This paper focus on factors attributing to casing failure, their failure mechanism and the resulting failure mode. The casing is a critical component in a well and the main mechanical structural barrier element that provide conduits and avenue for oil and gas production over the well lifecycle and beyond. The casings are normally subjected to material degradation, varying local loads, induced stresses during stimulation, natural fractures, slip and shear during their installation and operation leading to different kinds of casing failure modes. The review paper also covers recent developments in casing integrity assessment techniques and their respective limitations.The taxonomy of the major causes and cases of casing failure in different well types is covered. In addition, an overview of casing trend utilisation and failure mix by grades is provided. The trend of casing utilisation in different wells examined show deep-water and shale gas horizontal wells employing higher tensile grades (P110 & Q125) due to their characteristics. Additionally, this review presents casing failure mixed by grades, with P110 recording the highest failure cases owing to its stiffness, high application in injection wells, shale gas, deep-water and high temperature and high temperature (HPHT) wells with high failure probability. A summary of existing tools used for the assessment of well integrity issues and their respective limitations is provided and conclusions drawn.

Casing deformation during volume fracturing in shale gas horizontal wells is caused by both existing and induced stresses. These stresses jointly alter and compound the stress field around the casing leading to inefficient well stimulation as planned, lack of access into the well for recompletion, future workovers and present imminent danger of well integrity. Using two simulation scenarios, casing structural integrity was investigated in both radial and axial configurations under the mechanics of a combine system-casing, cement and formation rock. Results obtained show that time dependent rock slippage -creep during stimulation lead to an increase transverse displacement and corresponding stresses on the casing. In addition, the effect of combined loading results in significant increase in both displacements and stresses that can cause radial and axial permanent failure of the casing. This explains the lack of access in the casing during multi-stage hydraulic fracturing and future well intervention and recompletions and increased current understating of the downhole dynamics and casing structural integrity during volume fracturing.

Mathematical model of compression creep for Terminalia ivorensis (Black Afara) timber were developed and presented in this paper. One-year creep test was performed in this process on Terminalia ivorensis timber samples. The creep data were fitted to linear, exponential and logarithmic regression models. The coefficients of determination for each of the model was determined. The coefficients of determination of the linear, exponential and logarithmic models were determined as 0.689, 0.650 and 0.941 respectively. Since the logarithmic model has the highest correlation with coefficient of determination of 0.941, it gave the best compression creep prediction model for the Terminalia ivorensis timber.

No abstract

No abstract