Application of deterministic fault-seal analysis for fault-bounding trap: a case study in Than Nong 1B prospect, Block 05-1(a), Nam Con Son basin, offshore Vietnam
- Authors: Anh Tuan Truong 1, Tam Trung Le 1, Nhan Duc Dang 1, Tuan Anh Do 1, Lap Quoc Lai 2, Lan Tien-Hoang Nguyen 1*
1 PetroVietnam Domestic Exploration Production Operating Company Limited, Hanoi, Vietnam
2 Independent researcher, Hanoi, Vietnam
- Keywords: Fault-bounding structures, Fault seal analysis, Hydrocarbon column, Prospect evaluation, Trap analysis.
- Received: 4th-Aug-2022
- Revised: 13th-Nov-2022
- Accepted: 18th-Dec-2022
- Online: 1st-Feb-2023
- Section: Oil and Gas
Fault-seal analysis has long been applied for predicting potential hydrocarbon column for mitigating risk in exploration and appraisals. Than Nong 1B structure in Block 05-1(a), located nearby Dai Hung field, is a fault-bounding structure; thus, the fault seal capacity plays a major role in trapping hydrocarbon. In this study, the H50 reservoir is taken as an example of how fault-bounded prospects are evaluated in Block 05-1(a). For the case of Than Nong 1B, to meaningfully determine the potential of the structure, the fault geometric analysis is conducted to fully understand the 3D geometry of the structure. Moreover, vertical displacement of the faults is inspected to ensure the quality of input data and to understand how faults and horizons affect each other. After structural description conducted, the study applies all common methods of fault-seal analysis from the 1980s to the newest workflow published in 2016, such as 3D sand-shale juxtaposition analysis, SGR analysis, height-column-prediction algorithms by Yielding et al. (2010). The results of these methods are then combined by using Trap analysis workflow, proposed by Peter Bretan in 2017, to determine a unique location of fault leak point defining the trappable hydrocarbon column of the structure. The results suggest that the faults in Than Nong 1B prospect are able to hold a maximum column of 183 m hydrocarbon in H50 reservoir, significantly higher than the column of 125 m hydrocarbon defined by Fault-leak point. Furthermore, this study also proves that the Trap analysis is an effective method for evaluating structures with high level of fault linkage.
Bretan, P. (2017). Trap Analysis: an automated approach for deriving column height predictions in fault-bounded traps. Petroleum Geoscience, 23(1), 56-69.
Bretan, P., Yeilding, G., Jones, H. (2003). Using calibrated shale gouge ratio to estimate hydrocarbon column heights. AAPG Bullentin 87(3).397-413.
Clarke, S. M., Burley, S. D., and Williams, G. D. (2005). A three‐dimensional approach to fault seal analysis: fault‐block juxtaposition and argillaceous smear modelling. Basin Research, 17(2), 269-288.
Freeman, B., Boult, J. P., Yielding, G., Menpes S. (2010). Using empirical geological rules to reduce structural uncertainty in seismic interpretation of faults. Journal of Structural Geology 32(11), 1668-1676.
Hardman, R. F. P. and Booth, J. E. (1991). The significance of normal faults in the exploration and production of North Sea hydrocarbons. Geological Society, London, Special Publications 56(1), 1-13.
Knipe, R. J., Fisher, Q. J., Jones G., Clennel, M. R., Farmer, A. B., Harrison, A. B., Kidd B., Ncallister, E., Porter, J.R., White, E. A. (1997). Fault seal analysis: successful methodologies, application and future directions. In Norwegian Petroleum Society Special Publications, 7, 15-38. Elsevier.
Needham, D. T., Yielding, G., and Freeman, B. (1996). Analysis of fault geometry and displacement patterns. Geological Society, London, Special Publications, 99(1), 189-199.
Walsh, J. J, Nicol, A., Childs, C. (2002). An alternative model for the growth of faults. Journal of Structural Geology 24 (11), 1669-1675.
Yielding, G. (2015). Trapping of buoyant fluids in fault-bound structures. Geological Society, London, Special Publications 421(1). 219.
Yielding, G., Bretan, P., and Freeman, B. (2010). Fault seal calibration: a brief review. Geological Society, London, Special Publications, 347(1), 243-255.