Borehole petrophysical imaging using induction and acoustic measurements Borehole petrophysical imaging using induction and acoustic measurements Guozhong Gao, Aria Abubakar, and Tarek M. Habashy Schlumberger This paper was modified from paper G presented at the SPWLA 54th Annual Logging Symposium held in New Orleans, Louisiana June 22-26, 2013. Abstract Latest borehole induction and acoustic logging tools are capable of making three-dimensional(3D) measurements at multi-frequencies and mul- tiple depths of investigation. This significantly enhanced sensing capabil- ity in both spectral and spatial domain, and the availability of multi- physics measurements, make it possible to derive petrophysical images, such as porosity and fluid saturations, around the wellbore using advanced inversion techniques. A method is developed for directly obtaining in situ porosity and fluid saturation images simultaneously using borehole induction and acoustic measurements. We show that both high resolu- tion porosity and fluid saturation images can be obtained up to a fairly large distance(> 1.5m) away from the wellbore, thus improving formation evaluation significantly. Naturally occurred formation inhomogenoity and structures (i.e, dipping structures), or induced inhomogeneoity due to for- mation damage and mud-filtrate invasion, can be properly evaluated from the derived porosity and saturation images, thus leading to more accurate logging interpretation. Introduction Porosity and fluid saturation are two of the most important reservoir petro- physical properties for formation evaluation(Schlumberger, 1991). In general, these petrophysical properties are heterogeneously distributed, i.e., structurally distributed around the wellbore. In addition, formation mechanical and electri- cal properties are often altered due to formation damage(Civan, 2007), and/or mud-filtrate invasion(Schlumberger, 1991), during the drilling process. Forma- tion damage will alter the mechanical properties of the formation around the wellbore and result in a reduction in the natural capability of a reservoir to produce its fluids, such as a decrease in porosity or permeability, or both, thus affecting the acoustic measurements in such a way that accurate evaluation of the porosity distribution in the original formation will be affected. Damage 1