Abstract

SMG Microgels are pre-gelled polymers having a narrow size distribution and behaving like large polymer molecules whose stability is strongly enhanced by internal crosslinks. The largest species have a size of around 2 μm, which makes them suitable for Water Shutoff and Conformance Control applications in matrix reservoirs. SMG Microgels have been firstly used as water shutoff agents in gas storage wells and showed high efficiency to reduce water production while enhancing gas production. This paper reports a Conformance project which has been recently deployed in a heterogeneous sandstone reservoir. The pilot pattern consisted of one central injector, surrounded by 7 offset producers, with a spacing between 150 and 450 m. Reservoir permeability ranges between 10 and 1,000 mD with an average of 125 mD. Reservoir temperature is 48°C and salinity is 8,000 ppm TDS.

Soft SMG with size around 2 μm was chosen regarding reservoir conditions. Microgel size prevented invasion of lowest permeability zones and created flow resistance in highest permeability zones by adsorption on the rock. Microgel slug corresponded to 0.1 Pore Volume and was 10,000 m3. Microgel injection proceeded over a period of 3 months. WHP remained below max pressure authorized of 1,500 psi.

Closest producers responded within 3 months after microgel injection, with noticeable increase in oil rate along with a reduction of a few points of water cut. After one year 6 offset producers upon 7 were responding to the treatment. Three producers showed strong increase and sustained oil production, three had low response and one well lost both water and oil, showing diversion to the other wells. The trend remains steadily established in the pattern. After one year, 10,000 bbl of additional oil has been produced, along with a reduction of water production of 125,000 bbl.

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