Method to Detect Incremental Oil Production Arising from a Low Salinity Waterflood

A method for detecting incremental oil production from an oil-bearing reservoir comprised of a plurality of layers of reservoir rock wherein the reservoir is penetrated by at least one injection well, at least one production well and at least one surveillance well located between the injection well and production well, the process comprising:

• introducing logging equipment into the surveillance well;
• injecting a low salinity water into the reservoir from the injection well and recovering oil from the production well;
• utilizing the logging equipment over time to determine the period of time, t1, between commencing injection of low salinity water into the reservoir from the injection well(s) and the detection of the front of the low salinity water at the surveillance well;
• determining the interwell distance, L1, between the injection well(s) and surveillance well, and calculating the velocity, v, at which the front of the low salinity water advances through the reservoir, wherein v=L1/t1;
• determining the interwell distance, L2, between the surveillance well and production well(s) and using the frontal advance velocity, v, to predict the time, t2, at which the low salinity water breaks through into the production well, wherein t2=t1+L2/v;
• taking a baseline sample of oil from the reservoir and analyzing the baseline sample of oil to establish a baseline compositional signature for the oxygen-containing organic compounds in the oil;
• taking post-flood samples of the oil produced from the production well(s) over time and analyzing the samples of oil to establish post-flood compositional signatures for the oxygen-containing organic compounds in the oil to identify a difference between one or more of the post-flood compositional signatures for the oxygen-containing organic compounds in the oil and the baseline compositional signature for the oxygen-containing organic compounds in the oil that is characteristic of incremental oil released by the low salinity waterflood;
• increasing the frequency of at which post-flood samples of the produced oil are taken as the time approaches the predicted time, t2, at which low salinity injection water breaks through into the production well and using the identified difference between the post-flood and baseline composition signatures for the oxygen-containing organic compounds in the oil to determine the time at which incremental oil breaks through into the production well.