| The B oil group of the E Oilfield in the deep-water area of the Niger Delta Basin is composed of turbidite
channel and lobe complex. The comprehensive analysis of static and dynamic data shows that the B oil group develops
perched water. Based on seismic data and dynamic test data, the characteristics of perched water in reservoir B are
summarized: perched water can complicate the oil-water system of the reservoir, and different oil-water contact may
develop in the same oil-water system; MDT pressure analysis shows that reservoirs with perched water are generally with
a unified oil pressure line; static reservoir development analysis and dynamic data such as interference tests show that,
even though the same reservoir has different oil-water contacts, it has overall connectivity.
The cause of the perched water is furtherly analyzed for the B oil group, and its genesis needs specific geologic basis
and is highly related to the oil and gas charging process during the formation of the oil reservoir. Specifically, from the
actual situation of the development of perched water in the B oil group, the geological basis for its genesis is the saddle
area with a relatively low structure which forms a half-closed local structural depression surrounded by the high points on
two sides, and by parallel sealing faults on the other two. While the oil and gas are charged from the southwest flank of the
trap, which is the only open direction for the trap. One-way charging leads to the gradual reduction of the water body.
When the high points are filled with oil and gas, the reservoir comes from a bottom water reservoir to an edge water
reservoir, the water body in the saddle cannot be driven out and perched water is formed.
There are various genetic models for the development of perched water in reservoirs, and five genetic models are
proposed based on the genesis and mechanism analysis. Finally, understanding the perched water reservoir patterns is very
important for the exploration and development of oil and gas fields.Three aspects of risk and potential caused by perched
water are discussed. |
