--> Abstract: Monitoring Lithology Variations in Complex Exploration Area by the SWD Technology SEISBIT, by F. Poletto, F. Miranda, P. Corubolo, and F. Abramo; #90942 (1997).

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Abstract: Monitoring lithology variations in complex exploration area by the SWD technology SEISBIT

POLETTO F., F. MIRANDA, P. CORUBOLO , F. ABRAMO

During the drilling of an exploration well in a prospect where the lithologic sequence is not well known, the geology is structurally complex, and the seismic response is extremely poor, perforation can present some difficulties in the planning of the casing sequence and in the bit type to be used.

A seismic tool, the Vertical Seismic Profiles (VSP), is useful to recognize the seismic events in a well and below the TD of the well. In conventional VSP the drilling must be interrupted to convey a geophone down-hole, this implies drilling stand-by time besides operative risks. A solution to these problems is recording passive reciprocal VSPs using the drill-bit as an energy source. For this reason AGIP and OGS designed and built the SEISBIT system, capable of acquiring and pre-processing data directly on the field. These data are processed as standard VSPs. An advantage of SWD tools, compared to the other sources of data, is the capability of prediction "ahead of the bit"; moreover the seismic velocities obtained by SWD recording system can be used to convert the interpreted seismic sections in depth and to produce updated maps during the perforation. Other information may be derived also from logging while drilling measurement (LWD) and integrated with SWD can be used to improve the WD interpretation in area with poor seismic response.

This paper presents the results of several case histories where the SWD methodology has been used to monitor the lithologic sequence and helped to solve operative problems.

AAPG Search and Discovery Article #90942©1997 AAPG International Conference and Exhibition, Vienna, Austria