EAGE/SPE Joint Workshop - Closing the Loop: Reservoir Simulation and Geophysical Measurements

The 3D reservoir model has developed into an important reservoir management tool in recent years. One major remaining challenge is to provide a closer integration between the seismic inversion discipline on one side and reservoir modelling on the other. Seismic inversion results provide important information about the spatial distribution of reservoir properties between the wells but have limited vertical resolution compared to the scale of the reservoir model. In addition, the seismic inversion process is non-unique like many geophysical inverse problems, meaning that there are an infinite number of models that fit the seismic data equally well above some threshold misfit.

Rock physics is a key component of any quantitative seismic data integration within the reservoir
simulation workflow. It connects the petrophysical properties of the rocks and fluids to the seismic
response. A petroelastic model, PEM, is a forward set of rules that act as a link between the reservoir
and elastic domains.

For a SAGD process of a heavy oil reservoir, the influence factors for rock model are mainly
temperature, steam saturation. By introducing a new rock model, the simulation model is forward
modeled to generating elastic and seismic amplitude responses. Recently, a newly 3D seismic was
acquired seismic for the reservoir. A reservoir model is simulated for the SAGD process and history
matched. Based on the reservoir model, the rock model is applied for synthetic elastic and acoustic
property generation. By bundling with seismic, the SAGD steam chamber could be identified. The
seismic signature of steam chamber can be easily seen.

In the past years, we developed, improved and applied in the field a variety of different methodologies
for assisted history matching (AHM) and improved uncertainty management, such as Experimental
Design, Ensemble Kalman Filtering, Adjoint, streamlines. In most recent years, increasing emphasis
has been on bringing these methodologies to our field operations, and also include 4D seismic into the
history match process.

On Troll West area, the Sognefjord producing formation is thick (160 m) with very good reservoir
properties and with a thin Oil leg (<26 m). It is relatively shallow (1.5 km) under a structurally
straightforward overburden, leading to good quality seismic data. After more than a decade of Oil
production, more than 1 million meters of horizontal drains have been drilled and the fifth monitor
survey has been shot in 2009. This huge amount of data makes it a-priori particularly suitable for
seismic monitoring and should lead to quantitatively reliable follow-up of the thin Oil leg thickness
and production forecast. The following paper describes results from a R&D-collaboration between
Statoil and CGGVeritas.

The Habban field is a fractured basement reservoir hosted in structural highs formed by faultcontrolled
blocks in a rift setting (Redfern and Jones 1995[1]). The necessary integration of all
acquired data during the last development years leaded us to the creation of a new reservoir model.
Focus will be set on the new aspects and techniques used for the modelling of this uncommon field.

For many hydrocarbon fields under production there is a chance that operational problems related to
production and well completion might cause leakage of hydrocarbons into the subsurface. In some
cases a detailed monitoring of such events is desired, and in this paper I suggest to use site survey data
to monitor leakage of hydrocarbons into the subsurface formations. In most cases, old site survey data
are available, and such data might serve as a base data set. If a second data set is acquired after a
leakage event has occurred, it is suggested to use this data set as a conventional 4D monitor survey.
There are several limitations related to the proposed strategy, I will discuss some of them in this
paper, and then show results from a successful site survey monitoring campaign performed by Saga in
1989-1990.

Enfield was the first offshore hydrocarbon development in the Exmouth Sub-basin of
Western Australia. We present a case study to highlight how integration of 4D seismic and
production data has been critical in understanding the dynamic behaviour of the field, and
improving reservoir management practices.

Improvement on the knowledge of compartmentalization at the intermediate stages of development considerably affects the decisions taken on well numbers, well locations and, most importantly, on the success of the improved oil recovery (IOR) strategy implemented.