Apparatus and system for well placement and reservoir characterization

A modular downhole apparatus to control a drilling direction while drilling a wellbore, the apparatus being incorporated into a drill string comprising one or more downhole tools and drill pipe, the drill pipe being of the same or various lengths, the modular downhole apparatus comprising:

• a first module having one or more antennas, wherein the first module has connectors on both ends and is removeably connected to the drill string;
• a second module having one or more antennas, wherein the second module has connectors on both ends and is removeably connected to the drill string;
• and
• a processor capable of:
• actuating the modular downhole apparatus to make measurements;
• determining a bed boundary indicator using the measurements;
• and
• controlling the drilling direction of the drill string using the determined bed boundary indicator.

A method to obtain a depth of investigation of at least ten feet into a formation while drilling a wellbore, comprising:

• providing a modular downhole apparatus, the apparatus being incorporated into a drill string comprising one or more downhole tools and drill pipe, the drill pipe being of the same or various lengths, wherein each module in the modular downhole apparatus has connectors on both ends and is removeably connected to the drill string;
• spacing a first module and a second module of the modular downhole apparatus such that an antenna on the first module has a separation distance of at least ten feet from an antenna on the second module;
• making measurements by transmitting a signal from one of the antennas and receiving the signal in the other antenna;
• and
• investigating properties of the formation at a distance from the wellbore that is proportional to the separation distance between the antennas using the measurements.

A method to obtain a desired depth of investigation into a formation while drilling a wellbore, comprising:

• providing a modular downhole apparatus, the apparatus being incorporated into a drill string comprising one or more downhole tools and drill pipe, the drill pipe being of the same or various lengths, wherein each module in the modular downhole apparatus has connectors on both ends and is removeably connected to the drill string;
• selecting the desired depth of investigation for a measurement;
• spacing a first module and a second module of the modular downhole apparatus such that the separation distance between an antenna on the first module and an antenna on the second module is proportional to the desired depth of investigation;
• making the measurements by transmitting a signal from one of the antennas and receiving the signal in the other antenna;
• and
• investigating properties of the formation using the measurements.