“M” Field is located in Tarakan Island. Activity in the field commenced in 1984 by drilling M-1 well. Since then a total of 30 wells have been drilled in “M” Field. Generally, reservoirs can be divided into two depositional environment groups: fluvial dominated influence for upper reservoir zones and delta dominated influence for the lower zones. The objective of the study is to obtain the best method for generating a facies model of the fluvial reservoir in “M” Field, using reservoirs in 1550 MZ and 1525 MZ zone as case studies. Facies modeling plays a highly important role in the reservoir modeling process. Determining the distribution of rock properties, such as porosity, permeability and water saturation, should be relying on facies model. Limited data in “M” Field due to the absence of core data, the low to medium quality of the 2D seismic data, and the minimum reservoir pressure data, has made it difficult to identify facies, depositional environment and
reservoir connectivity. Based on GR log characteristics, all two reservoirs in the case study were interpreted as channel of fluvial sandstone. By determining the sand thickness for each reservoir zone in each well and by analyzing dipmeter data, the trend of fluvial channel can be defined relatively north to south. The trend of fluvial channel is based on a conceptual geological model which will be used as a guidance to distribute reservoir. It also combines with probability by using indicator transform method. The result is a probability map and as secondary data to distribute the facies, using Truncated Gaussian Simulation (TGS) method. Facies modeling using conceptual geological model as a guide produces better results than the facies model generated using software 100% desire. This method will accommodate geological meaning in facies model and rock properties distribution.
Author : Taufiq Lubis, Dian Kurniawan, Helby Ellen