Sunday, July 8, 2012

Shale Gas In Place Calculation

Original shale gas in place calculation consists of two volumes, desorbed gas and free gas volume. Desorbed gas volume can be estimated from the core measurement of total organic carbon (TOC) and gas content (Gc). Refer to my previous post for the determination of TOC with wireline logs.  The correlation of TOC and Gc from lab measurement gives the gas content as input for the desorbed gas volume calculation.

Desorbed gas volume = Gas Content * Shale Density * Thickness * Area
Free gas volume = Effective Shale Porosity * (1-Sw) * Thickness * Area
Total Shale Gas Volume = Desorbed gas volume + Free gas volume

* most cases, free gas volume refers to tight gas volume or gas volume from interbeded sand layers.

Thursday, July 5, 2012

Total Organic Carbon (TOC) calculation from well logs

This app allows you to estimate TOC content for source rock, using EXXON method, published by Passy et. al. (1990).  TOC is critical parameter for quantifying unconventional reseources, CBM or Shale gas. The adsorbed gas content is a correlation with TOC, derived from lab measured data.

The estimated TOC is best to calibrate with lab measurement by adjusting the Level of organic maturity,LOM.  Vitrinite Reflectance (Ro) from lab may be available to derive LOM with graph below.

Thursday, June 28, 2012

Hydrostatic Pressure Calculator

This app allows you to calculate the hydrostatic pressure of a fluid column. Fluid density (mud weight) and depth are required for the calculation. You can use this apps to cross check the formation tester hydrostatic pressure.

Tuesday, June 26, 2012

Water Resistivity - Salinity - Sigma Calculator

This is the updated version of RwCal. The calculation of neutron captured sigma of water is included. You can use this calcualtor in converting Resistivity - Salinity - Sigma.

Water sigma is normally required for sigma Sw calculation, with pulsed neutron sigma measurement.

Gas Properties Calculator

This calculator enable you to estimate gas density, specific gravity, compressibility and viscosity. The input required is reservoir pressure and temperature. Molecular weight for natural gas range from 17-20 g/mol, and this calculator uses 19.5 g/mol for natural gas. Methane molecular weight of 16.043 g/mol is also used.

The gas compresibility factor Z, is computed using the CNGA (California Natural Gas Association) correlation, which is suitable for pressures above 100 psig (below 100 psig, the compressibility factor is 1).

Gas viscosity calculation is based on the Lee, Gonzalez and Eakin correlation, which only requires the pressure, temperature and molecular weight of the natural gas.

You can run this calculator for gas properties as input to the NMR calculator for gas T1, D and Tw estimation for pre logging planing.

Friday, June 15, 2012

.Net Framework Initialization Error

If you have an error while running the apps, showing ".Net Framework Initialization Error", please install the latest .net framework 4.0 in your machine.

Thursday, June 14, 2012

Volume Conversion Table

Volume conversion table is now ready for download. Feel free to send your comments after trying.

Download link