Effect of in situ stress and production-induced changes in stress on permeability of naturally fractured reservoirs
- New Mexico Technology, Socorro, NM (United States)
- Sandia National Labs., Albuquerque, NM (United States)
Fractures are present in almost all hydrocarbon reservoirs, but it is only when fractures form an interconnected network that their effect on fluid flow becomes important. Fractures not only enhance the overall permeability of many reservoirs, they also create significant permeability anisotropy. Knowledge of the orientation and magnitude of permeability anisotropy has major economic importance in developing and managing a reservoir. It is commonly assumed that the horizontal permeability anisotropy of a naturally fractured reservoir will be elongate along the dominant trend of subsurface natural fracture systems. Although this can be demonstrated to apply in many simple geologic settings, this predictive concept must commonly be modified for stress changes caused by post-fracture geologic history of the reservoir, including local variations in stress magnitude and orientation caused by structures. In cases where the local stresses and fractures are superimposed on regional stresses and fractures, the fractures that are parallel to the in situ maximum horizontal stress may provide the dominant control on reservoir permeability anisotropy. Fracture reservoir permeability may also change over the life of a reservoir because peturbations in stress state, caused by drilling, production, and waterflood activities, create changes in the three-dimensional effective stress field, and thus in fracture conductivity. High angle fractures aligned with the local maximum horizontal stress will have the smallest decline in conductivity as the reservoir is produced. These conclusions are supported by core analyses, in situ stress measurements, well tests, and production histories of clastic and carbonate reservoirs.
- OSTI ID:
- 127717
- Report Number(s):
- CONF-950995--
- Journal Information:
- AAPG Bulletin, Journal Name: AAPG Bulletin Journal Issue: 8 Vol. 79; ISSN 0149-1423; ISSN AABUD2
- Country of Publication:
- United States
- Language:
- English
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