利用核磁共振测井判定低渗透砾岩储集层流体性质——以玛湖凹陷下三叠统百口泉组为例

Using NMR Logging to Determine Fluid Properties in Low-Permeability Conglomerate Reservoirs: A Case Study from the Lower Triassic Baikouquan Formation in Mahu Sag

准噶尔盆地玛湖凹陷百口泉组储集层岩性复杂,岩电参数变化大,常规测井方法难以有效识别其流体性质。利用核磁共振实验发现,洗油后饱和水岩样的T_2谱分布在横向弛豫时间100 ms之前,而对应深度的地层实际核磁共振测井T_2谱在横向弛豫时间100 ms之后仍有分布,反映油的信号。根据T_2谱的形态,以横向弛豫时间100 ms作为区分油和水的标志,构建敏感参数,建立流体识别图版。此方法对研究区储集层流体性质的识别与试油结论相吻合,在生产中具有较好的应用效果。

The Triassic Baikouquan formation in the Mahu sag of Junggar basin are characterized by complex lithology and large variationsof electrical parameters. Conventional logging methods can't be used to effectively identify fluid properties in low-permeability conglomer-ate reservoirs. NMR experiments show that T_2 spectrum of water-saturated rock sample is distributed ahead of the lateral relaxation time of100 ms, but the actual NMR T_2 spectrum of the layer at the corresponding depth is still distributed behind the lateral relaxation time of 100 ms, which reflects the signal of oil. According to the shape of the T_2 spectrum and taking the lateral relaxation time of 100 ms as the markerto identify oil and water, sensitivity parameters and fluid identification chart are established. The result of fluid property identification inthe reservoir of the study area by using the NMR method is consistent with the result of formation test, and good application effects hasbeen gained during production.