Sains Malaysiana 41(8)(2012): 953-959

A New Algorithm to Estimate Attenuation Using Frequency Shift Methods

(Algoritma Baru Penganggaran Atenuasi Menggunakan Kaedah Anjakan Frekuensi)

Maman Hermana*, Hammad Hazim Bin Mohd Azhar & Zuhar Zahir Tuan Harith

Geosciences and Petroleum Engineering Department, Universiti Teknologi PETRONAS

Bandar Seri Iskandar , 31750 Tronoh, Perak, Malaysia

Diserahkan: 16 December 2010 / Diterima: 3 Mac 2012

ABSTRACT

This paper presents the improvement of quality factor (Q) estimation using shift frequency method. A new method was developed based on two previous methods; peak frequency shift (PFS) method and centroid frequency shift (CFS) method. The proposed algorithm has been tested to gauge its performance using three different scenarios; Q variation, travel time variation, and signal to noise ratio (SNR) variation. The test was performed using the Ricker wavelet with random noise included. Based on the results obtained, it can be concluded that the new proposed method was able to improve Q estimation using shift frequency method. This method can also be implemented in the low and high Q condition, shallow and deep wavelet targets and in the low and high SNR conditions of seismic data. The limitations in the PFS and CFS methods can be reduced by this method.

Keywords: Attenuation; centroid frequency; peak frequency; variance; wavelet

ABSTRAK

Kertas ini membentangkan peningkatan penganggaran faktor kualiti (Q), menerusi kaedah anjakan frekuensi. Satu kaedah baru telah dibangunkan menggunakan 2 kaedah lazim yang sedia ada iaitu; kaedah anjakan puncak frekuensi(PFS) dan kaedah anjakan frekuensi centroid (CFS). Algoritma yang dicadangkan telah diuji untuk mengukur prestasi kaedah baru ini menggunakan tiga senario: perubahanQ, perubahan masa kembara dan perubahan nisbah isyarat ke hingar (SNR). Ujian ini dijalankan dengan menggunakan gelombang Ricker dengan disertakan hingar rawak. Berdasarkan kepada hasil keputusan yang diperoleh, boleh disimpulkan bahawa kaedah baru ini berupaya untuk meningkatkan penganggaran Q menggunakan kaedah anjakan frekuensi. Kaedah ini juga boleh diaplikasikan pada keadaan Q tinggi dan rendah, sasaran gelombang cetek dan dalam dan pada data seismik SNR tinggi dan rendah. Had-had sekatan bagiPFS dan CFS juga boleh dikurangkan dengan menggunakan kaedah ini.

Kata kunci: Atenuasi; frekuensi puncak; frekuensi tengah; varians; wavelet

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*Pengarang surat-menyurat; email: maman.h_g00921@utp.edu.my