The effect of rock properties in the analysis of amplitude variation with offset (AVO) on Baturaja carbonates formation at the northern part of West Java Basin

The effect of rock properties such as velocity, porosity, and diagenesis processes was comprehensively investigated to analyse the Amplitude Variation with Offset (AVO) on Baturaja carbonate formation at the northern part of the West Java Basin. The AVO analysis consists of the subsurface condition modeling and the AVO data field. Firstly, the subsurface carbonate modeling was applied by Shuey equation and Aki-Richard formula using P-wave, S-wave, density, Poisson's ratio, and porosity as the parameters. In this simulation, the amplitude corresponding to the angle or offset for each layers were obtained. The AVO attributes such as intercept (A) and gradient (B) were produced by analysing the amplitude. Interestingly, the value of A was positive and the gradient was negative which can be related to the carbonate formation. The property of the attributes was AVO class-II and the product of A and B which would be negative in the value are important for hydrocarbon indicator. AVO data field was analyzed, the preserve amplitude was obtained, and the noise was reduced. The subsurface condition modeling was applied in two different well locations and also the facies. It was found that the two wells showed different AVO attributes although the porosity distribution was relatively same around 18% and 20%. The AVO attributes in one of the wells was similar to the model with shifting polarization while another well has no shifting polarization. Overall, some parameters in AVO data analysis should be considered since not only the velocity and porosity can influence the amplitude but also the diagenesis processes of the rocks can do. We believe that our work is very useful to reduce some pitfalls and risks in AVO analysis on the carbonates formation.