LOW RESISTIVITY ANALYSIS USING TYPE CURVE AND ROCK TYPE IN "ATTAKA" FIELD, KUTAI BASIN

• Main Author: Putra Pratama, Ikhsansyah
• Format: Theses
• Language: Indonesia
• Subjects: Geologi, hidrologi & meteorologi
• Online Access: https://digilib.itb.ac.id/gdl/view/57284
• Institution: Institut Teknologi Bandung

Low resistivity is a zone with low contrast between the resistivity of a reservoir containing hydrocarbons and water. It causes reservoir containing hydrocarbons is neglected because it has high water saturation. This zone is indicated to be present in the Attaka Field, especially in the targeted formation interval at Late Miocene with a resistivity of 3.5 ohms. One of the low resistivity reservoirs which have been perforated at intervals of 36-0 with good hydrocarbons production. Therefore, this study was conducted to analyze the causes of low resistivity and then apply a rock type and a type curve to calculate a more logical Sw value at the 36-0 interval, so that it can be a benchmark for reevaluation of all 15 wells in the hope of finding new prospects. Based on the petrographic analysis, SEM, and XRD at intervals of 36-0, the main cause of low resistivity is high Swirr due to large micro porosity caused by dispersed clay and also clay bound water in smectite minerals which increase the Cation Exchange Capacity. Apart from that other minor causes are fine grains and the presence of conductive minerals. Based on these facts, the calculation of water saturation must be done specifically using the type curve method. Type curve is a reservoir fluid classification method based on electrical parameters by considering the value of water conductivity, rock conductivity, porosity, and also Swirr. This parameter will be used to modify the “Archie” parameter, namely the porosity exponent (m) and the saturation exponent (n) which are no longer ideal. The value of Swirr is obtained based on SCAL analysis which is classified based on the rock-type hydraulic flow unit (HFU) which will then be distributed for each interval. Based on the analysis, the research area has 5 rock types with Swirr from worst to best is 0.726, 0.65, 0.425, 0.376, and 0.34 with the average m and n values are 1.4 and 1.2. The results of the calculation of water saturation for all intervals in each well decreased by an average of 0.1 to 0.3 which is more reliable by the actual conditions. In addition, the pay thickness increased by 50%.