AN EXPERIMENTAL STUDY OF THE WELLBORE CEMENT BONDING AND SHEAR STRESS
Yi, Mi Chin
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Well Integrity is considered one of the most important topics in petroleum industries. A failure of well integrity causes many undesirable consequences such as loss of human lives, loss of drilling equipment or production facilities, loss of hydrocarbon reserves, and pollution. (Santos 2017) A successful cementing is a major contribution that leads wellbore integrity to be secured. Because cementing is a complex job that is involved with many variable factors, it is important to understand wellbore cementing behaviors in various environments and factors that affect to it. Wellbore integrity issues should be observed not only during a well is producing hydrocarbons but from the well construction phase to the well abandonment. Likewise, cementing should stay healthy throughout the entire well life. As more wells have been drilled and abandoned over the years, more researchers have started to pay attention to well integrity issues. With this trend, efforts to understand cement behaviors have been increased. As mentioned earlier, cementing is not as simple as it sounds due to various factors involved to its chemistry, mechanics and many others. Therefore, factors that cause cement failure can be diverse. Plenty of studies have focused on cement compressive and tensional strength to investigate cement mechanics affected by forces. Some researchers also have investigated bonding stresses of contact between cement and casings. These studies xi have found de-bonding at contacts between cement and casings or casing and formation to explain wellbore integrity failure. However, field data show that there is no correlation between de-bonding theory and the casing movement. If that is the case, the major assumption is made that cementing hardware such as centralizer or thread collars do not restrict casing axial movement, and the regional stresses caused at near couplings could be huge influences to wellbore failures. With this hypothesis, this master’s thesis introduced a new method to investigate special cement properties (pure cement shear, bonding, and Unconfined Compressive Strength) caused at near casing as well as coupling installed area by replicating the interaction between the casing coupling and cement in a lab size.
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