Prediction of the fracture development and fracture network modeling for basement reservoir, offshore Southern Vietnam.

Abstract

Japan Vietnam Petroleum Co., Ltd. (JVPC) confirmed oil accumulation in fractures of granitic basement at the Rang Dong Structure in Block 15-2, offshore Vietnam and has been producing oil from the Rang Dong Oil Field since 1998. These fractures are considered to be formed mainly by tectonic movement. Therefore, it is essential to conduct tectonic study for prediction of the fracture development and quantitative fracture network modeling. Since 1996, JVPC has conducted various tectonic studies, such as core/FMI data interpretation, topographic analysis of top basement surface, stress/strain analyses and map restoration, for more accurate fault interpretation, better understanding of fault movement and prediction of fracture development at the Rang Dong Field. By the tectonic studies, tectonic history of the fault movement and the concept of fracture distribution in various structural settings were suggested. Based on the concept of fracture distribution, the area of fracture development was predicted and development well locations have been selected accordingly. The concept was further refined by post well evaluation, such as FMI interpretation and DST results. Following the qualitative analysis by the tectonic studies mentioned above, 3D fracture network modeling as quantitative analysis is in progress for fracture reservoir management of the Rang Dong Field. To model heterogeneous fracture network, the Discrete Fracture Network (DFN) modeling method with the software of FracMan supplied from Golder Associates was introduced. This software is one of the tools for data analysis and modeling of discrete features like fractures, that integrates such input parameters as aperture, shape, size, direction and permeability of fractures from core/FMI fracture interpretation, DST/production data and well interference data. The DFN modeling is currently ongoing and will hopefully provide further conditional information for the geological concept (structural settings and fracture development). This should be critical in constructing a more realistic reservoir geological model for the fractured basement and optimizing the reservoir management.