CN111206919A - Long-well-section high-yield gas well reservoir section wellbore pressure calculation method - Google Patents

Long-well-section high-yield gas well reservoir section wellbore pressure calculation method Download PDF

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CN111206919A
CN111206919A CN201911325042.1A CN201911325042A CN111206919A CN 111206919 A CN111206919 A CN 111206919A CN 201911325042 A CN201911325042 A CN 201911325042A CN 111206919 A CN111206919 A CN 111206919A
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pressure
well
section
gas
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CN111206919B (en
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王香增
张磊
辛翠平
乔向阳
姚光明
白慧芳
吕明
王凯
刘春燕
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Shaanxi Yanchang Petroleum Group Co Ltd
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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
    • E21B47/06—Measuring temperature or pressure
    • 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
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06Q—INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR ADMINISTRATIVE, COMMERCIAL, FINANCIAL, MANAGERIAL OR SUPERVISORY PURPOSES; SYSTEMS OR METHODS SPECIALLY ADAPTED FOR ADMINISTRATIVE, COMMERCIAL, FINANCIAL, MANAGERIAL OR SUPERVISORY PURPOSES, NOT OTHERWISE PROVIDED FOR
    • G06Q50/00—Systems or methods specially adapted for specific business sectors, e.g. utilities or tourism
    • G06Q50/02—Agriculture; Fishing; Mining

Abstract

The invention relates to a method for calculating the wellbore pressure of a reservoir section of a long-well-section high-yield gas well. The method for calculating the wellbore pressure of the reservoir section of the long-well-section high-yield gas well comprises the following steps: 1) acquiring basic parameters of a target reservoir section; 2) calculating the initial value p of the bottom flow pressurewf,down(ii) a 3) Calculating the initial value p of the bottom flow pressurewf,downAverage flow pressure of corresponding target reservoir segment
Figure DDA0002328161270000011
And the mean flow pressure
Figure DDA0002328161270000012
Corresponding rhog、BgAnd f; 4) calculating to obtain wellbore pressure p 'by using a formula'wf,down(ii) a If the criterion is met, the wellbore pressure pwf,down＝p'wf,down(ii) a The calculation result of the invention is accurate and reliable, and the example calculation shows that the relative error between the calculation result and the actual measurement value is very small.

Description

Long-well-section high-yield gas well reservoir section wellbore pressure calculation method
Technical Field
The invention relates to a method for calculating the wellbore pressure of a reservoir section of a long-well-section high-yield gas well.
Background
The natural gas exploitation process comprises the following steps: the natural gas flows from the reservoir to the wellbore and then from below up the wellbore to the wellhead. Therefore, the mass flow of the natural gas at the bottom of the reservoir is minimum, the mass flow of the natural gas becomes maximum when reaching the top of the reservoir, and the mass flow of the natural gas does not change from the top of the reservoir to the wellhead because no natural gas flows in. The mass flow rate of natural gas is actually increasing from bottom to top along the wellbore.
In the existing methods and technologies, when this phenomenon is faced, the processing modes are divided into two types: first, in vertical/deviated wells, the fact that the mass flow rate increases from the bottom to the top of the reservoir is not considered; second, in horizontal wells, it is considered that the mass flow rate is constantly changing.
The first processing mode is that the change of the mass flow is not considered in a vertical well/an inclined well, and for a low-yield gas well with a reservoir interval of only a few meters to a dozen meters, the change of the mass flow is not considered, the reservoir interval is short, the yield of the gas well is low, so that the change amplitude of the mass flow from the bottom to the top of the reservoir interval is not too large, and the error range is within the error range allowed by engineering calculation.
In the second treatment mode, in the horizontal well, because the length of the horizontal section of the horizontal well is usually more than hundreds of meters, the change of the mass flow cannot be ignored.
For a long-well section and a high-yield gas well, the mass flow rate of the gas well is changed greatly from the bottom of the reservoir section to the top of the reservoir section, and if the change of the mass flow rate is ignored, the mass flow rate is still treated as a fixed value, and the engineering calculation error is too large.
Disclosure of Invention
The invention aims to solve the problems and provides a high-precision long-well-section high-yield gas well reservoir section wellbore pressure calculation method.
The technical scheme of the invention is as follows:
firstly, establishing a model.
The fluid in the reservoir section of the long-well-section high-yield gas well continuously flows into the well bore, the mass flow rate along the well bore is greatly changed, and the schematic diagram is shown in figure 1.
1) Assuming that the flow rate increases linearly from the bottom to the top of the reservoir, the flow rate q at any point in the reservoir interval of interestgThe following were used:
Figure BDA0002328161250000011
wherein q isgVolume flow at any point in the reservoir section for the purpose, in m3D; q is the total gas production in the corresponding shaft at the top of the target reservoir interval and is unit m3/d；QscIs the gas well gas production rate under the standard state, and the unit is m3/d；BgIs the gas volume coefficient; h is the thickness of the target reservoir section and is unit m; l is the length of the well section, and is H/sin theta with the unit m; theta is an included angle between a shaft and the horizontal direction, (°), and for a vertical well, theta is 90 degrees, and sin theta is 1;
2) the gas flow velocity v at any point in the target reservoir interval is as follows:
Figure BDA0002328161250000021
3) the pressure gradient equation of gas flowing in the shaft is composed of gravity pressure drop gradient, friction pressure drop gradient and acceleration pressure drop gradient, and the expression is as follows:
Figure BDA0002328161250000022
wherein p is wellbore pressure in MPa; rho is the density of the gas in kg/m3(ii) a g is gravity acceleration and takes 9.81m/s2(ii) a f is the friction coefficient and has no dimension; v is the velocity of the gas up the wellbore in m/s; d is the inner diameter of the oil pipe in m;
4) substituting equation (2) into equation (3) yields a pressure drop of:
Figure BDA0002328161250000023
where ρ isgIs mean flow pressure
Figure BDA0002328161250000024
Corresponding gas density in kg/m3；
5) And (3) integrating the pressure p and the pressure z at the two ends of the formula (4) respectively to obtain an analytic solution of the bottom hole flowing pressure:
Figure BDA0002328161250000025
wherein
ρsc＝ρgBg(6)；
Wherein p iswf,downThe unit of flow pressure at the bottom of a target reservoir section is MPa; p is a radical ofwf,upThe unit of the flow pressure at the top of the target reservoir section is MPa; rhoscThe density of the gas in the ground condition in kg/m3。
And secondly, a long-well-section high-yield gas well reservoir section wellbore pressure calculation method.
The method for calculating the wellbore pressure of the reservoir section of the long-well-section high-yield gas well comprises the following steps:
1) acquiring basic parameters of a target reservoir section;
2) calculating the initial value p of the bottom flow pressurewf,down；
pwf,down＝pwf,up(1+0.00008H)
3) Calculating the initial value p of the bottom flow pressurewf,downAverage flow pressure of corresponding target reservoir segment
Figure BDA0002328161250000026
And the mean flow pressure
Figure BDA0002328161250000027
Corresponding rhog、BgAnd f;
wherein
Figure BDA0002328161250000031
Figure BDA0002328161250000032
Figure BDA0002328161250000033
Figure BDA0002328161250000034
4) Calculating to obtain wellbore pressure p 'by using the following formula'wf,down；
Figure BDA0002328161250000035
Wherein the content of the first and second substances,
Figure BDA0002328161250000036
Figure BDA0002328161250000037
ρsc＝ρgBg
wherein p iswf,upThe flow pressure at the top of the reservoir is unit MPa; g is gravity acceleration and takes 9.81m/s2(ii) a Theta is an included angle between the shaft and the horizontal direction and is a unit degree; l is the well length in m; b isgThe gas volume coefficient is zero dimension; f is the friction coefficient and has no dimension; rhoscThe density of the gas under ground conditions in kg/m3(ii) a H is reservoir thickness in m; qscIs the gas well gas production rate under the standard state, and the unit is m3D; d is the inner diameter of the oil pipe in m; gamma raygIs the relative density of natural gas;
Figure BDA0002328161250000038
is mean flow pressure
Figure BDA0002328161250000039
A corresponding deviation factor; e is the absolute roughness of the tube wall in m;
Figure BDA00023281612500000310
average temperature for the reservoir section of interest, in K; rhogIs mean flow pressure
Figure BDA00023281612500000311
Corresponding gas density in kg/m3；
4) Setting criterion as | pwf,down-p'wf,down|/pwf,down< 0.01%, the wellbore pressure pwf,down＝p'wf,down；
If pwf,down-p'wf,down|/pwf,downNot less than 0.01%, then'wf,downIs taken as a new initial value p of the bottom flow pressurewf,downRepeat 3) -4) until p 'satisfying the criterion is obtained'wf,downThen wellbore pressure pwf,down＝p'wf,down。
Wherein the mean flow pressure
Figure BDA00023281612500000312
Corresponding gas deviation coefficient
Figure BDA00023281612500000313
The high-pressure physical property experimental data are obtained through interpolation.
The invention has the technical effects that:
1. a long well section and high-yield gas well reservoir section wellbore pressure calculation model is established, the model considers the variation of the gas production from the bottom of the reservoir section to the reservoir section in the wellbore along with the well depth, and the model is more in line with the actual conditions of the long well section and the high-yield gas well;
2. the calculation of the wellbore pressure calculation models of the long well section and the high-yield gas well reservoir section is very convenient, and can be directly solved by substituting relevant parameters without complex programming and software;
3. the calculation result is accurate and reliable, and the example calculation shows that the relative error between the calculation result and the actual measurement value is very small.
Drawings
FIG. 1 is a schematic representation of variable flow wellbore flow.
FIG. 2 is a flow chart of the calculation steps of the present invention.
Detailed Description
The thickness of a gas layer of a gas well is 334m, the well inclination angle of the gas well is 35.1 degrees (the pipe inclination angle is 54.9 degrees), and the relative density of the gas is gammag0.691, average temperature of target reservoir section
Figure BDA0002328161250000041
The inner diameter D of the oil pipe is 0.076m, and the absolute roughness e of the inner surface of the oil pipe is 0.016 multiplied by 10-3m, the top flow pressure of the target reservoir section is pwf,up＝36.72MPa，Qsc＝116×104m3And d. The method for calculating the pressure of the shaft by using the method provided by the invention comprises the following specific steps;
1. calculating the initial value p of the bottom flow pressurewf,down＝37.7012MPa；
2. Mean flow pressure
Figure BDA0002328161250000042
3. According to the high-pressure physical property experiment, the gas viscosity mu is obtainedg0.027, the average flow pressure is obtained by interpolation
Figure BDA0002328161250000043
Deviation coefficient of lower gas
Figure BDA0002328161250000044
4. Calculation of Bg＝0.003633、ρg＝228.4454kg/m3；ρsc＝0.8299kg/m3；Re＝6913577；f＝0.014058；
5. And is calculated to obtain p'wf,down＝37.8133MPa；
|pwf,down-p'wf,down|/pwf,down0.30% > 0.01%; then with pwf,downRecalculated at 37.8133 MPa.
The recalculation process is as follows:
2、
Figure BDA0002328161250000045
3. according to the high-pressure physical property experiment, the gas viscosity mu is obtainedg0.027, the average flow pressure is obtained by interpolation
Figure BDA0002328161250000046
Deviation coefficient of lower gas
Figure BDA0002328161250000047
4. Calculation of Bg＝0.003629、ρg＝228.6958kg/m3；ρsc＝0.8299kg/m3；Re＝6913577；f＝0.014058；
5. And is calculated to obtain p'wf,down＝37.8137MPa；
|pwf,down-p'wf,down|/pwf,down0.001% < 0.01%, thus pwf,down＝p'wf,down＝37.8137MPa。
TABLE 1 iterative computation procedure
Figure BDA0002328161250000051
The actual measurement results show that the pressure of the shaft is 37.87MPa, and the solving relative error of the calculation formula in the invention is 0.15%.

Claims (5)

1. The long-well-section high-yield gas well reservoir section wellbore pressure calculation method is characterized by comprising the following steps of: the method comprises the following steps:
1) acquiring basic parameters of a target reservoir section;
2) calculating the initial value p of the bottom flow pressurewf,down；
3) Calculating the initial value p of the bottom flow pressurewf,downAverage flow pressure of corresponding target reservoir segment
Figure FDA0002328161240000011
And the mean flow pressure
Figure FDA0002328161240000012
Corresponding rhog、BgAnd f;
4) calculating to obtain wellbore pressure p 'by using the following formula'wf,down；
Figure FDA0002328161240000013
Wherein the content of the first and second substances,
Figure FDA0002328161240000014
Figure FDA0002328161240000015
Figure FDA0002328161240000016
Figure FDA0002328161240000017
Figure FDA0002328161240000018
ρsc＝ρgBg
wherein p iswf,upThe unit of the flow pressure at the top of the target reservoir section is MPa; g is gravity acceleration and takes 9.81m/s2(ii) a Theta is an included angle between the shaft and the horizontal direction and is a unit degree; l is the well length in m; b isgIs mean flow pressure
Figure FDA0002328161240000019
The corresponding gas volume coefficient has no dimension; f is the friction coefficient and has no dimension; rhoscThe density of the gas under ground conditions in kg/m3(ii) a H is reservoir thickness in m; qscIs the gas well gas production rate under the standard state, and the unit is m3D; d is the inner diameter of the oil pipe in m; gamma raygIs the relative density of natural gas;
Figure FDA00023281612400000110
is mean flow pressure
Figure FDA00023281612400000111
A corresponding deviation factor; e is the absolute roughness of the tube wall in m;
Figure FDA00023281612400000112
average temperature for the reservoir section of interest, in K; rhogIs mean flow pressure
Figure FDA00023281612400000113
Corresponding gas density in kg/m3；
4) Setting criterion as | pwf,down-p'wf,down|/pwf,down< 0.01%, the wellbore pressure pwf,down＝p'wf,down。
2. The method for calculating the wellbore pressure of the reservoir section of the long-well-section high-productivity gas well as recited in claim 1, wherein the method is characterized in that: also includes if pwf,down-p'wf,down|/pwf,downNot less than 0.01%, then'wf,downIs taken as a new initial value p of the bottom flow pressurewf,downRepeat 3) -4) until p 'satisfying the criterion is obtained'wf,downThen wellbore pressure pwf,down＝p'wf,down。
3. The method for calculating the wellbore pressure of the reservoir section of the long-well-section high-productivity gas well as recited in claim 2, wherein the method comprises the following steps: the step 2) calculates the initial value p of the bottom flow pressurewf,downThe specific process comprises the following steps:
pwf,down＝pwf,up(1+0.00008H)。
4. the method for calculating the wellbore pressure of the reservoir section of the long-wellbore section high-productivity gas well as recited in claim 3, wherein the method comprises the following steps: in said 3) wherein
Figure FDA0002328161240000021
5. The method for calculating the wellbore pressure of the reservoir section of the long-wellbore section high-productivity gas well according to claim 4, wherein the method comprises the following steps: the mean flow pressure
Figure FDA0002328161240000022
Corresponding gas deviation coefficient
Figure FDA0002328161240000023
The high-pressure physical property experimental data are obtained through interpolation.
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