Prior to 2010, all oil from the K field was produced from the Lower Sihapas Formation, where oil could easily be identified from electrical logs in these thick, high-quality sands. Then, in 2010, something unusual happened. When drilling an infill well, we noticed good oil indications from mud logs in sands above the Lower Sihapas Formation, despite the low resistivity less than 4 ohm-m. We completed the sand and it flowed 146 BOPD with zero water. This unexpected result prompted us to conduct a short two-week study to identify other candidate wells. The study consisted of: collection of mud and wireline log data in all K wells; re-running petrophysical analysis using new a, m and n values for low resistivity sands; and ranking candidate wells based on sand quality, gas readings, oil shows, initial oil rate prediction, well cost and the chance of making money. The study identified 17 candidate wells to re-complete in the Upper Sihapas. To date, we have worked over seven wells with an oil gain of 700 BOPD and estimated incremental oil recovery of 175 million stock tank barrels. One of the worked-over wells, the one with the lowest EMV, flowed water. This paper describes the study, the resultant workover campaign and lessons learned.


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