Evaluation of water saturation in the low resistivity reservoir of Te Giac Trang field, block 16-1, Cuu Long basin, offshore Vietnam
Abstract
It is well known that there is a series of oil fields in the Cuu Long basin that were discovered in low resistivity Early Miocene sequences, and the Te Giac Trang field is a case that challenges formation evaluation for water saturation of the pay sands in the reservoirs. It is believed that the low resistivity is a result of the effects of many factors such as thin beds, the low degree of sand compaction, the presence of highly conductive minerals (pyrite etc.), and montmorillonite that significantly increases the surface conductivity, sorting of the sand and type of cement.
In the Te Giac Trang field, for the water saturation calculation, an approach was used with the traditional shaly sand model and modified Archie equation constants. The said method combined with the results of pressure pretests allows us to minimise the uncertainty of the estimated water saturation for these low resistivity pay sands.
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