Abstract
Considerable lost circulation of oil-based drilling fluid often occurs because of pores and fractures that develop in formations, which can significantly increase drilling costs. In this study, we prepared a ternary composite self-swelling oil-absorbing resin and investigated the synthesis conditions on its oil-absorption properties. The resin molecular structure and properties were characterized by infrared spectroscopy, thermal stability, and scanning electron microscope, and we subsequently analyzed the fracture plugging mechanism of the resin. The results indicated that when the content ratio of butyl acrylate and stearyl methacrylate was 2:1, the sodium-p-styrenesulfonate content was 1%, the initiator content was 0.3%, and the cross-linker dosage was 0.16%, the resin exhibited good toughness and oil-swelling performance. The unsaturated groups in the copolymer were grafted, forming a three-dimensional network structure. At 120 °C, composite resin particles were used to seal fractures with width of 1-3 mm, with the pressure bearing capacity reaching 4.7 MPa. The fracture was compacted and sealed through deformation, compaction, and filling. Compared to conventional lost circulation materials, the oil-absorbing resin exhibited good thermal stability and self-adaptability, and could easily enter pores and micro-fractures, effectively reducing lost circulation of the oil-based drilling fluid.
NSTL