High stability polymer gel for lost circulation control when drilling in fractured oil and gas formations

When drilling in fractured oil and gas formations, drilling fluid loss is prevalent, and polymer gels are commonly utilized as lost circulation materials to plug fractures in loss zones. A high stability polymer gel was synthesized in this study employing acrylamide as the polymerizable monomer, a self-synthesized microsphere containing active ethylene groups as the cross-linker, laponite as both a flow pattern regulator and a physical filler, and ammonium persulfate as the initiator. This polymer gel's complex network structure considerably adds to its mechanical and thermal resilience, and its best gelation time is 12 h at 248 degrees. Rheological properties of the gel were studied under various conditions. When the experimental temperature is 284 degrees, the Na+ concentration is 100,000 ppm, or the Ca2+ concentration is 1000 ppm, the G & PRIME; and G & DPRIME;of the polymer gel exceeded 1000 Pa and 200 Pa, suggesting that this gel has good thermal and salt stability. Contamination resistance studies reveal that the polymer gel has adequate contamination resistance for drilling fluid and formation water penetration, with G & PRIME; and G & DPRIME;exceeding 1500 Pa and 400 Pa when the volume ratio of external fluids to gellant is 6:4. Furthermore, the density of the polymer gel may be adjusted to 2.0 g/cm3 by employing barite as a weighting agent, and the addition of the barite contributed to improving the structural stability of the gel due to the filling effect in the gel's network structure. Using fractured steel cores and a visible fracture model, the dynamic filling and plugging capabilities of this polymer gel in fractures were measured. When compared to frequently used polymer gellants, the high stability polymer gellant entirely fills the fracture area and exhibits a little gravity differentiation effect in large-scale fracture. After gel formation, it exhibits outstanding plugging capability for various fracture scales at 248 degrees. Three successful field tests in the Tarim Basin, Xinjiang, China, demonstrated that the high stability polymer gel may be used to control lost circulation in fractured formations at high temperatures.