Using Tracer Data to Determine Polymer Flooding Effects in a Heterogeneous Reservoir, 8 TH Reservoir, Matzen Field, Austria

Abstract

Polymer injection pilot projects aim at reducing the uncertainty and risk of full-field polymer flood implementation. The interpretation of polymer pilot projects is challenging owing to the complexity of the process and fluids moving out of the polymer pilot area. The interpretation is increasingly more complicated with the heterogeneity of the reservoir.In the polymer pilot performed in the 8 TH reservoir of the Matzen Field in Austria, a polymer injection well surrounded by a number of production wells was selected. A tracer was injected one week prior to polymer injection. The tracer showed that the flow-field in the reservoir was dramatically modified with increasing amounts of polymers injected. Despite short breakthrough times of 4-10 weeks observed for the tracer, polymer breakthrough occurred only after more than 12 months although injection and production rates have not been substantially changed.The tracer signal indicated that the reservoir is heterogeneous with high flow velocities occurring in high permeable layers. By injecting polymers, the mobility of the polymer augmented water was reduced compared with water injection and lead to flow diversion into adjacent layers. The tracer response showed that the speed of the tracer moving from injection to production wells was reduced with increasing amount of polymers injected.This response was used to assess the changes of the amount of water flowing from injection to production well. After a match for the tracer curve was obtained, adsorption, residual resistance factor and dispersivity were calculated. The results showed that even for heterogeneous reservoirs without having good conformance of the pilot, the critical parameters for polymer injection projects can be assessed by analyzing tracer and polymer response. These parameters are required to determine whether implementation of polymer injection at field scale is economically attractive.Along the flow path, an incremental recovery of about 8 % was achieved. The polymer retention and inaccessible pore volume in the reservoir was in the same range as in core floods. Incremental oil recovery owing to acceleration along the flow path was estimated at contributing to about 30 % to the overall incremental oil production due to polymer injection and 70 % to improved sweep efficiency.

Operational Challenges and Monitoring of a Polymer Pilot, Matzen Field, Austria

“…Dissolved-iron concentrations varied between 0.2 and 1 ppm. The formed redox couples have a detrimental impact on the viscosity, and oxidative degradation is reported (Levitt et al 2011). Despite the moderate reservoir temperatures of 50 C, an oxygen scavenger was introduced at the inlet of the plant (see Fig.…”

Historical and recent observations in polymer floods: An update review

“…• Polymer losses in unconfined pilot patterns such as Matzen Field (Laoroongroj et al, 2015;Lüftenegger et al, 2015), Tambaredjo Field (Manichand et al, 2013) and Yariguí-Cantagallo Field (Maya et al, 2015) to just mention a few. This can lead to lower polymer production reducing the probability of reaching a potential threshold limit (if any) to cause productivity losses.…”

Operational Challenges and Monitoring of a Polymer Pilot, Matzen Field, Austria

“…Owing to the decreasing mobility ratio as well as flow diversion into adjacent layers, the velocity of water soluble polymers was slower than that of water and wider dispersion and later breakthrough compared to those tracers with water injection were observed. From the difference in breakthrough times between tracer and produced polymers ranges for adsorption, Inaccessible Pore Volume and dispersivity were determined (Laoroongroj et al 2015).…”

“…The oilcut as well as the polymer concentration seems to have levelled off. Along the flowpaths, incremental recovery of more than 10% was calculated and in addition improvement of sweep efficiency determined for details see Laoroongroj et al 2015.…”