RESERVOIR CHARACTERIZATION USING POISSON IMPEDANCE IN THE NORTH SUMATRA GG FIELD

• Main Author: Multi, Warni
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/54455
• Institution: Institut Teknologi Bandung

Acoustic impedance (AI) and Shear impedance (SI) parameters are commonly used parameters to identify the sensitivity of lithology and fluid separation. However, these parameters are less effective for separating lithology and fluids in the Belumai Formation in the GG Field in the North Sumatra basin. In this study, the Poisson Impedance (PI) application was used to analyze the lithological separation of sandstone and fluid layers in the field. PI is expressed mathematically as PI = AI – c * SI. The AI and SI values are obtained from the wells, while the c value is the PI optimization factor obtained from the Target Coefficient Correlation Analysis (TCCA) method. To identify the lithological separation, the value of c is needed which is obtained from the PI versus Gamma Ray correlation, while for the identification of the fluid the value of c is obtained by the correlation between PI and water saturation. The correlation results give a different c value which is used to form the lithology index component (LI) as an indicator of lithology using a c value of 2.3559 while the Fluid Index (FI) component as a fluid indicator uses a c value of 4.7046. Laterally, the LI and FI slices were obtained by extracting the AI and SI amplitudes from the seismic volume and reusing the c values. From the LI slice, a low impedance area of -5000 to -4000 m/s*g/cc is shown in the areas of the BGL-1, BGL-2, and BGL-3 wells which represent the distribution of sandstone reservoirs. The three wells are also well saturated with hydrocarbon gas, which in particular the BGL-1 well has proven gas. This is reinforced from the slice analysis of the FI distribution that the sandstone stretching integrates with the presence of gaseous hydrocarbon stretches indicated by a low impedance of -18000 to -20000 m/s*g/cc and also validated by a slice of Vp/Vs ratio with a low value, namely in the range of 1.5 - 1.7 unitless. Structurally, the position of the three wells is also located at the height of the structure. The spreading direction based on the LI slice is also validated by the structure map and the Vp/Vs slice shows that the sandstone reservoir in the sub-layer has the prospect of further development towards the North rather than the West towards BGL-3.