Examination of the Time-Dependent Seismic Signal of a Producing Carbonate Field Using Rock Physics

Rock physics studies help to gain a deeper understanding of the seismic response, and predict effects on the seismic signal caused by hydrocarbon production. Consequently, using rock physics together with 4D seismic is key to understand the time-varying behaviour of a producing field. These techniques are applied to the South Arne field, with the aim to understand how hydrocarbon production is affecting the chalk reservoir. The methods used include rock physics studies, time-shift analysis, amplitude and AVO analysis, and AVO seismic inversion. The main observations from the rock physics studies are that the Young’s modulus is highly dependent on porosity and the acoustic impedance dependent on oil saturation. The time-shift analysis reveals that a limited part of the reservoir is affected by compaction. This part of the reservoir correlates well with an area of high porosities and low Young’s modulus. Seismic hardening is observed for several locations of the reservoir, particularly where water is injected into the reservoir. This is expected based on the rock physics studies, which show that an increase in water saturation increases the acoustic impedance.