A naturally fractured reservoir (NFR) is a reservoir with a connected network of
fractures created by natural processes such as diastrophism and volume shrinkage
(Ordonez et al. 2001). There are two models to simulate this kind of reservoirs: the
discrete fracture model and the dual porosity model. In the dual porosity model, the
matrix blocks occupy the same physical space as the fracture network and are
identical rectangular parallelepipeds with no direct communication between isotropic
and homogeneous matrix blocks. However, each fracture and matrix property is
defined separately in the discrete fracture model.
Another feature of this thesis is tracer testing. In this process, a chemical or
radioactive element is injected to the reservoirs, and then it can be traced using the
devices, which are designed to detect the tracers. Tracer tests have several advantages
such as determining residual oil saturation, identifying barriers or high permeability
zones in reservoirs, and providing the information on flow patterns. Limited number of research studies has been done on performing tracer tests in
naturally fractured reservoirs. Also because there is not enough information about the
advantages and disadvantages of the discrete fracture and the dual porosity models,
researchers and engineers lack the expertise to confidently select either the discrete
fracture or the dual porosity models to simulate the different types of NFRs. In this thesis, we compared the oil and water productions, and tracer concentration
curves in various reservoir conditions, using both the discrete fracture and the dual
porosity models. We used the ECLIPSE, which is a commercial software package in
the area of petroleum industry, to model a naturally fractured reservoir. We
performed a simple waterflooding with two conservative tracers on the reservoirs.
The results presented in each section include the graphs of the oil production rate,
water production rate, and tracer concentration. In addition, we presented the oil
saturation profiles of a cross-section, which includes the production and injection
wells.
The results illustrated that both the discrete fracture and the dual porosity models are
in good agreement, except for a few special cases. Generally, the oil production using
the dual porosity model is more than in the discrete fracture model. The major
disadvantage of the dual porosity model is that the fluid distribution in the matrix
blocks is changing homogenously during the waterflooding period. In other words,
ECLIPSE shows a constant value of the oil and water saturations in each time step for
the matrix blocks. However, the dual porosity model is 3 to 4 times faster than the
discrete fracture model. In the discrete fracture model, the users have complete
control in defining the reservoirs. For example, the fracture aperture, fracture spacing,
and fracture porosities can be set by the user. The disadvantage of this model is that
millions of grid blocks are needed to model a large reservoir with small fracture
spacing. / text
| Identifer | oai:union.ndltd.org:UTEXAS/oai:repositories.lib.utexas.edu:2152/18728 |
| Date | 15 November 2012 |
| Creators | Lalehrokh, Farshad |
| Source Sets | University of Texas |
| Language | English |
| Detected Language | English |
| Format | electronic |
| Rights | Copyright is held by the author. Presentation of this material on the Libraries' web site by University Libraries, The University of Texas at Austin was made possible under a limited license grant from the author who has retained all copyrights in the works. |
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