BELUGA RIVER GAS FIELD GEOCELLULAR MODEL: MODELING
A COMPLEX FLUVIAL
RESERVOIR
LEVINSON, Rick A.1, SCHEIHING, Mark H.2, DELANEY, Peter3, SCHEEPENS, Claude2, SEIFERT, Dirk1, and BRADEN, John C.1, (1) ConocoPhillips Alaska, Inc, 700 G Street, Anchorage, AK 99501, [email protected], (2) ConocoPhillips Company, 600 North Dairy Ashford, Houston, TX 77079, (3) ConocoPhillips Comapny, P. O. Box 24750, Doha, Qatar
The Beluga River Gas Field (BRU), in northern Cook Inlet, Alaska, is at a
mature stage of development. A program is underway to mitigate the impacts of
declining pressure, water breakthrough, and sand production. As part of this
effort, a major re-description of the reservoir was undertaken and integrated
into a 3D geocellular model. A particular focus of the modeling
effort was to
identify gas volumes that might not yet be drained with existing perforations.
This model has proven to be a useful tool for reservoir management, and it has
helped to identify new production opportunities.
The producing intervals at BRU are Neogene-aged, fluvially deposited
sandstones of the high net-to-gross Sterling Fm. and underlying low net-to-gross
Beluga Fm. The structural and stratigraphic framework of the model was built
from 2D seismic
structure surfaces and a flow unit zonation based on correlation
of major coal zones. Within this framework, major fluvial facies associations
were distributed using object-based stochastic
modeling
techniques. Facies
proportions and dimensions were derived from 21 wells, and facies orientations
were based upon dipmeter logs and regional depositional trends. Permeability and
porosity were then distributed following the trend of facies objects using a
stochastic petrophysical model. Water saturation was based on J-functions
representing key rock types with multiple free water levels. A total of 10
realizations were created to appraise the uncertainty associated with the
stochastic component of the model. From these realizations, a probability cube
was calculated that identifies the most likely occurrence of net pay sandstones
in the field. A static connectivity analysis was also conducted to estimate gas
pore volume connected to existing perforations.
Results indicate that Sterling Fm. sandstones are 99% connected to existing well perforations, while the Beluga Fm. sandstones are only 81% connected. Connected original-gas-in-place in the model is 28% greater than that indicated by p/Z analysis, suggesting that there may be substantial opportunities for well work or new drilling to access isolated pay sands, mainly in the Beluga Fm. This has been tested in two recent workover operations, which have resulted in new pay sands being identified and perforated, leading to increased gas production.