Kelly Wrobel

Reducing Reservoir Characterization Uncertainties and Improving Field Recovery through Four-Dimensional Seismic Technology: An Integrated Four-Dimensional Seismic Interpretation Workflow

More than one-half of the worlds remaining hydrocarbon reserves are in carbonate rocks. Reservoir complexity and heterogeneity in carbonate reservoirs are commonly the main sources of uncertainty in reservoir models and thereby affect field recovery strategies. Four-dimensional seismic technology, which acquires three-dimensional seismic data over a producing field at different times, can provide valuable information on the reservoir changes induced by hydrocarbon production. This information can then be used to better understand the reservoirs complexity, heterogeneity, dynamic flow parameters, and production performance. The application of four-dimensional seismic technology in carbonates is still in an early stage because of many challenges such as detectability and repeatability of four-dimensional seismic data. This chapter provides an overview of the workflow, describes more details through an application to a giant carbonate oil field located onshore Abu Dhabi, and emphasizes reduction of reservoir uncertainties. The workflow consists of the following six steps: (1) rock physics analysis on the effects of fluid and pressure changes on the elastic properties of the reservoir rocks; (2) four-dimensional forward seismic modeling; (3) seismic acquisition geometry analysis, seismic data processing assessment, and postproduction processing data enhancement; (4) qualitative and quantitative four-dimensional seismic data analysis; (5) four-dimensional seismic updating of geologic models; and (6) reservoir simulation feedback using four-dimensional seismic data.

4D Seismic in Carbonates: From Rock Physics to Field Examples

We have carried out 4D seismic research on two giant carbonate fields in Abu Dhabi, UAE, employing an integrated approach. Our work process started from fundamental rock physics analysis. The Xu-White rock physics model, originally designed for clastic rocks, was extended to carbonates. With this model, we characterized the reservoir interval by different (geophysical) pore types, related them to petrophysical (sedimentalogical) pore types, and performed log conditioning to improve well to seismic ties. Laboratory ultrasonic measurements of core plugs and log analysis were conducted in combination with the rock physics model to examine the fluid and pressure sensitivities.