Sub-seismic Faults Can Seriously Affect Fluid Flow in the Njord Field off Western Norway - A Stochastic Fault Modeling Case Study

Abstract

Abstract The Njord Field is heavily faulted. A stochastic fault modeling study has been performed on a sector of the field to quantify the potential impact of sub-seismic faulting on the production. Emphasis was given to the sensitivity of the results to the number of sub-seismic faults, the fault orientation, and the fault sealing properties. The main conclusions are: - Sub-seismic faults have neglectable effect on recovery, nor on the shape of the production profile, unless they are almost completely sealing. - The distribution of strike directions had no effects on the production.–Recovery decreases with increasing number of sub-seismic faults.–A large number of sealing sub-seismic faults will on average reduce the sector production with 20–25 %, compared to a base case model without sub-seismic faults. In some cases the reduction is much worse.–The production from individual wells is much more sensitive than the sector total to sub-seismic faults. Reductions up to 80 % have been observed in the simulations. The HAVANA software has been used for the sub-seismic faults modeling. Irap RMS has been used for visualization and quality control, and the effects of the sub-seismic faults on production have been investigated using the fluid flow simulator Eclipse. HAVANA has proved to be very useful for this kind of studies. P. 295