System and methods for formation evaluation while drilling

A method for real-time processing of downhole logging data, comprising the steps of:

• a) drilling a borehole into a geologic formation;
• b) while drilling the borehole, applying a first data acquisition sequence to determine substantially in real time at least one parameter of a zone in the formation being traversed;
• c) selecting a second data acquisition sequence based upon the at least one determined parameter;
• and
• e) applying the selected second data acquisition sequence to determine additional properties of said zone of the formation.

A method for making nuclear magnetic resonance (NMR) measurements of a geologic formation using an NMR logging tool, comprising the steps of:

• applying oscillating magnetic fields according to a first pulse sequence
• τi−π/2(+x)−[tcp−π−tcp−echo]j−tcp−π/2(−x)
• where τi is a variable delay, and i≧1;
• j≧1;
• and +x and −x denote phases of the Larmor frequency of the carrier of the pulse with respect to a continuous wave Larmor frequency signal;
• tcp is the Carr-Purcell spacing;
• applying one or more times a chirped pulse sequence, comprising
• a radio frequency (RF) pulse covering a relatively wide range of frequencies to saturate nuclear magnetization in a volume within the geologic formation and a readout pulse sequence at a frequency within the range of covered frequencies, the readout pulse sequence following a predetermined wait time after the saturation pulse;
• receiving NMR echo signals corresponding to the first pulse sequence and to the one or more chirped pulse sequence;
• and
• processing the received NMR echo signals to determine properties of the geologic formation.