Optimized Fracture Designs with RPM to Control Water Cut in Ust Vakh Field in Western Siberia

Abstract

AbstractAs an effort to increase Russian oil production, major companies are developing areas that were previously relegated to low production and/or high water cut. One such area is the Ust Vakh field located in the middle of Western Siberia – approximately 20 km northeast of Nizhnevartovk and opposite the giant Samotlor oil field. Hydraulic fracturing stimulation is the primary method of enabling commercial production. However, this field is especially affected by high water cuts, which lead to uneconomical production when standard fracturing fluids are used. In order to reduce production of formation water, most jobs are now pumped with 1% of Relative Permeability Modifiers (RPMs) (conformance fracturing). The fracture treatment designs have been modified since their inception in September 2005. As a result of those modifications, the oil production has increased and in some wells, the water cut has been reduced from an average of about 80% to about 40%. These results have secured enough operator confidence to continue production operations in this area, which were nearly abandoned due to the increasing water production problem. As of June 2006, conformance fracturing treatments had been performed in 20 wells (18 production and 2 to be converted into injection). In the past year (June/06 to July/07) another 28 jobs were done, confirming the treatments' success. Case histories are included in the paper.Job designs varied from crosslinked gel fracturing treatments to linear gel treatments and finally a combination of linear gel with crosslinked polymer gel pumped at low rate and moderate proppant concentration to prevent proppant settling in the near-wellbore formation zone. Core test analysis supports the results obtained.The combination of field practices for fracture height growth control and proppant placement (including low-viscosity fracture fluid, low injection rates, slow changes in rates, and small pad size) has proven to be the right combination for water control stimulation.