Cement bond evaluation using well logs: A case study in Raniganj Block Durgapur, West Bengal, India

Abstract

Cement bond logs (CBL) and variable density log (VDL) are one of the vital logging techniques used to evaluate cement-casing-formation bonds before the well testing or execution of the production operation in the well. These logs are also crucial during the workover operation to maintain the integrity of the well. The logging techniques provide a clear view of the quality of cement bonds with casing and formation. The microannulus and other deviations in bonding between the cement and the casing or formation are recorded using this technique. Therefore, this technique is used by the regulatory authorities worldwide for the determination of the cement bond with casing and formation. In this paper, the CBL/VDL logging technique was used to determine the bonding between cement and casing and cement and formation at two different CBM wells from 850 to 1600 m depths in the Raniganj block of Durgapur, West Bengal. Two well, namely, A and B, were analyzed to determine the cement-casing-formation bonds in the study area's coal seam zone. The analysis was carried out at normal and pressure pass to investigate the integrity of the well using the CBL/VDL data. The normal and pressure pass in well A indicated the presence of microannulus in the bonding between cement and casing/formation in the coal seam zone. The corresponding analysis of well B showed poor cement and formation bond at the coal seam zone during the normal pass but good bonding after the pressure pass. Thus, it was observed that the CBL/VDL data were capable of determining the cement-casing-formation bonds in both the well of the study area and the well's integrity.