Inversion and geophysical modelling af fluid displacement in chalk reservoirs, 4D seismic
Monitoring movements of fluid fronts by use of 4D seismic data has been performed with success on sandstone reservoirs for the last 5-6 years, whereas the use on chalk reservoirs has been limited.
The project investigates the possibilities of using repeated seismic investigation (4D seismic) for determination of fluid movement and mapping of residual hydrocarbons in chalk reservoirs. This is done through a systematic investigation of the effects that the changes in fluid concentrations and the movements of fluid fronts have on the seismic response. This will ensure a higher rate of success for 4D seismic acquisition as the seismic data can be collected at the right time in the production. In the project there will be utilised reservoir simulation, rock physics, seismic modelling, seismic inversion, and texture classification
This has primarily been because of the general tightness of the chalk resulting in limited response to changes in fluid velocities and therefore uncertainties regarding seismic detectability of fluid fronts. The study shows that for the success of a 4D seismic study of a chalk field the porosity is the single most important parameter. It is shown that if changes above 5% point in acoustic impedance are required to detect with 4D seismic data the porosity of the reservoir has to be higher than 0.32. That means in practice that one comes into the zone in porosity where there is a possibility of the chalk to go through compaction. Compaction is giving an increased 4D signal, giving an even higher change of seismic detection. The study shows the importance of performing a feasibility study and how it can be done. The study furthermore shows the importance of applying seismic inversion to the seismic data before they are compared with the result from the reservoir simulator. The project have used the results from the EFP-98 Rock Physics of Chalk project
Key figures
Category
Participants
| Partner | Subsidy | Auto financing |
|---|---|---|
| COWI A/S |
Contact
Kroghsgade 1
DK-2100 København Ø, Denmark
Mørch Pedersen, Jacob , 35266011, jmp@oedan.dk
Øvr. Partnere: COWI Rådgivende Ingeniører AS
