Publications

Pore pressure analysis is one of the stages that needs to be done before drilling and it is intended to determine indication of overpressure zones that may endanger the drilling phase. Pore pressure analysis could be done with various variables from well and/or seismic data. This study is conducted at the JA Field, East Java Basin, and focused on the claystone interval of the Ledok – Ngrayong Formation. This study will focus on interval velocity and inversion velocity in the claystone formations, which is typically showing more sensitivity to heterogeneity in such conditions. Besides mapping overpressure zone indications, this study was conducted to determine the sensitivity of the velocity variables in analyzing pore pressure and to make 3D pore pressure distribution models, where in this study interval velocity and inversion velocity were used. In addition to using the 1D pore pressure models from Well A1, Well B2 and Well C3 as a comparison, a blind test was also carried out to validate whether the two 3D pore pressure distribution models qualitatively represented the JA Field. From the pore pressure analysis results, both on the 1D and 3D models, which were carried out based on the Eaton (1975) method, it is known that there is an indication of the overpressure zone in the Wonocolo Formation with the top of overpressure zone depth at 5900-6200 ft. The 3D pore pressure models showed the overpressure zone distribution is marked by the significant color changes tendency in the center of the study area. Qualitatively, the use of interval velocity and inversion velocity in creating the 3D models appears in the distribution of different pore pressure values. However, the two 3D pore pressure models have generally represented the JA Field pore pressure distribution as evidenced by the blind test result.