Applications of polymer gel for establishing zonal isolations and water shutoff in carbonate formations

In this paper, we present the results of successful applications of polymer gels to control water production in Mexico. We discuss three case studies that used a systematic methodology to correctly diagnose near-wellbore wate r channeling behind the casing. The methodology uses diagnostic plots based on the historical behavior of the water/oil ratio (WOR) as a function of t ime. These include correlation with information from original cement bond l ogs (CBL's), oxygen-activated logs during production to effectively determi ne the origin of the water, and saturation logs to determine the water leve ls independent of the salinity of the water produced. In addition, we present successful applications of polymer gels to re-estab lish zonal isolations in the three case studies previously mentioned. We di scuss gel placement and present the procedure followed in each case, e valu ate a water injectivity test followed by a temperature log taken before gel placement to determine the height propagation of the water, and anticipate potential zone damage of adjacent producing intervals during gel placement . In one case, a new interval completed perforating through the gel with ex cellent results. Another case involved a zone abandonment with gel, in whic h positive pressure was tested with 35 and 70 kg/cm(2) wellhead pressure at 2500 m. In all cases, the advantages of gel treatments over common cement squeezes are discussed. Finally, we present the treatment results, including the analysis of pressu res recorded during gel placement and the oil and water production before a nd after treatment.