Comparison of INPEFA technology and wavelet transform in sequence stratigraphic division of mixed reservoir: a case study of lower Es3 of KL oilfield in Laizhouwan Sag

Abstract

Sequence identification and division is an important basis for oil and gas exploration research. In view of the complex sedimentary environment, based on the previous element logging correction lithology, through the combination of logging curve and lithology data, in this paper, two methods of maximum entropy spectrum analysis and wavelet transform are used to identify the logging curve and divide the interface, and the high-resolution sequence identification of migmatite in the study area was completed. Compared with AC and SP logging curves, the overall and local trend inflection points of INPEFA-GR curve can improve the accuracy of medium-term and short-term cycle interface identification; wavelet transform and time–frequency spectrum analysis of different scale factors can realize the identification and comparison of medium-term and short-term cycle interfaces. The results show that maximum entropy spectrum analysis is more suitable for determining the third-level and fourth-level sequence interfaces. Wavelet transform is more suitable for the division of fifth-level sequences. By comparing and adjusting the two methods, the lower Es3 of KL Oilfield in Laizhouwan Sag can be divided into 1 long-term base-level cycle, 3 medium-term base-level cycle and 8 short-term base-level cycle. This study has certain reference significance for the construction of sequence stratigraphic framework in migmatite area and helps to better describe the reservoir.