Optimization of well construction process by utilizing more economical and efficient materials can help in reducing overall well expenditure. Plug and Abandonment (P& A) process can be very costly depending on well's situation and materials used for P&A. Plugging materials for abandonment needs to have pumpability, good shear bond, and compressive strength and reasonable shrinkage. Previous research on application of geopolymers in oil/gas wells was mainly unsuccessful due to failure to achieve a reasonable thickening time. The results presented in this work propose different mixtures of Class F fly ash Geopolymer binder with controllable thickening times in temperatures up to 250 °F. Mixtures were tested for unconfined compressive strength (UCS), shear bond strength, shrinkage, thickening time, durability and contamination. The Geopolymer mixtures in this work compose class F fly ash rich in Silicate, Aluminum and have elements of Potassium, Calcium, Iron, Sodium and Titanium. Mixture of Sodium Hydroxide and Sodium Silicate was used to activate the Fly ash mixtures. Geopolymer mixture designs tested in this work showed high compressive strength, shear bond strength, low shrinkage and suitable thickening time for applications in well abandonment purposes. In addition to good resistance to Oilbased Mud (OBM) contaminants, these alternative P&A materials can be produced cheaper with less environmental impact which fits well for applications in the oil and gas well cementing.