Experimental study on oil recovery in vertical wells using downhole water sink (DWS) technology.

摘要

The term water-coning refers to production of oil/gas and water together in oil/gas reservoirs underlain by water zone. This unwanted water not only decreases but also eventually seizes the oil flow. Moreover, oil and water separation problems and strict environmental regulations require huge surface separation facilities.;Since 1935, several technologies and methodologies have been used to mitigate produce water with oil and most have proved to be very useful in delaying water production but none of them have actually resolved this problem. Downhole Water Sink (DWS) is a developing technology that not only handles water production predicament but also avoids reduction in oil permeability due to water invasion in the oil zone. In this technology segregated production of both oil and water is achieved with a unique completion design. The completion design consists of at least two sets of perforations, one each in the oil and water zones. A packer isolates oil and water zones to avoid mixing of both fluids in the wellbore. DWS technology produces both oil and water simultaneously but from different paths to attain in-situ separation.;Some research and field tests show encouraging results. However, it remains to be established whether this technology actually reduces water production and causes an increase in oil recovery to a sufficient greater degree than conventional. The objective of this study is to answer these questions. The study in this research commences with the water-coning experiments in a physical scale laboratory model. Both conventional and DWS completion experiments are conducted to accomplish the aims of this research. During conventional completion runs, only oil is produced while in the DWS runs both the oil and water are produced simultaneously. Four sets of experiments are run to compare conventional and DWS completions. Each set consists of three experiments; one representing conventional completion and the remaining two representing DWS completion. Production data is collected and this data is used to compare oil recovery rates, cumulative water production, breakthrough time in both conventional and DWS completions. Experimental results are compared on the basis of equal production time and total production time. The results show that 8 to 12% increase in oil recovery is possible with DWS but on the other hand DWS produces 8 times more water than conventional completion. It requires design of an optimum combination of oil production and water drainage rate to effectively utilize DWS completion.