|
| US4134452 | 14 Sep 1977 | 16 Ene 1979 | Gulf Research & Development Company | Well testing tool |
| US4185689 | 5 Sep 1978 | 29 Ene 1980 | Halliburton Company | Casing bridge plug with push-out pressure equalizer valve |
| US4188999 | 27 Sep 1978 | 19 Feb 1980 | Baker International Corporation | Expendable plug and packer assembly |
| US4299281 | 21 May 1979 | 10 Nov 1981 | Otis Engineering Corporation | Compensating bridge plug |
| US5154228 | 22 May 1990 | 13 Oct 1992 | | Valving system for hurricane plugs |
