Underbalanced Drilling and Completion Design for Composite Materials

1. الجامعة المستنصرية كلية الهندسة قسم الهندسة الميكانيكية تكنولوجيا حفر مرحلة 4 COMPOSITE MATERIALSد. ناظم مجبل فالح تكنولوجيا حفر 8

2. Casing Design • Casing design for UBD is not significantly different than conventional • With air drilling, the casing tension should always be design with no buoyancy considered. • No difference in burst design - usually

3. Casing Design • Collapse design should always be based on an empty casing string • A collapse design factor for UBD should be ~1.2 for UBD instead of 1.125 (API design factor)

4. Casing Design - Corrosion control • For fluid filled wells, corrosion is usually not considered when drilling. • Corrosion is not a factor when drilling with dry air • Corrosion must be considered when drilling with mist, foam, or aerated fluids. • Corrosion inhibitors should be added to the system

5. Casing Design - Casing wear • Casing wear is accelerated with gas drilling • This is due to less lubrication by the drilling fluid • Most air drilled holes are drilled faster and less time is spent rotating • Doglegs add to casing wear

6. Completion Design • If a well is properly drilled under underbalanced conditions, but is completed using overbalanced methods, much if not all of the impairment-reducing benefits might be permanently lost. Harold Vance Department of Petroleum Engineering

7. Underbalanced Completion Techniques • Running production casing, liners, slotted liners and other tools underbalanced. • Controlled cementing of production casing or liners • Running production tubing and downhole completion assemblies • Perforating underbalanced Harold Vance Department of Petroleum Engineering

8. Running casing and liners underbalanced • If the completion is not open hole, casing or liners must be run • Surface pressures are usually reduced by bullheading a heavier fluid down the annulus. • This fluid may be more dense than that with which the well was drilled, but still must be light enough to prevent overbalance. Harold Vance Department of Petroleum Engineering

9. Running casing and liners underbalanced • For casing and un-slotted liners, the well is usually allowed to flow while running the casing. • This helps to prevent excessive surge pressures. • A snubbing unit might be required to get the casing started in the hole. Harold Vance Department of Petroleum Engineering

10. Running casing and liners underbalanced • Slotted liners do not allow the well to be shut-in when the liner is across the BOP stack. • It may be necessary to flood the backside with drilling fluid to allow the running of the slotted liner into the wellbore • Fluid is continuously pumped down the wellbore to reduce pressures Harold Vance Department of Petroleum Engineering

11. Cementing pipe underbalanced • If casing is run underbalanced, cementing should also be accomplished underbalanced. • HSP of the cement slurry can be reduced by entraining gas, or by reduced density additives. Harold Vance Department of Petroleum Engineering

12. Running tubing underbalanced • No matter the production casing/liner design, production will almost always be required. • With cemented casing and liners, the tubing can be run conventionally. Harold Vance Department of Petroleum Engineering

13. Running tubing underbalanced • Tubing can be run underbalanced in a number of ways • snubbing • CT • diverting flow • Setting a packer above the open zone with a temporary plug Harold Vance Department of Petroleum Engineering