Research And Application Of Self-healing Slurry In Well-cementing

In Jiangsu oil-field,the hole section with thin oil layer and thin barrier are prone to the failure of zone isolation,and the micro-gap or micro-crack may form on cement sheath,which may cause annular flow.To solve the problem,a new oil-gas triggering self-healing material RT was researched and its mechanism was analyzed.The RT can repair the micro-cracks and micro-gaps in cement sheath using self-healing phenomenon and mechanism.Through the laboratory compounding experiment,the admixture was selected,and the dosage of RT and additive amount were optimized.The formula of oil-gas triggered self-healing cement was determined,and its performance was evaluated in the laboratory.The oil-gas triggered self-healing material RT has been developed,which can rapidly absorb hydrocarbon substances in hydrocarbon medium,including C1-C18+(such as gasoline,kerosene,diesel oil and crude oil)and produce volume expansion.RT has a temperature resistance of up to 320℃,good co MPatibility with co mmon cement admixtures,and excellent comprehensive mechanical properties.The toughening material,water loss agent,expansion agent and retarder suitable for self-healing material were optimized through laboratory tests,and the formulation of oil-gas triggered self-healing cement slurry system(SHC)is determined as follows:Grade G oil well cement+9%self-healing material RT+5%accelerator+2%water loss reducing agent+3%expansion agent+0.4%reducing agent,and water-cement ratio is 0.44.The conventional and self-healing properties of oil-gas-triggered self-healing cement were evaluated.The cement matrix has good expansion sealing performance and remarkable internal fracture self-healing ability.With kerosene as the repair medium,the recovery rate of the bending strength after 7 days was 16.3%and 11.8%,respectively.Under the displacement pressure of 10 MPa,the kerosene flow rate through the internal penetrating fracture of the cement stone decreased from 3.2×10-3 mL·s-1to 4.0×10-5 mL·s-1(the reduction rate was nearly 100%)within 30 min.The self-healing effect was remarkable.The self-healing cement slurry system can enhance the bonding strength of the two cement interfaces.After curing in water bath with 80℃ for 1d and 3d,the bonding strength of the two interfaces of the oil-base slurry is 2.35 times and 12.25 times of that of the ordinary cement slurry,respectively.Field tests of oil-gas triggered self-healing cement slurry system were completed in 2 Wells in Shanian block of Jiangsu oilfield.CBL,VDL and SBT logging results showed that the first and second interfaces were well cemented,the cementing quality was improved co MPared with adjacent Wells,and the oil well productivity was significantly improved co MPared with adjacent Wells.