Elastic self-healing slurry system used for gas storage wells and its property evaluation

One role of gas storage is seasonal peak shaving. And during its operation, the set cement in the wellbore undergoes the alternating loads, and its sealing integrity tends to be damaged easily. To solve this problem, the self-healing evaluation method was selected. Then, a kind of crystalline self-healing agent (JHR-1) was researched and selected, and its self-repairing principle was analyzed. After combination fiber (JX46-12), styrene butadiene latex (PLT-100) and other additives were optimized, the elastic self-healing slurry system with the density of 1.89 g/cm³ was developed with the crystalline self-healing agent (JHR-1) as the main part. Finally, its properties were evaluated. It is indicated that its maximum crack healing width is over 150 μm after 14 days' maintenance and over 250 μm after 28 days' maintenance. The ratio of compressive strength to flexural strength and the anti-impact toughness after 7 days' maintenance are 4.52 and 3.87 J/cm², respectively, indicating better toughness. The cementing strength after 7 days' maintenance is 6.76 MPa. The elastic modulus is only 5 018 MPa, and the elastic limit stress and strain are 39 MPa and 0.67%, respectively, indicating good elasticity. After cyclic stress is loaded by 5 weeks, the elastic recovery rate is over 50%, which indicates that its elastic recovery capacity is good and the fatigue strength of set cement is high. When the wellhead pressure of gas storage well is in the range of 13-39 MPa, the set cement can be remained integral. And if micro-cracks are generated when the load is higher than the elastic limit stress of set cement, they can be healed quickly.