气水模型(T_2,D)二维核磁共振测井数值模拟及参数影响分析  

Inversion Simulation of(T_2,D) 2D NMR Logging and Analysis of Observation Parameters Effects in Gas-water Model

作　　者：谭茂金[1,2] 邹友龙[2] 刘兵开[3] 杨萱[3] 

机构地区：[1]地下信息探测技术与仪器教育部重点实验室中国地质大学,北京100083 [2]中国地质大学地球物理与信息技术学院,北京100083 [3]中国石化胜利石油管理局测井公司,山东东营257096

出　　处：《测井技术》2011年第2期130-136,共7页Well Logging Technology

基　　金：油气资源与探测国家重点实验室开放课题(2009009);中央高校基本科研业务费专项资金(2010ZY28);国家重大专项"大型油气田及煤层气开发"(2011ZX05014-001-001)

摘　　要：一维核磁共振测井在流体识别时有局限性。二维核磁共振测井不仅能够给出准确的物性参数,在流体识别方面具有明显的优势。针对(T2,D)二维核磁共振测井的弛豫机理,拟采用改进的截断奇异值分解法实现二维谱反演;对给定的不同含气饱和度的气水流体模型和气层模型分别在不同磁场梯度、不同回波间隔组合和不同信噪比下进行正演和反演实验,分析了不同饱和度模型的响应特征,计算了其反演精度,以研究上述参数对反演结果的影响。研究得出,在多回波间隔观测模式下,最佳磁场梯度在3.0×10-3T/cm左右;在回波等待时间相同的情况下,长回波间隔与短回波间隔的适当组合时的观测结果和反演的效果最好。信噪比对二维NMR观测数据和反演精度也有较大影响,信噪比的最低临界值约为150。One-dimension Nuclear Magnetic Resonance （1D NMR） logging technology is limited in some reservoirs. However, two-dimension Nuclear Magnetic Resonance （2D NMR） not only can give accurate porosity, but also is more advantageous in fluid typing than 1D NMR. First,according to the relaxation mechanism of （T2,D） 2D NMR in gradient field, an improved truncated singular value decomposition （TSVD） method is used to realize two-dimension spectrum inversion with diverse gas-bearing models. Then, point to gas saturation models, forward modeling and inversion tests are implemented in detail with different acquisition parameters such as different echo spacing （TE） groups, different magnetic field gradients （G） and different signal to noise ratio （SNR）, and the influences of observation parameters above on the inversion accuracy is investigated and analyzed. When the magnetic field gradient （G） is around 3.0 × 10^3 T/cm in multi-TE activation, the observation and inversion effects are both more suitable, and the observation results and inversion effects of hybrid echo spacing group with long echo spacing and short echo spacing are best in same waiting time （Tw）. Furthermore, the noise ratio （SNR） is important effect factor for 2D NMR observation data and inversion accuracy, and the lowest threshold of signal to noise ratio （SNR） is about 150.

关 键 词：二维核磁共振测井 多回波间隔观测模式 扩散系数 横向弛豫时间 含气饱和度 流体模型 

分 类 号：P631.84[天文地球—地质矿产勘探]