CN103678927B - The method determining Casing In Thermal Recovery Wells overall strain - Google Patents

Abstract

The invention discloses a kind of Casing In Thermal Recovery Wells overall strain computational methods, belong to drilling well and oil recovery technique field. Said method comprising the steps of: calculate total axial stress; Tubing string axial deflection is calculated to stressometer according to line shaft; Calculate tubing string deformation of creep amount; Tubing string axial deflection measures Casing In Thermal Recovery Wells overall strain plus the tubing string deformation of creep. The Casing In Thermal Recovery Wells overall strain that Casing In Thermal Recovery Wells overall strain computational methods of the present invention obtain, it is possible to judge that Casing In Thermal Recovery Wells is whether within the scope of tubing uniform elongation exactly, it is ensured that use safety.

Description

The method determining Casing In Thermal Recovery Wells overall strain

Technical field

The present invention relates to drilling well and oil recovery technique field, particularly to a kind of Casing In Thermal Recovery Wells overall strain computational methods.

Background technology

At present, what Casing In Thermal Recovery Wells method for designing adopted is strength design, it is calculated as master with loading stress suffered by tubing string, the total stress value drawn is qualified design without departing from tubing yield strength, this calculating is based on theory of elastic mechanics, and consider the thermal stress in thermal process, meet tubing under hot conditions and yield phenomenon will not occur. But, the set disfigurement formula such as the deformation of casing strings in heavy oil thermal production wells, necking down, shearing, fracture has absolutely proved during tubing is under arms and really there occurs plastic deformation, and plastic deformations different just causes tubing permanent deformation, even ruptures. In reality set damages, the dropout phenomenon of nipple absolutely proves, body just has occurred that comparatively significantly permanent deformation before this, causes irreversible damage. Therefore, only designing tubing string with stress intensity computational methods is it cannot be guaranteed that tubing string uses safety.

Because note adopts the circulation change of temperature in thick oil thermal extraction, not only can there is yield phenomenon in casing string, but also can produce strain hardening, stress relaxation and creep progressive damage etc., causes irreversible damage, low circumferential strain fatigue damage occurs. Therefore, design tubing string with stress intensity calculating merely and can not meet Oil Field job requirements.

Summary of the invention

The technical problem to be solved is to provide one can obtain Casing In Thermal Recovery Wells overall strain, it can be determined that whether Casing In Thermal Recovery Wells is within the scope of tubing uniform elongation, it is ensured that use the Casing In Thermal Recovery Wells overall strain computational methods of safety.

For solving above-mentioned technical problem, the invention provides a kind of Casing In Thermal Recovery Wells overall strain computational methods, comprise the following steps: step 1, calculate total axial stress; Step 2, calculates tubing string axial deflection according to described line shaft to stressometer; Step 3, calculates tubing string deformation of creep amount; Step 4, described tubing string axial deflection measures Casing In Thermal Recovery Wells overall strain plus the described tubing string deformation of creep.

Further, the computing formula of step 1 isWherein, shell material Poisson's ratio ��, casing inner diameter r₁, sleeve outer r₂, interior pressure p_pi, external pressure p_po, by the axial stress �� of body deadweight generation_a, dog-leg severity the bending stress �� that causes_b, variations in temperature the thermal stress �� that produces_T��

Further, the computing formula of step 2 is ${\mathrm{\ϵ}}_z=\left\{\begin{array}{cc}\frac{{\mathrm{\σ}}_z}{E_t}& {\mathrm{\σ}}_z\≤f_{\mathrm{yt}}\\ \frac{f_{\mathrm{yt}}}{E_t}+\frac{{\mathrm{\σ}}_z-f_{\mathrm{yt}}}{E_{\mathrm{pt}}}& {\mathrm{\σ}}_z>f_{\mathrm{yt}}\end{array}\right.;$ Wherein, E_tFor thermal recovery steam injecting temperature setting of casing elastic modelling quantity, E_ptFor thermal recovery steam injecting temperature setting of casing plastic modulus, f_ytFor steam injecting temperature setting of casing material yield strength.

Further, the computing formula of step 3 isWherein,A and B is the constant relevant with material behavior and temperature, test obtain; N is that note adopts round; t_hFor every round steam injection time.

Casing In Thermal Recovery Wells overall strain computational methods provided by the invention, by calculating total axial stress, then tubing string axial deflection is calculated according to line shaft to stressometer, calculate tubing string deformation of creep amount again, last tubing string axial deflection measures Casing In Thermal Recovery Wells overall strain plus the tubing string deformation of creep, such that it is able to judge that Casing In Thermal Recovery Wells is whether within the scope of tubing uniform elongation exactly, it is ensured that use safety.

Accompanying drawing explanation

The flow chart of the Casing In Thermal Recovery Wells overall strain computational methods that Fig. 1 provides for the embodiment of the present invention.

Detailed description of the invention

Referring to Fig. 1, a kind of Casing In Thermal Recovery Wells overall strain computational methods that the embodiment of the present invention provides, comprise the steps:

Step 1, calculates total axial stress ��_z. Pass through formulaObtain total axial stress; Wherein, shell material Poisson's ratio ��, casing inner diameter r₁, sleeve outer r₂, interior pressure p_pi, external pressure p_po, by the axial stress �� of body deadweight generation_a, dog-leg severity the bending stress �� that causes_b, variations in temperature the thermal stress �� that produces_T��

Step 2, calculates tubing string axial deflection �� according to line shaft to stressometer_z. Tubing string axial deflection computing formula is ${\mathrm{\ϵ}}_z=\left\{\begin{array}{cc}\frac{{\mathrm{\σ}}_z}{E_t}& {\mathrm{\σ}}_z\≤f_{\mathrm{yt}}\\ \frac{f_{\mathrm{yt}}}{E_t}+\frac{{\mathrm{\σ}}_z-f_{\mathrm{yt}}}{E_{\mathrm{pt}}}& {\mathrm{\σ}}_z>f_{\mathrm{yt}}\end{array}\right.;$ Wherein, E_tFor thermal recovery steam injecting temperature setting of casing elastic modelling quantity, E_ptFor thermal recovery steam injecting temperature setting of casing plastic modulus, f_ytFor steam injecting temperature setting of casing material yield strength.

Step 3, calculates tubing string deformation of creep amount ��_c. The computing formula of tubing string deformation of creep amount isWherein,A and B is the constant relevant with material behavior and temperature, test obtain; N is that note adopts round; t_hFor every round steam injection time.

Step 4, calculates Casing In Thermal Recovery Wells overall strain ��_��. The computing formula of Casing In Thermal Recovery Wells overall strain is ��_��=��_z+��_c��

A concrete application example is given below, as follows:

1) oil-field thick-oil directional well HD001 well be drilled well operating mode and note adopts working condition parameter respectively in Table 1 and table 2. The kickoff point (KOP) vertical depth 211.75m of this HD001 well, deflecting terminal vertical depth 278.14m, deflecting terminal depth measurement 279.25m, maximum hole angle 18 ��, build angle rate 8 ��/30m, projected depth 600m.

Table 1

Table 2

2) gas injection pressure is interior pressure, interior pressure p as shown in Table 2_pi=7MPa, calculates according to industry standard SY/T5724 and obtains external pressure p_poThe axial stress �� that the deadweight of=6.18MPa, body produces_a=46.21MPa, the bending stress �� caused by dog-leg severity_b=77.82MPa, the thermal stress �� produced by variations in temperature_T=448.06MPa, casing inner diameter r₁=r₂-8.05=169.75mm, shell material Poisson's ratio �� is 0.3, by formula I.e. total axial stress ��_z=570.73MPa��

3) test obtains creep rateTubing string deformation of creep amount formula isIf 6 years projected lives, annual 2 round steam injections, every round gas injection time is 15 days as shown in Table 2;Tubing string deformation of creep amount ��_c=7.61��10^-8%��6��2��15��24��3600=1.18%��

4) 80SH sleeve pipe at 270 DEG C, it is 469MPa that test measurement obtains yield strength, and elastic modelling quantity is 1.61 �� 10⁵MPa, plastic modulus 4.00 �� 10³MPa. Utilize

${\mathrm{\ϵ}}_z=\left\{\begin{array}{cc}\frac{{\mathrm{\σ}}_z}{E_t}& {\mathrm{\σ}}_z\≤f_{\mathrm{yt}}\\ \frac{f_{\mathrm{yt}}}{E_t}+\frac{{\mathrm{\σ}}_z-f_{\mathrm{yt}}}{E_{\mathrm{pt}}}& {\mathrm{\σ}}_z>f_{\mathrm{yt}}\end{array}\right.,$ Due to ��_z=570.73MP, i.e. ��_z> f_yt, so ��_z=469 �� 161000+(570.73-469) �� 4000=0.0283; Namely tubing string axial deflection �� is calculated_z=2.83%��

5) �� is utilized_��=��_z+��_c, the final dependent variable �� calculating this 80SH production casing post of acquisition_��=1.18%+2.83%=4.01%��

The Casing In Thermal Recovery Wells overall strain computational methods that the embodiment of the present invention provides, by calculating total axial stress, then tubing string axial deflection is calculated according to line shaft to stressometer, calculate tubing string deformation of creep amount again, tubing string axial deflection measures Casing In Thermal Recovery Wells overall strain plus the tubing string deformation of creep, such that it is able to judge that Casing In Thermal Recovery Wells is whether within the scope of tubing uniform elongation exactly, it is ensured that use safety.

It should be noted last that, above detailed description of the invention is only in order to illustrate technical scheme and unrestricted, although the present invention being described in detail with reference to example, it will be understood by those within the art that, technical scheme can be modified or equivalent replacement, without deviating from the spirit and scope of technical solution of the present invention, it all should be encompassed in the middle of scope of the presently claimed invention.

Claims (2)

1. the method determining Casing In Thermal Recovery Wells overall strain, it is characterised in that comprise the following steps: step 1, calculates total axial stress; Step 2, calculates tubing string axial deflection according to described line shaft to stressometer; Step 3, calculates tubing string deformation of creep amount; Step 4, described tubing string axial deflection measures Casing In Thermal Recovery Wells overall strain plus the described tubing string deformation of creep;

The computing formula of step 1 is ${\mathrm{\σ}}_z={\mathrm{\σ}}_a+{\mathrm{\σ}}_b+2\mathrm{\μ}\frac{p_{pi}{r}_1^2-p_{po}{r}_2^2}{r_2^2-r_1^2}+{\mathrm{\σ}}_T;$ Wherein, shell material Poisson's ratio ��, casing inner diameter r₁, sleeve outer r₂, interior pressure p_pi, external pressure p_po, by the axial stress �� of body deadweight generation_a, dog-leg severity the bending stress �� that causes_b, variations in temperature the thermal stress �� that produces_T;

The computing formula of step 2 is ${\mathrm{\ϵ}}_z=\{\begin{array}{cc}\frac{{\mathrm{\σ}}_z}{E_t}& {\mathrm{\σ}}_z\≤f_{yt}\\ \frac{f_{yt}}{E_t}+\frac{{\mathrm{\σ}}_z-f_{yt}}{E_{pt}}& {\mathrm{\σ}}_z>f_{yt}\end{array};$ Wherein, E_tFor thermal recovery steam injecting temperature setting of casing elastic modelling quantity, E_ptFor thermal recovery steam injecting temperature setting of casing plastic modulus, f_ytFor steam injecting temperature setting of casing material yield strength.

2. method according to claim 1, it is characterised in that: the computing formula of step 3 isWherein,A and B is the constant relevant with material behavior and temperature, test obtain; N is that note adopts round; t_hFor every round steam injection time.