【作者】 陈杰；

【导师】 廖广志；

【作者基本信息】 中国石油大学(北京) ， 地质资源与地质工程， 2021， 硕士

【摘要】 近年来,火山岩作为一种特殊的油气储集类型,探明储量不断提高,已成为当前勘探开发研究的热点之一。但目前针对基性火山岩储层的评价方法较少,许多研究还处于探索之中,因此准确评价基性火山岩储层对油气层开发具有指导意义。四川盆地火山岩以基性为主,基性火山岩的矿物蚀变程度较高,且蚀变产物以绿泥石这类顺磁性矿物为主,加上异源角砾及火山碎屑的影响使得地层的孔隙结构复杂,在进行核磁共振测量时会产生较大的内部梯度磁场,核磁共振测井信噪比较低、测井质量较差。本文通过一系列核磁共振实验来研究基性火山岩的核磁共振响应机理,发现在内部梯度影响下,基性火山岩的T₂谱主峰左移、面积减小、核磁孔隙度偏低,反应出的孔隙结构比实际情况小,在二维核磁上会使得水峰与气峰重叠造成流体性质识别困难。之后利用数值模拟的方法模拟了内部梯度与回波间隔对T₂测量的影响,发现内部梯度磁场越大,随着回波间隔增大T₂谱左移的速度越快,弛豫速率增加得越快,且更容易对长弛豫组分造成影响。依据核磁实验与数值模拟结果,对基性火山岩核磁共振测井的适应性以及影响核磁共振测井孔隙度的多种因素进行分析。最后,根据T₁受扩散弛豫影响较低的特点,提出通过T₁与T₂之间的关系建立基性火山岩孔隙结构评价方法。更多还原

【Abstract】 In recent years,as a special type of oil and gas reservoir,volcanic rock has continuously increased its proven reserves and has become one of the hot spots in current exploration and development research.However,there are currently few evaluation methods for basic volcanic rock reservoirs,and many studies are still under exploration.Therefore,accurate evaluation of basic volcanic rock reservoirs is of guiding significance for the development of oil and gas reservoirs.The volcanic rocks in the Sichuan Basin are mainly basic.Basic volcanic rocks have a high degree of mineral alteration,and the altered products are mainly paramagnetic minerals such as chlorite.The influence of heterogeneous breccias and pyroclasts makes formation pore structure complex.As a result,a large internal gradient magnetic field will be generated during NMR measurement,which will result in low signal-to-noise ratio and poor logging quality of NMR logging.In this paper,we design a series of experiments with nuclear magnetic resonance,which is found that under the influence of internal gradient,the T₂ spectrum peak of basic volcanic rocks shifts to the left,the area decreases,the nuclear magnetic porosity is low,and the pores are reflected.The apparent structure with NMR is smaller than the actual situation.It may make the water peak and the gas peak overlap in the two-dimensional NMR maps,which may difficult for the fluid property identification.After that,the influence of internal gradient and echo interval on T₂ measurement is simulated by numerical simulation method.The results show that as the interval between the internal gradient magnetic field and the echo is larger,the T₂spectrum shifts to the left faster,the relaxation rate increases faster,and the longer relaxation components are more likely to be affected.Later,based on the results of nuclear magnetic experiments and numerical simulations,we analyze the adaptability of nuclear magnetic resonance logging in basic volcanic rocks and the various factors that affect the porosity of nuclear magnetic resonance logging.Finally,based on the characteristic that T₁ is less affected by diffusion relaxation,we propose a method for evaluating the pore structure of basic volcanic rocks based on the relationship between T₁ and T₂.更多还原