A method includes introducing a first liquid composition into a well having a wellbore, introducing a second liquid composition into the well, and mixing the first and second liquid compositions within the well. The first liquid composition is kept separate from the second liquid composition until mixing the first and second liquid compositions within the well. Furthermore, the first liquid composition includes a first reactive component, the second liquid composition includes a second reactive component, and the first reactive component reacts with the second reactive component in response to mixing the first and second liquid compositions within the well. The method further includes causing the mixed compositions to engage the wellbore. In one example, the first reactive component may be an epoxy and the second reactive component may be a hardener that reacts with the epoxy to form a solid plug in the wellbore to seal off the well.