核磁共振测井在川西气田储层评价中的应用

The Application of the NMR Logging in the Reservoir Evaluation in Western Sichuan Gas Field

川西气田雷口坡组储层形成于潮坪相沉积环境,目前已处在开发建产阶段,且井型多为大斜度气井,常规测井测量的项目不全导致该区域储层评价工作存在一定难度。为充分了解储层各项参数和流体性质,对该区域大部分已完钻气井补充开展了核磁共振测井工作。在核磁共振测井原理基础上,对川西气田雷口坡组气藏储层开展一维核磁共振物性参数计算,并尝试使用核磁共振T2谱构建储层毛细管压力曲线,进而开展储层孔隙结构特征和裂缝研究。研究结果表明,利用一维核磁共振测井资料计算川西气田雷口坡组气藏储层物性参数的应用效果较好,计算结果和岩心分析数据、常规测井解释成果及测试结论一致;利用核磁共振T2谱构建的毛细管压力曲线的分布特征与岩心实测压汞曲线的分布特征规律一致,因此,当实测压汞曲线资料缺少时,可以利用核磁共振T2谱构建全井段的毛细管压力曲线,进而分析孔隙结构特征;由于裂缝型和孔隙型储层毛细管压力曲线形态不同,可以借助构建的毛细管压力曲线来评价储层裂缝分布情况。综上,核磁共振测井技术在川西气田雷口坡组气藏储层的应用效果较好。

The reservoir of Leikoupo formation in western Sichuan gas field is formed in the sedimentary environment of tidal flat facies.At present,it has entered development stage and the most of drilled gas wells are highly-deviated.So it is difficult to evaluate the reservoir because of the incomplete conventional logging items.In order to fully understand the reservoir parameters and fluid property,the most of the drilled wells have been additionally conducted the nuclear magnetic resonance(NMR)logging there.Hence based on the theory of the NMR logging,this paper calculates physical parameter by 1D NMR,and constructes the capillary pressure curves by T2 spectrum to research pore structure characteristics and fractures in the reservoir.The result of researches show that the physical parameters of reservoirs calculated from NMR logging has been made better results,which are consistent with the core analysis data,conventional logging interpretation data and testing conclusions.The distribution characteristics between the capillary pressure curves constructed by T2 spectrum and the measured mercury injection curves of the cores are roughly consistent.Therefore,when the mercury injection curves are unachievable,the T2 spectrum can be used to construct capillary pressure curves at any depth of the whole well to analyze pore structure characteristics.Because of the difference between the capillary pressure curves of fractured reservoirs and that of porous reservoirs,the constructed capillary pressure curves at any depth of the whole well can be used to analyze reservoir fractures distribution.In conclusion,the NMR logging technology has a good application effect in the Leikoupo formation gas reservoir in the west Sichuan gas field.