Use of the NMR Diffusivity Log To Identify and Quantify Oil and Water in Carbonate Formations
| Autor: | D. Di Rosa, A. Gyllensten, S. Chen, W. Li, D. Georgi, R. Tauk |
|---|---|
| Rok vydání: | 2008 |
| Předmět: | |
| Zdroj: | SPE Reservoir Evaluation & Engineering. 11:238-245 |
| ISSN: | 1930-0212 1094-6470 |
| DOI: | 10.2118/101396-pa |
| Popis: | Summary This paper reports on a successful example of using the 2D NMR technique for determining oil-water contact (OWC) in difficult carbonate environments. An NMR diffusion-based interpretation method was used to identify oil, water, and transition zones and to quantify oil saturation in a limestone reservoir. Hydrocarbon typing and saturation determination from NMR logging usually require high contrasts of intrinsic or apparent relaxation times, dif-fusivity, or both. Many carbonate reservoirs in the Middle East contain large pores, which together with the low relaxivity of carbonates, create long T1 and T2 times for water. Furthermore, because light oil has a long relaxation time, there is little contrast in T2 or polarization between water and oil. When these reservoirs contain very light or high-GOR oils, the diffusivity contrast between oil and water is also less pronounced. Hence, it is difficult to distinguish between the oil and water signals with most NMR hydrocarbon-typing techniques. The example shows that a diffusion log constructed from 2D NMR interpretation works well even for marginal diffusion-contrast cases. In addition, a modification to the Coates permeability model is presented that is applicable to carbonate formations having partially connected vugs. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|