Bond Strength Between Different Casing Materials and Cement

摘要

It is common practice to use steel casing when constructing and completing oil wells. However, well integrity issues caused by corrosion require well intervention operations which increase the non-productive time. This has led to investigations by researchers and engineers to improve the corrosion resistance of steel by modifying alloying elements. Some other researchers have suggested the use of aluminum alloy casing because of its resistance to corrosive H2S environments, and its lightweight characteristics. However, utilization of aluminum strings has not been reported in North Sea field applications. Although the durability of aluminum in corrosive environments is of interest, there are some other areas to be studied more in detail. These subjects include but are not limited to, mechanical properties of aluminum alloy, galvanic corrosion between the aluminum tubing and steel coupling, pipe wear, and interaction between cement and aluminum casing. Also the potential use of titanium casing elements can be of interest for selected applications. The primary goals of oil well cementing are achieving proper zonal isolation and anchoring the casing in the well. To evaluate these objectives, cement samples and casing alloys were tested in the lab prior to field operations. This lab testing includes measuring the hydraulic and shear bond strength between the cement and casing after the cement cures. In this study, shear bond strength and hydraulic bond strength between Portland cement and six different types of pipe were measured. The pipe samples tested were a titanium alloy and different aluminum alloys with coatings, and a steel pipe used as a reference. Three different Portland cements were used: two types of API Class G oil well cement and one rapid hardening cement. The obtained results showed that of these pipe systems, three showed a higher shear bond strength: titanium pipe, coated aluminum pipe, and steel pipe. Subsequently, these three pipes were used for measurements of hydraulic bond strength.