Excessive water production can detrimentally affect the profitability of hydrocarbon producing wells if not controlled properly. Water cut present in the oil stream coming from the wells producing in several of the offshore Mexico fields is an issue of critical importance because oil production is sent to exportation. In the beginning the operators didn't have water handling facilities, forcing operators to monitor wells with water cut as low as 60.0 %. Forced to control by decreasing the choke size, in some cases the operator can handle the water, but in many cases required shutting the well in completely causing a negative impact on the production of the fields. Two of the main drivers of excessive water production is the mature fields are the influx of water behind the casing and/or water flowing through the natural fractures of these carbonate reservoirs. This paper describes the best practices of using a selective hydrocarbon-based ultra-fine cement (UFC) slurry system to slow down water production in offshore Mexico wells.

The UFC slurry consists of ultra-fine cement with an average particle size of 2.5 μm, a surfactant, and a hydrocarbon carrier fluid (i.e. diesel). Because the slurry is hydrocarbon-based, it remains inactive when contacting an oil-producing zone. When the system contacts a water producing zone the slurry will remain mobile for an additional 20 to 30 minutes before beginning to set. The delayed setting of the cement slurry is ideal for placing the ultrafine cement slurry into water-bearing formation fractures some distance away from the wellbore. The slurry is designed to selectively shut off water flowing into the wellbore and is applicable up to 400°F (204°C).

This paper describes the successful best practices and mistakes of the implementation of the UFC slurry system in Offshore Mexico to seal off unwanted water flowing through natural fractures and/or behind the casing. A variety of case histories will be discussed in detail along with post-production numbers after the treatment. Up to date, more 100 UFC treatments have been performed in Southern Mexico

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