Study on Magnesium Oxysulfate Resin IPN Cementing Material and Its Application in Well Plugging

In large-scale natural gas and shale gas development, disadvantages of silicate oil well cement, such as brittleness, shrinkage on hardening, especially the vulnerability of set cement to mechanical failure during staged fracturing operations, damage the integrity of cement sheath and result in sustained casing pressure (SCP). One way to improve the job quality of well cementing is to develop new cementing materials having good mechanical properties, strong cementing capacity and characteristics of not shrinking after solidification.Using interpenetrating network (IPN) structure design principle, a new magnesium oxysulfate resin cementing material has been developed through selection of thermosetting resin and magnesium oxysulfate framework material. This material has density between 1.1 g·cm^-3 and 1.8 g·cm^-3, 24 h compressive strength greater than 14 MPa and elastic modulus between 2 GPa and 4 GPa. It has excellent sealing ability resistant to the damage of cement sheath integrity. Laboratory experiment and field application results showed that this magnesium oxysulfate cementing material can be used to partly replace oil well cement in sealing reservoir formations, removing SCP and well abandonment. It provides a new and economically efficient preventive method for resolving SCP problem prevailing in oil and gas fields.