In a drilling operation, the casing string is run into the wellbore after drilling different sections of the well to stabilize the wellbore and make the drilling operation safer at a deeper depth.&nbsp; The cement slurry is pumped in the wellbore to fill the annular area behind the casing.&nbsp; Following that, the cement is set and seals the gap between the formation and the casing interfaces.&nbsp; Together with holding the casing in place (shear bond strength), the set barrier material is functioned to provide a complete and durable zonal isolation and prevent fluid migration between different strata (Hydraulic bond strength).Ordinary Portland cement (OPC) is the frequently used material for the primary cementing operation.&nbsp; Along with the advantages including well-known chemistry and availability, the OPC revealed some shortcomings including, but not limited to degradation of mechanical properties, shrinkage and cracking due to low ductility.&nbsp; Such failures can cause well integrity failure owing to forming micro paths within the cement structure and/or at the interfaces with casing and formation.&nbsp; Thus, recruiting appropriate additives to improve the performance of the OPC or introducing alternative cementitious barrier materials has was always been considered by both researchers and engineers.In this experimental study, two different cementitious materials are selected to examine the hydraulic bond strength and shear bond strength and investigate the possible correlation between the measured properties.&nbsp; The barrier materials are (i) a class of expansive cement that is currently used for P&amp;A operations, and (ii) a non-cement based naturally occurring rock known as geopolymer.&nbsp; The results for the neat class G cement was used as a reference for comparing the test results.&nbsp; Moreover, two types of casing materials including clean machined steel and corroded steel exposed offshore weather conditions for two months are considered to measure both hydraulic and shear bond strengths.&nbsp; Three iterations were considered per each condition to improve the accuracy of the results.&nbsp; All the samples were cured at 90 °C considered as bottom-hole static temperature (BHST) and under elevated pressure of 172 Bar (2500 psi) for one week.The hydraulic sealability of the barrier materials with the casing metals was tested by applying differential pressure up to 34 bar (500 psi) at the interface of the barrier plug and casing pipe.&nbsp; The results indicated that additives used in slurry preparation have an impact on hydraulic sealability of the material at the barrier material/casing interface as well as the structural matrix of the cementitious materials.&nbsp; Additionally, for the same barrier material, the rusty corroded streel provided a better hydraulic sealability comparing to the clean machined steel.&nbsp; This may be ascribed by the porosities exist on the surface of the corroded steel. &nbsp;The shear bond strength of samples was tested by curing the barrier materials in an annular space surrounded by the steel pipe and rusty/clean bars in the middle of the sample.&nbsp; A correlation between hydraulic and shear bond is presented in the article.

Experimental Study of Hydraulic Sealability and Shear Bond Strength of Cementitious Barrier Materials

Paper Proceedings: https://asmedigitalcollection.asme.org/OMAE/OMAE2021/volume/85116

OMAE 2021

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