Method for drilling a well in unconsolidated and/or abnormally pressured formations

A method of stabilizing an unconsolidated formation traversed by a wellbore to permit forward drilling below said unconsolidated formation, said method comprising:

• a) under-reaming a section of said wellbore, wherein said under-reamed section includes all of said unconsolidated formation and extends slightly into formations both above and below said unconsolidated formation;
• b) installing in said wellbore a drillable metal liner assembly positioned to traverse said under-reamed section and to extend further into formations both above and below said unconsolidated formation;
• c) wherein said drillable liner is centralized in said wellbore and in said under-reamed section of said wellbore, thereby forming an annulus between said drillable liner and the wellbore wall;
• d) filling said annulus with a fiber reinforced foamed cement composition and permitting said cement composition to harden in said annulus;
• and
• e) milling out said drillable liner and a portion of said fiber-cement composition in said annulus using said drillable metal liner as a guide for a piloted mill tool, thereby leaving a thick-walled cement sheath liner for stabilizing said unconsolidated formation in said wellbore.