Heimdal monitoring. 3: Seismic monitoring, methods, and results
- Elf Aquitaine Production, Pau (France)
The operational objective of this study consisted in obtaining a quantitative estimate of the rise of the Gas-Liquid Contact from the seismic surveys acquired before and during production of the Heimdal gas field (Norway). To meet this objective, the authors checked (from cores and wireline log data) the sensitivity of elastic parameters to fluids. This corresponds to predictions obtained using Gassmann`s equations and justifies the used fan approach based on AVO (Versus-Offset) processing and of P-wave impedances. The best seismic-to-well ties were obtained, in the case of gas presence, provided the seismic lines had been properly AVO processed and the VSP data inverted in terms of acoustic impedance. Building on these results, the seismic monitoring method, that they deal with in this part 3, involves AVO processing. The gradient (or slope) attribute of the AVO process is used for picking Top of Gas. The migrated intercept attribute is used for typing-in with the wells. It also provides access to P-wave impedances by a multi-trace inversion algorithm. The most representative documents regarding water rise are then obtained by a statistical method applied to the ``differences in impedance`` sections acquired before (1986) and during (1993) field production. Interpretation of such differential sections relies, as a guide, on preliminary models based on Gassmann`s equation. The map of water rise in the field is deduced from a set of 11 paris of lines. It shows that average water rise is about 30 m. It is subsequently used as a constraint for the flow reservoir model which then becomes more reliable in its predictions. One immediate economic outcome of this study is that no further wells are needed for the moment to completely drain the gas in the field.
- OSTI ID:
- 80225
- Report Number(s):
- CONF-941015--
- Country of Publication:
- United States
- Language:
- English
Similar Records
Heimdal monitoring. 1: Establishing feasibility from cores and logs
Low-cost integrated teamwork and seismic monitoring improved reservoir management of Norwegian gas reservoir with active water drive