Description Applications Schematic illustration of the Resistivity- at-the-Bit tool (LWD-RAB). Specifications ODP Logging Services, Lamont-Doherty Earth Observatory, Rt. 9W, Palisades, NY 10964 Logging-While-Drilling Resistivity-at-the-Bit Tool ♦ Detection of resistivity heterogeneity via azimuthal resistivity images ♦ Lithology estimation ♦ Instantaneous detection of casing and coring points ♦ Accurate resistivity when mud is salty or formation resistivity is high ♦ Detection of early invasion of borehole fluids into the formation The Resistivity-at-the-Bit tool (LWD-RAB) makes azimuthal resistivity and gamma ray measurements while drilling. Using an azimuthal positioning system, measurements are acquired around the borehole to create a high resolution, 360-degree resistivity image of the drilled hole. The RAB tool may be connected directly behind the bit or further back in the bottom hole assembly. It may be run with other LWD tools such as the ADN, ISONIC or NMR. Typically, the RAB data are stored in memory within the tool and retrieved at the end of the bit run. As an option, the data may be transmitted to a surface acquisition system if a Measurement-While-Drilling (MWD) power pulse tool is run in conjunction with the RAB. Assembly of the RAB tool aboard the JOIDES Resolution. Optional uphole connector Batteries Upper sensor Middle sensor, containing focused ring electrode Azimuthal gamma ray Field-replaceable stabilizer Lower sensor Float valve bore Rbit electrode : t h g i e w l o o T m b l 0 0 2 1 : h t g n e l l o o T ) m 8 0 . 3 ( t f 1 . 0 1 : e g n a r e r u t a r e p m e T ) C ° 0 5 1 o t ° 5 2 - ( F ° 0 0 3 o t ° 3 1 - : r e t e m a i d e d i s t u o l a n i m o n r a l l o c l l i r D . n i 5 7 . 6 : ) l a h t u m i z a ( r e t e m a i d e d i s t u o . x a m r a l l o c l l i r D . n i 5 2 1 . 8 : r e w o P ) s r h + 0 0 2 ( k c a p y r e t t a b m u i h t i L : e u q r o t m u m i x a m d e d n e m m o c e R f b l - t f 0 0 0 , 6 1 : y c a r u c c a t n e m e r u s a e m y t i v i t s i s e R e g n a R e d o r t c e l e d e s u c o f & t i B l a h t u m i z A 1 - 2 . 0 % 0 2 - / + % 0 2 - / + 0 0 0 1 - 2 % 5 - / + % 5 - / + 0 0 0 2 - 0 0 0 1 % 0 1 - / + % 0 2 - / + 0 0 0 , 0 2 - 0 0 0 2 % 0 2 - / + - - - : s n o i t a c i f i c e p s y a r a m m a G : e g n a R s t i n u I P A 0 5 2 - 0 : y t i l i b a t a e p e r l a c i t s i t a t s a m g i s e n O r h / t f 0 0 1 t a % 3 < ) g n i g a r e v a l e v e l - 3 , n o i t a m r o f I P A - 0 1 ( r h / t f 0 5 t a % 2 < : e t a r w o l f m u m i x a M n i m / l a g 0 0 8 : e r u s s e r p g n i t a r e p o m u m i x a M i s p 0 0 0 , 8 1 : t i b n o t h g i e w m u m i x a M L / 0 0 0 , 0 0 0 , 4 7 = F 2 s i L e r e h w ( f b l ) t e e f n i s r e z i l i b a t s n e e w t e b e c n a t s i d : d a o l g n i r r a j m u m i x a M f b l 0 0 0 , 0 3 3