  It had been known that the Borel transforms of the twice quark pole mass 2*mq
and of the QCD q-barq static potential V(r) have leading infrared renormalons
at b=1/2 such that they cancel in the sum. The renormalon residue of 2*mq had
been determined with reasonably high precision from the known perturbative
coefficients of the ratio mq/(bar mq), where (bar mq) is the barMS
renormalon-free mass of the quark q. These values of the residues are used here
to estimate the hitherto unknown part of the three-loop coefficient of the
static potential V(r). Further, the method takes into account the fact that the
ultrasoft energy regime contributions must be excluded from the analysis. In
the b-barb quarkonium, aforementioned estimated part of the three-loop term
turns out to give a contribution to the binding energy comparable to the
nonpertubative contribution.
