EXPERIMENTAL INVESTIGATION OF THE CEMENT BOND INTEGRITY BY APPLICATION OF DIGITAL IMAGE CORRELATION (DIC) TECHNIQUE

Abstract

API Class G and H Portland cements are the most recommended cements for different well operations in order to have good well integrity throughout the life of the well. A loss of zonal isolation is a result of improper cementing jobs which could be a result of inadequate mud displacement, casing eccentricity, mud contamination and mud cake along the formation walls. This has required extensive investigation in order to meet flowability, placement and mechanical properties for particular subsurface conditions. There is limited information on the bonding dynamics of cement after placement. This could provide insight and expound on the detrimental effects of the aforementioned wellbore scenarios. There is also opportunity for research into viable cement systems that could have durable bonds for better well integrity. This research includes the application of Digital Image correlation (DIC) to critically study the strain development along the cement-steel and cement-formation interface of samples with a formation-cement-steel configuration. Microscope imaging of the interfacial bonds provides a paradigm to explain the formation of the bond as well. These samples were cured for 24 hours at an elevated temperature of 70oC and placed under Indirect Tensile stress conditions. The influence of mud-contamination, casing eccentricity and formation surface roughness on the strain development and the load required to shear the cement bonds was investigated. Two different cement recipes including nano-modified Class H cement and geopolymer cement were compared to Neat Class H cement under the aforementioned conditions as proposed cement systems with sufficient mechanical properties.