基于岩石物理实验的嘉二~1储层高伽马成因分析

Genesis Analysis on Characteristics of High Gamma Ray in T1J12 Reservoir Based on Petrophysics Experiments

与相邻嘉二2、嘉二3亚段储层低伽马特征相比,磨溪构造嘉二1亚段储层自然伽马值普遍相对较高。储层的高伽马特征给储层的测井定性识别与参数定量计算带来困难。对可能造成储层高伽马特征的黏土矿物类型与含量、特殊放射性矿物、有机质等因素,开展了反应堆中子活化分析、X衍射、电子探针分析等5项有针对性的岩石物理实验。对实验结果分析认为,该储层放射性元素主要为铀、钍、钾,无其他特殊放射性矿物与元素。该储层黏土含量较高,以伊利石为主;黏土矿物类型与含量是造成储层高伽马特征的主要因素。长石与有机质含量较少,也会对储层伽马产生一定影响,但并不是引起储层高伽马成因的主要因素。

Compared with the characteristics of low gamma ray value in T1J23 and T1J22 reservoir, the gamma ray value in T1J21 reservoir of Moxi structure is relatively higher, which leads to great challenges on reservoir＇s qualitative identifications and quantitative parameter calculations. Therefore, it is necessary to find out the cases leading to the reservoir＇s high gamma ray characteristics. According to the fact that the high gamma ray value may be caused by various factors, such as types and contents of clay, special radioactive minerals and organic matter, we have carried out five petrophysics experiments like neutron activation analysis, X-ray diffraction and electron microprobe analysis. The experiments show that apart form U, Th and K, there are no other special radioactive minerals in the reservoir. The reservoir has high clay content, which is mainly consist of illite. The content and types of clay are the main factor which leads to the high gamma characteristics of the reservoir. Feldspar and organic matter with low content still have certain impact on reservoir gamma ray, but not the main factors.