router = 2; (*outside radius*)
rinner = 1; (*inside radius*)
rsmall = 0.1; (*radius of small pores*)
nsmall = 40; (*number of small pores*)
radii = RandomReal[{rinner + 2*rsmall, router - 2 rsmall},nsmall];(*radial position of smallpores*)

angle1 = RandomReal[{0, 2 $Pi$},nsmall];(*angular position of small pores*)
coords = Map[radii[[#]]*{0, Sin[angle1[[#]]], Cos[angle1[[#]]]} &,Range[nsmall]];(*coordinates of small pores*)
hollowsphere = RegionDifference[Ball[{0, 0, 0}, 2], Ball[{0, 0, 0}, 1]];(*first region interesection*)
smallspheres =  RegionUnion[Map[Ball[coords[[#]], rsmall] &, Range[nsmall]]];(*combine small pores*)

hollowsphereminussmallspheres = RegionDifference[hollowsphere, smallspheres] (*second region interesection*)
r1 = ImplicitRegion[x < 0, {x, y, z}]; (*For visualization*)
rplot = RegionIntersection[r1, hollowsphereminussmallspheres];

RegionPlot3D[rplot, PlotPoints -> 100]