Summary Downhole gravity gradiometry is becoming an increasingly common technique to help understand the subsurface in the oil and gas industry. It can be combined with other techniques and logs to get a very in-depth interpretation of target formations. The development and methodology of downhole gravity gradiometry and how it can be used in downhole applications are explained along with the advantages and disadvantages of this method. Introduction Gravity gradiometry has been a widely used technique for surface applications in the petroleum industry, but its use as a Downhole tool provides a new way of investigating the wellbore and allows for better resolution in projects such as reservoir monitoring. Applications of surface gravity gradiometry have been successful in monitoring reservoir activity with flood operations, but well gravity gradiometry would overcome the depth of investigation limitations of surface surveys ( Neill, 2010 ). Downhole gradiometry also provides a deeper depth of investigation than nuclear measurements such as gamma-ray instruments. History and development The first underground gravity measurements were completed in England by Airy (1865) who used pendulums to measure the vertical gravity gradient between the top and bottom of a well. vertical tree (McCulloh, 1965). Gravitational gradiometry was also the first geophysical investigation applied to oil exploration. This was done in 1915 on the Egbell oil field in Slovakia, but this was only a cursory investigation using a torsion balance (Neill, 2010). A torsion balance is a pendulum designed by Hungarian physicist Baron Loránd Eötvös (1848-1919) that measures the density of the underlying rock. From 1915 to 1936 this technique was used quite extensively for geophysics...... half of the article ......ell Log Analysts (SPWLA) (1968): n. page Web. Neill, Francis. “Potential of Downhole Gravity Gradimetry for Reservoir Management.” World Oil 231.1 (2010): n. page World oil online. Network. March 5, 2014.Nekut, AG "Borehole gravity gradiometry." Geophysics 54.2 (1989): 225. SEG. Network. April 17, 2014.Nind, Chris JM, and Jeffery D. Macqueen. “The Borehole Gravity Meter: Development and Results.” Kochi 2013 (nd): n. page Network. March 5, 2014. Rim, Hyoungrea and Yaoguo Li. “Single-hole imaging using borehole gravity gradiometry.” Geophysics 77.5 (2012): G67-76. FOLLOWING Network. April 17, 2014. Seigel, HO, C. Nind, R. Lachapelle, M. Chouteau, and B. Giroux. “Development of a Borehole Gravity Meter for Mining Applications.” Soil and Borehole Geophysical Methods: Proceedings of Exploration 07: Fifth Decadal International Conference on Mineral Exploration (2007): 1143-147. Net.