Patent ID: 9714551
Date: 2017-07-25
CPC Classifications: E21B

Claim:
1. A plug for well drilling process provided with: (a) a mandrel formed from a degradable material, the degradable material being a polyglycolic acid having a weight average molecular weight of 180,000 to 300,000 and having a melt viscosity of 700 to 2,000 Pa·s as measured at a temperature of 270° C. and a shear rate of 122 sec (b) a pair of rings placed on an outer peripheral surface existing in the orthogonal to an axial direction of the mandrel, at least one of the rings being formed from a degradable material; and (c) at least one diameter-expandable circular rubber member placed at a position between the pair of rings on the outer peripheral surface existing in the orthogonal to the axial direction of the mandrel.