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==Methods for determining fluid contacts==
 
==Methods for determining fluid contacts==
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[[file:fluid-contacts_fig2.png|thumb|{{figure number|2}}Geometries of fluid contacts. (a) Horizontal contacts indicative of hydrostatic conditions in homogeneous reservoir rock. (b) Tilted, flat contacts resulting from hydrodynamic conditions. (c) Contact elevation is constant for each lithology type, but pool contact is irregular due to reservoir heterogeneity. (d) Irregular contacts due to semipermeable barrier in an otherwise homogeneous reservoir.]]
    
Methods for determining initial fluid contacts are listed in Table 1 and are discussed by Bradley.<ref name=pt10r3>Bradley, H. B., ed., 1987, Petroleum Engineering Handbook: Richardson, TX, Society of Petroleum Engineers.</ref> These include fluid sampling methods, saturation estimation from wireline logs, estimation from conventional and sidewall cores, and pressure methods. Once initial fluid contact elevations in control wells are determined, the contacts in other parts of the reservoir can be estimated. Initial fluid contacts within most reservoirs having a high degree of continuity are almost horizontal, so the reservoir fluid contact elevations are those of the control wells.
 
Methods for determining initial fluid contacts are listed in Table 1 and are discussed by Bradley.<ref name=pt10r3>Bradley, H. B., ed., 1987, Petroleum Engineering Handbook: Richardson, TX, Society of Petroleum Engineers.</ref> These include fluid sampling methods, saturation estimation from wireline logs, estimation from conventional and sidewall cores, and pressure methods. Once initial fluid contact elevations in control wells are determined, the contacts in other parts of the reservoir can be estimated. Initial fluid contacts within most reservoirs having a high degree of continuity are almost horizontal, so the reservoir fluid contact elevations are those of the control wells.
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| Most reliable for gas contacts Requires pressure tests from both fluid zones and assumed or measured fluid densities to estimate contact Requires accurate pressures
 
| Most reliable for gas contacts Requires pressure tests from both fluid zones and assumed or measured fluid densities to estimate contact Requires accurate pressures
 
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[[file:fluid-contacts_fig2.png|thumb|{{figure number|2}}Geometries of fluid contacts. (a) Horizontal contacts indicative of hydrostatic conditions in homogeneous reservoir rock. (b) Tilted, flat contacts resulting from hydrodynamic conditions. (c) Contact elevation is constant for each lithology type, but pool contact is irregular due to reservoir heterogeneity. (d) Irregular contacts due to semipermeable barrier in an otherwise homogeneous reservoir.]]
      
Some reservoirs have irregular or tilted fluid contacts ([[:file:fluid-contacts_fig2.png|Figure 2]]). Reasons for differences in contact elevation in different control wells must first be determined to properly extrapolate nonhorizontal fluid contacts to untested parts of a reservoir. Excluding interpretation or mechanical problems, the most common reasons for tilted fluid contacts are the following:
 
Some reservoirs have irregular or tilted fluid contacts ([[:file:fluid-contacts_fig2.png|Figure 2]]). Reasons for differences in contact elevation in different control wells must first be determined to properly extrapolate nonhorizontal fluid contacts to untested parts of a reservoir. Excluding interpretation or mechanical problems, the most common reasons for tilted fluid contacts are the following:

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