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Viabilities of PP-wave Ray and Elastic Impedance for Hydrocarbon-sand Discrimination
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 73rd EAGE Conference and Exhibition incorporating SPE EUROPEC 2011, May 2011, cp-238-00356
- ISBN: 978-90-73834-12-5
Abstract
Theoretical evaluation of elastic impedance (EI) and ray impedance (RI) has revealed that RI has a more reliable dimension and is less sensitive to errors than EI. In particular, RI appears to be more applicable than EI for characterizing tight gas sands. In this paper, a new measurement (RI) is proposed to estimate the ray impedance from elastic impedance, and can be expressed in the form of a normalization of the elastic impedance (EI). Tests of these three measurements are performed on the log data of three different types of reservoirs: a typical Class III marine gas sand, a Class I tight gas-sand and a thin sand-mud inter-bed. We show that RI is capable of characterizing all three types of reservoirs, whilst EI fails in the tight gas-sand case. The cross-plots of EI against acoustic impedance (AI) show approximately linear trends for all three cases. The RI estimated from the elastic impedance (EI) has a comparable dimension to the acoustic impedance (AI), and maintains the interpretation ability of the original RI.