## 3 Data Set and Methodology
### Methodology  
Well log and seismic data had a different domain where well log data had depth domain, and seismic data had time domain. Well seismic tie was needed to convert depth domain to time domain and vice versa. Wavelet and seismic ties were important in forwarding modeling to generate an actual earth model. The match was based on a selection wavelet that created for predicting the model response [5]. The well-seismic tie depended on measuring the density and sonic logs in generating  
Figure 3: Amplitude versus offset (AVO) modeling workflow for facies and fluid identification. an acoustic impedance log [17]. The acoustic impedance combined with the velocity data to derive a reflection coefficient series in time. The seismic data was essential to calibrate to the geology in a well to get a high-quality result of the AVO model. The first step in a well-seismic tie was calibrating the sonic log, density, and check-shot to create a time-depth relationship (Figure 4). In this project, statistical wavelet extracted from seismic data was the best wavelet for the well convolution. The convolution of reflection coefficient with the corrected wavelet generated synthetic seismograms. The well data that has tied with seismic can be used to interpret the seismic data. The bulk shift, stretch, and squeeze technique were applied in this process to get a higher correlation value. In this study, the range of bulk shift was 0-20 ms. Reducing an uncertainty of geological understanding was obtained following the high-quality correlation between seismic and synthetic seismic data, which created about 70-85% similarity of the extraction of statistic wavelet. The percentages meant the extracted wavelet provided a high correlation. The constant computation windows were between 600 to 1200 ms.  
Facies was a discrete variable that delineated the quality of rock categories and presented the scale of heterogeneities. Facies was characterized by using well log, where different facies showed different petrophysical properties. Petrophysical well log data was interpreted to identify facies which  
Figure 4: Well log seismic tie for I-2 log, (**a**) check shot correction in one of the logs, (**b**) statistical wavelet with timely response and respective amplitude spectrum on the bottom, (**c**) an example of a well seismic tie in the research area. The blue seismic traces were the calculated synthetic, and the red seismic traces were the real seismic data using statistical wavelet, and (**d**) seismic section which was tied with well log. was validated with core reports from some wells. Cut-off from the well log properties were used to characterize well logs facies in research area [18]. Four different facies classes were defined, i.e., shale, brine sand, gas sand, and coal. The well log responses were integrated with the seismic AVO result to identify facies and hydrocarbon distributions. The seismic AVO was extensively used in facies prediction and fluid parameter studies [5]. The AVO attribute was commonly applied to illustrate the relationship between rock physical properties and seismic [19]. Primary AVO attribute produced the intercept (A) and the reflection-coefficient gradient (B) [20]. AVO was classified to be four classes based on different amplitude response of gas-sands enclosed by shale. Class I showed the developments include high acoustic impedance sands and the amplitude decrease with offset. Class I had a positive intercept and a negative gradient. Class II produced sands surrounded by shale with small impedance contrast and the amplitude could either increase or decrease with offset. The intercept of class II value was positive or negative, and on the other hand the gradient was negative. Class III for low acoustic impedance sands that were usually gas sand. The amplitude class III increased along with offset and intercept, while the gradients were negatives. Class IV was added to the AVO class, which was mentioned the standard reflection coefficient as negative and decreases while the offset increases.