| Author's Name: PANG Xu, SHAO Dali, WANG Hongping, ZUO Guoping, YANG Liu,
WANG Chaofeng, ZHANG Yonggang, SHAO Guanming |
| The fluid properties of the pre-salt reservoir in Santos Basin, Brazil are extremely complex. In addition to
conventional oil and gas, there are also non-hydrocarbon gas layers dominated by supercritical CO2, condensate gas layers
containing supercritical CO2 and volatile oil layers. In the formation at depth of 4 000~6 000 m, the density of supercritical
CO2 is similar to that of oil, and the difference in response characteristics of conventional logging is small, so it is
extremely difficult to identify the fluid type. There are few studies on this in the world, and there is a lack of effective
technical means. In this paper, based on the physical property that CO2 does not contain hydrogen and its supercritical
condition is equivalent to the oil density, neutron logging, NMR logging while drilling and NMR logging and density
logging reflecting the hydrogen content index of the fluid are selected. By crossing of density porosity-neutron porosity
and density porosity-total porosity difference of NMR logging while drilling and NMR logging, the semi-quantitative
evaluation of supercritical CO2 and identification of fluid were realized by combining with formation test and oil test
results. The results show that the coincidence rate of the comprehensive identification of reservoir fluid types is up to
86.6%, which proves that the identification method has a good application effect in Santos Basin, Brazil. This technique is
an effective method to identify complex fluid containing supercritical CO2 and is of great significance to well logging
interpretation and evaluation. |
