Method of analyzing a subterranean formation and method of producing a mineral hydrocarbon fluid from the formation

Abstract

Method of analyzing a subterranean formation traversed by a wellbore. The method uses a tool comprising a transmitter antenna and a receiver antenna, the subterranean formation comprising one or more formation layers. The tool is suspended inside the wellbore, and one or more electromagnetic fields are induced in the formation. One or more time-dependent transient response signals are detected and analyzed. Electromagnetic anisotropy of at least one of the formation layers is detectable. Geosteering cues may be derived from the time-dependent transient response signals, for continued drilling of the well bore until a hydrocarbon reservoir is reached. The hydrocarbon may then be produced.

Description

CROSS REFERENCE TO EARLIER APPLICATION[0001]The present application claims benefit under 35 USC § 119(e) of U.S. Provisional application No. 60 / 797,556 filed 4 May 2006.FIELD OF THE INVENTION[0002]In one aspect, the present invention relates to a method of analyzing a subterranean formation traversed by a wellbore. In another aspect the invention relates to a method of producing a mineral hydrocarbon fluid from an earth formation. In still another aspect, the invention relates to a computer readable medium storing computer readable instructions that analyze one or more electromagnetic response signals.BACKGROUND OF THE INVENTION[0003]In logging while drilling (LWD) geo-steering applications, it is advantageous to detect the presence of a formation anomaly ahead of or around a bit or bottom hole assembly. There are many instances where “Look-Ahead” capability is desired in LWD logging environments. Look-ahead logging comprises detecting an anomaly at a distance ahead of a drill bit. ...

AI Technical Summary

Benefits of technology

[0013]The electromagnetic properties of a formation layer comprising a number of thin layers may be approximated by one formation layer comprising an electromagnetic anisotropy. It is thereby avoided to have to take into account each thin layer individually when inverting the responses.

[0014]Amongst other advantages of taking into account electromagnetic anisotropy, is that anisotropy information may be useful in precisely locating mineral hydrocarbon fluid containing reservoirs, as such reservoirs are often associated with electromagnetic anisotropy of formation layers.

[0016]Said method of analyzing a subterranean formation may be used in a geosteering application, wherein a geosteering cue may be derived from the one or more time-dependent transient response signals, taking into account electromagnetic anisotropy, and wherein a drilling operation may be continued in accordance with the derived geosteering cue in order to accurately place a well.

Problems solved by technology

However, the larger the number of layers, and particularly when the layers are thin, the more complicated the analysis is.

For instance, a thinly laminated sand / shale sequence would be difficult to analyze employing the methodology as set forth in US 2006 / 0038571.

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