This paper presents the ability and techniques in using porosity-permeability “multi” regression pared with rock cluster to obtain reasonable quality permeability prediction in shaly sand reservoirs. Multiple methods can be used to predict reservoir permeability, but the most common is using core data correlation. The availability and coverage of core data in Attaka field is inadequate and therefore the technique of permeability correlation from a conventional cored well to other non-cored wells is limited. Correlating permeability prediction from cores often results in reasonable data, in other instances poor data correlation results from the quality of the input parameters, doubtful technical methods or poor core analysis. The accuracy of porosity calculation as a key input parameter to predict permeability is very significant. Porosity can be calculated from many types of data, but porosity calculation from density log with matrix and fluid density input is commonly used. The calculation result is more reasonable if calibrated with core porosity data. To obtain an accurate porosity calculation result it is highly recommended to use “multiple matrix density” instead of using a single matrix where multiple rock types exists. The correlation of calculated porosity and core permeability data is generally used to predict permeability in “non cored wells”. A simple porosity-permeability regression in poor quality reservoirs of with multiple rock types, dominated by thin bedded shaly sands often shows a variability of results. But, using “multi” regression by rock cluster is strongly recommended to get more reasonable result of permeability prediction. Attaka Field is located in 180 feet of water offshore in the East Kalimantan PSC and discovered in 1970. The Attaka closure is a N-S trending four-way dip closure cut a series of major normal fault and by a series of intra-field antithetic and synthetic normal fault. A total 524 wells have been drilled in the field to date.
Author : Muhlis