Question: Error using pdsolve numeric - newbie question

I am trying to solve three simultaneous PDE where the first two PDEs are 1D while the third is 2D. When using pdsolve with numeric option I am getting the following error

Error, (in pdsolve/numeric/process_PDEs) PDEs can only contain dependent variables with direct dependence on the independent variables of the problem, got {Tg(t, z, 0.6985e-1)}. Can someone please help me with this.

restart;
T_well := 10. + 0.026*z;

PDE_in := -0.493381*diff(Ti(t, z), z) + diff(Ti(t, z), t) = 0.000176303*(-Ti(t, z) + To(t, z));
PDE_out := 0.186546*diff(To(t, z), z) + diff(To(t, z), t) = 0.0397694*(Tg(t, z, 0.06985) - To(t, z)) + 0.0000666597*(Ti(t, z) - To(t, z));
PDE_g := 0.22828*10^7/3.5*diff(Tg(t, z, r), t) = diff(Tg(t, z, r), r)/r + diff(Tg(t, z, r), r, r) + diff(Tg(t, z, r), z, z);
PDE := {PDE_g, PDE_in, PDE_out};
IC := {Tg(0, z, r) = T_well, Ti(0, z) = T_well, To(0, z) = T_well}
BC := {3.5*D[2](Tg)(t, 2000, r) = -3/40, 3.5*D[2](Tg)(t, z, 0.06985) = 0.0397694*(Tg(t, z, 0.06985) - To(t, z)), Tg(t, 0, r) = 10, Tg(t, z, 50) = 10 + 0.026*z, To(t, 0) = 10, To(t, 2000) = Ti(t, 2000)}
pdsolve(PDE, IC, BC, numeric)