TAMU Pemex Offshore Drilling

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TAMU PemexOffshore Drilling

• Lesson 5B
• High-Pressure Riser

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Based on
Low Riser Return and Mudlift System, by
Sigbjørn Sangesland and Børre Fossli. Proc. XIV
Deep Offshore Tech. Conf., New Orleans, Nov.
13-15, 2002.
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Low Riser Return and Mudlift System

• High-Pressure Small Diameter Riser
• Longer Hole Sections
• Fewer Casing Strings
• Mud Level in Riser far below Sea Level
• Mud-Lift Pump keeps Mud Level low

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Standard Deep-water Drilling System using 18 ¾
Wellhead and 21 Riser
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Pore Pressure,Fracture Pressure and Casing
Program
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13 5/8 Wellhead and 12 ½ Riser with Low Riser
Return System (LRRS)
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Pore Pressure,Fracture Pressure and Casing
Program for LRRS
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Cost Comparison between a Conventional 21 and a
14 (12 ½ ID) High-Pressure Riser System
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Some LRRS Advantages

• Wellbore pressures can be changed without
  changing the mud weight
• This is accomplished by raising or lowering the
  mud level in the riser
• Underbalanced drilling can often be achieved
• Drilling with water and a reduced fluid level
  in the riser results in abnormally low
  pressures in the wellbore
• The riser can act as a mud / gas separator

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More LRRS Advantages

• Well control is simplified
• The riser can handle high pressures
• No choke or kill lines are necessary
• Drilling costs are reduced
• Less time to run smaller riser
• Use smaller rig
• Fewer casing strings
• Potential for 30 reduction in well costs