Study On The Development And Mechanism Of Self-healing Hydrogel Lost Circulation Material

Lost circulation,especially malignant lost circulation,has become a ’stuck neck’ technical problem in drilling and completion projects.Pre-crosslinked gel particles have become a commonly used plugging material due to their good elasticity,toughness and adaptability.After entering the leaky layer,it was mainly based on extrusion and filling to form a plugging layer.Because it does not have the characteristics of forming a whole gel,the plugging layer is susceptible to pressure fluctuations and has low pressure bearing capacity.Aiming at the problem of "the plugging layer did not have integral gel properties and low pressure bearing capacity" existing in pre-crosslinked gel plugging materials,the method of combining laboratory experiments and theoretical analysis was adopted to introduce the concept of "self-healing" into the drilling fluid.Based on the principle of hydrophobic association,the self-healing material was synthesized by optimizing the ratio of hydrophobic monomer,crosslinking agent,surfactant,and gel system to water concentration through the emulsion polymerization method,and a self-healing gel plugging agent was constructed.The experimental results showed that it had good viscoelasticity and good healing performance under oscillating shear strain;its stress at break reached 159.34 k Pa,elongation was 1680%,and it had good dissipation performance and relatively good performance under cyclic loading.Strong toughness;it had good healing properties at room temperature to 80℃,and had a certain viscosity increasing effect on the rheology of bentonite drilling fluid,but it reduced fluid loss significantly.At 80℃,the high-permeability formation was simulated by the orifice plate model with a hole diameter of 1mm,and the self-healing gel plugging agent can reach a pressure of 6.9MPa.the fracture model with a fracture width of 1mm can be used to simulate a fractured formation,and the self-healing gel plugging agent can reach a pressure of 4.8MPa.The self-healing gel plugging agent entered the crack with a fan-shaped front edge.With the increase of gel particles,the gel particles gathered at the end of the crack,and then were squeezed,deformed,expanded and filled to form a plugging layer.The gel particles in the plugging layer were gradually healed to form a whole gel,and were adsorbed by interaction with the crack wall surface,which enhanced the strength and retention capacity of the plugging layer.The self-healing gel plugging agent studied in this paper can be simple to prepare,simplify the plugging process,and improve the plugging strength at the same time,providing theoretical support and technical countermeasures for solving the problem of lost circulation.