Abstract
The Lunskoye Field is a centrepiece of the Sakhalin II development, one of Shell's most significant current projects. Demand for LNG in the nearby Asia-Pacific market and availability of a large (18.2 Tcf GIIP) gas resource underpins the investment decision in a challenging offshore environment.
Robust suites of seismically-constrained integrated reservoir models were generated to evaluate short-, medium- and long-term subsurface uncertainties. Previous quantitative reservoir mModelling efforts were hampered by the existence of shallow gas over the crest of the structure, which masked the seismic response in the crestal area of the reservoir. This impacted the evaluation of structure and reservoir properties from seismic. To address this, a new 3D-survey was acquired in 2003, in an east-west direction, to undershoot the shallow gas deposits. The Pre-Stack Time Migration and Pre-Stack Depth Migration seismic results show the reservoir image is greatly improved, and there is improved confidence in the seismic signal that allows it to be used for the definition of rock property distribution.
In parallel to the seismic interpretation, a detailed evaluation of velocities, core, and well-log information was undertaken to provide input into an in-house probabilistic model-based seismic inversion (1). This fundamental work was used to:
construct an integrated and fully consistent structural and stratigraphic hierarchical framework, in the lateral and vertical domain;
update the view of the depositional setting, taking into account variations in provenance and relative sea-level;
define the petrophysical parameters for the rock property model, which underpins the inversion.
The results of the model-based inversion formed the basis of the detailed static models and analysis of key subsurface uncertainties. Results of the improved property models were upscaled and fed into the well inflow models and dynamic models to improve productivity estimates, long-term reservoir performance prediction and to support development planning and reservoir management.
This paper summarises all of the refinements undertaken as part of the new model building, including the improvement in the seismic data, the insight into the stratigraphic changes, the hierarchical framework, the rock property model, the probabilistic inversion, the well inflow modelling, and the dynamic simulation.
