unstable zone or formation 4 flowing an activator plug with fluid pumped through the drill string into the housing of the tool whereby the activator plug lands on the annular shoulder in the housing and the fluid is caused to flow through the tubular arm members and the fluid jet forming ports of the tool 5 if necessary pumping fluid through the jet forming ports at a rate while moving the tool through the portion of the well bore in the unstable zone or formation whereby the diameter of that portion of the well bore is enlarged by fluid jet erosion 6 pumping a cementitious material through the drill string and through the fluid jet forming ports at a rate while moving the tool through the enlarged portion of the well bore in the unstable zone or formation whereby the enlarged portion of the well bore is filled with the cementitious material 7 removing the drill string and well stabilization tool from the well bore while the cementitious material is allowed to set 8 reconnecting a drill bit to the drill string and placing the drill string and drill bit in the well bore and 9 drilling the well bore through the set cementitious material to thereby form a cementitious sheath in the well bore which stabilizes.