(32) WATER SHUTOFF CANDIDATE SELECTION METHOD IN THE GRAYBURG FORMATION IN WORLD FIELD - CROCKETT COUNTY TEXAS
Excess water production is a wide-spread and costly issue in the oil and gas industry. Polymer gel water shutoff treatments provide a valuable means of decreasing water production and reducing operating costs; however, successful treatments are dependent upon selecting viable candidate wells. The industry has long sought a reliable means of identifying wells to target with polymer gel treatments. Most studies into this problem have looked into a potential link between formation permeability and the success of treatments. This paper explores a new method: a correlation which uses the porosity and height of the treated zone to evaluate the viability of polymer-based water shutoffs.
This study proposes a selection method for water shutoff candidates in a dolomitized, oolitic highly-permeable carbonate reservoir in the Grayburg formation. Wells completed in this field often have issues with a high water-oil ratio (WOR), creating a need for water shutoff. The candidate selection method took shape while reviewing the data of several recent treatments in the field. The selection method is based on the formation porosity and height (ϕH) of the treated interval. It is proposed that a ϕH value within a given range is indicative of a potentially-successful treatment.
Once the initial idea was defined, the results of the first wells were compared to the proposed correlation. Using the function to identify candidates, additional wells were selected and treated. Results of these wells are presented in the paper and support the proposed model. For additional confirmation, the method was applied to the data for a series of wells treated with polymer gel in the same formation and field in 1997-8. The results of this study are also presented.
Polymer gel treatments have valuable water shutoff capabilities, but they must be applied to the correct candidate wells. The correlation presented in this study provides a system by which wells can be selected for treatment. This paper will demonstrate the viability of the method in a classic carbonate reservoir with high permeability variations.