Research and Application of New Anti-CO2 Pollution and Low Damage Water-based Drilling Fluid

Abstract

CO2 intrusion into the drilling fluid during bauxite drilling can cause hydration swelling and dispersion of clays and lead to massive foaming of them. Additionally, the formation develops micro-nano fractures, which also have a large difference in compressive strength and a high percentage of bound water. Once the foreign fluid invades, it will lead to wellbore destabilization and reservoir damage. Thus, the designed drilling fluid formulation does not contain solid phase particles such as bentonite. And we obtained the optimal proportion of hydrolocker, penetrant, and defoamer by Mixture Designs. Then the shielding plugging theory was introduced, and a temporary plugging gradation consisting of acid-soluble inert particles, deformable nano-sealers, and non-permeable sealers was constructed with the aid of BridgePro software. And other surfactants were optimized indoors to build a lowdamage, strong anti-CO 2 pollution water-based drilling fluid. It could resist the high temperature of 150℃ and has a remarkable ability to lower surface tension (17.3mN). The rolling recovery, the plugging rate, and permeability recovery value can reach more than 90%, the lubrication coefficient was around 0.125. The constructed drilling fluid completed 9 wells in field application, with an obvious reservoir protection effect and an average increase of more than 20% in single-well daily production compared to the expected daily production. It will be an important reference for future bauxite horizontal well drilling fluids to prevent CO2 contamination and reduce reservoir damage.