Patent ID: 9644453
Date: 2017-05-09
CPC Classifications: B29C,B29K,B29L,B32B,E21B,Y10T

Claim:
1. A frac ball for use in hydrocarbon resource recovery, the frac ball to be used in combination with a ball seat placed in a casing in a wellbore and having an opening smaller than that of the frac ball, wherein the frac ball has a diameter of at least about 25 mm and a generally spherical entire structure consisting of two main layers, a spherical core and a surface resin layer covering the spherical core, the surface resin layer consisting of one or more surface layers stacked on each other, wherein each of the two main layers consists of a compression-resistant polyglycolic acid having a weight-average molecular weight in a range of 70,000 to 500,000 and exhibiting a melt viscosity (JIS-K7199) in a range of 200 to 1,500 Pa-s, when measured under conditions of a shear rate of 120-sec −1 at a temperature which is the melting point of the polyglycolic acid plus 50° C.