Identifying compartmentalization of the E-M Field, Bredasdorp Basin (South Africa) using well logs and core data

Abstract

The E-M Field is situated in the Bredasdorp Basin off the south coast of South Africa. Production is taken place from Zone 2 of the upper shallow marine, the upper shallow marine is divided into five Zones numbered I-5.An investigation was done on the area after it was discovered that the hydrocarbons produces did not balance the hydrocarbon amounts estimated initially. Four boreholes were used for core analysis i.e. BH A, B, C and D. Cores were logged and facies were described in order to establish the depositional environment, it was identified that the environment intersected in Zone 3 is an estuarine system It was discovered from core analysis that Zone 3 contains barriers caused by mudstones of lagoon facies and baffles of tidal flat facies that prohibits the vertical flow of hydrocarbons from Zone 3 into Zone 2 where production is taken place. From the resistivity and neutron-density logs it was identified that only one out of the four boreholes i.e. BH A contains hydrocarbons while the other boreholes shows water bearing reservoirs. Borehole BH A contains a mudstone barrier which divides the Zone into two reservoir units and is capped by tidal flat facies which separates sandstone connectivity between Zone 3 and Zone 2. Using Petrel software it was possible to display the geometry of the environment in 3D and to visualize the barrier, baffles and the two reservoir units. It was identified from the structural model that the area is consists of 5 blocks, these blocks are divided by faults. Borehole BH A is situated in block 1. It is recommended that fluid samples be taken within Zone 3 for the identification of fluid type, it is also recommended that exploration of block 3 should be considered as this block has possible reservoir sandstones above the GWC and