Industry challenges

Carbon capture and storage represents one method for helping to mitigate the effects of increasing CO₂ concentrations on global climate. Whether the focus is on storage of CO₂ that originates from anthropogenic sources or as a by-product of natural-gas production, monitoring is an essential part of CCS operations. Furthermore, in situations in which CO₂ is used for enhanced oil recovery, monitoring can help control the injection process to maximise both oil recovery and CO₂ storage.

The lateral and vertical distribution of reservoir properties such as fluid type, facies, lithology, porosity, and permeability away from well control is a key source of uncertainty in geological modelling. Heterogeneities of these properties within the reservoir occur at different scales and thus influence individual well performance and overall field productivity. Predictions of rock and fluid distributions at the seismic scale are essential elements of successful exploration and field development efforts.

Unconventional gas and light oil reservoirs are typically associated with very low matrix permeabilities (<0.1 mD). These reservoirs can be clastic or carbonate. Many are composed of shale, which can also serve as the source rock. Because of the low matrix permeabilities, development of these reservoirs relies on horizontal drilling and stimulation by hydraulic fracturing in order to maximise contact of the formation with the well bore. Although unconventional reservoirs are often pattern-drilled and fractured, production on a well-to-well or fracture-stage basis can be extremely variable.

Pre-drill predictions of pore pressure, fracture gradient and effective stress are critical to drilling wells in a safe and cost-effective manner. These estimates are used to predict borehole stability so that appropriate mud weights, casing and cementing designs can be determined. In addition, predictions of pressure and stress can identify potential drilling hazards, aiding in the avoidance of kicks, fluid losses, and blowouts.

Time-lapse (or 4D) seismic is a reservoir monitoring technology, which has proven to be a reliable reservoir surveillance tool. By analysing differences of multiple seismic surveys acquired over a producing reservoir and by integration with conventional reservoir monitoring tools, 4D seismic data can provide valuable insight on dynamic reservoir properties such as fluid saturation, pressure and temperature.  Although 4D technology is relatively mature, the Curtin Reservoir Geophysics Consortium is working in areas that can help extract even more value from the data.

The effective management of exploration, development and production assets requires an accurate picture of the subsurface structures and properties. Seismic imaging is the process that positions reflections in their proper locations with their proper amplitudes and phase. Historically, imaging includes a number of processes that include signal enhancement, deconvolution, statics, velocity analysis and velocity model building, migration, and inversion. Although seismic imaging technology has seen significant advances in recent years, there remain challenges, especially in geological environments such as sub-salt, overthrust, and carbonate settings, or onshore in rugged terrains. In order to meet these challenges, researchers have focused on more accurate wave-equation-based migration algorithms such as reverse time migration (RTM).