Surface casing

• Surface casing is the outermost casing in oil and gas well casing program.
  After drilling holes drilled into the bedrock below the topsoil, or drilling up to a certain depth, down into surface casing.
  Role of surface casing has follows: isolate the upper aquifer, not to surface and groundwater to surface water borehole; II protecting the wellhead, sections lining of reinforced soil wall c into high pressure reservoirs down to go, surface casing is installed on blowout preventers to prevent blowout. Surface casing and wellbore clearance between all plugging with cement, cementing and Grouting cement, for mud and water out back, can play the role of isolated strata and protective wall.
  Surface casing depth of at least 100 m.