CN116446848A - Steam huff and puff productivity prediction method and system for offshore multilayer heavy oil reservoir - Google Patents
Steam huff and puff productivity prediction method and system for offshore multilayer heavy oil reservoir Download PDFInfo
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- 238000010793 Steam injection (oil industry) Methods 0.000 claims abstract description 48
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Classifications
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B47/00—Survey of boreholes or wells
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/01—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells specially adapted for obtaining from underwater installations
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/16—Enhanced recovery methods for obtaining hydrocarbons
- E21B43/24—Enhanced recovery methods for obtaining hydrocarbons using heat, e.g. steam injection
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B2200/00—Special features related to earth drilling for obtaining oil, gas or water
- E21B2200/20—Computer models or simulations, e.g. for reservoirs under production, drill bits
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A10/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE at coastal zones; at river basins
- Y02A10/40—Controlling or monitoring, e.g. of flood or hurricane; Forecasting, e.g. risk assessment or mapping
Abstract
The invention relates to a steam throughput capacity prediction method and a steam throughput capacity prediction system for an offshore multilayer heavy oil reservoir, comprising the following steps of: collecting basic parameters of the offshore multilayer heavy oil reservoir; calculating to obtain a well bottom steam parameter by using the acquired basic parameters and a pre-constructed shaft heat loss characterization model considering the offshore characteristics; and calculating the production dynamics of each layer of the offshore multilayer heavy oil reservoir based on the well bottom steam parameters and a pre-constructed steam throughput capacity prediction model. The invention characterizes the actual temperature distribution of the hot liquid area, considers the specificity of the offshore heavy oil reservoir, establishes the along-the-way heat transfer and pressure drop model of the steam injection development shaft of the offshore heavy oil reservoir, further forms the integrated throughput capacity evaluation prediction model considering the coupling of the shaft reservoir, can realize the accurate evaluation of the initial productivity of the offshore heavy oil throughput development, and provides important basis for the efficient development of the offshore heavy oil reservoir. Therefore, the invention can be widely applied to the technical field of oil reservoir development.
Description
Technical Field
The invention relates to a steam huff and puff productivity prediction method and system for an offshore multilayer heavy oil reservoir, and belongs to the technical field of reservoir development.
Background
The thermal oil extraction method of the heavy oil reservoir mainly comprises steam huff and puff, steam flooding, in-situ combustion and steam assisted gravity drainage. The steam throughput is used as a single well development mode, the single well is filled with steam and is produced in the same well, and the method has the characteristics of quick heating effect, less one-time investment, simpler process technology, quick yield increase, considerable yield in the earlier stage and the like, so that the technology is a thermal exploitation technology commonly adopted at present.
In recent years, the development of thermal recovery of offshore heavy oil reservoirs is gradually advanced on a large scale. Unlike the exploitation of conventional land heavy oil reservoirs, the exploitation of the steam injection of the offshore heavy oil reservoir needs to consider the influence of a riser on the heat transfer of a shaft. After the steam is injected into the oil layer, the gravity difference effect is generated due to the difference of the density of crude oil and steam, so that the steam is easy to move to the top of the oil layer, and the phenomenon of steam overburning occurs. The existence of the steam overburden aggravates the heat loss caused by heat conduction between the oil layer and the top and bottom cover layers. Unlike conventional crude oil, when a certain temperature is reached, the thick oil assumes a newtonian fluid state, while below this temperature value (conversion temperature), the thick oil assumes a non-newtonian fluid state, i.e. there is a start-up pressure gradient. The usual steam-huff heating radius calculation method assumes that the heating zone is an isothermal zone and that the temperature is equal to the bottom hole steam temperature. In practice, the heating zone temperature is gradually reduced from the steam temperature to the original formation temperature due to the constant outward diffusion of heat in the heating zone. Taking into account the temperature variation of the heating zone, a heating zone non-isothermal distribution model needs to be established.
However, existing heavy oil reservoir throughput models are mostly directed to single-layer heavy oil reservoirs, and do not consider the impact of wellbore heat loss on steam parameters.
Disclosure of Invention
Aiming at the problems, the invention aims to provide a method and a system for predicting the steam throughput capacity of an offshore multi-layer heavy oil reservoir, which are used for establishing a steam throughput capacity model of the offshore multi-layer heavy oil reservoir on the basis of considering heat loss of a shaft of the offshore heavy oil reservoir, so as to realize accurate evaluation of the initial capacity of the offshore heavy oil throughput development.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
in a first aspect, the invention provides a method for predicting steam huff and puff capacity of an offshore multi-layer heavy oil reservoir, comprising the following steps:
collecting basic parameters of the offshore multilayer heavy oil reservoir;
calculating to obtain a well bottom steam parameter by using the acquired basic parameters and a pre-constructed shaft heat loss characterization model considering the offshore characteristics;
and calculating the production dynamics of each layer of the offshore multilayer heavy oil reservoir based on the well bottom steam parameters and a pre-constructed steam throughput capacity prediction model.
Further, the method calculates a bottom hole steam parameter by using the collected basic parameters and a pre-constructed shaft heat loss characterization model considering offshore characteristics, and comprises the following steps:
subdividing a thermal production well tubular column of the offshore heavy oil reservoir along the axial direction, and establishing an along-path pressure gradient calculation model according to a momentum conservation equation;
respectively establishing a heat transfer quantity calculation model between a steam injection pipe column and the outer edge of the cement sheath and between the outer edge of the cement sheath and the stratum according to a steady-state heat transfer theory;
treating the heat transfer process of the sea water section and the mud section, and establishing a total heat transfer quantity calculation model of the sea water section;
considering the influence of the friction loss of the shaft on the steam dryness in the infinitesimal body, and establishing a steam dryness calculation model according to an energy conservation equation;
based on the acquired basic parameters, solving the calculation models by adopting a subdivision infinitesimal method to obtain the bottom-hole steam parameters, wherein the bottom-hole steam parameters comprise bottom-hole steam temperature and steam dryness.
Further, the calculating to obtain the production dynamics of each layer of the offshore multilayer heavy oil reservoir based on the bottom hole steam parameters and the pre-constructed steam throughput capacity prediction model comprises the following steps:
let the small number of layers j=1;
calculating to obtain production dynamics of different huff and puff rounds in the j-layer oil reservoir by utilizing the well bottom steam parameters and a pre-constructed steam huff and puff productivity prediction model;
comparing j with Z by the small layer number j=j+1, and stopping calculation if j > Z; and if j is less than or equal to Z, repeating the previous step until the production dynamics of each layer of the offshore multilayer heavy oil reservoir is obtained, wherein Z is the small number of layers of the reservoir.
Further, the calculating, by using the downhole steam parameters and the pre-constructed steam throughput capacity prediction model, the production dynamics of different throughput rounds in the j-layer oil reservoir includes:
the cycle number N=1, the oil reservoir stratum area of the small layer is divided into a steam area, a hot liquid area and a cold area when the steam injection stage is finished, and the heating radius of each area is calculated by utilizing the steam parameters at the bottom of the well;
determining the average temperature T of a steam zone at the end of well soaking savg Average temperature T of hydrothermal zone havg Average formation pressure of reservoir P avg,s Average water saturation S w And calculate daily oil production Q o ；
Determining the average temperature T of the steam zone in the production phase as Average temperature T of hydrothermal zone ah Average formation pressure of reservoir P avg,p Average water saturation S w Daily oil production Q is calculated o ；
Let the cycle number n=n+1, compare N with the throughput cycle number N max Of (A), e.g. N > N max Then the calculation is finished and the next step is carried out; if N is less than or equal to N max Then calculate the heating zone residual heat E of the period rs And E is rh And adding the residual heat of the heating area into the heat injected by the next cycle of throughput round, and repeating all the steps to obtain the production dynamics of different throughput rounds of each small layer.
Further, the dividing the stratum area of the small-layer oil reservoir at the end of the steam injection stage, and calculating the heating radius of each area by using the steam parameters at the bottom of the well, including:
dividing a stratum area into a steam area, a hot liquid area and a cold area when the steam injection stage is finished;
splitting each small layer of steam injection quantity according to the stratum coefficient, and calculating to obtain the steam zone heating radius and the hot liquid zone heating radius by utilizing the well bottom steam parameter and a pre-established steam zone and hot liquid zone heating radius calculation model.
Further, determining the average temperature T of the steam zone at the end of the soaking savg Average temperature T of hydrothermal zone havg Average formation pressure of reservoir P avg,s Average water saturation S w And calculate daily oil production Q o Comprising:
determining the average temperature T of a steam zone at the end of a soaking well savg And mean temperature T of hydrothermal zone havg And based on the average temperature T of the steam zone savg And mean temperature T of hydrothermal zone havg Calculating to obtain the average formation pressure P of the oil reservoir avg,s Average water saturation S w ；
Calculated reservoir average formation pressure P avg,s And a pre-constructed steam throughput capacity prediction model is used for calculating daily oil production when the well is closed.
Further, the average temperature T of the steam zone in the production stage is determined as Average temperature T of hydrothermal zone ah Average formation pressure of reservoir P avg,p Average water saturation S w Daily oil production Q is calculated o Comprising:
determining the production stage, the average temperature T of the steam zone as And mean temperature T of hydrothermal zone ah And based on the average temperature T of the steam zone as And mean temperature T of hydrothermal zone ah Calculating to obtain the average formation pressure P of the oil reservoir avg,p Average water saturation S w ；
Calculated reservoir average formation pressure P avg,p And a pre-constructed steam development productivity model is calculated to obtain daily oil production in the production stage.
In a second aspect, the present invention provides a steam huff and puff capacity prediction system for an offshore multi-layer heavy oil reservoir, comprising:
the data acquisition module is used for acquiring basic parameters of the offshore multilayer heavy oil reservoir;
the bottom hole steam parameter calculation module is used for calculating and obtaining a bottom hole steam parameter by utilizing the acquired basic parameters and a pre-constructed shaft heat loss characterization model considering the offshore characteristics;
and the oil reservoir comprehensive productivity prediction module is used for calculating and obtaining production dynamics of different huff and puff rounds of the multilayer heavy oil reservoir by utilizing the well bottom steam parameters and a pre-constructed steam huff and puff productivity prediction model.
In a third aspect, the present invention provides a processing device, at least including a processor and a memory, where the memory stores a computer program, and the processor executes the computer program to implement the steps of the steam throughput capacity prediction method of the offshore multi-layer heavy oil reservoir.
In a fourth aspect, the present invention provides a computer storage medium having stored thereon computer readable instructions executable by a processor to perform the steps of the steam throughput capacity prediction method for an offshore multi-layer heavy oil reservoir.
Due to the adoption of the technical scheme, the invention has the following advantages:
1. the invention establishes a steam throughput capacity model of the multilayer heavy oil reservoir, splits the small-layer steam injection quantity through stratum coefficients, and considers the influence of heat loss of a shaft on steam parameters;
2. the invention considers the steam overburden, corrects and considers the heating radius calculation model under the interlayer heat absorption;
3. the oil reservoir temperature three-partition assumption is that the hot liquid area considers nonlinear temperature distribution, and the temperature distribution of the hot liquid area is determined by a numerical inversion method of a sand filling pipe model of a laboratory scale;
4. taking the effect of the starting pressure gradient into consideration, wherein the starting pressure gradient is a function of fluidity, namely each layer can calculate the starting pressure gradient according to the corresponding oil reservoir permeability and crude oil viscosity respectively;
therefore, the invention can be widely applied to the technical field of oil reservoir development.
Drawings
Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. Like parts are designated with like reference numerals throughout the drawings. In the drawings:
FIG. 1 is a flow chart of a method for predicting steam throughput capacity of an offshore multi-layer heavy oil reservoir, provided by an embodiment of the invention;
FIG. 2 is a graph showing oil-water permeability at different temperatures according to an embodiment of the present invention;
FIG. 3 is a graph of the viscosity-temperature curve of crude oil according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of a thermal production well string for an offshore heavy oil reservoir, provided by an embodiment of the invention;
FIG. 5 is a schematic view of a wellbore micro-segment provided by an embodiment of the present invention;
FIG. 6 is a schematic diagram of a distribution of a steam-injection end heating zone according to an embodiment of the present invention;
FIG. 7 shows a dimensionless temperature distribution of a hydrothermal region according to an embodiment of the present invention;
FIG. 8 is a flowchart of a model calculation step provided in an embodiment of the present invention;
FIG. 9 is a graph showing a comparison of the results of predicting the steam throughput capacity of a multi-layer heavy oil reservoir on the sea of an oil field according to an embodiment of the present invention;
the figures are marked as follows:
1. a steam injection pipe; 2. a sleeve; 3. a sleeve; 4. a heat insulating pipe; 5. an air layer; 6. a sea water section; 7. a mud section; 8. a formation.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. It will be apparent that the described embodiments are some, but not all, embodiments of the invention. All other embodiments, which are obtained by a person skilled in the art based on the described embodiments of the invention, fall within the scope of protection of the 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 example embodiments in accordance with 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.
In some embodiments of the present invention, a method for predicting steam throughput capacity of an offshore multi-layer heavy oil reservoir is provided, where production dynamic data of any small-layer oil reservoir, such as oil production rate, accumulated oil production, etc., is first determined, and then production dynamic data of the whole multi-layer heavy oil reservoir can be obtained by synthesizing the production dynamic data of each small-layer. When calculating production dynamic data of any small-layer oil reservoir, obtaining a well bottom steam parameter according to a thermal production well shaft heat loss characterization model considering offshore characteristics; and calculating daily oil production at different stages according to the well bottom steam parameters and the steam throughput capacity prediction model. The invention can realize the accurate evaluation of the capacity of the offshore thickened oil in the early stage of huff and puff development.
In accordance therewith, further embodiments of the present invention provide a steam throughput capacity prediction system, apparatus, and storage medium for an offshore multi-layer heavy oil reservoir.
Example 1
As shown in fig. 1, the method for predicting steam throughput capacity of an offshore multi-layer heavy oil reservoir provided in this embodiment includes the following steps:
1) Collecting basic parameters of the offshore multilayer heavy oil reservoir;
2) Calculating to obtain a well bottom steam parameter by using the acquired basic parameters and a pre-constructed shaft heat loss characterization model considering the offshore characteristics;
3) And calculating the production dynamics of each layer of the offshore multilayer heavy oil reservoir based on the well bottom steam parameters and a pre-constructed steam throughput capacity prediction model.
Preferably, in the step 1), the collected basic parameters of the offshore multi-layer heavy oil reservoir include well structure parameters, steam injection parameters and reservoir parameters; wherein, the well structure parameters comprise the length of a riser, the inner (outer) diameter of a steam injection pipe, the inner (outer) diameter of the riser, the vertical depth of a shaft, and the like; the steam injection parameters comprise steam injection rate, wellhead steam dryness, wellhead injection temperature, steam injection time and the like; the oil reservoir parameters comprise the number of oil reservoir layers of the multi-layer oil reservoir, the permeability of each oil reservoir, the thickness of each oil reservoir, the initial pressure of the oil reservoir, the initial temperature of the oil reservoir, the initial porosity of the oil reservoir, the initial water saturation of the oil reservoir, the pore compression coefficient, the bottom hole flow pressure, the heat capacity of the oil reservoir, the heat conductivity of the oil reservoir, the oil-water phase permeability relationship (figure 2) at different temperatures, the crude oil viscosity-temperature relationship (figure 3) and the like.
Preferably, in the step 2), the wellbore heat loss characterization model which is constructed in advance and considers the offshore features in this embodiment is divided into four parts, namely an along-path pressure gradient calculation model, a heat transfer quantity calculation model, a sea water section total heat transfer quantity calculation model and a steam dryness calculation model. Specifically, the calculation of the downhole steam parameters includes the following steps:
2.1 Axially subdividing a thermal production well string of the offshore heavy oil reservoir, and establishing an along-path pressure gradient calculation model according to a momentum conservation equation.
As shown in fig. 4, a schematic diagram of a thermal production well string for an offshore heavy oil reservoir is shown. The offshore heavy oil reservoir thermal production well tubular column comprises a steam injection pipe, a sleeve, a heat insulation pipe and a water insulation pipe which are sequentially arranged from inside to outside, wherein a gap is reserved between the steam injection pipe and the sleeve and is used for injecting steam; the sleeve penetrates through the air layer, the sea water section, the mud section and the stratum from top to bottom in sequence, and the heat insulation pipe is sleeved outside the sleeve; the marine riser is arranged outside the thermal riser, and penetrates through the air layer, the sea water section and the mud section from top to bottom in sequence and enters the upper part of the stratum.
As shown in fig. 5, the thermal production well string wellbore is axially subdivided to obtain a schematic of the steam injection wellbore microelements. According to the momentum conservation equation, the micro-segment saturated steam pressure loss (along-path pressure gradient calculation) calculation model is expressed as:
wherein ρ is m Is the average density of water vapor in the micro-element section, kg/m 3 The method comprises the steps of carrying out a first treatment on the surface of the θ is the minor element section well bevel angle, deg; ρ 1 And ρ 2 The water vapor density of the front section and the rear section of the micro-element section respectively,kg/m 3 ；v 1 and v 2 The flow velocity of water vapor at the front and rear sections of the micro-element section is m/s respectively; τ f The friction force of the steam in the micro-element section is N; a is the cross-sectional area of the infinitesimal section, m 2 The method comprises the steps of carrying out a first treatment on the surface of the dp is pressure loss of the micro-segment and MPa; dz is the length of the micro-segment, m.
2.2 According to steady-state heat transfer theory, respectively establishing a heat transfer quantity calculation model between the steam injection pipe and the outer edge of the cement sheath and between the outer edge of the cement sheath and the stratum.
According to a steady-state heat transfer theory, a heat transfer quantity calculation model from the steam injection pipe to the outer edge of the cement sheath is expressed as follows:
wherein dQ is the heat transfer quantity of the micro-element section, W; t (T) sm The average temperature of the micro-element section is DEG C; t (T) c The temperature is the temperature of the outer edge of the cement sheath; r is R C1 Expressed as total heat transfer resistance:
wherein lambda is tub The heat conductivity coefficient of the steam injection pipe and the heat insulation pipe is W/(m DEG C); r is (r) 1 And r 2 The inner radius and the outer radius of the steam injection pipe are respectively m; ### ins The heat conductivity coefficient W/(m.DEG C) of the heat insulation material; r is (r) 3 And r 4 The inner radius and the outer radius of the heat insulation pipe are respectively m; h is a c And h r The annular space is filled with air, and the convection heat transfer coefficient is W/(m) 2 ·℃)；λ cas The heat conductivity coefficient of the sleeve is W/(m.DEG C); r is (r) ci And r co The inner radius and the outer radius of the sleeve are respectively m; lambda (lambda) cem The thermal conductivity of the cement sheath is W/(m.DEG C); r is (r) h Is the outer edge radius of the cement sheath, m.
The calculation model of the heat transfer quantity between the outer edge of the cement sheath and the stratum can be expressed as:
wherein lambda is e W/(m.DEG C) is the thermal conductivity of the stratum; t (T) e Is the formation temperature, DEG C; f (t) is a dimensionless stratum heat conduction time function, and is solved by adopting a Hasan formula:
wherein τ D For the dimensionless heat conduction time,alpha is the thermal diffusivity of the stratum, m 2 /h; τ is the steam injection time, h.
2.3 The heat transfer process of the sea water section and the mud section is processed, and a total heat transfer quantity calculation model of the sea water section is built.
Assuming that the temperature of the seawater is constant, the heat transfer process between the steam injection shaft and the seawater is a steady-state heat transfer process; for the mud section, the mud section can also be treated into a constant temperature zone (the heat transfer process treatment of the sea water section and the mud section). Thus, the total heat transfer amount calculation model of the sea water segment can be expressed as:
wherein T is sw The temperature is the temperature of the sea water section and is at the temperature of DEG C; r is R C2 The total heat transfer resistance of the sea water section is expressed as:
wherein lambda is iw W/(m.DEG C) is the heat conductivity coefficient of the water isolation pipe; r is (r) wi And r wo The inner radius and the outer radius of the water isolation pipe are respectively m; h is a sw W/(m) is the coefficient of convective heat transfer of seawater 2 ·℃)。
2.4 Taking the influence of the friction loss of the shaft on the steam dryness in the infinitesimal body into consideration, and establishing a steam dryness calculation model according to an energy conservation equation.
Wherein, the steam dryness calculation model is expressed as:
wherein dQ is the total heat transfer quantity of the infinitesimal section, W; dW is the friction force of the infinitesimal section Shui Zhengqi to apply work, W; h m Is the enthalpy of the water vapor, kJ/kg; i.e s Is the mass flow of water vapor, kg/s; v m The average flow rate of the water vapor in the micro-element section is m/s; l (L) v kJ/kg as latent heat of vaporization; x is the dryness of the steam in the infinitesimal section and the fraction; h w Is the enthalpy of saturated water, kJ/kg; g is gravity acceleration, m/s 2 。
2.5 Based on the basic parameters of the acquired multi-layer heavy oil reservoir, solving each calculation model in the steps 2.1) to 2.4) by adopting a subdivision micro-element method, namely dividing a shaft into a plurality of micro-element sections, calculating the sections from a wellhead to the bottom of the shaft section by section to obtain bottom-hole steam parameters, wherein the bottom-hole steam parameters comprise bottom-hole steam temperature and steam dryness.
Preferably, in the step 3), the production dynamics of each layer of the offshore multi-layer heavy oil reservoir is calculated based on the downhole steam parameters and a pre-constructed steam throughput capacity prediction model, and the method comprises the following steps:
3.1 J=1, and calculating to obtain production dynamics of different huff and puff rounds in j layers of oil reservoirs by utilizing the well bottom steam parameters and a pre-constructed steam huff and puff productivity prediction model;
3.2 J=j+1, comparing j with the small layer number Z of the oil reservoir, and stopping calculation if j is more than Z; if j is less than or equal to Z, repeating the step 3.1) until the production dynamics of all small layers of the offshore multilayer heavy oil reservoir are obtained.
Preferably, in the step 3.1), the method includes the steps of:
3.1.1 The cycle number N=1, the oil reservoir stratum area of the small layer is divided into a steam area, a hot liquid area and a cold area when the steam injection stage is finished, and the heating radius of each area is calculated by utilizing the steam parameters at the bottom of the well;
3.1.2 Determining the average temperature T of the steam zone at the end of the soaking savg Average temperature T of hydrothermal zone havg Average formation pressure of reservoir P avg,s Average water saturation S w And calculate daily oil production Q o ；
3.1.3 Determining the average temperature T of the steam zone during the production phase as Average temperature T of hydrothermal zone ah Average formation pressure of reservoir P avg,p Average water saturation S w Daily oil production Q is calculated o ；
3.1.4 Let the cycle number N=N+1, compare the cycle number N with the throughput cycle number N max Of (A), e.g. N > N max Then the calculation is finished, and step 3.1.2) is performed; if N is less than or equal to N max Then calculate the heating zone residual heat E of the period rs And E is rh And adding the residual heat of the heating area into the heat injected by the next cycle of throughput round, and then repeating the steps 3.1.1) to 3.1.3) to obtain the production dynamics of the small layer of different throughput rounds.
Preferably, in the step 3.1.1), the method includes the steps of:
3.1.1.1 Dividing the oil reservoir stratum area of the small layer into three areas of a steam area, a hot liquid area and a cold area at the end of the steam injection stage, and fitting the radius and temperature relation of the hot liquid area.
As shown in fig. 6, the present embodiment divides the reservoir formation region at the end of the steam injection phase into three regions, a steam region, a hot liquid region, and a cold region. The temperature of the steam zone is saturated steam temperature, and the temperature distribution of the hot liquid zone is determined by using a sand filling pipe model numerical inversion method based on laboratory scale.
For productivity evaluation of huff and puff wells in the thermal recovery process of heavy oil reservoirs, accurate characterization of the reservoir temperature is very critical. Therefore, the invention adopts a means of inversion of the sand filling pipe model value based on laboratory scale to research the temperature distribution rule of the hot liquid area. The concrete thought is to fit the oil production condition of the sand filling pipe experiment through a numerical simulation model, and obtain the temperature distribution simulation result of the hot liquid area on the basis. Based on the temperature distribution of the hot liquid area, the radius of the hot liquid area and the temperature of the hot liquid area can be treated in a dimensionless manner respectively, so that normalized temperature distribution of the hot liquid area (shown in figure 7) is obtained, and the fitting result of experimental data shows that the dimensionless radius of the hot liquid area and the dimensionless temperature accord with exponential function distribution.
Dimensionless radius of hydrothermal region:
dimensionless temperature of hydrothermal zone:
fitting the result by experimental data, wherein the dimensionless temperature and the dimensionless radius of the hydrothermal region meet the following relation:
wherein r is the distance from the hydrothermal area to the shaft, and m; r is (r) hl Radius of the hydrothermal area, m; t (T) h (r) is the temperature at the r position from the wellhead, DEG C; t (T) s Is the bottom hole steam temperature, DEG C; t (T) i Is the original reservoir temperature, deg.c.
3.1.1.2 Splitting each small layer steam injection amount according to stratum coefficients, and calculating to obtain a steam zone heating radius r by utilizing well bottom steam parameters and a pre-established steam zone and hot liquid zone heating radius calculation model s And a heating radius r of the hydrothermal region h 。
Each permeable small layer of the multi-layer heavy oil reservoir is separated by an impermeable layer, and steam is injected into the reservoir in a general steam injection mode, assuming that the steam can only enter the permeable small layers. Before determining the radius of each small layer heating area, determining the steam injection amount of each small layer, and splitting the steam injection amount of each small layer according to the stratum coefficient:
wherein I is s Kg/d for total steam injection rate; z is the small layer number of the oil reservoir; k (K) j The permeability of the j-th oil layer, mD; h is a j The thickness of the j-th oil layer is m; i.e s,j The steam injection rate for the j-th reservoir was kg/d.
Considering the effect of steam overburden, it is assumed that the steam zone is an inverted cone centered on the huff and puff well. According to the law of conservation of energy, the rate of heat injected into the oil reservoir is equal to the sum of the heat loss rate of the top and bottom cover layers and the energy increasing rate of the oil layer, and specifically, the heat injected into the steam zone is steam latent heat, so that the bottom heating radius of the steam zone can be obtained:
wherein r is b Heating the bottom of the steam zone to a radius, m; y is the ratio of the heating radius of the top and bottom cover layers; lambda (lambda) e ' is the heat conductivity coefficient of the top and bottom cover layers, kJ/(d.m.); lambda is the ratio of the oil layer heat capacity to the interlayer heat capacity, lambda=mr 2 /MR 1 ；MR 1 kJ/(m) is the heat capacity of the interlayer 3 ·℃)；MR 2 kJ/(m) for oil layer heat capacity 3 ·℃)；t D Is the dimensionless steam injection time, t D ＝4λ e ′t/(MR 1 h j 2 ) The method comprises the steps of carrying out a first treatment on the surface of the t is steam injection time, and d.
For ease of calculation of the production, the steam zone is equivalent to a cylinder, where the equivalent heating radius of the steam zone can be expressed as:
according to the law of conservation of energy, the rate of heat injected into the oil reservoir is equal to the sum of the heat loss rate of the top cover layer and the bottom cover layer and the energy increasing rate of the oil layer, and the heat injected into the hot liquid area is saturated hot water enthalpy, so that the oil reservoir is obtained
Wherein T is h The hydrothermal region temperature can be determined by the formulas (12) to (14):
T h (r)＝T i +T D ·(T s -T i ) (18)
F(r hl ) =0 is a nonlinear equation that can be used to solve for the radius of the hot fluid region using newton's iterative method:
wherein r is hl Radius of the hydrothermal area, m; h is a ws Is the enthalpy of saturated hot water, kJ/kg; h is a wr Is the enthalpy of water at the initial reservoir temperature, kJ/kg; m is M R Is the heat capacity of oil reservoir, kJ/(m) 3 C, a temperature; alpha' is the thermal diffusion coefficient of the top and the bottom of the oil reservoir, m 2 /d; erfc (x) is an error compensation function.
Preferably, in the step 3.1.2), the method includes the steps of:
3.1.2.1 Determining the average temperature T of the steam zone at the end of the soaking savg And mean temperature T of hydrothermal zone havg And based on the average temperature T of the steam zone savg And mean temperature T of hydrothermal zone havg Calculating to obtain the average formation pressure P of the oil reservoir avg,s Average water saturation S w 。
At the end of the steam injection phase, the steam zone temperature maintains the saturated steam temperature. In the soaking stage, the temperature reduction of the heating area caused by heat conduction is considered, wherein the temperature reduction comprises two aspects of vertical heat loss and radial heat loss, and when the soaking is finished, the steam area average temperature calculation model is as follows:
T savg ＝T i +(T s -T i )V rs V zs (20)
wherein T is savg The average temperature of a steam zone at the end of well soaking is DEG C; v (V) rs Is the radial heat loss coefficient of the steam zone; v (V) zs Is the vertical heat loss coefficient of the steam area.
At the end of the vapor injection phase, the mean temperature of the hydrothermal section (area weighted average) can be expressed as:
in the well soaking process, the temperature reduction caused by heat conduction needs to be considered, and the average temperature of a hot liquid area at the end of well soaking can be obtained by the following steps:
wherein T is havg The average temperature of the hydrothermal area at the end of the well soaking is set at DEG C; v (V) rh Is the radial heat loss coefficient of the hydrothermal area; v (V) zh Is the vertical heat loss coefficient of the hydrothermal area.
During the steam injection phase, steam injection causes an increase in reservoir pressure, as known from the mass balance equation: the volume of injected steam in the subsurface is equal to the sum of the expansion of the pore volume and the compression of the reservoir fluid volume. Thus, at the end of a kill, the reservoir average formation pressure may be expressed as:
wherein P is avg,s The average formation pressure of the oil reservoir at the end of the well soaking is MPa; p (P) i Is the initial reservoir pressure, MPa; g w To accumulate steam injection volume (surface cold water equivalent), m 3 ；B w Is the volume coefficient of water; n is the geological reserve of crude oil in the oil drainage area, m 3 ；B o Is a crude oil volume systemA number; c (C) e To synthesize compression coefficient, mpa -1 ；N os For the crude oil geological reserves in the steam zone, m 3 ；β e To synthesize thermal expansion coefficient, DEG C -1 ；N oh For the geological reserves of crude oil in the hydrothermal area, m 3 。
The average water saturation in the heating zone is equal to the sum of the initial water saturation and the water saturation changes caused by steam injection during the steam injection phase and by water production during the production phase, based on the conservation of mass of the aqueous phase. Thus, the water saturation can be expressed as:
wherein S is wi To irreducible water saturation; d, d wi For the initial moment the density of water, kg/m 3 ；d w To produce stage water density kg/m 3 The method comprises the steps of carrying out a first treatment on the surface of the Phi is the formation porosity.
3.1.2.2 Based on the calculated reservoir average formation pressure P avg,s And a pre-constructed steam throughput capacity prediction model is used for calculating daily oil production when the well is closed.
Based on a quasi-steady-state productivity model of a three-zone composite stratum, a round closed boundary and a central one-port huff-puff well, the steam development productivity model of a multi-layer directional well can be realized:
wherein Q is o For daily oil production, m 3 /d；P avg Average formation pressure of oil reservoir, MPa; p (P) wf Is the bottom hole flow pressure, MPa; TPG is the starting pressure gradient, MPa/m; r is R o1 R o2 R o3 Crude oil seepage resistance of a steam zone, a hot liquid zone and a cold zone respectively, (MPa.d)/m 3 ；r e And r w The oil drainage radius and the borehole radius are respectively m; k is the absolute permeability of the oil reservoir, mD; k (K) ros 、K roh And K roc The relative oil phase permeabilities of the steam zone, the hot liquid zone and the cold zone are respectively; mu (mu) os 、μ oh Sum mu oc The viscosity of crude oil in a steam zone, a hot liquid zone and a cold zone respectively, and mPa.s; s is the skin coefficient; t is t p D, production time; m is the throughput round.
When the reservoir temperature is low, the thickened oil presents a non-Newtonian fluid state, and the influence of the starting pressure gradient on the productivity is needed to be considered in the model. On the basis of experimental data, a starting pressure gradient model based on fluidity is constructed, and the experimental data and the associated type have higher fitting degree and are in a power exponent relationship. According to the fitting result of experimental data, starting the relation between the pressure gradient and the fluidity:
preferably, in the step 3.1.3), the method includes the steps of:
3.1.3.1 Determining the production phase, average temperature T of the steam zone as And mean temperature T of hydrothermal zone ah And based on the average temperature T of the steam zone as And mean temperature T of hydrothermal zone ah Calculating to obtain the average formation pressure P of the oil reservoir avg,p Average water saturation S w 。
In the production stage, the heat carried by the produced fluid is also considered, and the average temperature of the steam zone can be expressed as:
T as (t p ,M,j)＝T i +(T s -T i )(V rs V zs (1-O s )-O s ) (30)
wherein T is as The average temperature of a steam zone in the production stage is DEG C; t is t p D, production time; m is the throughput round; j is the j-th oil layer; o (O) s Is the dimensionless liquid production temperature of the steam area.
Similarly, the average temperature of the hydrothermal section at the production stage is expressed as:
wherein T is ah The average temperature of the hydrothermal area in the production stage is DEG C; o (O) h Is the dimensionless liquid production temperature of the hot liquid area.
Similarly, during the production phase, the production of fluid causes a drop in reservoir pressure, and the subsurface volume of produced fluid is equal to the sum of the reservoir fluid volume expansion and pore volume compression. Thus, during the production phase, the reservoir average formation pressure may be expressed as:
/>
wherein P is avg,p The average pressure of the oil reservoir in the production stage is MPa; n (N) w To accumulate the water yield, m 3 ；N o To accumulate oil production, m 3 。
3.1.3.2 Based on the calculated reservoir average formation pressure P avg,p And a pre-constructed steam development productivity model is calculated to obtain daily oil production in the production stage.
Preferably, in the above step 3.1.4), the effect of the residual heat of the previous round needs to be taken into account when starting a new throughput round. In the model, from the second round, the processing method of the residual heat quantity is that the oil reservoir temperature is still the initial oil reservoir temperature before steam injection is started, and the influence of the residual heat quantity is reflected in calculation of the radius of a heating area of the next huff and puff round. The amount of cyclic waste heat in the vapor zone and the hot liquid zone can be expressed as:
E rs ＝πr s 2 h j M R (T as (t p ,M,j)-T i ) (33)
E rh ＝π(r hl 2 -r s 2 )h j M R (T ah (t p ,M,j)-T i ) (34)
wherein E is rs kJ, the cycle residual heat of the steam zone; e (E) rh Is the period residual heat quantity of the hydrothermal area and kJ.
Example 2
Referring to fig. 1 to 8, well structure parameters, reservoir parameters and steam injection parameters (table 1) of a certain offshore oilfield are taken as input parameters of a model, the steam throughput capacity of the offshore oilfield is calculated by applying the method, and finally the calculation result is compared with a CMG numerical simulation result, as shown in fig. 9. The results show that the maximum daily oil production decreases with increasing throughput cycles, mainly due to the gradual decrease in formation pressure with fluid production. The productivity calculation result of the invention is better matched with the CMG simulation result, and the comparison result can be used for evaluating the initial productivity of the multilayer heavy oil reservoir.
Table 1 basic parameter table
/>
Example 3
In contrast to the above embodiment 1, which provides a method for predicting the throughput capacity of the multi-layer heavy oil reservoir on the sea, the present embodiment provides a system for predicting the throughput capacity of the multi-layer heavy oil reservoir on the sea. The system provided in this embodiment may implement the steam throughput capacity prediction method of the offshore multi-layer heavy oil reservoir of embodiment 1, and the system may be implemented by software, hardware or a combination of software and hardware. For example, the system may include integrated or separate functional modules or functional units to perform the corresponding steps in the methods of embodiment 1. Since the system of this embodiment is substantially similar to the method embodiment, the description of this embodiment is relatively simple, and the relevant points may be found in part in the description of embodiment 1, which is provided by way of illustration only.
The steam huff and puff productivity prediction system for the offshore multilayer heavy oil reservoir provided by the embodiment comprises:
the data acquisition module is used for acquiring basic parameters of the offshore multilayer heavy oil reservoir;
the bottom hole steam parameter calculation module is used for calculating and obtaining a bottom hole steam parameter by utilizing the acquired basic parameters and a pre-constructed shaft heat loss characterization model considering the offshore characteristics;
and the oil reservoir comprehensive productivity prediction module is used for calculating and obtaining production dynamics of different huff and puff rounds of the multilayer heavy oil reservoir by utilizing the well bottom steam parameters and a pre-constructed steam huff and puff productivity prediction model.
Example 4
The present embodiment provides a processing device corresponding to the method for predicting steam throughput capacity of an offshore multi-layer heavy oil reservoir provided in the present embodiment 1, where the processing device may be a processing device for a client, for example, a mobile phone, a notebook computer, a tablet computer, a desktop computer, etc., to execute the method of embodiment 1.
The processing device comprises a processor, a memory, a communication interface and a bus, wherein the processor, the memory and the communication interface are connected through the bus so as to complete communication among each other. The memory stores a computer program that can be run on the processor, and when the processor runs the computer program, the steam throughput capacity prediction method of the offshore multi-layer heavy oil reservoir provided in this embodiment 1 is executed.
In some embodiments, the memory may be a high-speed random access memory (RAM: random Access Memory), and may also include non-volatile memory (non-volatile memory), such as at least one disk memory.
In other embodiments, the processor may be a Central Processing Unit (CPU), a Digital Signal Processor (DSP), or other general purpose processor, which is not limited herein.
Example 5
The steam-throughput capacity prediction method of the offshore multi-layer heavy oil reservoir of this embodiment 1 may be embodied as a computer program product, which may include a computer readable storage medium having computer readable program instructions loaded thereon for performing the steam-throughput capacity prediction method of the offshore multi-layer heavy oil reservoir of this embodiment 1.
The computer readable storage medium may be a tangible device that retains and stores instructions for use by an instruction execution device. The computer readable storage medium may be, for example, but not limited to, an electronic storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any combination of the preceding.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims (10)
1. The steam throughput capacity prediction method of the marine multilayer heavy oil reservoir is characterized by comprising the following steps of:
collecting basic parameters of the offshore multilayer heavy oil reservoir;
calculating to obtain a well bottom steam parameter by using the acquired basic parameters and a pre-constructed shaft heat loss characterization model considering the offshore characteristics;
and calculating the production dynamics of each layer of the offshore multilayer heavy oil reservoir based on the well bottom steam parameters and a pre-constructed steam throughput capacity prediction model.
2. The method for predicting steam throughput capacity of an offshore multi-layer heavy oil reservoir according to claim 1, wherein the step of calculating a bottom hole steam parameter by using the collected basic parameters and a pre-constructed wellbore heat loss characterization model considering offshore characteristics comprises the following steps:
subdividing a thermal production well tubular column of the offshore heavy oil reservoir along the axial direction, and establishing an along-path pressure gradient calculation model according to a momentum conservation equation;
respectively establishing a heat transfer quantity calculation model between a steam injection pipe column and the outer edge of the cement sheath and between the outer edge of the cement sheath and the stratum according to a steady-state heat transfer theory;
treating the heat transfer process of the sea water section and the mud section, and establishing a total heat transfer quantity calculation model of the sea water section;
considering the influence of the friction loss of the shaft on the steam dryness in the infinitesimal body, and establishing a steam dryness calculation model according to an energy conservation equation;
based on the acquired basic parameters, solving the calculation models by adopting a subdivision infinitesimal method to obtain the bottom-hole steam parameters, wherein the bottom-hole steam parameters comprise bottom-hole steam temperature and steam dryness.
3. The method for predicting the steam throughput capacity of the offshore multi-layer heavy oil reservoir according to claim 2, wherein the calculating the production dynamics of each layer of the offshore multi-layer heavy oil reservoir based on the bottom hole steam parameters and the pre-constructed steam throughput capacity prediction model comprises the following steps:
let the small number of layers j=1;
calculating to obtain production dynamics of different huff and puff rounds in the j-layer oil reservoir by utilizing the well bottom steam parameters and a pre-constructed steam huff and puff productivity prediction model;
comparing j with Z by the small layer number j=j+1, and stopping calculation if j > Z; and if j is less than or equal to Z, repeating the previous step until the production dynamics of each layer of the offshore multilayer heavy oil reservoir is obtained, wherein Z is the small number of layers of the reservoir.
4. The method for predicting the steam throughput capacity of the offshore multi-layer heavy oil reservoir according to claim 3, wherein the calculating the production dynamics of different throughput rounds in the j-layer reservoir by using the bottom hole steam parameters and the pre-constructed steam throughput capacity prediction model comprises the following steps:
the cycle number N=1, the oil reservoir stratum area of the small layer is divided into a steam area, a hot liquid area and a cold area when the steam injection stage is finished, and the heating radius of each area is calculated by utilizing the steam parameters at the bottom of the well;
determining the average temperature T of a steam zone at the end of well soaking savg Average temperature T of hydrothermal zone havg Average formation pressure of reservoir P avg,s Average water saturation S w And calculate daily oil production Q o ；
Determining the average temperature T of the steam zone in the production phase as Average temperature T of hydrothermal zone ah Average formation pressure of reservoir P avg,p Average water saturation S w Daily oil production Q is calculated o ；
Let the cycle number n=n+1, compare N with the throughput cycle number N max Of (A), e.g. N > N max Then the calculation is finished and the next step is carried out; if N is less than or equal to N max Then calculate the heating zone residual heat E of the period rs And E is rh And adding the residual heat of the heating area into the heat injected by the next cycle of throughput round, and repeating all the steps to obtain the production dynamics of different throughput rounds of the specific small layer.
5. The method for predicting the throughput capacity of marine multi-layer heavy oil reservoir as recited in claim 4, wherein said dividing the small reservoir stratum area at the end of the steam injection stage and calculating the heating radius of each area by using the bottom hole steam parameters comprises:
dividing a stratum area into a steam area, a hot liquid area and a cold area when the steam injection stage is finished;
splitting each small layer of steam injection quantity according to the stratum coefficient, and calculating to obtain the steam zone heating radius and the hot liquid zone heating radius by utilizing the well bottom steam parameter and a pre-established steam zone and hot liquid zone heating radius calculation model.
6. The method for predicting steam-huff-puff capacity of an offshore multi-layer heavy oil reservoir as recited in claim 4, wherein said determining an average temperature T of a steam zone at end of soaking savg Average temperature T of hydrothermal zone havg Average formation pressure of reservoir P avg,s Average water saturation S w And calculate daily oil production Q o Comprising:
determining the average temperature T of a steam zone at the end of a soaking well savg And mean temperature T of hydrothermal zone havg And based on the average temperature T of the steam zone savg And mean temperature T of hydrothermal zone havg Calculating to obtain the average formation pressure P of the oil reservoir avg,s Average water saturation S w ；
Calculated reservoir average formation pressure P avg,s And a pre-constructed steam throughput capacity prediction model is used for calculating daily oil production when the well is closed.
7. The method for predicting steam-huff-puff capacity of an offshore multi-layer heavy oil reservoir as recited in claim 4, wherein said determining the average temperature T of the steam zone during the production phase as Average temperature T of hydrothermal zone ah Average formation pressure of reservoir P avg,p Average water saturation S w Daily oil production Q is calculated o Comprising:
determining the production stage, the average temperature T of the steam zone as And mean temperature T of hydrothermal zone ah And based on the average temperature T of the steam zone as And mean temperature T of hydrothermal zone ah Calculating to obtain the average formation pressure P of the oil reservoir avg,p Average water saturation S w ；
Calculated reservoir average formation pressure P avg,p And a pre-constructed steam development productivity model is calculated to obtain daily oil production in the production stage.
8. A steam huff and puff capacity prediction system for an offshore multi-layer heavy oil reservoir, comprising:
the data acquisition module is used for acquiring basic parameters of the offshore multilayer heavy oil reservoir;
the bottom hole steam parameter calculation module is used for calculating and obtaining a bottom hole steam parameter by utilizing the acquired basic parameters and a pre-constructed shaft heat loss characterization model considering the offshore characteristics;
and the oil reservoir comprehensive productivity prediction module is used for calculating and obtaining production dynamics of different huff and puff rounds of the multilayer heavy oil reservoir by utilizing the well bottom steam parameters and a pre-constructed steam huff and puff productivity prediction model.
9. A processing plant comprising at least a processor and a memory, said memory having stored thereon a computer program, characterized in that the processor executes the steps of the steam throughput capacity prediction method of an offshore multi-layer heavy oil reservoir according to any one of claims 1 to 7 when running said computer program.
10. A computer storage medium having stored thereon computer readable instructions executable by a processor to perform the steps of the steam throughput capacity prediction method of an offshore multi-layer heavy oil reservoir according to any one of claims 1 to 7.
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