Challenge: Identify bypassed hydrocarbons in a North Sea well shut in since 2005 because of high water cut and low pressure.
Solution: Run RST reservoir saturation tool to evaluate saturations and determine depths for shutting off existing perforations and reperforating.
Result: Identified three intervals for reperforating that are producing 27.5-MMcf/d gas, 997-bbl/d oil, and only 1.7% water.
An operator wanted to identify any bypassed hydrocarbons in a North Sea well that had been shut in because of high water cut and low pressure. The plan was to shut off the water-flushed producing zones and recomplete the new zones.
The innovative dual-detector spectrometry system of the through-tubing RST reservoir saturation tool records carbon and oxygen (C/O) and Dual-Burst thermal decay time measurements in the same pass. The C/O ratio is used to determine the formation oil saturation independent of the formation water salinity. The sigma log of the thermal neutron capture cross section is used to determine water saturation behind casing. Porosity is also measured for formation evaluation.
The well was logged with the RST tool under shut-in conditions. Schlumberger Data & Consulting Services (DCS) conducted an integrated evaluation of the RST data. Formation sigma and related gas indicators were used to identify gas-bearing zones, and the C/O logs were used to characterize the oil- and water-bearing zones. The source of the water was confirmed, and new potential oil and gas reservoirs were identified.
Download: RST Saturation Evaluation Finds Bypassed Oil and Gas Zones (0.59 MB PDF)