CHEMICAL TRACER STUDIES TO DETERMINE WATER SATURATION AT PRUDHOE BAY

The single-well chemical tracer (SWCT) method was used to measure resi dent water saturation in two wells in the Ivishak reservoir of the Pru dhoe Bay field. The tests, performed in 1981, were in API Wells 406 an d 488, both of which had been oil-base cored through the Ivishak. The results of the tracer test in Well API 406 were interpreted by convent ional SWCT simulation procedures. A three-layer simulator model was us ed to match the tracer production profiles measured during the test. T he average water saturation obtained from the simulator match was 16 /- 3% PV, in good agreement with the Dean-Stark analysis of the oil-ba se cores. The tracer-test results from Well API 488 were more difficul t to interpret because of the very low water saturation at this locati on in the Ivishak. The SWCT method requires a hydrolysis reaction to t ake place in the formation to produce a product tracer. In this case, the amount of water present was so small that very little product trac er was formed. The interpreted S-w for this well was 2 +/- 2% PV, agai n in reasonable agree ment with the oil-base-core measured value of 3. 8%.