Casing Wear Tests for Precise Wear Factor Evaluation

Abstract

Abstract The increasing complexities of wellbore geometry imply an increasing potential of damage resulting from downhole casing wear. The present method of using old wear factors results in unreliable predictions. The main objective of the present work is to develop new casing wear factors for drillpipes and casings to improve the accuracy of wear prediction. The paper focuses on design, manufacturing, control and measurements of important parameters contributing to casing wear as well as wear volume evaluation. A new casing wear testing facility is designed and built by repurposing and automating an old lathe machine. Real drillpipes with tool joints and casing sections made of different materials are used. The lathe spindle controls the mandrill rotational speed on which the DP is tightly mounted. The versatile casing section holder is fixed on a sliding system comprising a dynamometer and a step-motor with a microcontroller allowing for the control and measurement of the side loadings and lateral displacements. A slurry fluid pump system is designed to feed water-based or oil-based muds at the contact surfaces. The as-received drillpipes and casing materials were analyzed by microscope and optical emission spectrometry (OES) to determine their microstructure and chemical composition. The hardness of both casing and DP materials was also measured. The lathe main spindle was able to provide stable rotating speeds varying from 100 to 1000 rpm. Though the irregular tool joint hard-facing surface was machined to allow for better control of the side loadings, the measured radial load shows variations of +/− 15%. The designed pumping system was able to provide a continuous stream of water-based and oil-based mud, at the contact surface, during testing. The wear depth is measured both directly using a 3D optical profilometer and indirectly by the lateral sliding displacement, thus allowing for the establishment of a calibration curve that can be used for in-situ measurement of the wear depth and wear volume evaluation. The initial set of tests has shown that the designed system is performing satisfactorily. More tests are being performed to confirm the robustness of the design.