General Principles of Well Barriers

Khalifeh, Mahmoud; Saasen, Arild

doi:10.1007/978-3-030-39970-2_2

Cited by 5 publications

(1 citation statement)

References 27 publications

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“…In the mining industry, significant attention is paid to safety and production efficiency. In particular, this is reflected in the annual growth of efforts and costs aimed at ensuring the integrity of oil and gas wells [1][2][3]. The life cycle of a well includes several stages, such as design, construction, operation and abandonment.…”

Section: Introductionmentioning

confidence: 99%

Mechanism of Casing String Curvature Due to Displacement of Surface Strata

et al. 2022

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One of the main problems of well operation is the risk of uncontrolled leakage of hydrocarbons into the environment. This problem is especially relevant for the long-term operation of wells. The idea for this study was inspired by a real industrial problem that the authors of the article were involved in solving. At several operating gas wells, an abnormal slope of the production tree occurred, which raised the question of the safety of their further operation. An analysis of known studies and current regulatory documents did not allow us to assess the safety of using a gas well based on the measured kinematic parameters of production tree deviations. A mathematical model for the deformation of a package of casing strings when the surface layer of the rock is displaced is developed in the article. A boundary value problem is formulated for differential equations of pipe bending on an elastic foundation. Based on the results of solving this problem, an unambiguous relationship was established between the maximum bending stress in the surface pipe and the angle of inclination of the production tree. The quantitative characteristics of the connection depend on the geometric and mechanical properties of the pipes and on the thickness and mechanical parameters of the formations. It was established that the existing inclination of the production tree can be achieved due to the beginning of the plastic bending of the surface pipe under the slickenside, which does not exclude the exhaustion of the safety margin of the surface pipe and indicates the possible operation of the casing string in a pre-emergency state. In general, the obtained results develop analytical approaches to assessing the behavior of underground structures of a production well in unstable soil bodies.

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Section: Introductionmentioning

confidence: 99%

Mechanism of Casing String Curvature Due to Displacement of Surface Strata

et al. 2022

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Safety Recovery Around Failed Tree Seals in an Offshore Gas Well

Tyagi

Bates

Gurmin

2022

SPE Asia Pacific Oil &Amp; Gas Conference and Exhibition

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Safe production from oil and gas wells always entails a two-barrier policy. In the well of interest, the primary barrier was breached while the secondary barrier was holding, and well fluids were observed in one of the tree ports during routine maintenance operations. The well was quickly made safe by closing a primary barrier, the downhole surface-controlled subsea safety valve (SCSSSV), and installation of a secondary barrier in the form of plugs downhole. To bring production back, the root cause was investigated, and it was determined that the straight-bore metal-to-metal seal, which seals the tubing at the interface of the tree and the tubing hanger, was compromised. After a successful installation of a new seal, pressure integrity could not still be ensured as it was further determined that there was pitting corrosion, observed on the tubing hanger, which did not allow the seal to successfully seal the pressure across the tubing hanger neck. Restoration of the well would depend on the repair of the tubing hanger, which would have required a complete workover, an approach that was deemed prohibitively expensive. A novel approach was implemented to machine out an additional groove on the tree body to provide an additional elastomer seal as a secondary barrier as opposed to the traditional metal-to-metal seal. This paper demonstrates the approach and successful restoration of the safety and well production. The approach can be widely utilized in establishing safety barriers in similar situations.

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A Finite Element Study of Integrity of Formation/Casing Annulus Cement Sheath in Niger Delta

Etoh

Dosunmu

Oriji

et al. 2022

Day 3 Wed, August 03, 2022

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Cement sheath is a well barrier that prevents the unintentional and uncontrollable flow of fluids from, into a formation or back to its surface. However, during drilling and production operations, this cement is subjected to various stresses resulting from thermal stress, non-uniform geo-stress, compressive and tensile stresses. Therefore, this study describes a finite element analysis (FEA) simulation of a cement sheath of class G type under stress in a typical drilling and production scenario. With experiments, the rheological and mechanical properties of class G cement with varying water-cement ratio of 0.4, 0.5 and 0.6 were prepared and analyzed for their performance and workability. From the results, it showed that the cement system with the lowest water-cement ratio of 0.4, demonstrated the highest mechanical strength. This was attributed to lesser water in the mix triggering efficient interaction with cement. Hence, based on this study, 0.4 cement ratio is recommended if the ability to withstand compressive and tensile forces is desired. In cases where it is to be used for drilling and production operations characterised by fatigue and cyclic forces, its composition should be designed such that it is more ductile and flexible. An FEA software, ANSYS Mechanical APDL (ANSYS Parametric Design Language) was used to analyze stress to convergence. Material properties of 0.4 cement ratio was adopted for simulation based on experimental results. Also, well loading conditions were cycled at temperature and pressure of 0-104 0C and 250-290 bar simultaneously. Simulation results showed the time changes of equivalent (Von-Mises), maximum, minimum and shear stresses. Time changes of equivalent elastic strain, total deformation and stress intensity were also recorded. From the simulation results, it can be concluded that the yield point of the material occurred at a time (t) =1.3245×10−4 s under continuous stress. It is recommended that the contact point between the casing and the cement be monitored for deformation due to high stress response during stress analysis.

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General Principles of Well Barriers

Cited by 5 publications

References 27 publications

Mechanism of Casing String Curvature Due to Displacement of Surface Strata

Mechanism of Casing String Curvature Due to Displacement of Surface Strata

Safety Recovery Around Failed Tree Seals in an Offshore Gas Well

A Finite Element Study of Integrity of Formation/Casing Annulus Cement Sheath in Niger Delta

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