LECTURE 20

LECTURE 20

DRILLING
1. Types
  1. Onshore
  2. Offshore
    1. Jack-up rig
      1. able to stand on sea floor, floated into place, leg jacked down onto sea floor
      2. shallow water, <120m
    2. Semi-submersible rig
      1. <= 10,000 feet/ ~3000m
      2. stable in marine, watertight pontoons below ocean, wave base, operating deck is far from waves connected to pontoon by structural columns
2. Rotating system
  1. Rotary table
  2. Kelly and Kelly bushing
  3. Drillingstring assembly
    1. Swivel
      1. Decoupling of Kelley rotation and circulating system
    2. Drill pipe
      1. steel, 30-33 feet long
    3. Drill collars
      1. holds equipment for logging while drilling (LWD)
      2. Measurement while drilling (MWD)
      3. Add weight to drill bit
    4. Drill bit
      1. Tricone drill bit
      2. Diamond drag drill bits
      3. Decrease in well diameter with drilling depth
      4. different bits used for different hardness of formation rocks
3. Hoisting system
  1. Derrick
  2. Drawworks
  3. Crown block
  4. Travelling block
    1. Mud hose (circulating system)
4. Circulating system
  1. Mud
    1. Circulating - lubrication - cooling - cleaning of bit - removal of cutting - prevent fluids flowing into well from subsurface formations + chemical reaction with subsurface formations
  2. mud pump
  3. Shale shakers
    1. Remove drill cuttings from drilling fluid (mud)
  4. Mud tanks
  5. Mud volume
    1. gain
      1. Blowout
      2. Blowout preventers (BOPs)
    2. Lost (lost circulation)
      1. Fractures
      2. Fluid invasion of formation
5. Conventional drilling program
  1. Drill - log - case - cement - change for smaller bit+string - boost mud weight (density) - repeat...
    1. Casing cement in place
      1. prevent contaminations (fresh water aquifers), unstable formations from caving in
      2. enable use high density fluids in deep drilling, smooth internal bore for installing equipmnet
      3. isolate+ seal off high pressure zones
  2. new joint in mouse hole - swinging the swivel - stabbing the joint - reconnection
  3. Drill to final/total depth - cement casing & bottom hole assembly - perforate production well casting at target depths
  4. Mud log
    1. Geological interpretation of drill cutting, check rock types vs. prognosis
    2. Gas detect, composition analysis
    3. fluorescence (oil)
    4. Drilling (drilling rate), mud (density, resistivity, viscosity) data
    5. is basic record of drilling, cutting description of a lithology log
6. Deviated wells
  1. Access issues
    1. Environmental
    2. Onshore to offshore areas (cheaper drilling)
    3. from offshore platforms to many different parts of petroleum field
  2. Relief well for blowout
  3. Increased production due to
    1. Greater intersection with reservoir (thin/low permeable reservoir
    2. avoid fluid comming during production by gravity
    3. intersect/ stimulate fracture network
    4. Access multiple fuild/pressure compartments
7. Coring
  1. hollow drill bit captures a core (column of rock)
  2. core slabbed + interpret at surface
    1. Neotectonic structures (faults, fractures)
    2. sedimentary strcutures (cross/graded bedding)
    3. Plugs of core extracted to investigate
      1. porosity
      2. permeability
      3. seal capacity

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	Created by Hoa Truong over 9 years ago