NMR Logging is no longer just a speciality tool

NMR Logs respond to Porosity and the Texture of the Rock

Since major advancements in NMR logging tools in 1994, NMR Logging has qrown to be quite prevalent on most conventional wells today. One of the primary benefits of running NMR logs is that the NMR porosity is not dependent upon the mineralogy like most conventional porosity logging tools. In addition, the NMR log actually response to the texture of the rock through surface/volume. The more surface area of the rock the faster the NMR T2 signal declines over the NMR echo train experiment allowing us to estimate Clay Bound water, Capillary Bound water and the larger Free Fluid pore volumes directly related to reservoir quality.

Reduced Uncertainty in our Petrophysical Analysis

One of the primary objectives of running an NMR log is to supplement the Petrophysical interpretation to differentiate movable water from capillary bound waters. It the upper example above, the water saturations varies over the interval and just from conventional logs alone it is difficult to estimate where to perforate for water-free hydrocarbons. In the bottom portion of the example the NMR log indicates that the entire interval has no movable water since all the water is interpreted to be bound water.  This entire interval produced water-free hydrocarbons.  

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We generally use a joint conventional and NMR log interpretation scheme similar to what Coates proposed with his MRIAN analysis. These methods employ rigorous use of both Total vs. Effective porosity systems for the final analysis.