| Title | Balanced Pressure Techniques Applied to Geothermal Drilling |
|---|---|
| Authors | Dareing, Don W.; Kelsey, James R. |
| Year | 1981 |
| Conference | Geothermal Resources Council Transactions |
| Keywords | Drilling; Lost Circulation Zone; LCM; Aerated Mud; Drill Pipe; Density; Parasite Tube |
| Abstract | Geothermal drilling often takes place in high surface relief areas where groundwater tables are a considerable distance (-1000 ft) below rig level. Above the water table, the formation pressure gradient is zero, and below the water table, the formation pressure increase with depth. Pressure unbalance between wellbore drilling fluid and formation pressure exists from spud-in and drives drilling fluid into the drill bit. When this happens, drilling fluid does not return to eh rig because it is pumped into these voids and thus circulation of the drilling fluid is lost. Lost circulation is generally controlled by two techniques: 1) sealing formation so that drilling fluid will not flow into them and 2) reducing drilling fluid pressure in the wellbore so that it essentially balances formation fluid pressure. This paper deal with the second control technique, describing four balanced pressure drilling techniques and giving advantages and disadvantage of each. It is based on a study directed by Sandia Laboratories. |