DrNuc - The Nuclear Petrophysical Calculator

DrNuc® is the Nuclear Petrophysical Calculator. It is a scientific app that is used in the oil and gas industry. The app calculates 6 important nuclear parameters used by geologists, log analysts, petrophysicists and scientists in the oil industry to study and evaluate oil reservoirs. 

1. Bulk density (rhob) 
2. Electron density (rhoe) 
3. Photoelectric factor (PEF) 
4. Density porosity (DPHI) 
5. Hydrogen index (HI) 
6. Neutron capture cross section (sigma)  

The first 4 parameters are derived from or related to the nuclear litho-density measurement used in oil exploration. The 5th parameter, HI, is a key factor in interpretating neutron porosity measurements in new wells. And the 6th parameter (sigma) is critical for evaluating nuclear logs in producing wells. 

The inputs and outputs have been quite literally smashed onto an iPhone screen. While the interface is atypical for an app, it’s been designed to allow the user to enter specific values and to see all of the input parameters at one time. Values are typically typed, vs. using a slider or stepper included in many apps, so that precise environmental conditions can be specified. The DrNuc app calculates important values for making important decisions. Bad data is worse than no data.

Important results can be saved by the user and emailed to themselves or to others. No data is stored on the iPhone. The DrNuc app does not harvest any user information, and is suitable for all ages of scientists and future scientists. 

This problem can be easily handled by the Lithology Calculator, the Clay Calculator or the SuperNuc Calculator. Shown is a screen capture from the Lithology Calculator.  

In this case, there are only 4 input values:

1. Quartz matrix 
2. 20 pu porosity
3. Sw=100 (water saturation) 
4. 0 kppm water salinity  

• Bulk density (rhob)  
• Electron density (rhoe)  
• Photoelectric factor (PEF)  
• Density porosity (DPHI)  
• Hydrogen index (HI)  
• Neutron capture cross section (sigma)  

Because the water saturation is 100 s.u. (100%), the oil, gas and CO2 values are not needed.  By selecting the “Quartz” control, the calculator uses 2.65 g/cc SiO2 in the calculations. The user doesn’t even need to supply that data.   

The calculator has a short help guide on the page and a longer help guide on a separate page. The results can be saved and emailed to oneself or others. 

SuperNuc is really super.  The calculator will be able to handle just about any case you will encounter.

• 18 pu Shaly Sandstone
• 2.67 g/cc matrix density
• Matrix: 80% SiO2, 10% Kaolinite, 10% Al2O3  
• Fluids: 50% water, 100 kppm at 110°C, 4000 psi
• 40% oil, 0.82 g/cc, CH2.1 (downhole properties) 
• 10% gas, 0.1 g/cc, CH4.2 (downhole properties) 

The SuperNuc Calculator allows the user to define the composition of the rock and hydrocarbons. The user can use a mineral from the library, or can enter the chemical formula appropriate for their conditions. The "Kaolinite" in the first mineral input field uses the mineral definition from the mineral library. The Al2O3 in the second line is a chemical formula.

For this case, there are 18 inputs. The user specifies the composition and density of oil and gas. 

The calculated parameters are highlighted in yellow.

Challenge: Properties of 200 kppm saline water at 120°C and 5000 psi(a). 

This problem can be easily handled by the Saline Water Calculator or SuperNuc. Shown are results from the Saline Calculator. In this case, only 4 input values are needed:

• 200 kppm water salinity 
• 120 degrees
• °C temperature scale
• 5000 psia  

The calculator first checks to verify that the vapor pressure is below the specified pressure. The calculator then calculates the water density as a function of salinity, temperature and pressure. Finally, it calculates the hydrogen index (HI) and neutron capture cross section (cu). 

As with the other calculators, the results can be emailed to oneself or others.