Prediction of Methane Leakage Through Primary Cement Barrier in the High Island OPD, Gulf of Mexico

Abstract

With the increasing concern of greenhouse gases emitted from oil and gas wells, wellbore leakage has been a topic of interest lately. Previous research has shown that the annular cement used to complete the well and is a primary barrier of fluid migration can experience debonding to the casing causing a microannulus. The microannulus can propagate up the cement sheath to the top of cement depth causing a continuous leakage pathway. Previous methods quantify the corresponding leakage using laminar Hagen-Poiseuille flow assuming an incompressible fluid. That methodology is valid assuming water or oil as the leaking fluid but is voided for gas leakage. Therefore, an analytical laminar gas flow model including the effect of gravity was derived. The objective of this work is to investigate the difference between using Hagen-Poiseuille flow for analyzing gas flow data versus the developed gas flow model. The gas flow model is verified with experimental data, and the potential leakage of a previously studied Gulf of Mexico well is compared using the two models. The results show that analyzing gas leakage with Hagen-Poiseuille flow overestimates leakage rates by an order of magnitude when compared to the gas flow model.