Spectral Analysis of Petrophysical Logs to Determine the Stratal Surfaces of Dalan and Kangan Formation in one of the Gas Fields in Southern Iran using Wavelet Analysis and INPEFA Log

South Pars gas field is one of the fields in southwestern Iran in the Zagros sedimentary basin and includes two reservoirs, Kangan and Dalan. Kangan and Dalan formations that belong to Dahram group and are considered as the most important gas reservoirs in the Persian Gulf region. The use of well drilling logs in uncored wells to identify rock-related features has always been discussed by geologists.  In this study, based on wavelet analysis of gamma-neutron and sonic logs, stratal surfaces including sequence boundary and maximum flooding surface were identified.  In this study, using wavelet analysis of well log data such as GR, NPHI, RHOB, DT and also combining them with Cyclolog data, a suitable and low error method for automatic determination of these boundaries was presented. Also in this study, sequence stratigraphy was investigated by INPEFA method of Cyclolog software to determine sequence boundaries (SB) and maximum flooding surface (MFS) with positive inflection points and negative inflection points of available INPEFA log curves , respectively. In addition, the highstand system tract (HST) was identified by the negative trend of the INPEFA curve and the transgressive system tract (TST) was determined by the positive trend of this curve. Accordingly, sequence stratigraphy study of Dalan and Kangan formations was performed by INPEFA method in 4 wells of South Pars gas field.  Finally, the agreement between the automatic sequence boundaries obtained from the wavelet transform method and INPEFA and its comparison with the core information in four wells from the study field, shows satisfactory results.