CN103046925B - Binomial-based method and system for acquiring absolute unobstructed flow of condensate gas reservoir - Google Patents

Abstract

The invention relates to a method and a system for acquiring absolute unimpeded flow of a condensate gas reservoir under different formation pressures, wherein the method comprises the following steps: determining a binomial productivity equation under different formation pressures; according to the binomial productivity equation, acquiring the relation among a first coefficient, a second coefficient, a third coefficient and a fourth coefficient of the binomial productivity equation according to the first formation pressure, the second formation pressure, the first natural gas viscosity, the first deviation coefficient and the first gas phase permeability corresponding to the first formation pressure, and the second natural gas viscosity, the second deviation coefficient and the second gas phase permeability corresponding to the second formation pressure; and acquiring the absolute unimpeded flow of the condensate gas reservoir under different formation pressures according to the relation among the first coefficient, the second coefficient, the third coefficient and the fourth coefficient of the binomial productivity equation, the known absolute unimpeded flow of the first condensate gas reservoir, the known first formation pressure and the known second formation pressure.

Description

Binomial-based method and system for acquiring absolute unobstructed flow of condensate gas reservoir

Technical Field

The invention relates to the field of absolute unimpeded flow acquisition, in particular to a binomial-based method and a binomial-based system for acquiring absolute unimpeded flow of a condensate gas reservoir under different formation pressures.

Background

Document 1: the method provided by the oil and gas reservoir engineering practice [ M ]. Beijing oil industry Press, 2005, 142-:

$P_e^2-P_{wf}^2={\mathrm{aq}}_{sc}+{\mathrm{bq}}_{sc}^2$

wherein: $a=\frac{{\mathrm{TZ\μp}}_{sc}}{{\mathrm{\πkhT}}_{sc}{Z}_{sc}}(ln\frac{r_e}{r_w}+S_c+S_b);b=\frac{{\mathrm{\β\ρ}}_{sc}}{2{\mathrm{\π}}^2{h}^2}\frac{p_{sc}TZ}{Z_{sc}{T}_{sc}}\frac{1}{r_w{e}^{-s}}{S}_b=(\frac{1}{k_{rgc}}-1)ln\frac{r_b}{r_w};$ P_ethe formation pressure is MPa, and rho is the relative density of natural gas; p_wfIs bottom hole flowing pressure, MPa, mu is natural gas viscosity, mpa.s; z is natural gas deviation coefficient, T_scIs the ground standard temperature, K; t is the formation temperature, K; h is the effective thickness, m; r is_eControlling radius, m, r, for gas wells_wRadius of gas well shaft, m; k is the permeability, 10^-3μm²，S_cIs the completion skin factor; a and b are coefficients of binomial form, S_bThe coefficient of the condensed oil blocking skin is used; r is_bM is the condensate oil blocking radius, β is the non-Darcy seepage coefficient, K_rgcIs the relative gas-phase permeability at the critical condensate saturation.

Document 2: the method [ J ] for determining the gas well productivity under different formation pressures, natural gas technology, 2008,16(4):30-32, which takes into account the effect of formation pressure drop on gas well productivity, is expressed by the formula:

exponential type： $q_{{\mathrm{AOF}}_2}=\frac{c_2}{c_1}{\left(\frac{p_{e2}}{p_{e1}}\right)}^{2n}{q}_{{\mathrm{AOF}}_1}=\frac{Z_1{\mathrm{\μ}}_1}{Z_2{\mathrm{\μ}}_2}{\left(\frac{p_{e2}}{p_{e1}}\right)}^{2n}{q}_{{\mathrm{AOF}}_1}$

A binomial expression: $q_{AOF2}=\frac{p_{e2}}{p_{e1}}\sqrt{\frac{Z_1}{Z_2}}\·q_{AOF1}$

in the formula: a is₁、b₁And a₂、b₂Are respectively the coefficients of a binomial productivity equation, and the corresponding natural gas viscosity, deviation coefficient and gas phase permeability are respectively mu₁、Ζ₁、Κ₁And mu₂、Ζ₂、Κ₂；Ρ_e1And p_e2Respectively the formation pressures at the different production stages.

Document 3: zhenglikun, and the research [ J ] of a gas well unobstructed flow prediction method considering permeability stress sensitivity [ 2010,24(2) ].

The article considers the permeability stress sensitive effect of a reservoir caused by the reduction of the formation pressure, and provides a gas well non-resistance flow calculation method under different formation pressure conditions through a binomial productivity equation.

$\frac{k}{k_0}={\mathrm{be}}^{ap}$

$P_R^2-P_{wf}^2={\mathrm{Aq}}_g+{\mathrm{Bq}}_g^2$

$q_{AOF2}=\frac{P_{R2}}{P_{R1}}\sqrt{\frac{Z_1{\mathrm{\μ}}_{g1}{k}_2}{Z_2{\mathrm{\μ}}_{g2}{k}_1}}{q}_{AOF1}=\frac{P_{R2}}{P_{R1}}\sqrt{\frac{Z_1{\mathrm{\μ}}_{g1}}{Z_2{\mathrm{\μ}}_{g2}}{\mathrm{be}}^{ap}}{q}_{AOF1}$

The method has the defects that the method is only suitable for common dry gas reservoirs and cannot be applied to condensate gas reservoirs, because the calculation of the permeability in the article is based on the stress sensitive effect of rocks, and condensate oil precipitation does not influence the gas phase permeability of a reservoir. Although the influence of permeability on the calculation result is considered, the calculation method of permeability is fundamentally different in the two cases.

As can be seen from the above literature data, there are two equations to determine the absolute unobstructed flow of a gas well at present, based on the variation of the gas cap formation pressure. Firstly, if the pressure change is not large, the coefficient of the gas well productivity equation is considered to be unchanged in the development process, and the early gas well productivity equation can be directly utilized; secondly, the absolute unimpeded flow of the gas well under different formation pressures is deduced through a gas well productivity equation by considering the influence of formation pressure change on the aspects of gas viscosity, deviation coefficients and the like, but the current deduction process is based on the precondition that the reservoir permeability is unchanged, and in the process of calculating the viscosity and the deviation coefficients of the gas, the composition of the gas is considered to be unchanged, namely the molecular weight is not changed. This assumption holds for normal dry gas reservoirs, but for condensate gas reservoirs large calculation errors occur.

Disclosure of Invention

The invention aims to provide a binomial-based method and a binomial-based system for acquiring the absolute unobstructed flow of a condensate gas reservoir gas production well, so as to achieve the effect of improving the accuracy of acquiring the absolute unobstructed flow of the condensate gas reservoir gas production well.

In order to achieve the above object, the present invention provides a method for obtaining an absolute unimpeded flow rate of a condensate gas reservoir under different formation pressures, which is based on the changes of gas components and gas permeability in the condensate gas reservoir under different formation pressures; the method comprises the following steps:

determining a binomial productivity equation under different formation pressures;

according to the binomial productivity equation, acquiring the relation among a first coefficient, a second coefficient, a third coefficient and a fourth coefficient of the binomial productivity equation according to the first formation pressure, the second formation pressure, the first natural gas viscosity, the first deviation coefficient and the first gas phase permeability corresponding to the first formation pressure, and the second natural gas viscosity, the second deviation coefficient and the second gas phase permeability corresponding to the second formation pressure;

and acquiring the absolute unimpeded flow of the condensate gas reservoir under different formation pressures according to the relation among the first coefficient, the second coefficient, the third coefficient and the fourth coefficient of the binomial productivity equation, the known absolute unimpeded flow of the first condensate gas reservoir, the known first formation pressure and the known second formation pressure.

Optionally, in an embodiment of the present invention, the method for obtaining a gas phase permeability includes:

obtaining the condensate oil content under different formation pressures according to an isochoric failure experiment;

obtaining condensate oil saturation under different layer pressures according to the condensate oil content and the bound water saturation under different layer pressures;

according to the precipitation of the condensate oil, the form of an oil-gas phase permeability curve is not changed, and the gas phase relative permeability under different gas saturation degrees is obtained by utilizing the oil-gas phase permeability curve and the condensate oil saturation degrees under different formation pressures;

the gas phase permeability is obtained from the gas phase relative permeability and the air absolute permeability.

Optionally, in an embodiment of the present invention, the step of obtaining the condensate saturation degrees at different formation pressures according to the condensate content and the irreducible water saturation degrees at different formation pressures includes:

acquiring condensate oil saturation under different formation pressures according to the following formula;

S_o(p)＝[V_roCVD(p)](1-S_wi)

wherein S is_o(p) condensate saturation at different formation pressures; s_wiIrreducible water saturation; v_roCVD(p) condensate content at different formation pressures.

Optionally, in an embodiment of the present invention, the step of obtaining the gas phase permeability according to the gas phase relative permeability and the air absolute permeability includes:

obtaining the gas phase permeability according to the following formula;

K_rg＝K/K_a

wherein, K_rgRelative gas phase permeability; k_aThe absolute permeability of air is measured by a core experiment; k is qiPhase permeability.

Optionally, in an embodiment of the present invention, a relationship between the first coefficient, the second coefficient, the third coefficient, and the fourth coefficient of the binomial capacity equation is represented as:

$\frac{a_1}{a_2}=\frac{Z_1{\mathrm{\μ}}_1{K}_2}{Z_2{\mathrm{\μ}}_2{K}_1}\frac{b_1}{b_2}={\left(\frac{K_2}{K_1}\right)}^{1.1045}\frac{Z_1}{Z_2}$

wherein, a₁Is the first coefficient of the binomial capacity equation, a₂Is the second coefficient of the binomial capacity equation, b₁Is the third coefficient of the binomial capacity equation, b₂Is the fourth coefficient of the binomial capacity equation, Z₁For a corresponding first deviation factor at a first formation pressure,Z₂for a corresponding second deviation factor, mu, at a second formation pressure₁Is a corresponding first natural gas viscosity, μ, at a first formation pressure₂For a corresponding second natural gas viscosity, K, at a second formation pressure₁Is the corresponding first gas phase permeability, K, at the first formation pressure₂Corresponding to a second gas permeability at a second formation pressure.

Optionally, in an embodiment of the present invention, the calculation formula of the absolute unobstructed flow of the condensate gas reservoir under different formation pressures is as follows:

$q_{{\mathrm{AOF}}_2}=\frac{p_{e2}}{p_{e1}}\sqrt{\frac{Z_1}{Z_2}}{\left(\frac{K_2}{K_1}\right)}^{0.5502}\·q_{{\mathrm{AOF}}_1}$

wherein,for the absolute unimpeded flow of condensate gas reservoirs at different formation pressures,for known absolute unimpeded flow of condensate gas reservoir, Z₁Is a corresponding first deviation factor, Z, at a first formation pressure₂For a corresponding second deviation factor, K, at a second formation pressure₁Is the corresponding first gas phase permeability, K, at the first formation pressure₂Is the corresponding second gas phase permeability at the second formation pressure, Pp_e1Is the first formation pressure, p_e2Is the second formation pressure.

In order to achieve the above object, the present invention further provides a system for acquiring an absolute unimpeded flow rate of a condensate gas reservoir under different formation pressures, wherein the system acquires the absolute unimpeded flow rate based on changes in gas composition and gas permeability of the condensate gas reservoir under different formation pressures; the method comprises the following steps:

the binomial productivity equation determining unit is used for determining the binomial productivity equation under different laminating pressures;

the binomial coefficient relation determining unit is used for obtaining the relation among a first coefficient, a second coefficient, a third coefficient and a fourth coefficient of the binomial productivity equation according to the binomial productivity equation and through the first natural gas viscosity, the first deviation coefficient and the first gas phase permeability corresponding to the first formation pressure and the second natural gas viscosity, the second deviation coefficient and the second gas phase permeability corresponding to the second formation pressure;

and the absolute unimpeded flow acquiring unit is used for acquiring the absolute unimpeded flow of the condensate gas reservoir under different formation pressures according to the relation among the first coefficient, the second coefficient, the third coefficient and the fourth coefficient of the binomial productivity equation, the known absolute unimpeded flow of the condensate gas reservoir, the first formation pressure and the second formation pressure.

Optionally, in an embodiment of the present invention, the binomial coefficient relation determining unit includes:

the isovolumetric failure module is used for obtaining the condensate oil content under different formation pressures according to an isovolumetric failure experiment;

the condensate oil saturation acquisition module is used for acquiring the condensate oil saturation under different stratum pressures according to the condensate oil content and the bound water saturation under different stratum pressures;

the relative permeability value acquisition module is used for obtaining the relative permeability of gas phase under different gas saturation degrees by utilizing the oil-gas phase permeability curve and the condensate oil saturation degrees under different layer pressures according to the condition that the form of the oil-gas phase permeability curve is not changed during the precipitation of the condensate oil;

and the gas phase permeability acquisition module is used for acquiring the gas phase permeability according to the gas phase relative permeability and the air absolute permeability.

Optionally, in an embodiment of the present invention, the condensate saturation obtaining module obtains the condensate saturation at different formation pressures according to the following formula;

S_o(p)＝[V_roCVD(p)](1-S_wi)

wherein S is_o(p) condensate saturation at different formation pressures; s_wiIrreducible water saturation; v_roCVD(p) condensate content at different formation pressures.

Optionally, in an embodiment of the present invention, the gas permeability acquiring module acquires the gas permeability according to the following formula;

K_rg＝K/K_a

wherein, K_rgRelative gas phase permeability; k_aThe absolute permeability of air is measured by a core experiment; k is the gas phase permeability.

Optionally, in an embodiment of the present invention, a relationship among the first coefficient, the second coefficient, the third coefficient, and the fourth coefficient of the binomial capacity equation obtained by the binomial coefficient relationship determining unit is represented as:

$\frac{a_1}{a_2}=\frac{Z_1{\mathrm{\μ}}_1{K}_2}{Z_2{\mathrm{\μ}}_2{K}_1}\frac{b_1}{b_2}={\left(\frac{K_2}{K_1}\right)}^{1.1045}\frac{Z_1}{Z_2}$

wherein, a₁Is the first coefficient of the binomial capacity equation, a₂Is the second coefficient of the binomial capacity equation, b₁Is the third coefficient of the binomial capacity equation, b₂Is the fourth coefficient of the binomial capacity equation, Z₁Is a corresponding first deviation factor, Z, at a first formation pressure₂For a corresponding second deviation factor, mu, at a second formation pressure₁Is a corresponding first natural gas viscosity, μ, at a first formation pressure₂For a corresponding second natural gas viscosity, K, at a second formation pressure₁Is the corresponding first gas phase permeability, K, at the first formation pressure₂Under the pressure of a second formationCorrespondingly a second gas permeability.

Optionally, in an embodiment of the present invention, the absolute unimpeded flow of the condensate gas reservoir obtained by the absolute unimpeded flow acquiring unitThe calculation formula is as follows:

$q_{{\mathrm{AOF}}_2}=\frac{p_{e2}}{p_{e1}}\sqrt{\frac{Z_1}{Z_2}}{\left(\frac{K_2}{K_1}\right)}^{0.5502}\·q_{{\mathrm{AOF}}_1}$

wherein,for the absolute unimpeded flow of condensate gas reservoirs at different formation pressures,for known absolute unimpeded flow of condensate gas reservoir, Z₁Is the first placeCorresponding first deviation factor, Z, under lamination pressure₂For a corresponding second deviation factor, K, at a second formation pressure₁Is the corresponding first gas phase permeability, K, at the first formation pressure₂Is the corresponding second gas phase permeability at the second formation pressure, Pp_e1Is the first formation pressure, p_e2Is the second formation pressure.

The technical scheme has the following beneficial effects: because the technical scheme provided by the application considers the influence of the condensate oil on the gas phase permeability and the change of the condensate gas components, the absolute unimpeded flow is more accurately obtained, so that the condensate gas reservoir can be guided to be reasonably and effectively developed.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a flow chart of a method for acquiring absolute unimpeded flow of a condensate gas reservoir under different formation pressures based on binomial equations, which is provided by the invention;

FIG. 2 is a schematic diagram of a system for acquiring absolute unimpeded flow of condensate gas reservoirs under different formation pressures based on binomial equations according to the present invention;

FIG. 3 is a structural diagram of a binomial coefficient relation determining unit in the system for acquiring absolute unobstructed flow of condensate gas reservoirs under different stratigraphic pressures based on binomial equations provided by the invention;

FIG. 4 is a graph of the change in molecular weight of a mixture with pressure;

FIG. 5 is a graph of gas phase permeability as a function of pressure;

FIG. 6 is a graph of absolute unobstructed flow of a binomial condensate reservoir as a function of formation pressure;

fig. 7 is a flow chart of a method for obtaining gas phase permeability according to the present invention.

Detailed Description

The technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Condensate gas reservoirs are a special, complex gas reservoir. In the development process, the condensate gas well presents different flow areas along with the reduction of the formation pressure, and the different flow areas are accompanied by different seepage equations. The method has the advantages that accurate oil-gas subsections and corresponding oil-gas phase permeability curves of different areas are difficult to obtain, on the basis of detailed analysis and continuous attempts, an approximate gas phase permeability calculation method is adopted, a good effect is achieved, calculation errors are reduced, and the requirement of engineering calculation precision is met.

As shown in fig. 1, one of the flow charts of the method for acquiring absolute unimpeded flow of a condensate gas reservoir under different formation pressures based on a binomial equation is provided, and the method is based on the acquisition of absolute unimpeded flow of gas component change and gas phase permeability change in the condensate gas reservoir under different formation pressures; the method comprises the following steps:

step 101: and determining a binomial capacity equation under different lamination pressures.

Step 102: from the binomial productivity equation, by formation pressure p_e1And p_e2And formation pressure p_e1Corresponding natural gas viscosity μ₁Coefficient of deviation Z₁And gas phase permeability K₁And formation pressure p_e2Corresponding natural gas viscosity μ₂Coefficient of deviation Z₂And gas phase permeability K₂Obtaining a binomial productivity equation coefficient a₁、a₂、b₁And b₂The relationship between them.

Step 103: according to the binomial productivity equation coefficient a₁、a₂、b₁And b₂Relation between, known absolute unobstructed flow of condensate reservoirAnd formation pressure p_e1And p_e2To obtain the absolute non-resistance flow of condensate gas reservoir under different formation pressures

Fig. 7 is a flow chart of a method for obtaining gas phase permeability according to the present invention. The method comprises the following steps:

step a: obtaining the condensate oil content under different formation pressures according to an isochoric failure experiment;

step b: obtaining condensate oil saturation under different layer pressures according to the condensate oil content and the bound water saturation under different layer pressures;

step c: according to the precipitation of the condensate oil, the form of an oil-gas phase permeability curve is not changed, and the gas phase relative permeability under different gas saturation degrees is obtained by utilizing the oil-gas phase permeability curve and the condensate oil saturation degrees under different formation pressures;

step d: the gas phase permeability is obtained from the gas phase relative permeability and the air absolute permeability.

Optionally, in an embodiment of the present invention, the step of obtaining the condensate saturation degrees at different formation pressures according to the condensate content and the irreducible water saturation degrees at different formation pressures includes:

acquiring condensate oil saturation under different formation pressures according to the following formula;

S_o(p)＝[V_roCVD(p)](1-S_wi)

wherein S is_o(p) condensate saturation at different formation pressures; s_wiIrreducible water saturation; v_roCVD(p) condensate content at different formation pressures.

Optionally, in an embodiment of the present invention, the step of obtaining the gas phase permeability according to the gas phase relative permeability and the air absolute permeability includes:

obtaining the gas phase permeability according to the following formula;

K_rg＝K/K_a

wherein, K_rgRelative gas phase permeability; k_aThe absolute permeability of air is measured by a core experiment; k is the gas phase permeability.

Optionally, in an embodiment of the present invention, the binomial productivity equation coefficient a₁、a₂、b₁And b₂The relationship between them is expressed as:

$\frac{a_1}{a_2}=\frac{Z_1{\mathrm{\μ}}_1{K}_2}{Z_2{\mathrm{\μ}}_2{K}_1}\frac{b_1}{b_2}={\left(\frac{K_2}{K_1}\right)}^{1.1045}\frac{Z_1}{Z_2}.$

optionally, in an embodiment of the present invention, the condensate gas reservoir has absolutely no resistance flowThe calculation formula is as follows:

$q_{{\mathrm{AOF}}_2}=\frac{p_{e2}}{p_{e1}}\sqrt{\frac{Z_1}{Z_2}}{\left(\frac{K_2}{K_1}\right)}^{0.5502}\·q_{{\mathrm{AOF}}_1}.$

fig. 2 is a schematic diagram of a system for acquiring absolute unobstructed flow of condensate gas reservoirs at different formation pressures based on binomial equations. The system acquires absolute unimpeded flow based on the change of gas components and the change of gas phase permeability in the condensate gas reservoir under different formation pressures; the method comprises the following steps:

a binomial productivity equation determining unit 201, configured to determine a binomial productivity equation under different formation pressures;

a binomial coefficient relation determining unit 202 for determining from the formation pressure p the binomial productivity equation_e1And p_e2And formation pressure p_e1Corresponding natural gas viscosity μ₁Coefficient of deviation Z₁And gas phase permeability K₁And formation pressure p_e2Corresponding natural gas viscosity μ₂Coefficient of deviation Z₂And gas phase permeability K₂Obtaining a binomial productivity equation coefficient a₁、a₂、b₁And b₂The relationship between;

an absolute unimpeded flow obtaining unit 203 for obtaining the coefficient a according to the binomial productivity equation₁、a₂、b₁And b₂Relation between, known absolute unobstructed flow of condensate reservoirAnd formation pressure p_e1And p_e2To obtain the absolute non-resistance flow of condensate gas reservoir under different formation pressures

As shown in fig. 3, it is a structural diagram of a binomial coefficient relationship determining unit in the system for acquiring absolute unobstructed flow of condensate gas reservoirs under different stratigraphic pressures based on binomial equations provided by the present invention. The binomial coefficient relation determining unit 202 includes:

the isochoric failure module 2021 is used for obtaining the condensate oil content under different formation pressures according to an isochoric failure experiment;

the condensate oil saturation acquisition module 2022 is configured to obtain the condensate oil saturation under different formation pressures according to the condensate oil content and the irreducible water saturation under different formation pressures;

the relative permeability value acquisition module 2023 is configured to obtain the gas phase relative permeability under different gas saturation degrees by using the oil-gas permeability curve and the condensate saturation degrees under different layer pressures, without changing the form of the oil-gas permeability curve according to the precipitation of the condensate;

a gas phase permeability obtaining module 2024, configured to obtain a gas phase permeability according to the gas phase relative permeability and the air absolute permeability.

Optionally, in an embodiment of the present invention, the condensate saturation acquiring module 2022 acquires the condensate saturation at different formation pressures according to the following formula;

S_o(p)＝[V_roCVD(p)](1-S_wi)

wherein S is_o(p) condensate saturation at different formation pressures; s_wiIrreducible water saturation; v_roCVD(p) condensate content at different formation pressures.

Optionally, in an embodiment of the present invention, the gas phase permeability obtaining module 2024 obtains the gas phase permeability according to the following formula;

K_rg＝K/K_a

wherein, K_rgRelative gas phase permeability; k_aThe absolute permeability of air is measured by a core experiment; k is the gas phase permeability.

Optionally, in an embodiment of the present invention, the binomial coefficient relation determining unit 202 obtains twoCoefficient of polynomial energy production equation a₁、a₂、b₁And b₂The relationship between them is expressed as:

$\frac{a_1}{a_2}=\frac{Z_1{\mathrm{\μ}}_1{K}_2}{Z_2{\mathrm{\μ}}_2{K}_1}\frac{b_1}{b_2}={\left(\frac{K_2}{K_1}\right)}^{1.1045}\frac{Z_1}{Z_2}.$

optionally, in an embodiment of the present invention, the absolute unimpeded flow of the condensate gas reservoir obtained by the absolute unimpeded flow acquiring unit 203 is obtained by the absolute unimpeded flow acquiring unitThe calculation formula is as follows:

$q_{{\mathrm{AOF}}_2}=\frac{p_{e2}}{p_{e1}}\sqrt{\frac{Z_1}{Z_2}}{\left(\frac{K_2}{K_1}\right)}^{0.5502}\·q_{{\mathrm{AOF}}_1}.$

the device provided by the invention does not need a main station, a sub station and a complex communication device for line load distribution in the power distribution network automation device realized by using the design of a general processor, a digital signal processor, an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other programmable logic devices, discrete gate or transistor logic, discrete hardware components, a computer device or any combination of the above.

Those of skill would further appreciate that the various illustrative logical blocks, elements, and steps described in connection with the apparatus of the present invention may be implemented as electronic hardware, computer software, or combinations of both. The various illustrative components, elements, and steps described above have been described generally in terms of their functionality for the purpose of illustrating hardware and software interchangeability (interchangeability). Whether such functionality is implemented as hardware or software depends upon the particular application and design requirements of the overall device. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present embodiments.

The various illustrative logical blocks, or elements, described in connection with the apparatus of the invention may be implemented or performed with a general purpose processor, a digital signal processor, an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a digital signal processor and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a digital signal processor core, or any other similar configuration.

The steps of a method or algorithm described in connection with the apparatus of the invention may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may be stored in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. For example, a storage medium may be coupled to the processor such the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. The processor and the storage medium may reside in an ASIC, which may be located in a user terminal. In the alternative, the processor and the storage medium may reside in different components in a user terminal.

In one or more exemplary designs, the functions described in the apparatus of the present invention may be implemented in hardware, software, firmware, or any combination of the three. If implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Computer-readable media includes both computer storage media and communication media that facilitate transfer of a computer program from one place to another. Storage media may be any available media that can be accessed by a general purpose or special purpose computer. For example, such computer-readable media can include, but is not limited to, RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to carry or store program code in the form of instructions or data structures and which can be read by a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor. Additionally, any connection is properly termed a computer-readable medium, and so forth, if the software is transmitted from a website, server, or other remote source over a coaxial cable, fiber optic cable, twisted pair, Digital Subscriber Line (DSL), or wireless equations such as infrared, radio, and microwave, for example, is also included in the computer-readable medium. Such discs (disk) and disks (disc) include compact disks, laser disks, optical disks, DVDs, floppy disks and blu-ray disks where disks usually reproduce data magnetically, while disks usually reproduce data optically with lasers. Combinations of the above may also be included in the computer-readable medium.

For a condensate gas reservoir, after the pressure of a local layer is reduced to be lower than the dew point pressure, heavy components in the condensate gas are gradually reverse-condensed into a stratum, so that the composition of the condensate gas can be changed, and meanwhile, reverse-condensed condensate oil can adsorb the surface of a rock to influence the seepage flow capacity of a reservoir. The technical scheme of acquiring the absolute unimpeded flow of the condensate gas reservoir under different formation pressures is discussed in the embodiment of the invention, and the gas well productivity equation of the condensate gas reservoir under different formation pressures can be deduced by researching the influence of formation pressure reduction on gas phase permeability and condensate gas composition and utilizing a binomial productivity equation and an exponential productivity equation so as to guide the reasonable and effective development of the condensate gas reservoir.

The main differences between condensate and dry gas reservoirs are the following two aspects: first, the change in gas composition. FIG. 4 is a graph showing the molecular weight of the mixture as a function of pressure; second, the change in gas phase permeability. As shown in fig. 5, is a graph of gas phase permeability as a function of pressure. Among them, the influence of the change in gas composition on the productivity is mainly reflected in the change in molecular weight of the gas mixture. According to the existing gas testing data, the molecular weight of the gas under different laminar pressures can be obtained by using a mathematical method. When the condensate oil is separated out from the gas, the permeability of the gas phase can be changed, and the permeability of the gas phase under different gas saturation degrees can be obtained according to a phase permeability curve obtained by experiments.

In the present application, the method for obtaining the gas phase permeability under different lamination pressures:

the change in gas phase permeability K is due to the effect of gas phase flow on condensate precipitation, which is determined by the specific properties of the condensate reservoir, rather than stress-sensitive permeability changes.

The condensate oil content under different formation pressures can be obtained according to a CVD (chemical vapor deposition) experiment, and at the moment, three phases of oil, gas and water and the saturation S of bound water can appear in rock pores_wiCan be obtained from the measured data by the formula S_o(p)＝[V_roCVD(p)](1-S_wi) The condensate saturation S under different layer pressures can be obtained_o(p) of the formula (I). And assuming that the precipitation of the condensate does not change the form of an oil-gas phase permeability curve, and obtaining the relative permeability values of the oil phase and the gas phase under different gas saturation degrees according to the oil-gas phase permeability curve and the condensate saturation degrees under different layer pressures.

Among the existing methods for obtaining gas phase permeability, the condensate gas reservoir has the following characteristics:

A) the method comprises the following steps The oil-gas phase permeability curve under the actual stratum state is difficult to obtain;

B) the method comprises the following steps According to actual core data, an oil-gas phase permeability curve can be obtained in a laboratory;

C) the method comprises the following steps The phase permeability curve reflects the oil-gas two-phase seepage characteristics, and the gas phase permeability under different layer pressures can be approximately calculated by obtaining the condensate oil content under different layer pressures through a CVD (chemical vapor deposition) experiment. In a word, the method can obtain the flow effect similar to oil and gas phases in a real stratum state by using limited conditions, and greatly reduces the calculation error of the unimpeded flow of the condensate gas reservoir gas well.

Example (b):

according to a binomial capacity equation: $P_e^2-P_{wf}^2={\mathrm{aq}}_{sc}+{\mathrm{bq}}_{sc}^2;$

suppose that at two different stages of production, the formation pressures are each P_e1And P_e2The coefficients of the binomial productivity equation are respectively a₁、b₁And a₂、b₂And the corresponding natural gas viscosity, deviation coefficient and gas phase permeability are respectively mu₁、Z₁、K₁And mu₂、Z₂、K₂Then the following relationship can be obtained:

$\frac{a_1}{a_2}=\frac{Z_1{\mathrm{\μ}}_1{K}_2}{Z_2{\mathrm{\μ}}_2{K}_1}\frac{b_1}{b_2}={\left(\frac{K_2}{K_1}\right)}^{1.1045}\frac{Z_1}{Z_2};$

according to the binomial productivity equation coefficient a₁、a₂、b₁And b₂Relation between, known absolute unobstructed flow of condensate reservoirAnd formation pressure p_e1And p_e2To obtain the absolute non-resistance flow of condensate gas reservoir under different formation pressures

$q_{AOF2}=\frac{p_{e2}}{p_{e1}}\sqrt{\frac{Z_1}{Z_2}}{\left(\frac{K_2}{K_1}\right)}^{0.5502}\·q_{AOF1}$

Fig. 6 is a graph showing absolute unobstructed flow of a binomial-based condensate reservoir as a function of formation pressure in the example. The E curve in fig. 6 does not take into account the effect of condensate on reservoir permeability and gas molecular weight, and the F curve takes into account both the effect of formation drawdown on gas molecular weight and reservoir permeability. As can be seen from the figure, when the formation pressure is reduced to be lower than the dew point pressure, the calculation result is more accurate by considering the influence of the condensate oil on the gas phase permeability and the change of the condensate gas components.

As can be seen from the calculation result values in table 1 below, the absolute open-flow rate of the gas well is calculated by using a common dry gas reservoir calculation method and a binomial-based condensate gas reservoir calculation method under different formation pressures according to actual gas test data of an oil field and a detection analysis report of the well. The calculation results show that the gas well yield of the condensate gas reservoir calculated by adopting the dry gas reservoir calculation method has larger errors which exceed the precision requirement (0-10%) of engineering calculation, and the condensate gas reservoir calculation method under different formation pressures based on the binomial greatly reduces the calculation errors and meets the precision requirement of the engineering calculation, so the method can well guide the production of the oil field.

Table 12007Q 1 well binomial calculation results and errors

The above-mentioned specific implementation equations are used to further explain the objects, technical solutions and advantages of the present invention, and it should be understood that the above-mentioned specific implementation equations are merely illustrative of the present invention and are not intended to limit the scope of the present invention, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (10)

1. The method for acquiring the absolute unimpeded flow of the condensate gas reservoir under different formation pressures is characterized in that the method is used for acquiring the absolute unimpeded flow based on the change of gas components and the change of gas phase permeability in the condensate gas reservoir under different formation pressures; the method comprises the following steps:

determining a binomial productivity equation under different formation pressures;

according to the binomial productivity equation, acquiring the relation among a first coefficient, a second coefficient, a third coefficient and a fourth coefficient of the binomial productivity equation according to the first formation pressure, the second formation pressure, the first natural gas viscosity, the first deviation coefficient and the first gas phase permeability corresponding to the first formation pressure, and the second natural gas viscosity, the second deviation coefficient and the second gas phase permeability corresponding to the second formation pressure;

acquiring the absolute unimpeded flow of the condensate gas reservoir under different formation pressures according to the relation among a first coefficient, a second coefficient, a third coefficient and a fourth coefficient of a binomial productivity equation, the known absolute unimpeded flow of the first condensate gas reservoir, the known first formation pressure and the known second formation pressure;

the gas phase permeability obtaining method comprises the following steps:

obtaining the condensate oil content under different formation pressures according to an isochoric failure experiment;

obtaining condensate oil saturation under different layer pressures according to the condensate oil content and the bound water saturation under different layer pressures;

according to the precipitation of the condensate oil, the form of an oil-gas phase permeability curve is not changed, and the gas phase relative permeability under different gas saturation degrees is obtained by utilizing the oil-gas phase permeability curve and the condensate oil saturation degrees under different formation pressures;

the gas phase permeability is obtained from the gas phase relative permeability and the air absolute permeability.

2. The method of claim 1, wherein the step of deriving condensate saturations at different formation pressures based on condensate content and irreducible water saturation at different formation pressures comprises:

acquiring condensate oil saturation under different formation pressures according to the following formula;

S_o(p)＝[V_roCVD(p)](1-S_wi)

wherein S is_o(p) condensate saturation at different formation pressures; s_wiIrreducible water saturation; v_roCVD(p) condensate content at different formation pressures.

3. The method of claim 1, wherein the step of obtaining the gas phase permeability from the gas phase relative permeability and the air absolute permeability comprises:

obtaining the gas phase permeability according to the following formula;

K_rg＝K/K_a

wherein, K_rgRelative gas phase permeability; k_aThe absolute permeability of air is measured by a core experiment; k is the gas phase permeability.

4. The method according to any one of claims 1 to 3, wherein the relationship between the first coefficient, the second coefficient, the third coefficient and the fourth coefficient of the binomial productivity equation is represented as:

$\frac{a_1}{a_2}=\frac{Z_1{\mathrm{\μ}}_1{K}_2}{Z_2{\mathrm{\μ}}_2{K}_1}\frac{b_1}{b_2}={\left(\frac{K_2}{K_1}\right)}^{1.1045}\frac{Z_1}{Z_2}$

wherein, a₁Is the first coefficient of the binomial capacity equation, a₂Is the second coefficient of the binomial capacity equation, b₁Is the third coefficient of the binomial capacity equation, b₂Is the fourth coefficient of the binomial capacity equation, Z₁Is a corresponding first deviation factor, Z, at a first formation pressure₂For a corresponding second deviation factor, mu, at a second formation pressure₁Is a corresponding first natural gas viscosity, μ, at a first formation pressure₂For a corresponding second natural gas viscosity, K, at a second formation pressure₁Is the corresponding first gas phase permeability, K, at the first formation pressure₂Corresponding to a second gas permeability at a second formation pressure.

5. The method according to any one of claims 1 to 3, wherein the calculation formula of the absolute unimpeded flow of the condensate gas reservoir at different formation pressures is as follows:

$q_{{\mathrm{AOF}}_2}=\frac{p_{e2}}{p_{e1}}\sqrt{\frac{Z_1}{Z_2}}{\left(\frac{K_2}{K_1}\right)}^{0.5502}\·q_{{\mathrm{AOF}}_1}$

wherein,for the absolute unimpeded flow of condensate gas reservoirs at different formation pressures,for known absolute unimpeded flow of condensate gas reservoir, Z₁Is a corresponding first deviation factor, Z, at a first formation pressure₂For a corresponding second deviation factor, K, at a second formation pressure₁Is the corresponding first gas phase permeability, K, at the first formation pressure₂Is the corresponding second gas phase permeability at the second formation pressure, Pp_e1Is the first formation pressure, p_e2Is the second formation pressure.

6. The system for acquiring the absolute unimpeded flow of the condensate gas reservoir under different formation pressures is characterized in that the system acquires the absolute unimpeded flow based on the change of gas components and the change of gas phase permeability in the condensate gas reservoir under different formation pressures; the method comprises the following steps:

the binomial productivity equation determining unit is used for determining the binomial productivity equation under different laminating pressures;

the binomial coefficient relation determining unit is used for obtaining the relation among a first coefficient, a second coefficient, a third coefficient and a fourth coefficient of the binomial productivity equation according to the binomial productivity equation and through the first natural gas viscosity, the first deviation coefficient and the first gas phase permeability corresponding to the first formation pressure and the second natural gas viscosity, the second deviation coefficient and the second gas phase permeability corresponding to the second formation pressure;

the absolute unimpeded flow acquiring unit is used for acquiring the absolute unimpeded flow of the condensate gas reservoir under different formation pressures according to the relation among a first coefficient, a second coefficient, a third coefficient and a fourth coefficient of the binomial productivity equation, the known absolute unimpeded flow of the condensate gas reservoir, the first formation pressure and the second formation pressure;

wherein the binomial coefficient relation determining unit includes:

the isovolumetric failure module is used for obtaining the condensate oil content under different formation pressures according to an isovolumetric failure experiment;

the condensate oil saturation acquisition module is used for acquiring the condensate oil saturation under different stratum pressures according to the condensate oil content and the bound water saturation under different stratum pressures;

the relative permeability value acquisition module is used for obtaining the relative permeability of gas phase under different gas saturation degrees by utilizing the oil-gas phase permeability curve and the condensate oil saturation degrees under different layer pressures according to the condition that the form of the oil-gas phase permeability curve is not changed during the precipitation of the condensate oil;

and the gas phase permeability acquisition module is used for acquiring the gas phase permeability according to the gas phase relative permeability and the air absolute permeability.

7. The system of claim 6 wherein the condensate saturation acquisition module acquires condensate saturation at different formation pressures according to the following equation;

S_o(p)＝[V_roCVD(p)](1-S_wi)

wherein S is_o(p) condensate saturation at different formation pressures; s_wiIrreducible water saturation; v_roCVD(p) condensate content at different formation pressures.

8. The system of claim 6, wherein the gas phase permeability obtaining module obtains the gas phase permeability according to the following formula;

K_rg＝K/K_a

wherein, K_rgRelative gas phase permeability; k_aThe absolute permeability of air is measured by a core experiment; k is the gas phase permeability.

9. The system according to any one of claims 6 to 8, wherein the relation between the first coefficient, the second coefficient, the third coefficient and the fourth coefficient of the binomial productivity equation obtained by the binomial coefficient relation determination unit is represented as:

$\frac{a_1}{a_2}=\frac{Z_1{\mathrm{\μ}}_1{K}_2}{Z_2{\mathrm{\μ}}_2{K}_1}\frac{b_1}{b_2}={\left(\frac{K_2}{K_1}\right)}^{1.1045}\frac{Z_1}{Z_2}$

wherein, a₁Is the first coefficient of the binomial capacity equation, a₂Is the second coefficient of the binomial capacity equation, b₁Is the third coefficient of the binomial capacity equation, b₂Is the fourth coefficient of the binomial capacity equation, Z₁Is a corresponding first deviation coefficient at a first formation pressure，Z₂For a corresponding second deviation factor, mu, at a second formation pressure₁Is a corresponding first natural gas viscosity, μ, at a first formation pressure₂For a corresponding second natural gas viscosity, K, at a second formation pressure₁Is the corresponding first gas phase permeability, K, at the first formation pressure₂Corresponding to a second gas permeability at a second formation pressure.

10. The system according to any one of claims 6 to 8, wherein the condensate gas reservoir absolute unimpeded flow rate obtained by the absolute unimpeded flow rate obtaining unitThe calculation formula is as follows:

$q_{{\mathrm{AOF}}_2}=\frac{p_{e2}}{p_{e1}}\sqrt{\frac{Z_1}{Z_2}}{\left(\frac{K_2}{K_1}\right)}^{0.5502}\·q_{{\mathrm{AOF}}_1}$

wherein,for the absolute unimpeded flow of condensate gas reservoirs at different formation pressures,for known absolute unimpeded flow of condensate gas reservoir, Z₁Is a corresponding first deviation factor, Z, at a first formation pressure₂For a corresponding second deviation factor, K, at a second formation pressure₁Is the corresponding first gas phase permeability, K, at the first formation pressure₂Is the corresponding second gas phase permeability at the second formation pressure, Pp_e1Is the first formation pressure, p_e2Is the second formation pressure.