Study on Failure Behavior of Drillpipe Wiper Plug in High-Temperature Liner Cementing Operations

Summary

With the deepening of oil and gas exploration, failures of liner cementing drillpipe wiper plugs (DPWP) occur frequently under high-temperature conditions. The traditional design of the DPWP relies solely on the room-temperature mechanical properties of rubber materials, and the failure evaluation system is incomplete. In this paper, the constitutive model of hydrogenated nitrile butadiene rubber (HNBR) was obtained through high-temperature uniaxial tensile tests. A simulation model for the contact behavior between the rubber cup and drillpipe was established based on moment equilibrium and verified experimentally. Parameter sensitivity analysis was performed to study the effects of cup diameter, thickness, angle, and center rod diameter on deformation resistance. The results indicate that the failure risk of the rubber cup first increased and then decreased with increasing diameter, and first decreased and then increased with increasing angle, while they decreased monotonically with increasing thickness and central rod diameter. Based on Box-Behnken design and analysis of variance (ANOVA), the influence of key parameters was ranked as follows: center rod diameter >thickness > angle >diameter. An optimal parameter combination was subsequently identified: diameter: 129 mm, thickness: 7 mm, angle: 25°, and central rod diameter: 29 mm. This combination reduced stress by 36.33% and strain by 16.72%, while increasing load-bearing capacity by 25%. The resulting optimized DPWP was successfully applied in the fifth-spud cementing of the well “Shenditake 1.”