CN103726795A - Design method for strength of casing string - Google Patents
Design method for strength of casing string Download PDFInfo
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- CN103726795A CN103726795A CN201210414728.XA CN201210414728A CN103726795A CN 103726795 A CN103726795 A CN 103726795A CN 201210414728 A CN201210414728 A CN 201210414728A CN 103726795 A CN103726795 A CN 103726795A
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Abstract
The invention discloses a design method for the strength of a casing string. The method includes the steps of determining the steel grade and wall thickness of the first section of a casing, determining the length of the first section of the casing tripping in a well, carrying out internal pressure strength check on the first section of the casing, computing the length of the first section of the casing tripping in the well, and designing the second section of the casing, the third section of the casing and the like according to the steps until the designed casing reaches the well depth. The design method can be successfully applied to the strength design for the casing strings, the design method and process are simple, and the design cost is greatly reduced.
Description
Technical field
The present invention relates to a kind of strength design of casing string.
Background technology
Along with deepening continuously of exploration and development, the quantity of directional well, horizontal well, extended reach well is more and more, particularly, for the exploitation of sea, beach and offshore oilfield, owing to being subject to the needs of restriction and final-period management and the exploitation of position of platform, all adopt directional well, horizontal well to develop.In recent years, along with the exploration Xiang Tanhai of offshore oilfield and the development at deep-sea, extended reach well, because the advantage on its cost is adopted by oil field more and more, is also had higher requirement to the Strength Design of Casing Strings of extended reach well.Because hole angle is large, open hole well segment length, sleeve pipe is also darker under more, and the load acting on Oil/gas Well sleeve pipe also becomes increasing and becomes increasingly complex.In sleeve design process, not only to consider the impact of frictional resistance, also will consider the impact of additional axial force that casing buckling produces, casing wear, sleeve pipe dynamic loading.In the petroleum gas casing strength design industry standard (SY/T5322-2000) of using at present, the axial force of sleeve pipe has only been considered the effect of buoyant weight, do not consider the impact of frictional resistance and dynamic load, therefore, be necessary that research is suitable for Strength Design of Casing Strings theory and the method for extended reach well.
There is following subject matter in traditional sleeve design:
1) understanding to sleeve stress.Think what the suffered axial force of sleeve pipe was just caused by buoyant weight, do not consider the frictional resistance of sleeve pipe rising, in lower process, and the sleeve pipe shock loading of being obstructed suddenly.
2) understanding to casing strength.Think that sleeve pipe is desirable body, the intensity of sleeve pipe is exactly API casing strength, and in fact in cover pipe manufacturer and manufacturing process, comprises a lot of defects, and simultaneously due to the raising of technique and production technology, collapse resistance is no longer original intensity.
Casing wear is a problem can not be ignored during deep-well, ultradeep well, horizontal well and extended reach well drilling well and well workover, wearing and tearing reduce the functional performancies such as the collapsoing strength, internal pressure strength of casing string, the safety of casing string has been formed to serious threat, it may cause Oil/gas Well control problem, even can make almost to want the well of finishing drilling to scrap flatly when serious.China, when carrying out tubular column structure design, does not consider the wear problem of sleeve pipe substantially at present.
In sum, extended reach well sleeve design theory and method and conventional directional well have larger difference, must study for the theory and the method that are suitable for extended reach well Strength Design of Casing Strings.In addition, the variation of the abrasion mechanism of extended reach well middle sleeve and wearing and tearing rear sleeve intensity, is also a problem meriting attention, and improves the strength design of casing string, not only has theory significance, also has actual application value.
Early stage design of casing string is to adopt simple stress design.Adopt while designing in this way, do not consider the interaction of the suffered various power of sleeve pipe, think that various power is separate to the effect of sleeve pipe.The domestic method of safety coefficients such as general, the sleeve design method that also has external edge load method, peak load method, the former Soviet Union and West Germany, also have the method for designing of U.S. Amoco etc., be mostly take that biaxial stress method is as basis, these methods for designing respectively have feature.
(1) method of safety coefficients such as: the method for safety coefficients such as whole casing string is comprised of the multistage sleeve pipe of varying strength, and the minimum safety factor of each section should equal the safety factor of regulation, and Here it is.The method of safety coefficients such as past are general only gets into row design according to tension with anti-.Abroad in Recent Years is is mostly first to carry out internal pressure strength design, first selects to carry out tension after satisfactory sleeve pipe again and squeeze design with anti-.
(2) edge load method: in edge load method anti-, press with anti-squeeze method for designing with etc. method of safety coefficients identical, just at middle and upper part sleeve pipe, change while being designed by tension, without tensile strength coefficient, except resulting usable intensity, but the edge load that the tensile resistance designing with tension with first paragraph and safety factor are determined is calculated intensity and is selected above each section of sleeve pipe.
(3) peak load method: its essence is the actual load of bearing according to physical condition lower casing string, then consider that certain coefficient designs casing string.Its step is for first designing by effective internal pressure and then according to effective external pressure and pulling force, and considers the impact of biaxial stress on collapsoing strength, and the length of each section of sleeve pipe is determined by graphical method.
(4) former Soviet Union's design of casing string feature is to provide different times, internal pressure and the external pressure design formulas at each position of operating condition lower casing string in different wells.Will be according to the concrete condition of this well during design, calculate the suffered effective internal pressure in each position of sleeve pipe and effective external pressure, and according to this as the foundation of selection of casing.
The biaxial stress of take is widely used all over the world as basic method for designing.But, needs along with development and the exploration and development of drilling technology, drilling depth is more and more darker, geological conditions becomes increasingly complex, oil well condition of work is also more and more severe, simple stress design and biaxial stress design can not meet the requirement of drilling well and Oil/gas Well exploitation, the destruction in advance of usually causing Oil/gas Well sleeve pipe.The problem that biaxial stress method exists is while adopting the design of biaxial stress method, although considered outer the influencing each other of power, internal pressure and axial force of squeezing, has ignored the impact of radial stresses.When considering that axial force is externally squeezed affecting of power, ignored internal pressure.Simultaneously, when considering axial force on the affecting of internal pressure, ignored the outer power of squeezing.The experimental data of related documents shows, occurs the test specimen of collapse failure, and the oval theoretical curve of its experimental data and biaxial stress is far apart, and both matching degrees are not high, and this experimental result shows that biaxial stress method for designing exists defect.In fact, pipe-in-pipe is not subject to the effect of which power, is to be subject to triaxial stress after all.Therefore, casing strength design should be considered the impact that axial force, outer crowded power and internal pressure interact on casing strength simultaneously.
Casing strength depends on the factor of three aspects: 1) geometry of sleeve pipe self and mechanical property; 2) situation of the suffered external force of sleeve pipe; 3) working environment of sleeve pipe.According to the statistics of existing sleeve pipe damage, the working environment of the geometry of sleeve pipe and mechanical property and sleeve pipe, be not the main cause of the improper damage of sleeve pipe, and stratum is the basic reason that causes the improper damage of sleeve pipe to the active force of sleeve pipe on stream.In down-hole, sleeve stress is quite complicated, but which power is pipe-in-pipe be not subject to, and, no matter how these power produce, is the effect that is subject to triaxial stress (axial stress, radial stresses and circumferential stress) after all yet.
Summary of the invention
The object of the invention is to overcome the shortcoming and defect of above-mentioned prior art, a kind of strength design of casing string is provided, the method can be successfully applied to the Intensity Design of casing string, and method for designing is simple, and design process is simple, greatly reduces design cost.
Object of the present invention is achieved through the following technical solutions: a kind of strength design of casing string, comprises the following steps:
(a) calculate effective outer extruding force at sleeve pipe place, and grade of steel and the wall thickness of root selection first paragraph sleeve pipe, according to casing strength formula or find casing strength, list casing strength and sleeve pipe performance parameter table;
(b) primary election first paragraph sleeve pipe be lowered to length, by the calculation procedure of three-dimensional rigid model, determined the axial tension of sleeve pipe, check the tensile strength at its top, make three axle collapsoing strengths of first paragraph sleeve pipe be more than or equal to axially outer the carrying of casing section maximum;
(c) first paragraph sleeve pipe is carried out to internal pressure strength check;
(d) according to three axle internal pressure strength formula, calculate three axle internal pressure strengths and effective internal pressure at first paragraph sleeve pipe top, according to internal pressure strength and effective inner gauge, calculate the anti-interior safety factor of pressing of first paragraph sleeve pipe.
(e) calculate the length that is lowered to of this section of sleeve pipe under triaxial stress.
(f), by above-mentioned steps design second segment, the 3rd section of sleeve pipe etc., until design well depth.
In sum, the invention has the beneficial effects as follows: can be successfully applied to the Intensity Design of casing string, and method for designing is simple, design process is simple, greatly reduces design cost.
The specific embodiment
Below in conjunction with embodiment, the present invention is described in further detail, but embodiments of the present invention are not limited only to this.
Embodiment:
The strength design of a kind of casing string the present invention relates to, (a) calculate effective outer extruding force at sleeve pipe place, and root selects grade of steel and the wall thickness of first paragraph sleeve pipe, according to casing strength formula or find casing strength, list casing strength and sleeve pipe performance parameter table;
(b) primary election first paragraph sleeve pipe be lowered to length, by the calculation procedure of three-dimensional rigid model, determined the axial tension of sleeve pipe, check the tensile strength at its top, make three axle collapsoing strengths of first paragraph sleeve pipe be more than or equal to axially outer the carrying of casing section maximum;
(c) first paragraph sleeve pipe is carried out to internal pressure strength check;
(d) according to three axle internal pressure strength formula, calculate three axle internal pressure strengths and effective internal pressure at first paragraph sleeve pipe top, according to internal pressure strength and effective inner gauge, calculate the anti-interior safety factor of pressing of first paragraph sleeve pipe.
(e) calculate the length that is lowered to of this section of sleeve pipe under triaxial stress.
(f), by above-mentioned steps design second segment, the 3rd section of sleeve pipe etc., until design well depth.
The above, be only preferred embodiment of the present invention, not the present invention done to any pro forma restriction, every foundation technical spirit of the present invention, and any simple modification, equivalent variations that above embodiment is done, within all falling into protection scope of the present invention.
Claims (1)
1. a strength design for casing string, is characterized in that, comprises the following steps:
(a) calculate effective outer extruding force at sleeve pipe place, and grade of steel and the wall thickness of root selection first paragraph sleeve pipe, according to casing strength formula or find casing strength, list casing strength and sleeve pipe performance parameter table;
(b) primary election first paragraph sleeve pipe be lowered to length, by the calculation procedure of three-dimensional rigid model, determined the axial tension of sleeve pipe, check the tensile strength at its top, make three axle collapsoing strengths of first paragraph sleeve pipe be more than or equal to axially outer the carrying of casing section maximum;
(c) first paragraph sleeve pipe is carried out to internal pressure strength check;
(d) according to three axle internal pressure strength formula, calculate three axle internal pressure strengths and effective internal pressure at first paragraph sleeve pipe top, according to internal pressure strength and effective inner gauge, calculate the anti-interior safety factor of pressing of first paragraph sleeve pipe.
(e) calculate the length that is lowered to of this section of sleeve pipe under triaxial stress.
(f), by above-mentioned steps design second segment, the 3rd section of sleeve pipe etc., until design well depth.
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| CN201210414728.XA CN103726795A (en) | 2012-10-15 | 2012-10-15 | Design method for strength of casing string |
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| CN201210414728.XA CN103726795A (en) | 2012-10-15 | 2012-10-15 | Design method for strength of casing string |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109538190A (en) * | 2017-09-22 | 2019-03-29 | 中国石油化工股份有限公司 | Rod-pumped well roofbolt stress method for early warning |
| CN110529053A (en) * | 2019-08-28 | 2019-12-03 | 济南市坤鹏技术开发中心 | A kind of oil drill rocker |
| CN110889183A (en) * | 2018-08-15 | 2020-03-17 | 中国石油天然气股份有限公司 | Method and device for determining casing checking safety coefficient |
| CN114414176A (en) * | 2022-03-30 | 2022-04-29 | 风凯换热器制造(常州)有限公司 | Processing method and leakage detection method for double-layer conveying pipeline |
-
2012
- 2012-10-15 CN CN201210414728.XA patent/CN103726795A/en active Pending
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109538190A (en) * | 2017-09-22 | 2019-03-29 | 中国石油化工股份有限公司 | Rod-pumped well roofbolt stress method for early warning |
| CN110889183A (en) * | 2018-08-15 | 2020-03-17 | 中国石油天然气股份有限公司 | Method and device for determining casing checking safety coefficient |
| CN110889183B (en) * | 2018-08-15 | 2022-11-01 | 中国石油天然气股份有限公司 | Method and device for determining casing checking safety coefficient |
| CN110529053A (en) * | 2019-08-28 | 2019-12-03 | 济南市坤鹏技术开发中心 | A kind of oil drill rocker |
| CN110529053B (en) * | 2019-08-28 | 2020-12-11 | 南通恒通机械制造有限公司 | Petroleum drill pipe |
| CN114414176A (en) * | 2022-03-30 | 2022-04-29 | 风凯换热器制造(常州)有限公司 | Processing method and leakage detection method for double-layer conveying pipeline |
| CN114414176B (en) * | 2022-03-30 | 2022-06-03 | 风凯换热器制造(常州)有限公司 | Processing method and leakage detection method for double-layer conveying pipeline |
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Application publication date: 20140416 |