CN110929458A - Method for calculating annulus comprehensive hydraulic equivalent diameter of irregular borehole section - Google Patents
Method for calculating annulus comprehensive hydraulic equivalent diameter of irregular borehole section Download PDFInfo
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Abstract
The invention discloses a calculation method of annulus comprehensive hydraulic equivalent diameter aiming at irregular well bore sections, which comprises the steps of obtaining well diameter series data and well drilling data; calculating the axial length of the irregular borehole section, the length of the borehole wall curve section and the ratio of the axial length to the length of the borehole wall curve section; monitoring to obtain the sum of the flow pressure drop inside and outside the pipe of the irregular well hole section; presetting an annulus hydraulic equivalent diameter, and calculating the sum of the flow pressure drop inside and outside the pipe corresponding to the annulus hydraulic equivalent diameter; and comparing the calculated and monitored flow pressure drop, adding or subtracting a preset small value to or from the preset annulus hydraulic equivalent diameter when the difference value is not smaller than the preset minimum difference value, adopting an iterative calculation method to enable the difference value to be smaller than the preset minimum difference value, and taking the annulus hydraulic equivalent diameter when the difference value is smaller than the preset minimum difference value as the calculated annulus comprehensive hydraulic equivalent diameter. The method can quickly and conveniently determine the comprehensive annular hydraulic equivalent diameter of the irregular borehole section, improve the calculation performance and convenience of annular flow pressure drop, and further accurately and conveniently calculate the annular pressure.
Description
Technical Field
The invention relates to the technical field of cementing in drilling and production engineering, in particular to a calculation method for an annular comprehensive hydraulic equivalent diameter of an irregular well bore section.
Background
Due to the influence of the heterogeneity of the stratum, the diameter expansion phenomenon of different degrees often exists in the stratum with different depths, and an irregular borehole such as an irregular borehole or a sugarcoated haw is very easy to form. Such irregular wellbores do not facilitate determining the annulus hydraulic equivalent diameter, directly affecting the annulus flow pressure drop calculation. At present, when annular flow pressure drop is calculated, an annular is assumed to be a regular smooth straight borehole and is inconsistent with actual working conditions, so that annular pressure is not calculated accurately enough. Thus, the prior art has yet to be improved and enhanced.
Disclosure of Invention
In view of the defects of the prior art, the invention aims to provide a method for calculating the comprehensive annular hydraulic equivalent diameter of the irregular borehole section, which can conveniently determine the comprehensive annular hydraulic equivalent diameter of the irregular borehole section and improve the accuracy and convenience of annular flow pressure drop calculation.
In order to achieve the purpose, the invention adopts the following technical scheme:
a method for calculating the comprehensive hydraulic equivalent diameter of an annulus of an irregular borehole section comprises the following steps:
acquiring the hole diameter series data and well drilling data of all measuring points in the irregular hole section selected from the hole diameter curve graph;
drawing an irregular borehole diameter curve graph according to the selected borehole diameter series data of the irregular borehole section, and calculating the axial length of the irregular borehole section, the length of a borehole wall curve section and the ratio of the axial length to the length of the borehole wall curve section;
drilling when the casing shoes are respectively positioned in the top depth and the bottom depth of the irregular well hole section from the casing running construction recordWell head pressure P during construction of well fluid circulation discharge Q1And P2And calculating the sum delta P of the flow pressure drop inside and outside the pipe of the monitored irregular well hole section1；
Presetting an annulus hydraulic equivalent diameter, and calculating the sum delta P of the flow pressure drop inside and outside the pipe corresponding to the preset annulus hydraulic equivalent diameter when the drilling fluid is circulated by the discharge capacity Q through a drilling fluid flow pressure drop calculation formula2；
Comparing the sum of the pressure drops of the flow inside and outside the pipe to be monitored1The sum delta P of the flow pressure drop inside and outside the pipe corresponding to the preset annulus hydraulic equivalent diameter2；
When Δ P1And Δ P2When the difference value is not less than the preset minimum difference value, adding or subtracting a preset small value to or from the preset annular hydraulic equivalent diameter to form a new annular hydraulic equivalent diameter, calculating the sum of the flow pressure drop inside and outside the new pipe, and repeatedly and iteratively calculating until the sum is delta P1And Δ P2When the difference value of the annular water power equivalent diameter is smaller than a preset value, the final annular water power equivalent diameter is used as the calculated annular comprehensive water power equivalent diameter.
Compared with the prior art, the method for calculating the comprehensive hydraulic equivalent diameter of the annulus of the irregular well hole section comprises the steps of obtaining well diameter series data and well drilling data; calculating the axial length of the irregular borehole section, the length of the borehole wall curve section and the ratio of the axial length to the length of the borehole wall curve section; calculating the sum of the flow pressure drop inside and outside the pipe of the monitored irregular well hole section; presetting an annulus hydraulic equivalent diameter, and calculating the sum of the flow pressure drop inside and outside the pipe corresponding to the annulus hydraulic equivalent diameter; and comparing the calculated and monitored flow pressure drop, adding or subtracting a preset small value to or from the preset annulus hydraulic equivalent diameter when the difference value is not smaller than the preset minimum difference value, adopting an iterative calculation method to enable the difference value to be smaller than the preset minimum difference value, and taking the annulus hydraulic equivalent diameter when the difference value is smaller than the preset minimum difference value as the calculated annulus comprehensive hydraulic equivalent diameter. The method can conveniently and quickly determine the comprehensive annular hydraulic equivalent diameter of the irregular borehole section, improve the accuracy and convenience of annular flow pressure drop calculation, and further accurately and conveniently calculate the annular pressure.
Drawings
FIG. 1 is a flow chart of a preferred embodiment of a method for calculating an annulus comprehensive hydraulic equivalent diameter of an irregular wellbore section according to the present invention;
fig. 2 is a flowchart illustrating a preferred embodiment of the step S400 in the method for calculating an annular comprehensive hydraulic equivalent diameter of an irregular wellbore section according to the present invention.
Detailed Description
In view of the defects that the annular hydraulic equivalent diameter cannot be accurately determined, annular flow pressure drop calculation is influenced and the like in the prior art, the invention provides the annular comprehensive hydraulic equivalent diameter calculation method for the irregular borehole section, which can conveniently and quickly determine the annular comprehensive hydraulic equivalent diameter of the irregular borehole section and improve the accuracy and convenience of annular flow pressure drop calculation.
In order to make the objects, technical solutions and effects of the present invention clearer and clearer, the present invention is further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Referring to fig. 1, it is a flowchart of a method for calculating an annulus comprehensive hydraulic equivalent diameter of an irregular wellbore section according to a preferred embodiment of the present invention, including the following steps:
s100, acquiring the hole diameter series data and the well drilling data of all measuring points in the irregular hole section selected from the hole diameter curve graph.
In this embodiment, the irregular wellbore section may be a "belly" wellbore section, a "sugarcoated haw" wellbore section, etc., and for convenience of description, the "belly" wellbore section is used in the following description, but it should be understood that the irregular wellbore section of the present invention is not limited to the "belly" wellbore section, and the wellbore diameter series data at least includes the measuring point depth HjAnd measure point caliper DjWherein j is a natural number from 1 to m, and m is the number of logging points of the irregular well bore section; the well data includes at least a casing outer diameter DoInner diameter of casing DiDrilling fluid density rho, drilling fluid circulating discharge capacity Q, drilling fluid fluidity index n and drilling fluid consistency coefficient k.
S200, drawing an irregular borehole diameter curve graph according to the selected borehole diameter series data of the irregular borehole section, and calculating the axial length of the irregular borehole section, the length of a borehole wall curve section and the ratio of the axial length to the length of the borehole wall curve section.
In this embodiment, the calculation formula of the axial length is as follows: l is1＝Hm-H1Wherein H ismDepth of m-th point, H1Depth of point 1, L1Is the axial length; the calculation formula of the well wall curve segment length is as follows:
wherein D isj+1The hole diameter of the j +1 th measuring point, DjThe hole diameter of the jth measuring point Hj+1Depth of the j +1 th measurement point, HjIs the depth of the jth point, L2The axial length is the length of the curve segment of the well wall, and the ratio of the axial length to the length of the curve segment of the well wall is calculated according to the formula that η is equal to L1/L2Wherein η is the ratio of the axial length to the borehole wall curve segment length.
S300, acquiring wellhead pressure P when a casing shoe is respectively placed in the top depth and the bottom depth of the irregular borehole section and circulates according to the discharge capacity Q of drilling fluid from the casing running construction record1And P2And calculating the sum delta P of the flow pressure drop inside and outside the pipe of the monitored irregular well hole section1。
In the embodiment, a large-belly well bore section is taken as an example, in the casing running process, a casing shoe is placed in the deep position of the top of the large-belly well bore section, the discharge capacity Q of drilling fluid in the well drilling construction record is used for circulation, and the wellhead pressure P is recorded1(ii) a Then the casing shoe is placed in the deep position of the bottom of the big belly well hole section, circulation is carried out according to the discharge quantity Q of the drilling fluid in the well drilling construction record, and the pressure P of the well mouth is recorded2(ii) a The sum of the flow pressure drops inside and outside the pipe of the monitored big belly well hole section is delta P1＝P2-P1。
S400, presetting an annulus hydraulic equivalent diameter, and calculating the preset annulus hydraulic equivalent through a drilling fluid flow friction resistance pressure drop calculation formulaSum of pressure drop Δ P of flow inside and outside pipe corresponding to measurement diameter2。
In this embodiment, according to the annular flow pressure drop calculation formula, it can be known that the annular hydraulic equivalent diameters are different, and the corresponding annular fluid friction coefficients are also different, so that the corresponding annular flow pressure drops are also different. Therefore, the invention firstly assumes an annular hydraulic equivalent diameter DhThe sum of the pressure drops flowing inside and outside the pipe is calculated, and the detailed flowchart of step S400 refers to fig. 2.
Please refer to fig. 2, which is a flowchart of the step S400, including the following steps:
s401, presetting an annulus hydraulic equivalent diameter, and calculating the drilling fluid annulus flow rate and the drilling fluid Reynolds number corresponding to the preset annulus hydraulic equivalent diameter;
s402, calculating the flow friction resistance coefficient of the drilling fluid according to the calculated Reynolds number of the drilling fluid;
s403, calculating the sum delta P of the flowing pressure drop inside and outside the pipe corresponding to the preset annulus hydraulic equivalent diameter and circulating with the drilling fluid discharge capacity Q according to the drilling fluid flowing friction resistance coefficient and the drilling data2。
Specifically, in S401, the flow velocity V in the drilling fluid pipe needs to be calculated firstiAnd annular flow velocity VoRespectively corresponding reynolds numbers Re of drilling fluid pipe flowPLiAnd drilling fluid annular flow Reynolds number RePLoSpecifically, the following table shows:
further, in the step S402, when calculating the drilling fluid flow friction coefficient, the fluid state of the drilling fluid needs to be determined first, and then the drilling fluid flow state is calculated according to a corresponding formula, where the method for determining the drilling fluid flow state is shown in the following table:
| fluid state | Pipe flow | Annular flow |
| Laminar flow | RePLi≤RePL1 | RePLo≤RePL1 |
| Transition flow | RePL1＜RePLi＜RePL2 | RePL1＜RePLo＜RePL2 |
| Turbulent flow | RePLi≥RePL2 | RePLo≥RePL2 |
Wherein, RePL1Represents the upper critical Reynolds number, RePL2Represents the lower critical Reynolds number, the upper critical Reynolds number RePL1The calculation formula of (2) is as follows: rePL13250 and 1150 × n, the lower critical reynolds number is calculated as: rePL24150-; after the flow state of the drilling fluid is judged, the calculation of the laminar flow state friction coefficient can be carried out through the following table:
when the flow state is turbulent flow, the flow friction coefficient of the fluid in any geometric shape can be calculated according to the following empirical formula:
wherein the constants A, B may beDetermined from the power law index (drilling fluid fluidity index) n, as shown in the following table. If n is not found in the table, linear interpolation can be used to determine A, B.
| n | A | B |
| 0.2 | 0.0646 | 0.349 |
| 0.3 | 0.0685 | 0.325 |
| 0.4 | 0.0712 | 0.307 |
| 0.6 | 0.074 | 0.281 |
| 0.8 | 0.076 | 0.263 |
| 1.0 | 0.0779 | 0.250 |
When the flow state is transition flow and the friction coefficient is calculated, the friction coefficient when the Reynolds number is equal to the lower critical Reynolds number can be calculated according to the laminar flow state, the friction coefficient when the Reynolds number is equal to the upper Reynolds number can be calculated according to the turbulent flow state, and finally linear interpolation is carried out according to the actual Reynolds number.
In step S403, the drilling fluid flow friction pressure drop calculation formula is:
wherein the content of the first and second substances,
Dhis the annulus hydraulic equivalent diameter, fiIs the flow friction coefficient in the drilling fluid pipe, ViFor the flow velocity in the drilling fluid pipe, foIs the annular flow friction coefficient of the drilling fluid, VoIs the drilling fluid annulus flow rate.
Therefore, the sum of the flow pressure drop inside and outside the pipe corresponding to the preset annular hydraulic equivalent diameter can be obtained by substituting the preset annular hydraulic equivalent diameter into the formulas.
S500, comparing the sum delta P of the flow pressure drops inside and outside the monitored pipe1The sum delta P of the flow pressure drop inside and outside the pipe corresponding to the preset annulus hydraulic equivalent diameter2；
S600, when delta P1And Δ P2When the difference value is not less than the preset minimum difference value, adding or subtracting a preset small value to the preset annular hydraulic equivalent diameter, forming a new annular hydraulic equivalent diameter, calculating the sum of the flow pressure drop inside and outside the new pipe, and repeatedly and iteratively calculating until the sum is delta P1And Δ P2When the difference value of the annular water power equivalent diameter is smaller than a preset value, the final annular water power equivalent diameter is used as the calculated annular comprehensive water power equivalent diameter.
In this embodiment, the step S600 specifically includes:
when Δ P1<ΔP2Adding a preset small value to the preset annular hydraulic equivalent diameter to form a new annular hydraulic equivalent diameter, substituting the new annular hydraulic equivalent diameter into a drilling fluid flow friction resistance pressure drop calculation formula, calculating the sum of new flow pressure drops inside and outside the pipe, and repeatedly and iteratively calculating until the sum of the flow pressure drops inside the pipe is zeroΔP1-ΔP2|<At 0.01, | Δ P1-ΔP2|<Taking the annular hydraulic equivalent diameter at 0.01 as the required annular hydraulic equivalent diameter; when Δ P1>ΔP2And then subtracting a preset small value from the preset annular hydraulic equivalent diameter to form a new annular hydraulic equivalent diameter, substituting the new annular hydraulic equivalent diameter into a drilling fluid flow friction resistance pressure drop calculation formula, calculating the sum of new flow pressure drops inside and outside the pipe, and repeatedly and iteratively calculating until the total value of the total value is delta P1-ΔP2|<At 0.01, | Δ P1-ΔP2|<The annular hydraulic equivalent diameter at 0.01 is used as the comprehensive annular hydraulic equivalent diameter.
In particular, the sum Δ P of the pressure drops flowing inside and outside the pipe being monitored in comparison1And the sum of the calculated pressure drop Δ P of the flow inside and outside the pipe2Then, if Δ P1<ΔP2Then at the assumed annular hydraulic equivalent diameter DhAdding a small value epsilon on the basis, and adding a new annulus hydraulic equivalent diameter DhcSubstituting into the formula of step S400 to calculate, and repeating iteration until | Δ P1-ΔP2|<Assumed D at 0.01hcThe final annulus comprehensive hydraulic equivalent diameter is obtained; if Δ P1>ΔP2Then assuming the annular hydraulic equivalent diameter DhSubtracting a small value epsilon on the basis, and obtaining a new annular hydraulic equivalent diameter DhcSubstituting into the formula of step S400 for calculation, repeating the iteration until | Δ P1-ΔP2|<Assumed D at 0.01hcNamely the final annulus comprehensive hydraulic equivalent diameter due to the final delta P1And Δ P2The difference value of (2) is extremely small, so that the deviation between the calculated annular hydraulic equivalent diameter and an actual result is extremely small, and the accuracy is higher.
Preferably, the method for calculating the comprehensive hydraulic equivalent diameter of the annulus of the irregular wellbore section further comprises the following steps:
and drawing a change curve of the comprehensive annular hydraulic equivalent diameter along with the ratio of the axial length to the borehole wall curve section length, and forming a relation table of the comprehensive annular hydraulic equivalent diameter and the ratio of the axial length to the borehole wall curve section length.
Specifically, in order to facilitate subsequent engineering application, after the ratio of the plurality of axial lengths to the well wall curve segment lengths and the corresponding comprehensive annular hydraulic equivalent diameter are calculated, a corresponding change curve chart and a corresponding relation table are drawn, and during subsequent application, the corresponding comprehensive annular hydraulic equivalent diameter can be found directly according to the chart, so that the method is convenient and rapid.
In a preferred embodiment, the method for calculating the annulus comprehensive hydraulic equivalent diameter of the irregular wellbore section further comprises the following steps:
and calculating the flow pressure drop inside and outside the pipe in unit length when the unit of the regular well bore section circulates according to the drilling fluid discharge capacity Q, and calculating the comprehensive conversion coefficient of the flow pressure drop inside and outside the pipe of the irregular well bore section corresponding to the ratio of the axial length to the length of the well wall curve section relative to the flow pressure drop inside and outside the pipe of the regular well bore section in the same axial length under the condition of the same circulation discharge capacity.
In the embodiment, in the casing running process, a casing shoe is placed at the top depth L3 of a regular wellbore section (without diameter expansion phenomenon), well mouth vertical pressure P3 is recorded by using discharge Q circulating drilling fluid, then the casing shoe is placed at the bottom depth L4 of the regular wellbore section, well mouth vertical pressure P4 is recorded by using discharge Q circulating drilling fluid, and the pressure drop of the inside and outside flows of the regular wellbore section under the unit length is (P4-P3)/(L4-L3), so that under the condition of the same circulating discharge capacity, the ratio η of the axial length to the length of a well wall curve section to the pressure drop of the inside and outside flows of the irregular wellbore section is compared with the comprehensive conversion coefficient lambda (P2-P1) (L4-L3)/L (P4-P3) of the inside and outside flows of the regular wellbore section with the same axial length, and the analogy is carried out in turn according to obtain the comprehensive conversion coefficient lambda (P2-P1) of the inside and outside flows of the irregular wellbore section corresponding to the different η values, thereby providing reference.
For ease of understanding, the following description will be given by way of example:
the method comprises the following steps: obtaining the outer diameter value D of a casing produced in a certain well of a land oilfield in one runo0.1397m and inner diameter D of sleevei0.11862m, selecting a certain 'big belly' borehole section from the hole diameter curve chart, and obtaining the depth of all measuring points in the sectionThe data series of the degree and the hole diameter are shown in the table 1; simultaneously obtaining the density value rho of the drilling fluid which is 1140kg/m3The drilling fluid circulating displacement value Q is 0.03m3The drilling fluid fluidity index n is 0.856, and the drilling fluid consistency coefficient k is 0.145 Pa.sn。
And step two, calculating the axial length L of the borehole section of the big belly to be 1002.8-1001 to be 1.8m, the length of the borehole wall curve section to be 1.80695m, and the ratio η of the axial length to the length of the borehole wall curve section to be 0.99615.
Step three: in the casing running process, a casing shoe is placed at the top depth (1001m) of a large-belly well bore section, the drilling fluid is circulated according to the discharge capacity Q being 30L/s, and the vertical pressure P of a well mouth is recorded110.162 MPa; then, the casing shoe is placed at the bottom depth (1010m) of the big belly well hole section, the drilling fluid is circulated with the discharge capacity Q being 30L/s, and the vertical pressure P of the well mouth is recorded210.18 MPa; the pressure drop of the circulation inside and outside the pipe with the big belly well hole section is delta P1＝0.018MPa。
Step four: assuming one annular hydraulic equivalent diameter Dh0.2159m, calculating the sum delta P of the flow pressure drop inside and outside the pipe of the big belly well hole section according to the step four2Obtaining the final annulus comprehensive hydraulic equivalent diameter D by iterative calculation under the pressure of 0.025MPahc0.2382m, and by analogy with the calculation method, the comprehensive hydraulic equivalent diameter of the annulus corresponding to different η values can be obtained, so that reference is provided for other wells.
And fifthly, in the casing running process, placing a casing shoe at a position with the top depth L3 being 1005m, using the discharge capacity Q being 30L/s to circulate the drilling fluid, recording the wellhead vertical pressure P3 being 10.2MPa, then placing the casing shoe at a position with the bottom depth L4 being 1010m, using the discharge capacity Q being 30L/s to circulate the drilling fluid, recording the wellhead vertical pressure P4 being 10.27MPa, wherein the pressure drop of the inside and outside flows of the regular borehole section in unit length is 0.014MPa/m, therefore, under the same circulation discharge capacity condition, the pressure drop of the inside and outside flows of the irregular borehole section corresponding to the ratio η of the axial length to the curve section length of the borehole wall is 0.7143 relative to the pressure drop comprehensive conversion coefficient lambda of the inside and outside flows of the regular borehole section in the same axial length, and the analogy is carried out in sequence according to the above calculation method, thereby obtaining the comprehensive conversion coefficient of the inside and outside flows of the irregular borehole section corresponding to different η values, and providing reference for the quick calculation of the pressure drop of the irregular borehole section.
It should be understood that although the steps in the flowcharts of fig. 1 and 2 are shown in order as indicated by the arrows, the steps are not necessarily performed in order as indicated by the arrows. The steps are not performed in the exact order shown and described, and may be performed in other orders, unless explicitly stated otherwise.
In conclusion, the method can conveniently determine the comprehensive annular hydraulic equivalent diameter of the irregular borehole section, improve the accuracy of annular flow pressure drop calculation, and further accurately calculate the annular pressure.
It should be understood that equivalents and modifications of the technical solution and inventive concept thereof may occur to those skilled in the art, and all such modifications and alterations should fall within the scope of the appended claims.
Claims (10)
1. A method for calculating the comprehensive hydraulic equivalent diameter of an annulus of an irregular borehole section is characterized by comprising the following steps:
acquiring the hole diameter series data and well drilling data of all measuring points in the irregular hole section selected from the hole diameter curve graph;
drawing an irregular borehole diameter curve graph according to the selected borehole diameter series data of the irregular borehole section, and calculating the axial length of the irregular borehole section, the length of a borehole wall curve section and the ratio of the axial length to the length of the borehole wall curve section;
obtaining wellhead pressure P when a casing shoe circulates at a drilling fluid discharge Q when the casing shoe is respectively positioned at the top depth and the bottom depth of the irregular borehole section from a casing running construction record1And P2And calculating the sum delta P of the flow pressure drop inside and outside the irregular borehole section pipe1；
Presetting an annulus hydraulic equivalent diameter, and calculating the sum delta P of the flow pressure drop inside and outside the pipe when the preset annulus hydraulic equivalent diameter corresponds to the discharge Q circulation of the drilling fluid through a drilling fluid flow pressure drop calculation formula2；
Comparing the sum of the pressure drops of the flow inside and outside the pipe to be monitored1The sum delta P of the flow pressure drop inside and outside the pipe corresponding to the preset annulus hydraulic equivalent diameter2；
When Δ P1And Δ P2When the difference value is not less than the preset minimum value, adding or subtracting a preset small value to the preset annular hydraulic equivalent diameter, forming a new annular hydraulic equivalent diameter, calculating the sum of the flow pressure drop inside and outside the new pipe, and repeatedly and iteratively calculating until the sum is delta P1And Δ P2When the difference value of the annular water power equivalent diameter is smaller than a preset value, the final annular water power equivalent diameter is used as the calculated annular comprehensive water power equivalent diameter.
2. The method for calculating the comprehensive hydraulic equivalent diameter of the annulus of the irregular borehole section according to claim 1, wherein the borehole diameter series data at least comprise measuring point depths HjAnd measure point caliper DjWherein j is a natural number from 1 to m, and m is the number of logging points of the irregular well bore section; the well data includes at least a casing outer diameter DoInner diameter of casing DiDrilling fluid density rho, drilling fluid circulating discharge capacity Q, drilling fluid fluidity index n and drilling fluid consistency coefficient k.
3. The method for calculating the annulus comprehensive hydraulic equivalent diameter of the irregular borehole section according to claim 2, wherein the calculation formula of the axial length is as follows:
L1＝Hm-H1，
wherein HmDepth of m-th point, H1Depth of point 1, L1Is the axial length.
4. The method for calculating the annulus comprehensive hydraulic equivalent diameter of the irregular borehole section according to claim 3, wherein the calculation formula of the borehole wall curve section length is as follows:
wherein D isj+1The hole diameter of the j +1 th measuring point, DjThe hole diameter of the jth measuring point Hj+1Depth of the j +1 th measurement point, HjIs the depth of the jth point, L2Is the length of the curve section of the well wall.
5. The method for calculating the annulus comprehensive hydraulic equivalent diameter of the irregular borehole section according to claim 4, wherein the ratio of the axial length to the borehole wall curve section length is calculated according to the formula:
η＝L1/L2wherein η is the ratio of the axial length to the borehole wall curve segment length.
6. The method for calculating the annulus comprehensive hydraulic equivalent diameter of an irregular wellbore section according to claim 5, wherein the sum of the monitored flow pressure drops inside and outside the pipe of the irregular wellbore section is Δ P1The calculation formula of (2) is as follows: delta P1＝P2-P1。
7. The method for calculating the annulus comprehensive hydraulic equivalent diameter of the irregular borehole section according to claim 6, wherein the annulus hydraulic equivalent diameter is preset, and the sum Δ P of the flow pressure drops inside and outside the pipe corresponding to the preset annulus hydraulic equivalent diameter is calculated by a drilling fluid flow pressure drop calculation formula2Comprises the following steps:
presetting an annulus hydraulic equivalent diameter, and calculating the drilling fluid annulus flow rate and the drilling fluid Reynolds number corresponding to the preset annulus hydraulic equivalent diameter;
calculating the flow friction resistance coefficient of the drilling fluid according to the calculated reynolds number of the drilling fluid;
calculating the sum delta P of the flow pressure drop inside and outside the pipe corresponding to the preset annulus hydraulic equivalent diameter according to the flow friction coefficient of the drilling fluid and the drilling data2。
8. The method for calculating the annulus comprehensive hydraulic equivalent diameter of the irregular borehole section according to claim 7, wherein the calculation formula of the drilling fluid flow friction resistance pressure drop is as follows:
wherein D ishIs the annulus hydraulic equivalent diameter, fiIs the flow friction coefficient in the drilling fluid pipe, ViFor the flow velocity in the drilling fluid pipe, foIs the annular flow friction coefficient of the drilling fluid, VoIs the drilling fluid annulus flow rate.
9. The method of claim 8, wherein the delta P is a measure of annulus hydraulic equivalent diameter1And Δ P2When the difference value is not less than the preset minimum difference value, adding or subtracting a preset small value to the preset annular hydraulic equivalent diameter, forming a new annular hydraulic equivalent diameter, calculating the sum of the flow pressure drop inside and outside the new pipe, and repeatedly and iteratively calculating until the sum is delta P1And Δ P2When the difference value is smaller than the preset value, the step of taking the final annular hydraulic equivalent diameter as the solved annular comprehensive hydraulic equivalent diameter specifically comprises the following steps:
when Δ P1<ΔP2Adding a preset small value to the preset annulus hydraulic equivalent diameter to form a new annulus hydraulic equivalent diameter, substituting the new annulus hydraulic equivalent diameter into a drilling fluid flow friction resistance pressure drop calculation formula, calculating the sum of new flow pressure drops inside and outside the pipe, and repeatedly and iteratively calculating until the total value of the total value is delta P1-ΔP2|<At 0.01, | Δ P1-ΔP2|<The annular hydraulic equivalent diameter at 0.01 is taken as the obtained annular comprehensive hydraulic equivalent diameter; when Δ P1>ΔP2And then subtracting a preset small value from the preset annular hydraulic equivalent diameter to form a new annular hydraulic equivalent diameter, substituting the new annular hydraulic equivalent diameter into a drilling fluid flow friction resistance pressure drop calculation formula, and calculating a new annular hydraulic equivalent diameterAnd repeatedly and iteratively calculating the sum of the pressure drops of the inner flow and the outer flow until the pressure is | delta P1-ΔP2|<At 0.01, | Δ P1-ΔP2|<The annular hydraulic equivalent diameter at 0.01 is used as the comprehensive annular hydraulic equivalent diameter.
10. The method for calculating the annulus comprehensive hydraulic equivalent diameter of an irregular wellbore section according to claim 9, further comprising:
and drawing a change curve of the comprehensive annular hydraulic equivalent diameter along with the ratio of the axial length to the borehole wall curve section length, and forming a relation table of the comprehensive annular hydraulic equivalent diameter and the ratio of the axial length to the borehole wall curve section length.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN112727438A (en) * | 2021-01-04 | 2021-04-30 | 西南石油大学 | Annular pressure drop calculation method suitable for long open hole section of ultra-deep well |
| CN112727438B (en) * | 2021-01-04 | 2022-02-18 | 西南石油大学 | Annular pressure drop calculation method suitable for long open hole section of ultra-deep well |
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| CN110929458B (en) | 2023-08-18 |
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