Permeability of naturally fractured reservoirs

Conference · Fri Mar 01 00:00:00 EST 1991 · AAPG Bulletin (American Association of Petroleum Geologists); (United States)

OSTI ID:7271757

Teufel, L W ^[1]

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1. Sandia National Labs., Albuquerque, NM (United States)

Hydraulic fracture stress data collected from carbonate and clastic reservoirs show that the minimum horizontal in situ stress decreases with reservoir depletion and pore pressure drawdown. The reduction in minimum horizontal stress is, in part, a poro-elastic effect that is linear with pore pressure drawdown and can be approximated by an unlaxial compaction model. The observed change in horizontal stress is equal to 40% to 80% of the net change in pore pressure. This type of stress behavior has important implications for reservoir management of naturally fractured reservoirs, because conductivity of fractures is highly stress sensitive. Laboratory studies clearly demonstrate that with increasing effective normal stress fracture apertures close and conductivity decreases. Accordingly, in sharp contrast to the standard procedure, predictions of changes in fracture permeability during reservoir depletion should not be made simply as a function of pore pressure drawdown, but more importantly should be based on how the effective in situ stresses change during drawdown and the orientation of natural fractures relative to the in situ stress field. The increase in the effective overburden stress will be the largest and equal to the magnitude of the pore pressure decline because the overburden stress is constant and does not change with drawdown. However, the increase in the effective minimum horizontal stress will be much smaller. Accordingly, for a reservoir with several sets of fractures with similar morphology, the reduction in fracture conductivity during drawdown will be greatest for horizontal fractures and least for vertical fractures aligned with the maximum horizontal stress direction.

• OSTI ID: 7271757
• Report Number(s): CONF-910403-; CODEN: AABUD
• Journal Information: AAPG Bulletin (American Association of Petroleum Geologists); (United States), Vol. 75:3; Conference: Annual meeting of the American Association of Petroleum Geologists (AAPG), Dallas, TX (United States), 7-10 Apr 1991; ISSN 0149-1423
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
03 NATURAL GAS
FRACTURED RESERVOIRS
PERMEABILITY
STRESS ANALYSIS
NATURAL GAS DEPOSITS
PETROLEUM DEPOSITS
GEOLOGIC FRACTURES
RESERVOIR PRESSURE
RESERVOIR ROCK
GEOLOGIC DEPOSITS
GEOLOGIC STRUCTURES
MINERAL RESOURCES
RESOURCES
020200* - Petroleum- Reserves
Geology
& Exploration
030200 - Natural Gas- Reserves
Geology
& Exploration