中文摘要：

TDA（时域分析）方法是核磁共振测井的主要方法之一,在判断储层流体类型、性质和孔隙度计算方面有很大的优势,但在应用中却存在一定的局限性.针对TDA方法在流体识别中存在的一些问题,通过数值模拟不同条件的地层对其在油气识别中的影响因素及适用性进行分析.研究结果表明：TDA主要用来识别轻烃,采用D9TW采集模式采集核磁自旋回波串,TDA能识别的轻质油粘度〈9mPa.s;长极化时间不变,短极化时间TWS提高到2s,TDA能识别的轻质油粘度〈4mPa.s.双TW回波串的差（差值信号,转换为孔隙度单位称为差分孔隙度）与地层孔隙度、含烃饱和度、含氢指数、极化函数等影响因素正相关.对于低信噪比的核磁数据,综合各影响因素,发现烃的差分孔隙度要〉1.5p.u.,TDA方法才能有效识别油气和计算孔隙度.

英文摘要：

Time-domain analysis（TDA） is one of the most important NMR methods used in fluid identification and porosity calculation.It shows great advantages in reservoir evaluation,but there are also certain limitations.In order to investigate the adaptability of TDA in hydrocarbon identification under different reservoir conditions,numerical simulation was used in this study to analyze the factors influencing the outcomes of TDA,including longitudinal relaxation time T1,polarization time TW,porosity,hydrocarbon saturation,hydrogen index HI and polarization function.It is concluded that when acquisition mode D9TW is chosen,the viscosity of oil that can be measured by TDA is less than 9 mPa.s.After changing the short waiting time up to 2 s while keeping the long waiting time constant,the minimal viscosity reduces to less than 4 mPa.s.We also found the intensity of differential signals correlated positively with all the influencing factors mentioned above.With real low SNR NMR data,TDA can effectively identify hydrocarbon and calculate porosity only under the conditions that the differential porosities of hydrocarbon are greater than 1.5 p.u.