Cementless Well Construction Opens the Full Control on Well Integrity for the Life of the Well

Abstract

Well construction has relied on two main elements, casing and cement, to achieve the well goals while maintaining the highest possible well integrity. Can cementless well construction achieve similar goals? This paper is investigating the various well construction concepts proposed over the years and will analyze the cement's ability to withstand long term well loads. First, a review of various well construction concepts such as slimhole, conventional, pre-salt and horizontal wells. We will normalize the casing to cement thickness ratio by validating and proposing a simple mathematical calculation for establishing this ratio. Our calculations have shown that in the case of slimhole well concept, the thin cement sheath cannot serve as a strong well barrier as defined by current standards, and thus a new solution might be necessary. The second part will look at current new trends in wellbore construction that include external casing packers and other solutions such as metallic wellbore isolation solutions. Hydraulically expanded metal packers are a robust and reliable alternative to cement. They are each mounted to a casing joint and can be rotated while running in hole. They have a proven deployment track record of high diametrical expansion, conforming to the wellbore geometry, while isolating differential pressures more than 15,000psi. Exploration of load carrying capabilities will be completed using Finite Element Analysis (FEA), simulating the different well scenarios as described in the previous paragraph. This will enable us to establish which well types can use this novel technology for the replacement of cement. The paper will conclude with one possible solution that could be used to mitigate cement problems by shifting the well construction concept to a cementless new era. Also, understanding that the cement manufacturing process is highly CO2 intensive, emissions per well could be reduced through the newly proposed concept.