| Abstract | The Fang basin is located in the northern Thailand. The Defense Energy Department (DED) under the Royal Thai Government takes responsibility for this site. Fang basin has many oil fields; some of them have been produced for many decades and are now depleted. DED has to explore the new ones, and the Pongsaikham is one of them. The main objective of this study is to evaluate petrophysical properties, i.e.,porosity, permeability, and water saturation of Mae Sod formation. Available data in this study consist of geological, well logging, and core data. Well logging data come fromone well of Pongsaikham oil field,andnamely,FA-PK-56-07whereas core data were extracted from another well in Mae Soon oil field,namely,FA-MS-27-44, of the same formation, Mae Sod.One of the difficult tasks is that some logssuch asresistivity (LLD) and density (RHOB) logs were recorded in paper.To do well log analysis, these logs were digitized by aMATLAB code.After digitizing, GR, DT, RHOB, NPHI, and LLDlogs were depth-matchedare available in digital format.Thewell logging data interpretation was done by using Techlog software,which was donated by Schlumberger to AIT. Well logging interpretation identified five reservoir intervals. The density porosity values were calculated based on density values read from RHOBlog.The valueof the matrix densityof 2.67 g/ccis based on core data.The calculated porosity values arein the range of 0.15-0.29.Water saturation was estimated by Archie and Waxman-Smits methods.The water saturation values varyfrom 0.43-0.71. The relationship between porosity and water saturationas proposed byWyllie and Rose method(Crain, 2000),were used to estimate permeabilitybecause of the limited core testingdata. Log-derived poroperm is plotted only to showthe relationship between porosity and permeability derived from well log.At the first timesonic log (DT) was missing in some intervals.Log Response Equation (LRE) and Artificial Neural Network (ANN) were usedto reconstruct DT curve. The synthetic DT has a good matching with the measured DT. The percentage error of the interval transit time (t) calculated by using LRE and ANNare 14.04and 9.78,respectively. The main findingsof this study were identification of 5 reservoir zones, i.e., zone 1 from 3,630 to 3,633ft, zone 2 from 3,769 to 3,802 ft, zone 3 from 3,820to 3,831ft,etc., among which zone 5 coincides with the perforated zone having oil show.It is hoped that the newly found reservoirsbased onWL interpretation will help to increase HC productivityfor Pongsaikham oil field. |