Relative permeability modifiers (RPM), hydrophobic in nature, are used to selectively reduce permeability to water with minimum impact on permeability to oil. Lab studies and field application reveal that RPM polymers, in some conditions, may damage the permeability to oil resulting in reduction/ or lost of oil production.

Single and parallel core flow tests were conducted on carbonate and sandstone cores at reservoir conditions. Single core flow tests showed that RPM polymers can damage tight cores (less than 1 md) by forming an external filter cake on the injection face of the cores. Accumulation of RPM polymers at the face of the core means that these chemical will not properly propagate inside the core, which significantly reduces their ability to minimize water production.

Parallel core-flood experiments conducted at reservoir temperature (200°F) showed that RPM damaged the permeability to oil when there was a large permeability contrast (greater than 1:5) in favor of the oil-saturated core. Due to the high permeability contrast, most of RPM polymer solution preferentially entered the oil-saturated zone, thus damaged the oil production zone. Field data supported lab findings and showed that oil production of an oil well dropped significantly following RPM polymer treatment. It was found that polymer injection rate was a key factor to minimize damage to the oil-saturated core whenever we have a large permeability contrast in the favor of oil-saturated core. Injection of RPM polymer at low rate (1 cm3/min) was found to minimize damage to the oil-saturated core.

Field results showed that application of water control treatment using RPM polymer on an oil well resulted in a significant loss in oil production. Post treatment analysis indicated that RPM polymer solution entered mainly the oil-saturated zone, which was attributed to the large permeability contrast in favor of the oil-saturated zone. This paper will present detailed lab studies and field data obtained and will recommend the proper RPM polymer application method to avoid damaging oil producing zones.

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