Changes

{| class = "wikitable"

{| class = "wikitable"

|-

|-

! Step

! Step || Action

! Action

|-

|-

| 1

| 1 || Plot points of matching [[porosity]] and true resistivity (R_t ) on log-log paper.

| Plot points of matching [[porosity]] and true resistivity (R_t ) on log-log paper.

|-

|-

| 2

| 2 || Plot R_w point on the R_t scale.

| Plot R_w point on the R_t scale.

|-

|-

| 3

| 3 || Determine ''m'' using the table of values.

| Determine ''m'' using the table of values.

|-

|-

| 4

| 4 || Plot the 100% S_w line.

| Plot the 100% S_w line.

|-

|-

| 5

| 5 || Plot the lines representing lower values of S_w .

| Plot the lines representing lower values of S_w .

|}

|}

==Step 1: Plot points==

==Step 1: Plot points==

[[file:predicting-reservoir-system-quality-and-performance_fig9-36.png|left|thumb|300px|{{figure number|1}}Plot points of matching porosity and true resistivity (R_t) values obtained from well logs on 2×4 cycle log-log paper.]]

[[file:predicting-reservoir-system-quality-and-performance_fig9-36.png|thumb|300px|{{figure number|1}}Plot points of matching porosity and true resistivity (R_t) values obtained from well logs on 2×4 cycle log-log paper.]]

Plot points of matching porosity and true resistivity (R_t) values obtained from well logs on 2×4 cycle log-log paper, as shown in [[:file:predicting-reservoir-system-quality-and-performance_fig9-36.png|Figure 1]]. Use the x-axis for the resistivity (R_t) scale and the y-axis for the porosity (Φ) scale.

Plot points of matching porosity and true resistivity (R_t) values obtained from well logs on 2×4 cycle log-log paper, as shown in [[:file:predicting-reservoir-system-quality-and-performance_fig9-36.png|Figure 1]]. Use the x-axis for the resistivity (R_t) scale and the y-axis for the porosity (Φ) scale.

==Step 2: plot r_w point==

==Step 2: plot r_w point==

[[file:predicting-reservoir-system-quality-and-performance_fig9-37.png|thumb|{{figure number|2}}Plot the R_w value (resistivity of formation water) by plotting the R_w point along the R_t scale on the x-axis at the top of the graph grid where porosity is 100%.]]

[[file:predicting-reservoir-system-quality-and-performance_fig9-37.png|300px|thumb|{{figure number|2}}Plot the R_w value (resistivity of formation water) by plotting the R_w point along the R_t scale on the x-axis at the top of the graph grid where porosity is 100%.]]

Plot the R_w value (resistivity of formation water) by plotting the R_w point along the R_t scale on the x-axis at the top of the graph grid where porosity is 100%, as shown in [[:file:predicting-reservoir-system-quality-and-performance_fig9-37.png|Figure 2]]. R_w values are published by logging companies, or we can calculate them from the SP log.

Plot the R_w value (resistivity of formation water) by plotting the R_w point along the R_t scale on the x-axis at the top of the graph grid where porosity is 100%, as shown in [[:file:predicting-reservoir-system-quality-and-performance_fig9-37.png|Figure 2]]. R_w values are published by logging companies, or we can calculate them from the SP log.

{| class = "wikitable"

{| class = "wikitable"

|-

|-

! Porosity type

! Porosity type || Value for m

! Value for m

|-

|-

| Sandstones with diagenetic or detrital clay in pores

| Sandstones with diagenetic or detrital clay in pores || 1.7–1.8

| 1.7–1.8

|-

|-

| Formations with clean, macro- to micro-sized pore throats (Archie rocks)

| Formations with clean, macro- to micro-sized pore throats (Archie rocks) || 2

| 2

|-

|-

| Formations with vuggy porosity (touching to nontouching)

| Formations with vuggy porosity (touching to non touching) || 2.2–3.0

| 2.2–3.0

|}

|}

==Step 4: Plot the 100% S_w line==

==Step 4: Plot the 100% S_w line==

[[file:predicting-reservoir-system-quality-and-performance_fig9-38.png|thumb|{{figure number|3}}How to plot an ''m'' of 2.]]

[[file:predicting-reservoir-system-quality-and-performance_fig9-38.png|300px|thumb|{{figure number|3}}How to plot an ''m'' of 2.]]

On a Pickett plot, the value of ''m'' determines the slope of the S_w lines. The first S_w line plotted on a Pickett plot is the 100% S_w line. To plot this line, draw a line with a negative slope equal to ''m'' that begins at the R_w point. Use a linear scale to measure the slope; for example, go down [[length::1 in.]] and over 2 in.

On a Pickett plot, the value of ''m'' determines the slope of the S_w lines. The first S_w line plotted on a Pickett plot is the 100% S_w line. To plot this line, draw a line with a negative slope equal to ''m'' that begins at the R_w point. Use a linear scale to measure the slope; for example, go down [[length::1 in.]] and over 2 in.

==Step 5: plot s_w lines==

==Step 5: plot s_w lines==

[[file:predicting-reservoir-system-quality-and-performance_fig9-39.png|thumb|{{figure number|4}}An example of plotting the lower percentages of S_w.]]

[[file:predicting-reservoir-system-quality-and-performance_fig9-39.png|300px|thumb|{{figure number|4}}An example of plotting the lower percentages of S_w.]]

After plotting the 100% S_w line, plot the lines representing lower percentages of S_w using this procedure.

After plotting the 100% S_w line, plot the lines representing lower percentages of S_w using this procedure.

{| class = "wikitable"

{| class = "wikitable"

|-

|-

! Step

! Step || Action

! Action

|-

|-

| 1

| 1 || Find the intercept of R_t = 1 and the 100% S_w line (made in the last procedure).

| Find the intercept of R_t = 1 and the 100% S_w line (made in the last procedure).

|-

|-

| 2

| 2 || From this intercept, draw a line parallel to the x-axis across the plot. Any point on this line has the same porosity.

| From this intercept, draw a line parallel to the x-axis across the plot. Any point on this line has the same porosity.

|-

|-

| 3

| 3 || Where this line passes through R_t of 2, 4, 6, 8, 14, and 20, draw a series of lines parallel to the 100% S_w line.

| Where this line passes through R_t of 2, 4, 6, 8, 14, and 20, draw a series of lines parallel to the 100% S_w line.

|-

|-

| 4

| 4 || Points on these lines correspond to S_w of 71, 50, 41, 35, 27, and 22%. These percentages are calculated from the Archie equation using ''m'' = 2 and ''n'' = 2 at R_t of 2, 4, 6, 8, 14, and 20.

| Points on these lines correspond to S_w of 71, 50, 41, 35, 27, and 22%. These percentages are calculated from the Archie equation using ''m'' = 2 and ''n'' = 2 at R_t of 2, 4, 6, 8, 14, and 20.

|}

|}