# A Concise Guide to Geopressure: Spreadsheets Chapter 9

Downloadable spreadsheets to accompany A Concise Guide to Geopressure.

## Chapter 9: Trap Integrity

Download all Chapter 9 spreadsheets

### Spreadsheet 9.1: Capillary Seal

**Download** Spreadsheet (zip)

*Note: Zip archive contains one macro-enabled Excel spreadsheet (xlsm).*

The spread sheet ‘Capillary Seal’ graphically calculates the column height that will be trapped by a seal with a given migration pressure according to Eq. 9.1 of Flemings, 2021:

$$ ℎ _{FWL} = {u _{cmig} \over \Delta \rho g}. \hspace{20pt} \textnormal{Eq. 9.1}$$

The height of the hydrocarbon column (ℎ_{FWL}), measured from the free-water level (the depth where the capillary pressure is zero, see discussion of free water level in Chapter 2), is equal to the migration pressure through the seal (*u _{cmig}*) divided by the difference in the static pressure gradient of each fluid phase (\(\Delta \rho g\)).

The user inputs a migration pressure (*u _{cmig}*) from laboratory-derived mercury-air measurements (e.g., Fig. 9.4). Equation 2.22 is used to covert this mercury-air pressure to an oil-brine and a gas-brine migration pressure at

*in situ*conditions:

$$ u _{cow} = u_{cHg-air} \left( { \gamma _{ow} \hspace{3pt} cos \theta _{ow} \over \gamma _{Hg-air} \hspace{3pt} cos \theta _{Hg-air}} \right) \hspace{20pt} \textnormal{Eq. 2.22}$$

The default values in the spreadsheet produce the results shown in Fig. 9.5.

### Spreadsheet 9.2: Mechanical Seal

**Download** Spreadsheet (zip)

*Note: Zip archive contains one macro-enabled Excel spreadsheet (xlsm).*

The spread sheet ‘Mechanical_Seal’ graphically calculates the column height that will be trapped by either hydraulic fracturing (Eq. 9.3 and 9.4) or by shear failure (Eq. 9.3 and Eq. 9.5):

$$ u _{res} ^{crit} = \sigma ^{seal} _3 , \hspace{20pt} \textnormal{Eq. 9.3} $$

$$ ℎ _{FWL} = {u ^{res}_{crit} \hspace{3pt} – \hspace{3pt} u ^{res}_{w} \over \Delta \rho g} , \hspace{20pt} \textnormal{Eq. 9.4}$$

$$ u ^{res} _{crit} = { \sigma ^{seal} _h – \left( {1-sin \phi ^\prime \over 1+sin \phi ^\prime} \right) \sigma _v \over \left[ 1 – \left( {1-sin \phi ^\prime \over 1+sin \phi ^\prime} \right) \right] }. \hspace{20pt} \textnormal{Eq. 9.5} $$

The user inputs the least principal stress (\(\sigma ^{seal} _3\)) in the overlying seal, the water pressure at the crest of the reservoir (\(u^{res}_w\)), the fluid densities (\(\Delta \rho g \)) and the friction angle (\( \phi ^\prime\)) and the height to free water level is calculated. The spread sheet is populated with the parameters to produce the prediction of Figure 9.14a (Flemings, 2021).