Laboratory research on protective agents for reservoirs was carried out to solve the problem of reservoir damage during drilling in Biyang Sag of Henan Oilfield.Under alkaline conditions,starch microspheres were prepared with corn starch, epichlorohydrin, and polyethylene glycol 20000 as the main raw materials, and then the starch?based protective agent DYB for reservoirs was prepared by the compound of the starch microspheres, regenerated fiber, calcium carbonate (QS?2), and emulsified asphalt (SFT). Scanning electron microscope and thermogravimetric analyzer were used to study the micromorphology and thermal stability of the synthesized product and evaluate the performance of DYB, such as shale rolling recovery and plugging. The results indicate that the particle size of starch microspheres is in the range of 3~5 μm, and the shale recovery rate of DYB in the base slurry is over 85.0%, the API filtration loss of the base slurry after aging at 120~180 ℃ is controlled within 12 mL. After 3.0% DYB is added to the simulated field drilling fluid, its pressure?bearing capacity in the sand bed can reach 4.00 MPa, while the membrane pressure?bearing capacity in the artificial core is over 10.00 MPa, and the recovery value of core permeability is over 82.0%.

A micropore throat plugging material was prepared by emulsion polymerization. Its structural characteristics were analyzed by Fourier transform infrared (FT?IR) spectrum analysis, Raman spectrum analysis, and thermogravimetric?differential thermal analysis (TG?DTA). The particle size range of the synthesized product was determined by a laser particle size analyzer. The inhibition performance and plugging performance of the micropore throat plugging material were also investigated. The results show that the thermal decomposition temperature of the synthesized product is 321.0 °C and that its particle size distribution is between 500 nm and 2 250 nm. When the quantity of the micropore throat protection material used is 1.5%, it performs excellently in inhibiting clay hydration. Moreover, the inhibition effect significantly improves when the micropore throat plugging material is compounded with 0.5% sodium chloride. The filter membrane plugging experiment proves that the filter membrane with a pore diameter of 0.45~10.00 μm can be effectively plugged by the proposed material, and the plugging time is up to 35.43 min when the plugging quantity is 1.5%. After aging at 120 °C for 16 h, the high temperature and high pressure filtration loss is 10.0 mL when the amount of the micropore throat plugging material added is 1.5%.