Designing Hydraulic Fractures in Russian Oil and Gas Fields To Accommodate Non-Darcy and Multiphase Flow

Abstract

Summary Non-Darcy and multiphase flow effects in hydraulic fractures have been well documented in the last several years. The pressure losses caused by these phenomena are accepted widely to be of great significance in most gas-well completions in the United States and elsewhere (Palisch et al. 2007; Forchheimer 1901; Milton-Tayler 1993a; Penny and Jin 1995; Flowers et al. 2003; Miskimins et al. 2005; Handren et al. 2001; Lolon et al. 2004; Vincent 2004; Olson et al. 2004). Although 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 bubblepoint, and oil wells producing below the bubblepoint. For each category, the authors describe the significance of non-Darcy and multiphase flow effects by use of the fracture-flow theory and 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 and the many oil wells found in Russia that are producing below the bubblepoint. Historically, Russian oil wells have been operated intentionally above the bubblepoint. However, more-aggressive well designs have recently been shown to increase production more than threefold. The authors explore the economics of producing these wells below the bubblepoint 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 with 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 the 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 oil field, the BP12 formation of the Vyngayakhinskoe oil field, the Priobskoye and Sugmutskoe oil fields, and Gazprom's Yamburgskoe gas-condensate development.