Non-Darcy and multiphase flow effects in hydraulic fractures have been well documented during the last several years. The pressure losses due to these phenomena are widely accepted to be of great significance in most gas well completions in the United States and elsewhere. While the importance in gas wells is evident, the authors pose the question of whether non-Darcy and multiphase flow effects are of concern in typical oil wells in Russia.
For the analysis, the authors evaluate three primary categories of Russian production wells: gas wells, oil wells producing above the bubble point, and oil wells producing below the bubble point. For each category, the authors describe the significance of non-Darcy and multiphase flow effects using fracture flow theory as well as state-of-the-art fracture production models. This paper will illustrate that non-Darcy and multiphase flow effects can substantially decrease the production potential of gas wells, as well as many of the oil wells found in Russia that are producing below the bubble point.
Historically, Russian oil wells have been intentionally operated above the bubble point. However, more aggressive well designs have recently been shown to increase production by over three-fold. The authors explore the economics of producing these wells below the bubble point and show that for these more aggressive strategies, the effects of non-Darcy and multiphase flow can be significant and should be accommodated during fracture design.
The authors propose solutions for mitigating these effects through various modifications to the fracture design including the impact of proppant selection on performance. Several operators within Russia have already successfully accounted for these phenomena in their fracture designs, and new field examples are explored, analyzed and presented in the paper. Recent field results are presented for Gazpromneft's Achimovskoya formation BV8 in Tomsk region (Western Siberia) and BP-TNK's field near Buzuluk in the Orenburg region (Volga-Urals). The results found here are compared to published results from the Achimovskoya sandstone in the Kalchinskoye oilfield, the BP12 formation of the Vyngayakhinskoe field, the Priobskoye and Sugmutskoe oilfields, and Gazprom's Yamburskoe gas condensate development.