Influence of Casing Pressure Test on Seal Integrity of Cementing First Interface

2019 ◽  
Vol 944 ◽  
pp. 1020-1027
Author(s):  
Ji Wei Jiang ◽  
Jun Li ◽  
Gong Hui Liu ◽  
Yan Xi ◽  
Wai Li
Keyword(s):  
Elastic Modulus ◽  
Internal Pressure ◽  
Great Influence ◽  
Pressure Increase ◽  
Cement Stone ◽  
Pressure Relief ◽  
Seal Integrity ◽  
Pressure Test ◽  
Cement Sheath ◽  
Casing Pressure

Casing pressure test is an important link of the oil and gas well cementing, but excessive casing pressure test may cause stress failure or plastically deformation of the cement sheath, and generate micro-annulus on the casing-cement sheath cemented surface, then lose seal integrity of the cement sheath. According to the basic theory of elastoplastic mechanics and considering the volume invariance of plastic strain and the influence of elastic strain on volume change, the Mohr-Coulomb criterion is used to establish the casing-cement sheath-surrounding rock combination model. The paper also derived the formula for calculating the micro-annulus of the casing pressure test, and analyzed the influence of the internal pressure of the casing during the pressure test and the elastic modulus of the cement sheath on the radial contact stress of the cement sheath cementation interface after the cementing operation is completed. Results show that: (1) The generation of micro-annulus of casing pressure test is determined by the pressure increase process and the pressure relief process. The pressure increase process may lead the cement sheath into plasticity, and the radial stress at the interface turns into tensile stress and the micro-annulus could appear at the first interface by the decrease of internal pressure during pressure relief process. (2) The varying internal pressure has a great influence on the fatigue failure of the cement sheath, so the continuous multiple casing pressure test should be avoided after the cementing is completed. (3) Under the condition of maintaining the integrity of the cement sheath, increasing the tensile strength of the cement stone and reducing the elastic modulus of the cement stone can improve the pressure bearing capacity of the first interface during the casing pressure test. The model can provide a theoretical basis for the mechanical parameter design of the cement sheath, and provide guidance for on-site construction to reduce or avoid the risk of failure of the first interface seal integrity for the casing pressure test.

scholarly journals Numerical Simulation Study on Propagation of Initial Microcracks in Cement Sheath Body during Hydraulic Fracturing Process

Energies ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1260
Author(s):  
Yuqiang Xu ◽  
Yan Yan ◽  
Shenqi Xu ◽  
Zhichuan Guan
Keyword(s):  
Elastic Modulus ◽  
Hydraulic Fracturing ◽  
Internal Pressure ◽  
Element Model ◽  
Fluid Viscosity ◽  
Fracturing Fluid ◽  
Zone Method ◽  
Geological Conditions ◽  
Fracturing Process ◽  
Cement Sheath

Microcracks caused by perforating operations in a cement sheath body and interface have the potential to further expand or even cause crossflow during hydraulic fracturing. Currently, there are few quantitative studies on the propagation of initial cement-body microcracks. In this paper, a three-dimensional finite element model for the propagation of initial microcracks of the cement sheath body along the axial and circumferential directions during hydraulic fracturing was proposed based on the combination of coupling method of fluid–solid in porous media and the Cohesive Zone Method. The influence of reservoir geological conditions, the mechanical properties of a casing-cement sheath-formation system, and fracturing constructions in the propagation of initial axial microcracks of a cement sheath body was quantitatively analyzed. It can be concluded that the axial extension length of microcracks increased with the increase of elastic modulus of the cement sheath and formation, the flow rate of fracturing fluid, and casing internal pressure, and decreased with the increase of the cement sheath tensile strength and ground stress. The elastic modulus of the cement sheath had a greater influence on the expansion of axial cracks than the formation elastic modulus and casing internal pressure. The effect of fracturing fluid viscosity on the crack expansion was negligible. In order to effectively slow the expansion of the cement sheath body crack, the elastic modulus of the cement sheath can be appropriately reduced to enhance its toughness under the premise of ensuring sufficient strength of the cement sheath.

Very thin torispherical pressure vessel ends under internal pressure: Test procedure and typical results

1981 ◽  
Vol 16 (3) ◽  
pp. 171-186 ◽  
Author(s):  
P Stanley ◽  
T D Campbell
Keyword(s):  
Stainless Steel ◽  
Internal Pressure ◽  
Elastic Stress ◽  
Test Procedure ◽  
Pressure Vessels ◽  
Time Dependent ◽  
Test Installation ◽  
Stress Indices ◽  
Pressure Test ◽  
Strain Data

Very thin cylindrical pressure vessels with torispherical end-closures have been tested under internal pressure until buckles developed in the knuckles of the ends. These were prototype vessels in an austenitic stainless steel. The preparation of the ends and the closed test vessels is outlined, and the instrumentation, test installation, and test procedure are described. Results are given and discussed for three typical ends (diameters 54, 81, and 108in.; thickness to diameter ratios 0.00237, 0.00158, and 0.00119). These include measured thickness and curvature distributions, strain data and the derived elastic stress indices, and pole deflection measurements. Some details of the observed time-dependent plasticity (or ‘cold creep’) are given. Details of two types of buckle that developed eventually in the vessel ends are also reported.

Evaluation of the cement sheath safety after shaped charge perforation considering the criterion of cement stone destruction

2021 ◽  
pp. 50-53
Author(s):  
S.E. Chernyshov ◽  
◽  
S.G. Ashikhmin ◽  
Yu.A. Kashnikov ◽  
A.D. Savich ◽  
...  
Keyword(s):  
Shaped Charge ◽  
Cement Stone ◽  
Cement Sheath

Sustained Casing Pressure Calculation of A Annulus Induced by Downhole Operation Load

2012 ◽  
Vol 430-432 ◽  
pp. 2067-2070
Author(s):  
Zhang Zhi ◽  
Tai Ping Xiao ◽  
Zheng Mao Chen ◽  
Tai He Shi
Keyword(s):  
Internal Pressure ◽  
Safety Evaluation ◽  
Calculation Model ◽  
Extrusion Force ◽  
External Diameter ◽  
Gas Well ◽  
Seal Failure ◽  
Theoretical Support ◽  
Sustained Casing Pressure ◽  
Casing Pressure

Currently the annulus pressure of gas well becomes more common, so the safe production of several wells has been seriously affected. The annulus pressure mechanism is relatively complex, and it can be approximately classified into annulus pressure induced by temperature effect, by ballooning effect and by leakage or seal failure etc. The article mainly focuses on the annulus pressure mechanism induced by ballooning effect and the corresponding calculation model. For the tubing column with two ends fixed and closed, when tubing internal pressure is larger than the external extrusion force, the external diameter of the tubing column balloons (i.e. ballooning effect). It reduces the annular volume between the tubing and the casing, and consequentially induces annulus pressure. Based on the fundamental theory of elastic-plastic mechanics, the tubing column is simplified into the thin walled cylinder so as to deduce the relation models between the internal pressure and its swell capacity and A annulus pressure value, which provide theoretical support for safety evaluation on annulus pressure and the next treatment program.

Mechanical Properties of Carbon Cathodes during Aluminium Electrolysis

2011 ◽  
Vol 399-401 ◽  
pp. 2155-2159
Author(s):  
Qing Sheng Liu ◽  
Hui Fang
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Elastic Modulus ◽  
Great Influence ◽  
Strain Curve ◽  
Experimental Simulation ◽  
Ambient Conditions ◽  
Aluminium Electrolysis ◽  
Electrolysis Condition ◽  
Carbon Cathode

Based on the service ambient with aluminium electrolysis condition, the evolution of compressive strength, elastic modulus and stress-strain curve of carbon cathode samples under various conditions are investigated by experimental simulation method; the deterioration mechanism of the mechanical of carbon cathode is also studied. Results show that different carbon cathode materials and ambient conditions have great influence on strength and elastic modulus of carbon cthode. The mechanical properties such as compressive strength and elastic modulus of carbon catodes can be degraded by the erosion of sodium and molten salt during aluminium electrolysis, that has been confirmation by the SEM and XRD analysis.

Maximum Condensable Pressure in a Sealed Container With Arbitrary Temperature Distribution

2020 ◽  
Author(s):  
J. I. Watjen ◽  
M. T. Schifano ◽  
M. N. Sexton
Keyword(s):  
Temperature Distribution ◽  
Internal Pressure ◽  
Strong Relationship ◽  
Pressure Vessels ◽  
Large Temperature ◽  
Internal Temperature ◽  
Seal Integrity ◽  
Arbitrary Temperature ◽  
Vapor Mixtures ◽  
Saturated Boiling

Abstract Pressure vessels and sealed canisters are designed to maintain seal integrity under a maximum internal pressure. When the temperature inside the canister rises, the internal pressure rises accordingly. The presence of condensable liquid-vapor mixtures can create a strong relationship between the pressure and temperature. An isothermal container admits a straightforward thermodynamic pressure calculation; however, large temperature gradients inside the container require complex multiphase conjugate heat transfer calculations to predict accurate pressures. A simplified prediction using the peak internal temperature to find the saturated pressure of the condensable fluid may introduce unrealistic pressures when significant fluid mass exists in a cooler location of the container. This work presents methodology to calculate the pressure of a condensable fluid in a sealed container with large internal temperature differences using a two-temperature approach to predict saturated boiling and superheating of the vapor phase. An arbitrary temperature distribution allows for pressure calculations by considering the expected location of the liquid mass and the peak internal temperature. An enthalpy balance provides the effects of the temperature distribution and the peak pressure condition is easily predicted using the proposed method. This work provides a means to calculate the maximum internal pressure of a sealed container with a condensable fluid without the need for complex multiphase computer modeling.

Effect of Rock on Cement Sheath Integrity: Shale vs. Sandstone

2019 ◽  
Author(s):  
Ragnhild Skorpa ◽  
Benjamin Werner ◽  
Torbjørn Vrålstad
Keyword(s):  
Experimental Studies ◽  
Young Modulus ◽  
Surrounding Rock ◽  
Degradation Mechanisms ◽  
X Ray ◽  
Pressure Cycling ◽  
Cement Sheath ◽  
Set Up ◽  
Casing Pressure ◽  
Radial Cracks

Abstract It is crucial to understand cement sheath degradation mechanisms, since the cement sheath is an important well barrier element. Repeated pressure cycling is known to cause radial cracks and microannuli in the cement sheath, and the stiffness of the surrounding rock determines how much pressure the cement withstands before failure. However, experimental data on the effect of surrounding rock (shale vs. sandstone) on cement sheath integrity are scarce. In this paper we present experimental studies on how different surrounding rocks influence cement sheath integrity. We have used our unique downscaled experimental set-up to perform pressure cycling tests with both shale and sandstones, where cement sheath integrity is visualized in 3D by X-ray computer tomography (CT). The obtained results confirm that a cement sheath surrounded by a rock with a relative higher Young’s modulus can withstand higher casing pressure compared to a cement sheath surrounded by rock with relative lower Young modulus. All cracks were initially observed as small defects in the cement sheath prior to expanding to full radial cracks and propagation into the surrounding formation.

Research on Residual Strength of Corroded Tubing of Gas Well With Sustained Casing Pressure

2015 ◽  
Author(s):  
Li Sun ◽  
Jianchun Fan ◽  
Xing Meng ◽  
Ximing Zhang ◽  
Yuting Sun ◽  
...  
Keyword(s):  
Internal Pressure ◽  
Residual Strength ◽  
Equivalent Stress ◽  
External Pressure ◽  
Defect Depth ◽  
Gas Well ◽  
Sustained Casing Pressure ◽  
Von Mises Equivalent Stress ◽  
Von Mises ◽  
Casing Pressure

Corrosion and sustained casing pressure have serious threats to the integrity of tubing of gas well. Researching the residual strength of corroded tubing has great significance to ensure the safety of gas well. The finite element method was used to study the relationships between residual strength and corrosion defects size, internal pressure, external pressure, axial load. The results show that, for tubing with uniform corrosion, the defect depth, internal pressure and external pressure have greater impacts on the von Mises equivalent stress of tubing, and the defect width and defect length have little effects on it. For tubing with pitting corrosion, the defect depth, internal pressure and external pressure have greater impacts on the von Mises equivalent stress of tubing, while the defect radius has little effect on it. These simulation data were fitted into the functions of residual strength of corroded tubing according to different corrosion morphology types. Both of the verifications of the fitting results show that most of the error between the original calculation data and the fitting calculation data is less than 4%. The fitting formulas can be used conveniently to evaluate the safety of the tubing of gas well with sustained casing pressure.

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