Frac Size Matters: The Experience of Achimov Deposits Development in Urengoyskoe Gas Condensate Field

Alexey, Yudin (Schlumberger) | Dmitry, Kubyshkin (Schlumberger) | Konstantin, Lyapunov (Schlumberger) | Yuriy, Zakharzhevskiy (Rosneft) | Alexey, Snokhin (Rosneft) | Sergey, Romashkin (Rosneft) | Alexey, Prokhorov (Rosneft)



Urengoyskoe oil and gas condensate field is second large conventional reserve of gas condensate in the world. Active development of Achimov deposits of this field is in progress now. Specific features of Achimov layers are low permeability, extremely high reservoir pressure and 15-90 meters of Net Pay. Increase of hydraulic fracture frac half-length is main strategy for such environment to optimize well productivity and reservoir fluid recovery. Logistic in tough arctic conditions is challenge here. Method to increase volume of hydraulic fracturing treatment and its effect on well productivity is described in this article.

Some technological tasks were solved to optimize hydraulic fracturing process of Achimov deposits. Pumped proppant volume was a main one. Treatment design was modified to be more aggressive step by step to decrease used slurry volume and enhance fracture geometry. Full laboratory support was provided for this project. Fracturing fluid composition was optimized to provide fluid stability during approx. 7 hours fracturing job as well as fluid friction decrease to meet surface limitations of treatment pressure. Using open channel fracturing technology allowed to optimize logistics in limited space well pads without additional pad construction works and increase job efficiency. The technology provides required size of hydraulic fracture due to proppant pulsing method with proppant consumption decrease.

Before 2014, fracturing treatment size was in a range from 50 to 300 tons of proppant. It did not provide parameters of optimal fracture geometry for pay zones having average Net Pays of 76 m. Increase of frac tanks amount and special frac fleet equipment units combined with permanent technological and laboratory support allowed increasing pumped proppant volume per job up to 400 tons providing high quality of operations. Implementation of open channel fracturing technology was next step in direction of frac job volume increase (up to equivalent of 700 tons of proppant) keeping the same resources and from the same size of well pad. Analysis of efficiency of open channel fracturing technology in comparison with conventional fracturing treatment in wells having similar geological conditions and stimulated with the same slurry volumes was done. It confirmed success of channel fracturing technology using results of the conducted well tests.

Implemented hydraulic fracturing optimization workflow was effective to increase well productivity in turbidite reservoir. To date, sizes of hydraulic fractures created in Urengoyskoe field are one of the largest worldwide. Experience accumulated in Achimov deposits development could be successfully used in other hydrocarbon fields having similar geological challenges.