A new wire line tool has successfully retrieved the nuclear sources and formation data from a measurement while drilling (MWD) tool stuck, in a deep, highly deviated well in the Gulf of Mexico.
On Nov. 8, 1993, Schlumberger Wireline & Testing and Anadrill ran a logging-while drilling inductive coupling (LINC) tool on conventional wire line to fish the gamma ray and neutron sources from a compensated density, neutron (CDN) tool stuck in a well at 19,855 ft with an inclination greater than 80.
The CDN tool logs a formation while drilling, before mud invasion or well bore damage may occur, to improve gas detection and analysis of potential pay zones.
The CDN tool's two nuclear sources and any stored formation data are designed to be retrieved by wire line (Fig. 1). Conventional MWD tools have side loaded sources, which requires fishing the full tool to retrieve the nuclear sources and logging data.
Retrieving the nuclear sources from a stuck MWD bottom hole assembly reduces the environmental risks of leaving the sources downhole.
To ensure against loss of well data if the bottom hole assembly is not subsequently recovered, formation data stored in the CDN tool are dumped into the LINC tool through an inductive coupling between the two tools. The data are then transmitted to the surface through the electric line in about 30 min.
The LINC tool has a 1 11/16 in. diameter and is about 10 ft long.
The nuclear source fish is about 3 ft long.
Fishing with wire line in complex trajectory wells or in deep wells (such as this one) is difficult because excess weight and friction may cause the cable tension at the surface to exceed the fishing cable's breaking strength before the tool's shear pins can be broken.
The LINC tool alleviates this problem because it uses a surface controlled downhole electrical motor to engage and extract the dual-source fishing head mechanically, with no need for excess cable pull or tension at the surface.
The mechanism can free the fish in just a few minutes, and clear indications are sent to the surface to confirm pin shearing and source extraction.
Once the fish is pulled to the surface, standard shields and nuclear source handling procedures are used.
Copyright 1994 Oil & Gas Journal. All Rights Reserved.
