Mature field management and oil recovery optimization are growing concerns in current production strategies worldwide. In mature fields, the increase in water production is a key issue that must be considered early in the field management process.

A typical brownfield well in Argentina produces a small fraction of oil with 95% to 99% of water cut. To reduce produced water, companies in Argentina have started water shutoff projects.

Cerro Dragon, is the largest oilfield in terms of oil production in Argentina and is not immune to this problem. In recent years this field started to experience problems with the water management, and the need to take strategic decisions to close layers of high WOR (water oil ratio) to improve water balance became a priority. Different techniques were tested in the attempt to identify water-production layers; the most common methodology so far has been swabbing independent zones. To date, none of the techniques have given the results expected by the operator or some partial solution that could help reduce the produced water.

Panamerican began searching for new technologies to optimize the workover for Water Shut Off projects (WSO). After evaluating different alternatives, they began to use production logging below the electrosumergible pump, the first time production logging data could be recorded in a well that did not flow naturally in 5 ½" casing.

A unique methodology involving wireline, artificial lift, and data services allowed the characterization of the producing intervals (water, oil, and gas) with high water cut. This technology evaluates non-naturally flowing wells using cable-deployed production logging, while producing the well with a simultaneously conveyed electric submersible pump. Obtaining the production profile of each of the multiple pay zones allowed later sealing of water-producing zones, thereby drastically reducing the amount of water treated at surface.

Because less than 1% of oil net production was identified in the lowest limit of the oil and gas holdup measurement in front of every interval, the operator decided to isolate water-producing zones and recomplete the producing interval with a mechanical pump.

A pilot project with three wells started in 2010 with positive results. In subsequent years it was decided to continue the use of the technology to extend its application to various fields of Cerro Dragon.

The principal benefits of this technique are identification of layers with high water/oil ratio in dynamic conditions, also the technology showed its value providing information for the dynamic model of the reservoir, detection of layers with low productivity index but with high net production, identification of crossflow in static and dynamic conditions, identification of skin damage in perforations, follow-up of waterflooding projects, shutting off of layers with water production, and selection of these layers before well completion.

In conclusion, the use of this technology not only brought about the reduction of water in producing wells with high RAP, also provided us with valuable information to optimize secondary recovery projects in the Cerro Dragon field.

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