Different pressure drops across 2 reservoirs

[vijaysin2000]

Dears,
We operate a well producing gas from 2 different layers. The upper layer produces about 47mmscfd clean gas whereas the lower layer produces about 8mmscfd with 2000bbls of water per day. Total production from the well is about 55 mmscfd.

The well started producing from both layer about 1.5 yrs back. The pressure drops in the lower layer (say L2) is about 725 psi whereas in the upper layer is only 140 psi. The two layers are about 350m apart. (@ 1700m and 2050m)

Production is made through smart completion. My belief is that the pressure drop in both the sections should be more or less equal unless the permeability in the upper layer is drastically low; which is not the case.

Does any one have experience and share the reasons.

Cheers
Vj

[vinomarky]

....

[vijaysin2000]

The pressures 140 and 725 psi are drops in upper and lower layer pressures respectively i.e. the pressures have dropped by these values in the 1.5yrs of production. Each of the 2 zones have pressure sensors just above them and therefore should be recording flowing bottom hole pressures respectively. In that case the hydrostatic heads therefore should not ideally effect the guage pressures due to the presence of NRVs.
Regards
Vijay

[Yengineer]

Are those pressures static reservoir pressures OR flowing pressures?
In the first case pressures indicate differet sized reservoirs.
In the second case it might be water encroachment.