NUCLEAR MAGNETIC RESONANCE EXPERIMENT ANALYSIS OF TIGHT GAS SANDSTONE RESERVOIR

摘要

In this paper, we conducted NMR (nuclear magnetic resonance) experiments on 93 tight sandstone samples collected from the Permian Shihezi Formation in the Sulige gas field. The T_2 relaxation time response characteristics and their fluid identification ability of different types of pores were analyzed. We found six types of typical T_2 relaxation time spectrum in the studied tight sandstone, indicating that small pores (0.1 〜0.5µm) are most developed, followed by mesopores (0.5 ~2.5µm)and mi- cropores ( 10 µm) is almost non-existent. The T_2 cut-off value of the tight sandstone is mainly distributed between 1 ms and 15 ms, with an average of 5.5 ms. The movable water saturation ranges from 1 to 18 with an average of 6.2. There is a good negative correlation between T_2 cut-off value and movable water saturation. For the development of this tight sandstone gas reservoir, we should prefer the gas layer with gas saturation greater than 50 and movable water saturation smaller than 8. When the movable water saturation in the formation is greater than 11, the gas-bearing layer generally has no development value. In the current development stage, the target reservoirs will still maintain a higher gas production capacity under reasonable construction measures and reservoir protection conditions.