Multiporosity and Multiscale Flow Characteristics of a Stimulated Reservoir Volume (SRV)-Fractured Horizontal Well in a Tight Oil Reservoir

Abstract

There are multiporosity media in tight oil reservoirs after stimulated reservoir volume (SRV) fracturing. Moreover, multiscale flowing states exist throughout the development process. The fluid flowing characteristic is different from that of conventional reservoirs. In terms of those attributes of tight oil reservoirs, considering the flowing feature of the dual-porosity property and the fracture network system based on the discrete-fracture model (DFM), a mathematical flow model of an SRV-fractured horizontal well with multiporosity and multipermeability media was established. The numerical solution was solved by the finite element method and verified by a comparison with the analytical solution and field data. The differences of flow regimes between triple-porosity, dual-permeability (TPDP) and triple-porosity, triple-permeability (TPTP) models were identified. Moreover, the productivity contribution degree of multimedium was analyzed. The results showed that for the multiporosity flowing states, the well bottomhole pressure drop became slower, the linear flow no longer arose, and the pressure wave arrived quickly at the closed reservoir boundary. The contribution ratio of the matrix system, natural fracture system, and network fracture system during SRV-fractured horizontal well production were 7.85%, 43.67%, and 48.48%, respectively in the first year, 14.60%, 49.23%, and 36.17%, respectively in the fifth year, and 20.49%, 46.79%, and 32.72%, respectively in the 10th year. This study provides a theoretical contribution to a better understanding of multiscale flow mechanisms in unconventional reservoirs.

Effects of Microstructure and Rock Mineralogy on Movable Fluid Saturation in Tight Reservoirs

“…The Ordos Basin is the second largest basin in China, − with rich oil and gas resources, and the sedimentary environment is a river-delta environment. The studied samples are from the tight sandstones of the Triassic Ordovician tight oil strata, and they are given sample numbers from 1 to 12.…”

“…Tight oil is an important unconventional resource, which has wide distribution and abundant reserves. , In recent years, the application of horizontal well multistage fracturing technology and the development of horizontal wells have made tight sandstone reservoirs commercially exploitable. , Their exploitation has greatly improved the energy supply structure and has attracted extensive attention from international scholars in the world. After multistage operations, a large amount of injected fracturing fluid is retained in the tight oil, leading to low flowback efficiency (less than 30%). − It may be related to low fluid movability in tight reservoirs, which is influenced by the complex pore structure and mineral composition. The tight reservoirs develop multiscale pores .…”

Recent Advances in Flow and Transport Properties of Unconventional Reservoirs

“…Based on the dual-media theory and discrete-fracture network models, Ren et al [13] built a mathematical flow model of a stimulated reservoir volume fractured horizontal well with multiporosity and multipermeability media. The differences of flow regimes between triple-porosity, dual-permeability and triple-porosity, triple-permeability models were identified.…”