Changes

}}

}}

[[file:evaluating-fractured-reservoirs_fig1.png|thumb|{{figure number|1}}Crosspiot showing the relative positions of fractured reservoir types 1 through 3 and normal matrix reservoirs (''m'') in the percentage of porosity and permeability space. Symbols: ''k''_''f'' = fracture permeability, ϕ_''f''= fracture porosity, ''k''_''r''= matrix permeability, ϕ_''r''= matrix porosity.]]

[[file:evaluating-fractured-reservoirs_fig1.png|thumb|300px|{{figure number|1}}Crosspiot showing the relative positions of fractured reservoir types 1 through 3 and normal matrix reservoirs (''m'') in the percentage of porosity and permeability space. Symbols: ''k''_''f'' = fracture permeability, ϕ_''f''= fracture porosity, ''k''_''r''= matrix permeability, ϕ_''r''= matrix porosity.]]

Anticipated exploration and development problems associated with these four reservoir types are summarized in Table 1.

Anticipated exploration and development problems associated with these four reservoir types are summarized in Table 1.

==Core and well log analysis==

==Core and well log analysis==

[[file:evaluating-fractured-reservoirs_fig2.png|thumb|{{figure number|2}}Schematic of typical features to measure and record in core analysis. © van Golf-Racht, 1982; courtesy of Elsevier. Typical recording format from <ref name=pt06r108>Reiss, L. H., 1980, The reservoir engineering aspects of fractured formations: Houston, TX, Gulf Publishing Company, 108 p.</ref>; courtesy of Gulf Publishing Co.]]

[[file:evaluating-fractured-reservoirs_fig2.png|300px|thumb|{{figure number|2}}Schematic of typical features to measure and record in core analysis. © van Golf-Racht, 1982; courtesy of Elsevier. Typical recording format from <ref name=pt06r108>Reiss, L. H., 1980, The reservoir engineering aspects of fractured formations: Houston, TX, Gulf Publishing Company, 108 p.</ref>; courtesy of Gulf Publishing Co.]]

The following procedures have proven useful in fracture analyses of core (after <ref name=pt06r95 />):

The following procedures have proven useful in fracture analyses of core (after <ref name=pt06r95 />):

* Photograph all outcrops measured and take block samples (about 10” × 6” × 5”) of all major units of interest for petrophysical and possibly mechanical testing.

* Photograph all outcrops measured and take block samples (about 10” × 6” × 5”) of all major units of interest for petrophysical and possibly mechanical testing.

[[file:evaluating-fractured-reservoirs_fig3.png|left|thumb|{{figure number|3}}Total reservoir permeability due to fractures plotted as a function of fracture width, fracture spacing, and matrix permeability. © Nelson, 1985; courtesy of Gulf Publishing Co.]]

[[file:evaluating-fractured-reservoirs_fig3.png|300px|thumb|{{figure number|3}}Total reservoir permeability due to fractures plotted as a function of fracture width, fracture spacing, and matrix permeability. © Nelson, 1985; courtesy of Gulf Publishing Co.]]

==Crossplots==

==Crossplots==

[[file:evaluating-fractured-reservoirs_fig4.png|thumb|{{figure number|4}}Total reservoir pore volume due to fractures plotted as a function of fracture width, fracture spacing, and matrix porosity. © Nelson, 1985; courtesy of Gulf Publishing Co.]]

[[file:evaluating-fractured-reservoirs_fig4.png|300px|thumb|{{figure number|4}}Total reservoir pore volume due to fractures plotted as a function of fracture width, fracture spacing, and matrix porosity. © Nelson, 1985; courtesy of Gulf Publishing Co.]]

In doing core and outcrop analyses of fractures to determine reservoir properties and reservoir type, it is often difficult to judge the relative effect of the fracture system. Two crossplots can be used to alleviate this problem ([[:file:evaluating-fractured-reservoirs_fig3.png|Figures 3]] and [[:file:evaluating-fractured-reservoirs_fig4.png|4]]). These plots are the percentage of total reservoir permeability ([[:file:evaluating-fractured-reservoirs_fig3.png|Figure 3]]) and porosity ([[:file:evaluating-fractured-reservoirs_fig4.png|Figure 4]]) as a function of fracture width and fracture spacing for various orders of magnitude of matrix values. Assumptions can be made for width of the fractures at depth. Matrix properties are determined from core analyses, thin sections, etc. and the relative contribution of the fracture system for various spacings can then be read off the graph. Ideally, ranges in values for width and spacing of fractures are used and a box or area created on the graph within which the actual value is likely to occur. These figures assume one set of regularly spaced fractures, hydraulic apertures, and parallel plate laminar flow.<ref name=pt06r95 />

In doing core and outcrop analyses of fractures to determine reservoir properties and reservoir type, it is often difficult to judge the relative effect of the fracture system. Two crossplots can be used to alleviate this problem ([[:file:evaluating-fractured-reservoirs_fig3.png|Figures 3]] and [[:file:evaluating-fractured-reservoirs_fig4.png|4]]). These plots are the percentage of total reservoir permeability ([[:file:evaluating-fractured-reservoirs_fig3.png|Figure 3]]) and porosity ([[:file:evaluating-fractured-reservoirs_fig4.png|Figure 4]]) as a function of fracture width and fracture spacing for various orders of magnitude of matrix values. Assumptions can be made for width of the fractures at depth. Matrix properties are determined from core analyses, thin sections, etc. and the relative contribution of the fracture system for various spacings can then be read off the graph. Ideally, ranges in values for width and spacing of fractures are used and a box or area created on the graph within which the actual value is likely to occur. These figures assume one set of regularly spaced fractures, hydraulic apertures, and parallel plate laminar flow.<ref name=pt06r95 />