TIME-LAPSE GRAVITY INVERSION USING GENETIC ALGORITHM (2 BIT) EKO JANUARI WAHYUDI Supervised by: Dr. Wawan Gunawan A Kadir Dr. Hendra Grandis EKO JANUARI WAHYUDI Supervised by: Dr. Wawan Gunawan A Kadir Dr. Hendra Grandis

INTRODUCTION 4D MICROGRAVITY FLUID SUBSTITUTION GENETIC ALGORITHM PERFORMANCE TEST REAL DATA INVERSION CONCLUSION OUTLINE INSTITUT TEKNOLOGI BANDUNG

As technology advance gravimeter also improve in accuracy and give the possibility to monitor pore fluids redistribution in permeable layer. Especially in Indonesia, 4D microgravity becomes considerable choice because: (1) relatively cheaper, (2) strong response (in many cases), (3) fast in acquisition, (4) less social and environmental conflict. Focus of this study is inversion programming using genetic algorithms (GA's). This study was inspired by publication Krahenbuhl & Li (2008). They used binary formulation to inverse borehole and surface gravity data. INTRODUCTION INSTITUT TEKNOLOGI BANDUNG

Pore fluids (gas, oil, & water) are subject in gravity forces, because they have different densities. Mass redistribution will cause changes in the gravity attraction. 4D MICROGRAVITY INSTITUT TEKNOLOGI BANDUNG

Δ ρ max = (in g/cc) Assumption: Porosity = 30% Water Density = 1.00 g/cc Oil Density = 0.80 g/cc Gas Density = 0.01 g/cc FLUID SUBSTITUTION INSTITUT TEKNOLOGI BANDUNG

GA is optimization method that combines biology genetic concept with optimization function  maximize fitness through artificial evolution process Genetic algorithm using the principal of survival for the fittest GENETIC ALGORITHM INSTITUT TEKNOLOGI BANDUNG Krahenbuhl (2005)

GA does not need any derivatives or curvature information GA's strongly can handle non-linier inversion and give sharp characterization of fluid contact movement in permeable layer. GENETIC ALGORITHM INSTITUT TEKNOLOGI BANDUNG The objective function

GA’s RESULTS INSTITUT TEKNOLOGI BANDUNG Inversion Result Krahenbuhl & Li (2009) Data Observation Inversion Performance

1 BIT, 2 BIT INSTITUT TEKNOLOGI BANDUNG 1 bit Inversion n=2 bit Inversion

PERFORMANCE TEST INSTITUT TEKNOLOGI BANDUNG Inversion Result Synthetic Model

REAL DATA INVERSION INSTITUT TEKNOLOGI BANDUNG Inversion Result Data Observation

Genetic algorithm can be applied in 4D gravity inversion Using 2 bit GA inversion give the possibility to characterize 3 type density changes in reservoir Inversion results from real data show the characterization of mass increase, mass decrease, and stable zone in permeable layer CONCLUSION INSTITUT TEKNOLOGI BANDUNG

THANKS