Bauschinger Effect Evaluation Method for Casing in Heavy Oil Steam Huff and Puff Thermal Recovery Wells
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A technology of the Bauschinger effect and evaluation method, which is applied in the direction of testing the strength of materials by applying repetitive force/pulse force, and can solve problems such as scrapping, wellbore damage, and wellbore instability.
Active Publication Date: 2016-07-13
BC P INC CHINA NAT PETROLEUM CORP +2
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Problems solved by technology
When the yield strength of the material is lower than the critical value, the wellbore will be unstable, resulting in wellbore damage or even scrapping
[0004] At present, the evaluation method for casings used in heavy oil steam thermal recovery wells is only to measure the yield strength of casing materials at room temperature and high temperature, but does not involve the evaluation of material yield strength changes under tension-compression cycles. Therefore, it is necessary to establish a Bauschinger effect evaluation method for casing materials to improve the safety and reliability of the wellbore
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Embodiment 1
[0031] This embodiment provides a Bauschinger effect evaluation method for casings used in heavy oil steam huff and puff thermal recovery wells. The evaluation method includes the following steps:
[0032] S1, the measured initial yield strength σ of the casing material under evaluation 0 and tensile strength σ t . Preferably, the casing material to be evaluated is a round bar sample, the surface roughness within the gauge range is less than or equal to R0.8, and the gauge length is greater than or equal to 5 times the diameter. Obtain the initial yield strength σ of the casing material under evaluation 0 and tensile strength σ t When using uniaxial stretching method, the stretching rate is less than or equal to 0.5mm / min. Among them, the initial yield strength is the stress corresponding to the residual plastic deformation of 0.2%.
[0033] S2, in step S1, the casing sample is taken from the casing material under evaluation, and the casing sample is subjected to multiple...
Embodiment 2
[0045] The embodiment of the present invention provides a Bauschinger effect evaluation method for casings used in heavy oil steam huff and puff thermal recovery wells. The Bauschinger effect evaluation method uses three casing materials for thermal recovery wells in a domestic oilfield as evaluation objects , the specific evaluation steps and situations are as follows:
[0046] Working condition:
[0047] 1) The depth of the well is about 260 meters;
[0048] 2) The steam injection temperature at the wellhead is 260-300°C;
[0049] 3) The design life is 6 years;
[0050] 4) 3 to 4 rounds of steam injection per year;
[0051] 5) The casing steel grade is N80.
[0052] Evaluation process:
[0053] 1) The three casing materials are numbered A, B, and C respectively, and the uniaxial tensile specimens (that is, the initial yield strength σ 0 and tensile strength σ t The diameter of the gauge section is 6.5mm, the gauge length is 40mm, the end is M16 thread, the transition ...
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Abstract
The invention discloses a method for evaluating the Bauschinger effect of casings used in heavy oil steam huff and puff thermal recovery wells, belonging to the field of oil and gas exploitation, including: S1, measuring the initial yield strength σ of casing materials to be evaluated 0 and tensile strength σ t ; S2, take the casing sample, conduct multiple tension-compression symmetric cycle tests, and measure the yield strength σ of each tension stage 1 , σ 2 , σ 3 , ...; S3, calculate the increment Δσ of the yield strength after each cycle of tension-compression 1 , Δσ 2 , Δσ 3 , ..., define the average value of each yield strength increment as Δσ; S4, according to the formula Δσ T =A×B×ΔσPredict the total increment of yield strength Δσ within the service life of the casing T ; S5, if Δσ is positive, and the formula Δσ T ≤σ t -σ 0 If it is established, the tested casing material is qualified, otherwise it is unqualified; if Δσ is a negative value, and the formula σ 0 +Δσ T ≥σ c If it is established, the tested casing material is qualified, otherwise it is unqualified. By measuring and calculating the average value Δσ of the yield strength increment, the invention visually judges whether the casing material under evaluation belongs to cyclic softening or cyclic hardening, and further judges whether the casing material under test is qualified.
Description
technical field [0001] The invention relates to the field of petroleum and natural gas exploitation, in particular to a method for evaluating the Bauschinger effect of casings used in heavy oil steam huff and puff thermal recovery wells. Background technique [0002] The Bauschinger effect is a phenomenon that a small amount of plastic deformation occurs when a metal material is pre-loaded, and then loaded in the same direction after unloading, the specified residual stress increases; reversely loaded, the specified residual stress decreases. The Bauschinger effect is related to changes in resistance to dislocation motion in metallic materials. Heavy oil is one of the main types of oil and gas resources at home and abroad. Domestically, heavy oil is mainly exploited in Xinjiang, Liaohe, and Shengli Oilfields. The most important technology for heavy oil production is steam huffing and puffing. Due to the constraints of the formation and cement sheath, the casing will bear co...
Claims
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