Changes

Analytical procedures vary slightly with sample type. For conventional core plugs and sidewall cores, gas volume is determined by mercury injection. Oil and water volumes are determined by high temperature distillation. Sidewall core measurements are all carried out on one sample. In conventional core analysis, gas volume is determined on one sample while oil and water volumes are measured on a second sample. Significant variations in pore system quality between samples can cause errors in fluid saturation and porosity values.<ref name=pt05r114 />

Analytical procedures vary slightly with sample type. For conventional core plugs and sidewall cores, gas volume is determined by mercury injection. Oil and water volumes are determined by high temperature distillation. Sidewall core measurements are all carried out on one sample. In conventional core analysis, gas volume is determined on one sample while oil and water volumes are measured on a second sample. Significant variations in pore system quality between samples can cause errors in fluid saturation and porosity values.<ref name=pt05r114 />

Gas volume of whole core samples is determined by evacuating the sample and resaturating with water while measuring the weight of water absorbed. With vuggy samples, water injected to refill the gas volume may drain from the surface vugs causing errors in the measured gas saturation.<ref name=pt05r90>Keelan, D. K., 1972, A critical review of core analysis techniques: Journal of Canadian Petroleum Technology, v. 2, p. 42–55.</ref> The oil and water volumes are determined by retorting the core under vacuum. The recovered water volume corresponds to the sum of the pore water and the gas volumes. Low API gravity oils are only partly recovered by this process, thus recovered oil volume may be low.<ref name=pt05r90 /> (For more on determining porosity from core samples, see [[Porosity]].)

Gas volume of whole core samples is determined by evacuating the sample and resaturating with water while measuring the weight of water absorbed. With vuggy samples, water injected to refill the gas volume may drain from the surface vugs causing errors in the measured gas saturation.<ref name=pt05r90>Keelan, D. K., 1972, A critical review of core analysis techniques: Journal of Canadian Petroleum Technology, v. 2, p. 42–55.</ref> The oil and water volumes are determined by retorting the core under vacuum. The recovered water volume corresponds to the sum of the pore water and the gas volumes. Low [[API gravity]] oils are only partly recovered by this process, thus recovered oil volume may be low.<ref name=pt05r90 /> (For more on determining porosity from core samples, see [[Porosity]].)

==Residual fluid saturation==

==Residual fluid saturation==

<gallery mode=packed heights=300px widths=300px>

<gallery mode=packed heights=300px widths=300px>

overview-of-routine-core-analysis_fig1.png|{{figure number|1}}Comparison of water saturation data<ref name=pt05r82 /> from sidewall and conventional cores shows that sidewall core values are almost always higher than conventional core values. Sample values from gas condensate zones are 10 to 15% higher, while values from oil zones are 5 to 10% higher.

overview-of-routine-core-analysis_fig1.png|{{figure number|1}}Comparison of water saturation data<ref name=pt05r82 /> from sidewall and conventional cores shows that sidewall core values are almost always higher than conventional core values. Sample values from gas condensate zones are 10 to 15% higher, while values from oil zones are 5 to 10% higher.

overview-of-routine-core-analysis_fig2.png|{{figure number|2}}Comparison of saturation data<ref name=pt05r82 /> indicate that sidewall cores from gas condensate zones may have measured oil saturation values that are 2% higher than conventional core samples. In oil zones the relationship is less clear. The agreement between oil saturation values In sidewall and conventional cores may vary with such oil characteristics as API gravity.

overview-of-routine-core-analysis_fig2.png|{{figure number|2}}Comparison of saturation data<ref name=pt05r82 /> indicate that sidewall cores from gas condensate zones may have measured oil saturation values that are 2% higher than conventional core samples. In oil zones the relationship is less clear. The agreement between oil saturation values In sidewall and conventional cores may vary with such oil characteristics as [[API gravity]].

</gallery>

</gallery>