Application of Continuous Wavelet Transform to Layer Boundaries Detection from Gamma Ray Log Arya Dwi Candra(a*), Bambang Yudho Suranta(a), Sulistyono(a), Nur L. Maulidiyah(b), Andri Syafriya(c), Dessy Widya(c), Sungkono(b)
a) Oil and Gas Production Engineering Department, Politeknik Energi dan Mineral Akamigas, 58315, Indonesia
b) Department of Physics, Faculty of Science and Data Analytics, Institut Teknologi Sepuluh Nopember, 60111, Indonesia
c) PetroChina International Jabung Ltd., Jakarta, Indonesia.
Abstract
Layer boundary analysis is an important process in determining the net pay value. Although the layer boundary can be determined manually through mud log data, it can also be determined automatically by signal analysis using wavelet transform. This analysis uses the gamma ray (GR) log data and the resistivity log. The type of wavelet used is Continuous Wavelet Transform (CWT). The CWT workflow begins with a blocking trace process to find inflection points in the GR log data and the resistivity log based on derivative analysis by convoluting the signal with the wavelet operator that matches the original frequency. Several parameters are required as input of the wavelet transform method such as number of layers detected and minimum thickness requirements which are 3 and 1. As for the input, the percentage of layer extract varies from 25%, 30% and 35%. The result of the comparison of layer boundaries from mud log data with CWT has the lowest difference in the yield of layer extract 35%. Where the results of the layer boundary on the mud log data on NP 1, NP 2, P 1, P 2 and P 3 wells are 155, 248, 29, 10 and 343, respectively, while the results of the bed boundary with 35% layers extract at NP 1, NP 2, P 1, P 2 and P 3 wells are 168, 192, 30, 11 and 312 layers, respectively. The big difference of layer number identification in the NP1, NP2 and P3 is presumably because the CWT algorithm does not involve thin layer analysis (less than 1 ft).
Keywords: Layer boundary- Continuous Wavelet Transform- Log Gamma Ray- Mud Log- Talang Akar Formation, South Sumatra Basin
