Microannulus and Cement Evaluation: Effectiveness of Cement Evaluation Using Sonic and Ultrasonic Technologies in Wells with Microannulus Between Casing and Cement Sheath

Abstract

Abstract Detailed cement evaluation with good azimuthal coverage is paramount for many wells in Chinarevskoe field, western Kazakhstan, as it affects perforation placement for acid treatment of thinly layered formation that is very heterogeneous, with varying permeability, reservoir pressure and water saturation. Analysis in these wells is performed not only to evaluate cement quality, but also to relate it to casing centricity with respect to formation or outer casing walls to help reaching objectives for cementing jobs in future wells. Cement evaluation with wireline tools is one of the primary means for determining whether the objectives of a cementing job have been reached once the job is finished. Several logging techniques are currently available for measuring cement quality, including sonic cement bond logs (CBL) and ultrasonic logs. These logs are affected by a microannulus to various extents, and this can make a big difference in our interpretation of cement placement quality. The sonic CBL and ultrasonic imaging log were run to evaluate cement quality in wells in Chinarevskoe field. Most of the wells exhibit the presence of a microannulus between the casing and cement sheath that develops just after the cementing job is completed. We observe that sonic CBL logs are affected by the presence of the microannulus. Cement evaluation is further complicated by the presence of contaminated cement where the acoustic impedance of the mud is close to the acoustic impedance of the contaminated cement. In these wells, a new generation cement evaluation service with enhanced ultrasonic measurements was deployed. A comparison of the results with traditional ultrasonic and sonic measurements shows that analysis of the enhanced ultrasonic logs improves cement evaluation in the presence of microannulus.