Distinguish commercial gas and improve reservoir drilling success.
Solution
Employ a multidisciplinary team of petrotechnical experts to evaluate well-seismic relationships and extract previously unattainable information.
Results
Rank drilling locations by prospectivity and risk.
Noncommercial gas pockets
An operator working offshore needed to distinguish between commercial and noncommercial gas accumulations. Typically, the measurement needed to determine gas aggregation is density. The company performed drilling based on the interpretation of stacked seismic amplitudes and AVO responses. It made numerous gas discoveries, some of which were nonproductive (residual gas saturation only). The operator needed some way to manage the risk and cost of drilling nonproductive wells.
Schlumberger Reservoir Seismic Services used a multidisciplinary team of petrotechnical experts to glean unseen value from the surface seismic data. The operator selected an innovative Schlumberger process that calculates density from surface seismic data through an AVO inversion process. The key factor that usually limits this measurement is angle range of the seismic gathers. The project successfully extended the seismic angle range from 30° to 54°, allowing good density determination.
Prestack well-to-seismic ties were used to monitor the changes to the surface seismic data during the data optimization process. Proprietary rock physics tools were used to understand the logged acoustic measurements in terms of porosity and water saturation. These values allow the customer to assess reservoir volumetrics, decide commercial viability, and statically model the reservoir. This approach is viable anywhere high-resolution, high-fidelity seismic data is available and complemented with at least one borehole containing acoustic log measurements.
Well cost savings
Project results and recommendations from Schlumberger helped determine that a prospect would be unproductive before spending the money to drill a well. The operator was able to use the results to evaluate other potential prospects. It is using the seismically derived reservoir measurements to manage field development and as an additional quantifiable evaluation to discern commercial viability.
