APPLICATION OF STOCHASTIC INVERSION AND CURVED PSEUDO ELASTIC IMPEDANCE (CPEI) TO DETECT CARBONATE RESERVOIR IN BATURAJA FORMATION

• Main Author: Rafael Rumondor, Roxy
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/69889
• Institution: Institut Teknologi Bandung

Carbonate reservoirs are one of the most important targets in world oil and gas exploration. Oil and gas reserves in carbonate reservoirs account for up to half of the world's oil and gas reserves (Burchette, 2014). The Baturaja Formation is one of the gas reservoirs in the South Sumatra basin. The Baturaja Formation is a limestone formation with a wide carbonate platform but has a relatively thin layer thickness. This study attempts to model and interpret the carbonate reservoir in the Baturaja formation using the seismic inversion method. Seismic inversion itself has many methods for modeling lithology and interpreting it based on well log data and seismic data. Prior to the seismic inversion stage, the "Tuning Thickness" analysis was first carried out. Tuning Thickness analysis is carried out to determine the thickness of the rock layers based on seismic data. In this study, Tuning Thickness is very helpful because the thickness of the target zone in the Baturaja formation is relatively thin. The thickness of the gas reservoir target zone is 50 meters, while the thickness of the reservoir target zone based on seismic data is 57.47 meters. Then proceed to the seismic inversion stage. Seismic inversion itself has many methods to model lithology and interpret it based on well log data and seismic data. The inversion method commonly used is the deterministic inversion method. The deterministic method used is Linear Programming Sparse Spike Inversion (LPSSI). The LPSSI method works by modeling the reflectivity in the form of a spike and then correlates it with a seismic trace to produce a simple geological model as the result of the inversion. However, the inversion method is not optimal for modeling the lithology of a thin carbonate gas reservoir in the Baturaja formation, so the Stochastic Seismic Inversion method is used. Stochastic inversion is used to overcome the shortcomings of deterministic inversion to model thin layers. Stochastic inversion results provide optimal results for detecting and interpreting the lithology of carbonate gas reservoirs. To support the seismic version required physical rock analysis. Avseth et al (2014) introduced a method according to the Rock Physic Template (RPT) which takes into account compaction, cementation and sensitivity to air saturation, the method is Curved Pseudo Elastic Impedance. According to Palgunadi et al (2016) the CPEI method approach can be done by making a curve model that approximates the RPT using the trigonometric equation function. Where the curve model approach based on this trigonometric function is simpler. In its application, this trigonometric curve model will be used in crossplot analysis of elastic parameters to determine the p