Time-lapse analogue reservoir modelling of turbidite channel sands

Abstract

This paper describes a research program at the Australian Resources Research Centre (ARRC) to establish and use an analogue model of a turbidite channel reservoir to gain insight into issues of uncertainty in reservoir simulations of channelised fields and their seismic expression. The project is unique in that it integrates seismic and reservoir engineering research in a controlled laboratory environment. The research is based around a cementation technique that allows synthetic sandstones to be fabricated with predetermined physical properties such as porosity, permeability, and impedance. These laboratory models provide real data that do not rely on assumptions, and are therefore useful to compare with numerical simulations of both the seismic and fluid-flow response. The 1:1000 scale model comprises two intersecting sandstone channels within an impermeable acrylic matrix. Fluid communication between the channels exists in two separate intersecting areas with contrasting flow connectivity. Production from the initially oil-saturated model was performed via water?flood, and the injected water was dyed blue to allow the displacement process to be recorded on video. Production rates and data such as time to water breakthrough, produced water-oil ratio, and cumulative recovery were recorded and used to history-match reservoir simulations of the production response. Scaled time-lapse 3D data were acquired before and after production at frequencies of 50 kHz and 1 MHz. The 1 MHz data provides high-resolution images and accurate monitoring of the oil and water distribution. The 50 kHz data honours the correct scaling of the relative seismic wavelength-to-channel size, where the individual channels are within tuning thickness, and provide data for valid comparisons with seismic attributes in field data from similar reservoirs. An analysis of velocity dispersion indicates that the measured acoustic response to changes in saturation at 50 kHz is representative of the expected lower frequency seismic response.