吉木萨尔页岩油储层二维核磁响应特征

Two-dimensional NMR characteristics of Jimsar shale oil reservoir

为研究吉木萨尔页岩油储层二维核磁响应特征,对不同饱和状态下的页岩油储层岩心进行二维核磁共振实验,得到孔隙度和弛豫特性,进而构建T_(2)−T_(1)核磁流体识别图版,并改进得到适用于核磁共振测井的流体解释图版,总结不同岩性储层核磁响应规律。研究结果表明:减去干样信号的核磁孔隙度与气测孔隙度相一致,核磁共振能准确表征页岩储层的孔隙流体信息;页岩油储层T_(2)−T_(1)二维谱中,黏土矿物会导致在T_(2)=0.10 ms、T_(1)/T_(2)<100的区域显示黏土吸附水响应,泥岩在T_(2)<1.00 ms、T_(1)/T_(2)>100固体有机质区域的信号占比最高,白云质粉砂岩在1.00 ms<T_(2)<10.00 ms束缚流体区域所占比例最大,泥质粉砂岩以可动流体响应为主、弛豫特征T_(2)>100.00 ms,表明大孔隙较为发育。将流体识别图版应用于二维核磁测井流体饱和度评价,发现芦草沟组页岩油下甜点可动油饱和度高、可采性好,相应水平井含水率更低。

In order to study the two-dimensional nuclear magnetic resonance(NMR)response characteristics of Jimsar shale oil reservoir,2D NMR experiments were carried out on shale oil reservoir cores under different saturation conditions.The porosity and relaxation characteristics were obtained through experiments.Then,the T_(2)−T_(1) NMR fluid identification map was constructed,and the fluid interpretation map suitable for NMR logging was improved.The NMR response laws of reservoirs with different lithology were summarized.The results show that the result of NMR porosity minus the dry sample signal is consistent with the gas measured porosity.The NMR technique can accurately characterize the pore fluid information of shale reservoirs.In the T_(2)−T_(1) two-dimensional spectrum of shale oil reservoirs,clay minerals lead to the response of clay-adsorbed water in the region of T_(2)=0.10 ms and T_(1)/T_(2)<100.The mudstone has the highest signal proportion in the solid organic matter region of T_(2)<1.00 ms and T_(1)/T_(2)>100.The dolomite siltstone has the highest proportion of signal in the bound fluid region of 1.00 ms<T_(2)<10.00 ms.The argillaceous siltstone is mainly characterized by movable fluid response and relaxation characteristic T_(2)>100.00 ms,indicating that its macropores are relatively developed.The fluid identification map is applied to the evaluation of fluid saturation in 2D NMR logging,and it is found that the lower sweet spot of Lucaogou Formation shale oil has high movable oil saturation,good recoverability,and lower water ratio in corresponding horizontal wells.