A Discussion of Geothermal Well Integrity Using Long-Term Experimental Bonding and RE-Bonding Data

Abstract

Geothermal wells are by default exposed to thermal loads, which will induce thermal degradation in the well construction materials but also thermal loads that in time can affect the wellbore integrity in various ways. Generally, the use of cement or similar products is to seal the space behind the casing and formation but also is intended to hinder the casing movement. One such important movement is the surface casing rising due to thermal expansion. Casing – cement bonding has been recently seen as one of the important parameters to estimate and evaluate wellbore integrity including geothermal wells. Although information about casing -cement bonding is relatively scarce, lately many publications are focusing on how to measure bonding experimentally and quantify this mathematically. This paper will show some recent experiments carried on the so call casing-cement interfacial bonding shear strength and will focus on post debonding phenomenon. The post debonding analysis is trying to consider the possible effect of the casing-cement friction on one side as well as the so-called re-bonding process that has been observed in laboratory tests. Finally, the paper will conclude with an extensive discussion on how the geothermal well integrity can be evaluated in the light of new experiments. The new results will highly impact the future geothermal well construction solutions.