Click to view page image in pdf format.
7th Middle East Geosciences Conference and Exhibition
Manama, Bahrain
March 27-29, 2006
Seismic
Impedance to Locate a Discovery Well, South of Ghawar Field
Saudi Aramco, Dhahran, Saudi Arabia, phone: 9663-873-0480,
[email protected]
A seismic
impedance volume derived from
seismic
amplitude inversion was used as second order control, in conjunction
with first order structural control, to assist the location of an oil discovery in Well 2, in Saudi Arabia. The impedance volume
enabled us to locate vertically co-incident estimates of high porosity in the two target reservoirs, within the target structure.
The upper target, the Jurassic Hanifa reservoir, flowed oil. The lower target was the Permo -Carboniferous Unayzah
reservoir. The discovery well was a follow-up to a discovery in Well 1, in an independent structure about 10-15 km from
Well 2. In Well 1, the Hanifa reservoir flowed oil and the Unayzah was wet. The impedance log from Well 1, and
seismic
horizons at the two reservoirs, were used to define the initial model for the inversion. Impedance
attribute
maps showed that
the initially proposed Well 2 location did not fall within an impedance minimum. The impedance minimum is the ideal, given
an inverse relationship between impedance and porosity. Due to the exploration nature of the well, structural considerations
played the primary role in its location. Structure maps at both targets showed that there was freedom to move the proposed
location to the final location, into an estimated impedance minimum at both reservoirs, and stay at the same structural
position. A comparison of the predicted impedance from
seismic
, with the impedance from Well 2, shows that the inversion
did a good job of predicting the impedance at the discovery well, in both the Hanifa and Unayzah reservoirs.