Chapter 4 of the thesis

Today, I read the thesis ‘Permeability Characterization and Prediction a Tight Oil Reservoir, Edson Feld, Alberta’ Chapter 4 (4.1-4.4) and make a conclusion of this week's work.

After skimming and scanning on Chapter 4 of the thesis, I think that some parts of them is still helpful for my research. So I want to finish reading it. I will not read other parts of the thesis.

Summary

Extremely low and highly variable values and the changing scales of these variations are major challenges to tight rock permeability prediction.

NMR logs have been used to predict permeability in conventional sandstone rocks with good success but their application in tight rocks has been more problematic.

Two empirical models have been widely used in conventional reservoirs:

SDR: Schlumberger-Doll Research model.

TIM: Timur-Coates model.

SDR does not cover all pore information and ignores contributions from small ppores.

TIM depends on T2 cut-off determination. 33 ms is selected for T2 cut-off in sandstone, which is an overestimate in tight formations. Core analysis may resolve the problem as I see in other papers.

The NMR T2 relaxation time depends on fluid in the rock pores. There are mainly three relaxation components: bulk fluid process, surface relaxation, and magnetic field gradient diffusion.

Many researches show that pore size is log normal distribution (LND). Since T2 is directly proportional to pore size, the T2 spectrum is also expected to be LND.

The volume of investigation of the NMR response will likely include several lithofacies, the log (T2) distribution may be expected to be a mixture of several normal distributions.

People used three Gaussian distribution to decompose the log (T2) spectrum.

, where ,

,  was used to assess the match.

For the pore size related facies model, there are three lithofacies with weights of . If  is consistent with the proportion from core analysis, it suggests that interpretation of  is correct (fine pore-size).

The medium and coarse pore-size related facies are not easily identified in the tight Cardium formations.

In general, the decomposition interpretation is consistent with core characteristics. The results are shown as follows:

Tomorrow, I will finish reading Chapter 4.