Publications

Stratigraphy is a key concept in understanding the depositional unit of a sedimentary layer and its prospects for petroleum. Generally, stratigraphy analysis uses a convenient qualitative approach to interpret the sedimentary packages. Despite the fact that the aforementioned method is well received among geologists as to conduct depositional environment and facies analysis, it is obvious that it is biased toward different extents of experience and basis of assumptions. Moreover on several stratigraphic cases, explorationists deal with the lost interval, which in a long run, will affect the confidence of the interpretation from abundant amounts of well data. The Markov Chain method, a statistical method that can predict the probability of the next process in a sedimentary cycle system by knowing the previous process, is able to provide a more objective interpretation of core data. The research objective is to understand better the application of the Markov Chain and graph algorithm method to predict sedimentary cycles while dealing with a “blank” interval on core data. Integrating core and wireline log data was undertaken to determine quantitatively the results from the Markov Chain method. The core data were taken from one of the sedimentary basins in Sumatra with a length from 4490–4561 feet. Seven facies were determined from the core data. The depositional facies show the interdistributary channel and distributary channel environments. The results show the probability series of facies: F4, F3, F2, F9, F20, and F1. Based on this pattern, it could be interpreted that the lost interval at 4499–4502 feet from the core is F2 facies (planar cross bedding coarse sandstone). Finally, a graph algorithm method was utilized to construct a facies depositional model based on the occurrence of well data assumed as a discrete system of the depositional environment. Quantitative stratigraphy analysis using the Markov Chain combined with the graph algorithm method is useful to encourage and enrich the concept of petroleum exploration and development.