CN114151070B - Crude oil cracking gas reservoir fluid ancient pressure recovery method - Google Patents
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- 239000010779 crude oil Substances 0.000 title claims abstract description 178
- 238000000034 method Methods 0.000 title claims abstract description 70
- 238000005336 cracking Methods 0.000 title claims abstract description 47
- 239000012530 fluid Substances 0.000 title claims abstract description 44
- 238000011084 recovery Methods 0.000 title claims abstract description 35
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims abstract description 146
- 239000007789 gas Substances 0.000 claims abstract description 139
- 239000003345 natural gas Substances 0.000 claims abstract description 64
- 230000015572 biosynthetic process Effects 0.000 claims abstract description 39
- 239000010426 asphalt Substances 0.000 claims abstract description 27
- 238000004364 calculation method Methods 0.000 claims abstract description 26
- 230000006835 compression Effects 0.000 claims abstract description 20
- 238000007906 compression Methods 0.000 claims abstract description 20
- 230000002706 hydrostatic effect Effects 0.000 claims abstract description 14
- 238000000197 pyrolysis Methods 0.000 claims abstract description 9
- 239000004215 Carbon black (E152) Substances 0.000 claims description 19
- 229930195733 hydrocarbon Natural products 0.000 claims description 19
- 150000002430 hydrocarbons Chemical class 0.000 claims description 19
- 238000007872 degassing Methods 0.000 claims description 16
- 239000003921 oil Substances 0.000 claims description 15
- 238000010438 heat treatment Methods 0.000 claims description 14
- 238000004088 simulation Methods 0.000 claims description 12
- 239000000126 substance Substances 0.000 claims description 9
- 238000005303 weighing Methods 0.000 claims description 8
- 239000000463 material Substances 0.000 claims description 2
- 230000008569 process Effects 0.000 abstract description 14
- 238000005755 formation reaction Methods 0.000 description 30
- 239000011435 rock Substances 0.000 description 11
- 238000009933 burial Methods 0.000 description 7
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- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 2
- 239000010931 gold Substances 0.000 description 2
- 229910052737 gold Inorganic materials 0.000 description 2
- 230000002427 irreversible effect Effects 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 1
- 230000002159 abnormal effect Effects 0.000 description 1
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- 239000003208 petroleum Substances 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 238000004227 thermal cracking Methods 0.000 description 1
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- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B49/00—Testing the nature of borehole walls; Formation testing; Methods or apparatus for obtaining samples of soil or well fluids, specially adapted to earth drilling or wells
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B47/00—Survey of boreholes or wells
- E21B47/06—Measuring temperature or pressure
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Abstract
The invention provides a crude oil pyrolysis gas reservoir fluid ancient pressure recovery method, which comprises the following steps: determining the hydrostatic pressure, formation temperature and natural gas compression factor of a gas reservoir when crude oil is completely cracked; measuring the volume coefficient of crude oil, the density of asphalt and the cracking rate of crude oil; and calculating the pressure of the gas reservoir fluid according to a real gas state equation, and finishing the recovery of the ancient pressure of the crude oil cracking gas reservoir fluid. The ancient pressure recovery method provided by the invention can quantitatively calculate the highest pressure of the gas reservoir after the crude oil is cracked, does not need volume parameters in the calculation process, improves the reliability and accuracy of the calculation result, and has stronger practicability.
Description
Technical Field
The invention relates to the technical field of oil and gas reservoir dynamics, in particular to a crude oil cracking gas reservoir fluid ancient pressure recovery method.
Background
The reservoir forming dynamics is a comprehensive discipline for researching the formation, evolution and migration processes and aggregation rules of the oil gas of the sedimentary basin through energy field evolution and chemical dynamics, fluid dynamics and kinematic process analysis controlled by the energy field evolution in the basin evolution history and under the transmission grid by comprehensively utilizing geology, geophysics, geochemistry means and computer simulation technology. The basis of the hidden dynamics research is basin evolution history and fluid transportation grid, and the core of the research is the evolution of energy fields (including temperature fields, pressure fields and stress fields) and the chemical dynamics and fluid dynamics processes controlled by the energy fields. In recent years, due to the development of deep and multidisciplinary joint research of oil and gas exploration, reservoir formation dynamics have made important progress in various aspects of fluid conducting systems, basin energy field evolution and fluid flow patterns, oil and gas reservoir mechanism, filling history analysis and the like.
The formation fluid pressure is the result of the comprehensive actions of deposition evolution, construction movement, hydrodynamic force, water-rock interaction and the like, and is one of the essential parameters for researching the reservoir formation dynamics aspects of reservoir formation process, hydrocarbon source rock evolution, reservoir evolution and the like. Formation pressure can be obtained through drill pipe testing nowadays, but the ancient fluid pressure is difficult to obtain, because of the irreversible property of the geological process, and thus, the recovery of the geological process is quite difficult. Currently, there are many methods for restoring the paleo-fluid pressure, for example, determining the paleo-pressure according to the equilibrium relationship between the uniform temperature of the fluid inclusion and the fluid composition (fluid inclusion method for short); from mudstone acoustic time difference data, an irreversible principle of mudstone compaction is utilized to deduce an ancient fluid pressure (called acoustic time difference method for short) and a basin simulation method, wherein the basin simulation method is based on a physical-chemical mechanism of pressure generation, and can be used for carrying out one-dimensional Shan Jingjing pressure evolution reconstruction and carrying out pressure history simulation analysis of two-dimensional sections and even three-dimensional.
The recovery of the paleo-pressure by using the fluid inclusion is limited by the sampling position, inclusion capture temperature and capture period of the sample, and can only simulate the paleo-pressure change within a uniform temperature change range, so that the uniform pressure or the minimum capture pressure is obtained when the fluid is filled, and the overpressure limit value generated by crude oil cracking lacks more inclusion evidence, so that the overpressure generated by crude oil cracking is difficult to determine. The acoustic time difference method calculates the ancient fluid pressure in the mudstone, and cannot calculate the fluid pressure in the reservoir; not suitable for non-mudstone formations, nor are other abnormal pressure formation mechanisms beyond under-compaction. The basin simulation method can reflect the ancient pressure and the evolution process of the ancient pressure from the area, but a mathematical model adopted by basin simulation software is simplified for complex geological conditions, the parameters are numerous, uncertain factors are too many, and great errors exist between the result and the actual geological conditions.
Disclosure of Invention
In order to solve the problems, the invention aims to provide the crude oil cracking gas reservoir fluid ancient pressure recovery method, which utilizes a real gas state equation to quantitatively calculate the highest pressure of the gas reservoir after crude oil cracking is completed, does not need volume parameters in the calculation process, improves the reliability and accuracy of a calculation result, and has stronger practicability.
In order to achieve the above purpose, the invention provides a crude oil pyrolysis gas reservoir fluid ancient pressure recovery method, wherein the ancient pressure recovery method comprises the following steps:
determining the hydrostatic pressure, the stratum temperature and the natural gas compression factor of a gas reservoir when crude oil is completely cracked;
measuring the volume coefficient of crude oil, the density of asphalt and the cracking rate of crude oil;
and thirdly, calculating the pressure of the gas reservoir fluid according to a real gas state equation, and finishing the recovery of the ancient pressure of the crude oil cracking gas reservoir fluid.
In particular embodiments of the invention, "formation crude oil" refers to crude oil produced by a hydrocarbon source rock of a gas reservoir, or crude oil produced by a hydrocarbon source rock of the same type as the hydrocarbon source rock of the gas reservoir under formation conditions of the gas reservoir, i.e., crude oil that has not been degassed; "crude oil" (or: surface degassing crude oil) refers to crude oil obtained after the formation crude oil is degassed at the surface.
According to a specific embodiment of the present invention, in step one, the hydrostatic pressure and formation temperature are obtained by simulation using basin simulation software. In some embodiments, the hydrostatic pressure and formation temperature may be obtained by basin simulation software modeling the buried history, the ground temperature history, the hydrocarbon generation history of a single well; specifically, the burial depth and the formation temperature corresponding to the middle part of the gas reservoir can be read through the generated gas Shi Quxian given by the basin simulation software, and then the hydrostatic pressure is calculated according to the read burial depth. The basin simulation software may be PetroMod1D or the like.
According to an embodiment of the invention, in step one, the natural gas compression factor is typically obtained by reading on a gas compression factor plate based on the hydrostatic pressure and formation temperature. In some embodiments, the primary component of natural gas is methane, and the natural gas compression factor is typically a methane compression factor.
According to a specific embodiment of the present invention, in the second step, the volume coefficient of the crude oil is also called as the underground volume coefficient of the crude oil, and is defined as the ratio of the volume of the crude oil under the ground (i.e. the volume of the crude oil in the stratum) to the volume of the crude oil after the crude oil is degassed at the ground (i.e. the volume of the crude oil).
According to an embodiment of the present invention, in the second step, the volume coefficient of the crude oil may be calculated according to the formation temperature, the volume ratio of the dissolved gas and the oil in the crude oil of the formation, the relative density of the surface dead crude oil and the relative density of the separated gas, for example, may be calculated according to a Standing empirical formula.
According to an embodiment of the present invention, the above-mentioned volume ratio of dissolved gas and crude oil in formation crude oil, the relative density of surface-degassing crude oil, and the separated gas relative density can be obtained by experimental measurement. For example, the second step of the above-mentioned ancient pressure recovery method may further comprise standing and degassing the formation crude oil on the ground, weighing the volumes and masses of the crude oil before and after degassing, and calculating the volume ratio of the dissolved gas and the oil in the formation crude oil, the relative density of the ground and the degassing crude oil, and the relative density of the separated gas.
According to a specific embodiment of the present invention, in the second step, the crude oil volume coefficient is calculated according to the following formula:
B o ＝0.972+1.1213×10 -2 F 1.175 ，
wherein Bo is the crude oil volume coefficient; rs is the volume ratio of dissolved gas to oil in the crude oil of the formation; ro is the relative density of the ground degassing crude oil, and is dimensionless; rg is the relative density of the separated gas (air density 1kg/m 3 ) Dimensionless; t is the formation temperature in K.
According to a specific embodiment of the invention, in step two, the crude oil density is measured at surface conditions, for example at 20 ℃,0.101MPa. In some embodiments, when crude oil in a gas reservoir to be restored to the ancient pressure is cracked and cannot be sampled, stratum crude oil generated by hydrocarbon source rocks of the same type as the hydrocarbon source rocks of the gas reservoir can be selected as a sample, and crude oil density under ground conditions can be measured.
According to a specific embodiment of the invention, in the second step, the asphalt density and the crude oil cracking rate are obtained through hydrocarbon generation simulation experiments. In some embodiments, the hydrocarbon generation simulation experiment may include heating the crude oil (typically controlled to 800 ℃) to complete cracking, weighing the mass and volume of the crude oil before and after heating, and calculating the crude oil cracking rate and bitumen density (bitumen being the residue left after complete cracking of the crude oil, bitumen density being the density of the residue after thermal cracking).
According to the specific embodiment of the invention, the calculation formula of the crude oil cracking rate is generally: x is X m ＝(m 1 -m 2 )/m 1 Wherein X is m For crude oil cracking rate, m 1 For the mass of crude oil before heating, m 2 Is the quality of crude oil after heating and cracking.
In particular embodiments of the present invention, the results of the above calculation of crude oil cracking rates may be a range, due to factors such as the type, maturity, and composition of crude oil, which may result in different samples being selected for measurement of cracking rates.
According to a specific embodiment of the present invention, in step three, the true gas state equation is PV g ZnRT, where P is the fluid pressure of the gas reservoir in Pa; v (V) g Is the volume of natural gas in a gas reservoir, and has the unit of m 3 The method comprises the steps of carrying out a first treatment on the surface of the Z is a natural gas compression factor; n is the amount of the substance of the natural gas in the gas reservoir, and the unit is mol; r is molar gas constant, 8.3145 can be taken; t is the formation temperature in K.
According to a specific embodiment of the present invention, the calculation formula of the amount of the substance of the natural gas of the gas reservoir may include:
n＝X m ×ρ o ×V/(M×B o )，
where n is the mass of the natural gas in the gas reservoir, M is the molar mass of the natural gas (typically methane relative to the molecular mass), X m For crude oil cracking rate, V is the total reservoir space of the gas reservoir (i.e. the sum of the volume of natural gas in the gas reservoir and the volume of asphalt), and the unit is m 3 ；ρ o Is the density of crude oil, and the unit is g/m 3 ；B o Is the volume coefficient of crude oil. The formula can be derived by the following derivation process:
(1) Calculating the mass of natural gas in a gas reservoir: according to the principle of conservation of mass, the mass of natural gas in a gas reservoir is equal to the cracking mass of crude oil, and the method comprises the following steps:
m＝X m ×m o ＝X m ×ρ o ×V/B o ，
wherein m is the mass of natural gas, X m For crude oil cracking rate, m o The unit is g for crude oil reserves of ancient reservoirs; ρ o Is the density of crude oil, and the unit is g/m 3 The method comprises the steps of carrying out a first treatment on the surface of the V is the total reservoir space of the gas reservoir, and the unit is m 3 ；B o Is the volume coefficient of crude oil;
(2) Substituting the natural gas mass M calculation formula in the step (1) into n=m/M (n is the amount of natural gas materials in the gas reservoir, and M is the natural gas molar mass), to obtain: n=m/m=x m ×ρ o ×V/(M×B o )。
According to a specific embodiment of the present invention, the volume of the natural gas in the gas reservoir can be calculated according to the following formula:
V g ＝V[1-(1-X m )×ρ o /(ρ b ×B o )]，
wherein V is g Is the volume of natural gas in a gas reservoir, and has the unit of m 3 The method comprises the steps of carrying out a first treatment on the surface of the V is the total reservoir space of the gas reservoir, and the unit is m 3 ；X m Is the cracking rate of crude oil; ρ o Is the density of crude oil, and the unit is g/m 3 ；ρ b Is asphalt density in g/m 3 ；B o Is the volume coefficient of crude oil.
The natural gas volume V of the gas reservoir g The calculation formula of (2) can be obtained through the following deduction process:
volume of asphalt V b The reservoir space occupied by the asphalt is: v (V) b ＝m b /ρ b Wherein the asphalt mass m b ＝(1-X m )×m o And crude oil mass m o ＝ρ o ×V/B o Substituting the asphalt volume into a calculation formula to obtain: v (V) b ＝(1-X m )×ρ o ×V/(ρ b ×B o ) The method comprises the steps of carrying out a first treatment on the surface of the Thus, the natural gas volume V g The calculation formula of (2) is as follows: v (V) g ＝V-V b ＝V[1-(1-X m )×ρ o /(ρ b ×B o )]。
According to a specific embodiment of the present invention, in the third step, the calculation formula of the reservoir fluid pressure may be:
wherein P is the fluid pressure of the gas reservoir in Pa; z is a natural gas compression factor; r is molar gas constant; t is the formation temperature, and the unit is K; x is X m Is the cracking rate of crude oil; ρ o Is the density of crude oil, and the unit is g/m 3 ；ρ b Is asphalt density in g/m 3 ；B o Is the volume coefficient of crude oil; m is the molar mass of natural gas, and the unit is g/mol.
According to a specific embodiment of the present invention, the above-mentioned ancient pressure recovery method may include the following processes:
1. the buried history, the geothermal history and the hydrocarbon generation history of a single well were simulated using basin simulation software. Judging the moment when the natural gas stops generating according to the gas history curve, namely, the geological period when the crude oil is completely cracked into the natural gas, reading the corresponding burial depth and stratum temperature T (with the unit of K) in the middle part of the gas reservoir in the geological period, and calculating the hydrostatic pressure according to the burial depth;
2. reading a natural gas compression factor Z on the methane compression factor plate according to the stratum temperature and the hydrostatic pressure obtained in the step 1;
3. placing a certain amount of stratum crude oil on the ground for standing and degassing, weighing the volume and the mass of the crude oil before and after degassing, calculating the volume ratio Rs of dissolved gas and oil, the relative density Ro of the ground and the degassing crude oil and the relative density Rg of separated gas, and then calculating the volume coefficient B of the crude oil according to the following formula o ：
B o ＝0.972+1.1213×10 -2 F 1.175 ，
4. SelectingCrude oil generated by hydrocarbon source rocks with the same type of hydrocarbon source rock in a gas reservoir, and measuring density ρ of the crude oil under ground standard conditions o (in g/m) 3 )；
5. According to the thermal simulation experiment step of raw hydrocarbon, heating the crude oil (preferably at 800 ℃) until the crude oil is completely cracked, and weighing the mass m of the crude oil before heating 1 Mass after heating m 2 ，X m ＝(m 1 -m 2 )/m 1 Calculation of crude oil cracking Rate X m And measure asphalt density ρ b (in g/m) 3 )；
6. Calculating the amount n of substances of natural gas in a gas reservoir, wherein the calculation formula is as follows:
n＝m/M＝(X m ×ρ o ×V)/(M×B o )，
wherein M is the mass of natural gas in the gas reservoir, M is the relative molecular mass of natural gas, and the unit is g/mol; v is the total reservoir space of the gas reservoir, and the unit is m 3 ；B o The volume coefficient of the crude oil measured in the step 3; ρ o For the crude oil density measured in step 4, the unit is g/m 3 ；X m The crude oil cracking rate calculated for step 5.
7. Calculating the volume V of natural gas in a gas reservoir g (unit is m 3 ) The calculation formula is as follows:
V g ＝V[1-(1-X m )×ρ o /(ρ b ×B o )]；
wherein V is the total reservoir space of the gas reservoir, and the unit is m 3 ；B o The volume coefficient of the crude oil measured in the step 3; ρ o For the crude oil density measured in step 4, the unit is g/m 3 ；X m The crude oil cracking rate calculated for step 5; ρ b For the bitumen density measured in step 5, the unit is g/m 3 。
8. According to the real gas state equation PV g ZnRT, the mass n of the gas reservoir natural gas in step 6, the volume V of the gas reservoir natural gas in step 7 g Substituting, calculating the pressure of the fluid in the gas reservoir:
wherein P is the pressure of the gas reservoir fluid, and the unit is Pa; r is molar gas constant.
The invention has the beneficial effects that:
the method for recovering the fluid ancient pressure of the crude oil pyrolysis gas reservoir is a method for calculating the highest fluid pressure of the crude oil pyrolysis gas reservoir of a carbonate reservoir, which is reasonable in design and quantitative, overcomes the limitations and the defects of the existing oil-gas-containing basin ancient pressure recovery technology, can quantitatively calculate the highest pressure of the gas reservoir after the completion of crude oil pyrolysis without volume parameters according to experimental parameters (petroleum density, asphalt density, crude oil volume coefficient, natural gas compression factor, crude oil pyrolysis rate and the like), improves the reliability and the accuracy of calculation results, and has stronger practicability.
Drawings
Fig. 1 is a flowchart of the ancient pressure recovery method of example 1.
FIG. 2 is a gas history plot for a single well of the gas reservoir of example 1.
Detailed Description
The technical solution of the present invention will be described in detail below for a clearer understanding of technical features, objects and advantageous effects of the present invention, but should not be construed as limiting the scope of the present invention.
Example 1
The embodiment provides a crude oil pyrolysis gas reservoir fluid ancient pressure recovery method, and fig. 1 is a workflow diagram of the ancient pressure recovery method of the embodiment. The ancient pressure recovery method is applied to a process of obtaining fluid pressure of a gas reservoir of a temple group milch block of a mountain temple group of an AnYue gas field of a Sichuan basin, and specifically comprises the following steps:
1. obtaining burial depth, hydrostatic pressure and formation temperature of the old gas reservoir:
the buried history, the geothermal history and the hydrocarbon history of a single well were simulated using PetroMod1D basin simulation software. FIG. 2 is a graph of the gas history of a single well. According to fig. 2, the moment when the natural gas stops being generated, namely, the geological period when the crude oil is completely cracked is judged, the corresponding burial depth in the middle of the gas reservoir in the geological period is 7000m, the corresponding stratum temperature is 473K (200 ℃), and the hydrostatic pressure is calculated according to the burial depth to be 68.6MPa.
2. Reading the natural gas compression factor:
for crude oil pyrolysis gas reservoirs, the main component of natural gas is methane, and the methane compression factor is 1.6 in the methane compression factor chart according to the hydrostatic pressure and the formation temperature obtained in the step 1.
3. Obtaining the volume coefficient of crude oil:
taking out a certain amount of stratum crude oil, and immediately measuring the mass m of the stratum crude oil a1 And volume V a1 Then the stratum crude oil is stood for a period of time, after the dissolved natural gas in the stratum crude oil is separated, the mass m of the crude oil after degassing is measured a2 And volume V a2 The volume of the separated natural gas is V a3 The density of air is ρ a ：
Calculating the volume ratio rs=v of dissolved gas and oil in the formation crude oil a3 /V a2 ；
Surface degassing crude oil relative density ro=m a2 /(ρ a ×V a2 )；
Relative density of separated gas rg= (m a1 -m a2 )/(ρ a ×V a3 )；
The crude oil volume factor is calculated according to the following formula:
B o ＝0.972+1.1213×10 -2 F 1.175 ，
wherein B is o Rs is the volume ratio of dissolved gas to oil in the formation crude oil; ro is the relative density of the ground degassing crude oil, and is dimensionless; rg is the relative density of the separated gas and has no dimension; t is the formation temperature, and the unit is K; finally calculate to obtain B o 1.243.
4. Determination of crude oil density under surface conditions:
selecting stratum crude oil generated by hydrocarbon source rock with the same type as the hydrocarbon source rock of the gas reservoir, and measuring the density rho of the degassed crude oil under ground standard conditions (20 ℃ and 0.101 MPa) o 8.575 ×10 5 g/m 3 。
5. And measuring the quality and density of asphalt, and calculating the cracking rate of crude oil:
weighing the mass m according to the hydrocarbon production thermal simulation experiment step 1 Injecting the weighed crude oil into a gold pipe by a glass injector, heating the crude oil in the gold pipe to 800 ℃ until the crude oil is completely cracked, and weighing the mass m of the cracked crude oil 2 The asphalt quality is obtained, and the density of the cracked crude oil is calculated at the same time, namely the asphalt density;
according to the measurement result of the hydrocarbon production thermal simulation experiment, calculating the crude oil cracking rate X m ＝(m 1 -m 2 )/m 1 Obtaining X m 0.4-0.5.
6. The method comprises the following steps of calculating the mass of natural gas in the gas reservoir:
according to the principle of conservation of mass, the mass of natural gas in a gas reservoir is equal to the cracking mass of crude oil, i.e
m＝X m ×m o ＝X m ×ρ o ×V/B o ，
Wherein m is the mass of natural gas in the gas reservoir, and the unit is g; x is X m Is the cracking rate of crude oil; m is m o The unit is g, which is the total mass of crude oil; ρ o Is the density of crude oil, and the unit is g/m 3 The method comprises the steps of carrying out a first treatment on the surface of the V is the total reservoir space of the gas reservoir, and the unit is m 3 ；B o Is the volume coefficient of crude oil.
Substituting the calculation formula of the mass m of the natural gas in the gas reservoir into the calculation formula of the mass of the natural gas in the gas reservoir:
n＝m/M＝(X m ×ρ o ×V)/(M×B o )，
wherein m is the mass of natural gas in the gas reservoir, and the unit is g; m is the molar mass of natural gas (methane relative molecular mass in this example) in g/mol; x is X m Is the cracking rate of crude oil; m is m o The unit is g, which is the mass of crude oil; v is the total reservoir of the gas reservoirSpace in m 3 ；B o Is the volume coefficient of crude oil.
7. The volume of the natural gas (namely the total reservoir space of the gas reservoir) of the gas reservoir is calculated, and the specific process is as follows:
according to asphalt mass m b ＝(1-X m )×m o Calculating the reservoir space V occupied by asphalt b ：
V b ＝m b /ρ b ＝(1-X m )×m o /ρ b ，
Let m o ＝ρ o ×V/B o Substituting, the above formula is:
V b ＝m b /ρ b ＝(1-X m )×ρ o ×V/(ρ b ×B o )，
thus, the volume of natural gas in the gas reservoir is V g ＝V-V b ＝V[1-(1-X m )×ρ o /(ρ b ×B o )]，
Wherein V is g Is the volume of natural gas in a gas reservoir, and has the unit of m 3 The method comprises the steps of carrying out a first treatment on the surface of the V is the total reservoir space of the gas reservoir, and the unit is m 3 ；X m Is the cracking rate of crude oil; ρ o Is the density of crude oil, and the unit is g/m 3 。
8. Calculating the gas reservoir fluid pressure according to a real gas state equation:
substituting the calculation formula of the amount of the substances of the natural gas in the gas reservoir in the step 6 and the calculation formula of the natural gas volume in the gas reservoir in the step 7 into a real gas state equation PV of the natural gas in the gas reservoir g =znrt, yielding:
wherein P is the pressure of the gas reservoir fluid, and the unit is Pa; z is a methane compression factor; t is the formation temperature, and the unit is K; x is X m Is the cracking rate of crude oil; r is molar gas constant and has a value of 8.3145; ρ o Is the density of crude oil, and the unit is g/m 3 ；ρ b Is asphalt density in g/m 3 The method comprises the steps of carrying out a first treatment on the surface of the M is the phase of methaneFor molecular mass, the unit is g/mol; bo is the crude volume coefficient.
The values read, measured, calculated in steps 1-7 are summarized in table 1.
TABLE 1
| Z | R | T(K) | X m | B o | M | ρ o (g/m 3 ) | ρ b (g/m 3 ) |
| 1.6 | 8.3145 | 473 | 0.4-0.5 | 1.243 | 16 | 8.575×10 5 | 1.9×10 6 |
From the data of table 1, a reservoir fluid pressure p= 138.75MPa (corresponding to X m =0.4), p= 165.74MPa (corresponding to X m =0.5), i.e. the paleo pressure value of the temple group milch block is 138.75-165.74MPa.
The ancient pressure of the same block is restored by using a basin simulation means, and the obtained ancient pressure value of the block is 125-130MPa, which is similar to the ancient pressure value restored by adopting the method provided by the embodiment.
The embodiment proves that the ancient pressure recovery method provided by the invention can quantitatively calculate the highest pressure of the gas reservoir after the crude oil is cracked, and the calculation result of the method has the advantages of reliability, accuracy and strong practicability and is easy to popularize.
Claims (17)
1. A method for recovering the paleo-pressure of a crude oil pyrolysis gas reservoir fluid, wherein the paleo-pressure recovery method comprises:
determining the hydrostatic pressure, the stratum temperature and the natural gas compression factor of a gas reservoir when crude oil is completely cracked;
measuring the volume coefficient of crude oil, the density of asphalt and the cracking rate of crude oil;
thirdly, calculating the pressure of the gas reservoir fluid according to a real gas state equation, and finishing the recovery of the ancient pressure of the crude oil cracking gas reservoir fluid;
in the third step, the calculation formula of the gas reservoir fluid pressure is as follows:
wherein P is the pressure of the gas reservoir fluid, and the unit is Pa; z is a natural gas compression factor; r is molar gas constant; t is the formation temperature, and the unit is K; x is X m Is the cracking rate of crude oil; ρ o Is the density of crude oil, and the unit is g/m 3 ；ρ b Is asphalt density in g/m 3 ；B o Is the volume coefficient of crude oil; m is the molar mass of natural gas, and the unit is g/mol.
2. The method of paleo-pressure recovery of claim 1, wherein in step one, the hydrostatic pressure and formation temperature are obtained by basin simulation software.
3. The method of paleo-pressure recovery of claim 1 or 2, wherein in step one, the natural gas compression factor is obtained from reading on a gas compression factor plate as a function of the hydrostatic pressure and formation temperature.
4. The paleo-pressure recovery method of claim 1, wherein in step two, the crude oil volume factor is calculated from the formation temperature, a volume ratio of dissolved gas and oil in formation crude oil, a relative density of surface-degassed crude oil, and a relative density of separated gas.
5. The paleo-pressure restoration method according to claim 1 or 4, wherein the second step further comprises the following operations:
and placing the stratum crude oil on the ground for standing and degassing, weighing the volume and the mass of the crude oil before and after degassing, and calculating the volume ratio of dissolved gas and oil in the stratum crude oil, the relative density of the ground and the degassed crude oil and the relative density of separated gas.
6. The paleo-pressure recovery method of claim 1 or 4, wherein in step two, the crude oil volume coefficient is calculated according to the following formula:
B o ＝0.972+1.1213×10 -2 F 1.175 ，
wherein Bo is the volume coefficient of crude oil, rs is the volume ratio of dissolved gas and oil in stratum crude oil; ro is the relative density of the ground degassing crude oil, and is dimensionless; rg is the relative density of the separated gas and has no dimension; t is the formation temperature in K.
7. The paleo-pressure recovery method of claim 5, wherein in step two, the crude oil volume factor is calculated according to the following formula:
B o ＝0.972+1.1213×10 -2 F 1.175 ，
wherein Bo is the volume coefficient of crude oil, rs is the volume ratio of dissolved gas and oil in stratum crude oil; ro is the relative density of the ground degassing crude oil, and is dimensionless; rg is the relative density of the separated gas and has no dimension; t is the formation temperature in K.
8. The archaic pressure recovery method of claim 1, wherein in step two, the crude oil density is measured at ground conditions in g/m 3 。
9. The paleo-pressure recovery method of claim 8, wherein the ground condition is 20 ℃,0.101MPa.
10. The paleo-pressure recovery method of claim 1, wherein in step two, the bitumen density and crude oil cracking rate are obtained by hydrocarbon generation simulation experiments.
11. The paleo-pressure restoration method according to claim 1 or 10, wherein the second step includes the following operations:
heating the crude oil to complete cracking, weighing the mass and the volume of the crude oil before and after heating, and calculating the cracking rate of the crude oil and the asphalt density.
12. The paleo pressure recovery method of claim 11, wherein the crude oil is heated to a temperature of 800 ℃.
13. The paleo-pressure recovery method of any one of claims 1, 10 or 12, wherein in step two, the calculation formula of the crude oil cracking rate includes:
X m ＝(m 1 -m 2 )/m 1 ，
wherein X is m For crude oil cracking rate, m 1 For the mass of crude oil before heating, m 2 Is the quality of crude oil after heating.
14. The paleo-pressure recovery method of claim 11, wherein in step two, the calculation formula of the crude oil cracking rate includes:
X m ＝(m 1 -m 2 )/m 1 ，
wherein X is m For crude oil cracking rate, m 1 For the mass of crude oil before heating, m 2 Is the quality of crude oil after heating.
15. The paleo-pressure restoration method of claim 1, wherein in step three, the true gas state equation includes:
PV g ＝ZnRT，
wherein P is the pressure of the gas reservoir fluid, and the unit is Pa; v (V) g Is the volume of natural gas in a gas reservoir, and has the unit of m 3 The method comprises the steps of carrying out a first treatment on the surface of the Z is a natural gas compression factor; n is the amount of the substance of the natural gas in the gas reservoir, and the unit is mol; r is molar gas constant; t is the formation temperature in K.
16. The paleo-pressure recovery method of claim 15, wherein the calculation formula of the amount of material of the gas reservoir natural gas includes:
n＝X m ×ρ o ×V/(M×B o )，
wherein n is the amount of substances of natural gas in the gas reservoir, and the unit is mol; x is X m Is the cracking rate of crude oil; v is the total reservoir space volume of the gas reservoir, and the unit is m 3 ；ρ o Is the density of crude oil, and the unit is g/m 3 The method comprises the steps of carrying out a first treatment on the surface of the M is the molar mass of natural gas, and the unit is g/mol; b (B) o Is the volume coefficient of crude oil.
17. The paleo-pressure recovery method of claim 15 or 16, wherein the volumetric calculation formula of the gas reservoir natural gas includes:
V g ＝V[1-(1-X m )×ρ o /(ρ b ×B o )]，
wherein V is g Is the volume of natural gas in a gas reservoir, and has the unit of m 3 The method comprises the steps of carrying out a first treatment on the surface of the V is the total reservoir space volume of the gas reservoir, and the unit is m 3 ；X m Is the cracking rate of crude oil; ρ o Is the density of crude oil, and the unit is g/m 3 ；ρ b Is asphalt density in g/m 3 ；B o Is the volume coefficient of crude oil.
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