Method for forming drain holes from a cased well
US4397360A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jul 6, 1981 |
| Grant date | Aug 9, 1983 |
| Priority date | — |
| Expiry date | Jul 6, 2001 |
Classification
- Technology area (CPC E)Fixed Constructions
- CPC primaryE21B7/061
- WIPO fieldCivil engineering
- WIPO sectorOther fields
Abstract
A method and apparatus for forming substantially horizontal drain holes into a subterranean formation from a substantially vertical cased wellbore. A casing anchor is set in the casing adjacent the formation and a whipstock is used to mill a window in the casing. A flexible drill string is then used to drill the horizontal drain hole through the window. In one modification, a deflection tool having a deflection surface which has a radius of curvature of between 11 and 28 feet is used for both the milling and drilling operations. In another modification, the milling operation is carried out with a sidetracking whipstock which is then replaced with the above-described deflection tool to carry out the drilling operation. In still another modification, a whipstock adaptor is positioned onto a sidetracking whipstock after the milling operation to convert the sidetracking whipstock into a deflecting tool having the desired radius of curvature for carrying out the drilling operation.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.