The experimental investigation on the geo-polymerization of water-based filtercake at the second interface of the oil-gas well

Abstract

The quality of bond along the second interface of sandstone oil-gas well is of an utmost important in order to ensure long-term zonal isolation throughout the lifecycle of the well by preventing the potential leakage of hydrocarbon fluids. Attaining effective long-term zonal isolation for the lifetime of oil-gas wells depends on the sealing capacity at second interface (SI). Existence of untreated filtercake at SI acts as weak point of potential leakage of hydrocarbon. Different techniques were developed to improve the situation; however, it is still difficult to cleaned up completely by chemical washes and spacers. Therefore, it is imperious to develop a method that can make a filtercake which can provide an effective bonding between the formation and the cement sheath. The experimental work introduces a novel KN solution developed in the laboratory, simulated wellbore as sandstone formation under the wellbore simulated conditions.The results revealed that the samples treated with KN solution had higher shear bond strength over untreated samples. The bond quality increased with the increase of curing time (3, 7, 14, and 28 days). The improvement was due to geopolymerization of remained water-based filtercake took place which led to formation of cementitious material such as Calcium-Silicate-Hydrate (C–S–H) and FTIR analysis revealed the formation of cementitious material (Calcium-Silicate-Hydrate (C–S–H)) and other geopolymers like Calcium-Aluminium-Silicate-Hydrate (C-A-S-H) and Sodium-Aluminium-Silicate-Hydrate (N-A-S-H)) along the interface which filled the existed pores hence reducing porosity hence high strength of bond at high concentration to treated samples. The untreated samples were observed at low transmittance revealing the low content of inorganic geopolymers hence poor bond quality. Thick water-based filtercake films at second interface, which prevented the complete reaction of cement hydration between rock grains and cement slurry material to form a chemical binder at the interface.This technique is of an utmost important as compared to the other means of improving shear bong strength. This chemical solution tends to convert the clay material into cementitious product (geopolymers) which will enhance the bonding strength. In addition, the formed products are high durable as it can withstand harsh environmental conditions such as higher elevated temperature and salinity condition hence leading to remedial cost reduction.