PNNL

Abstract

Wellbore failure at the cement lining is one of the most common drivers of reservoir intervention during geothermal energy and unconventional oil/gas production. The main sources for cement fracturing are chemical, mechanical, and thermal stresses. As a result, expensive and time-intensive production shutdowns and repairs are required. Intervention costs average $1.5million per wellbore without taking into consideration the economic losses as a result of production stoppage, which can be several million dollars depending on the time frame of plant in non-production mode. To address these problems, we developed a thermally stable polymer-cement composite with self-healing properties while maintaining the required rheological (during pumping) and mechanical properties of typical wellbore cement. In this work we report on the composition and mineralogy, the mechanical properties and self-healing ability of these novel cement composites as compared to standard wellbore cement. The self-healing capability of the composite materials was demonstrated by the consistent permeability reduction of mechanically-induced fractures in the 0.3-0.5mm aperture range. These polymer-cement composite materials could represent a definite solution to wellbore failure, production stoppage and reservoir intervention during geothermal energy production.