unconventional oil reservoirs.
Description
technical field [0001] The invention relates to the technical field of oil and gas field development and gas injection enhanced recovery, in particular to a method and device for determining the minimum miscible pressure of oil and gas. Background technique [0002] Gas injection (such as CO injection 2 ) flooding has the advantages of wide application range and remarkable effect of enhanced oil recovery, and has great application potential in oil production, especially in tight oil production. Gas injection flooding is divided into miscible flooding and immiscible flooding. The oil displacement efficiency of miscible flooding is much higher than that of immiscible flooding. Determining the minimum miscible pressure (MMP) of injected gas and crude oil is an important research content when formulating gas injection EOR scheme and economic evaluation. [0003] The existing methods for determining the minimum miscible pressure are divided into experimental method, empirical f...
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