随钻核磁共振测井在南海文昌油田低阻油层流体识别中的应用

Application of NMR logging while drilling in fluid identification of low resistivity reservoirs in Wenchang Oilfield, South China Sea

随钻核磁共振测井在南海文昌油田低阻油层的开发中以安全高效的测井方式提供了孔隙度、渗透率等参数,且在定性识别轻质油层方面发挥了关键作用。为了进一步提升随钻核磁共振测井在文昌油田低阻油层流体识别中的使用价值,从孔隙结构和流体性质2个影响因素出发,提出了T2谱含油特征指标法并引入纯水谱重构法开展流体定量识别。其中T2谱含油特征指标法以消除孔隙结构的影响为基础,利用轻质油和水的横向弛豫时间差异提取轻质油真实的拖尾现象达到定量识别流体的目的;水谱重构法则采用球管模型和正态分布模型分别构建束缚水谱和可动水谱,并将两者之和作为纯水谱,通过与实测核磁T2谱的对比提取流体性质信息,达到识别流体性质的目的,2种方法在文昌油田低阻油层的流体识别中均取得了良好的应用效果,可在低阻油层、水淹层等储层流体的定量识别中发挥显著作用。

In the development of low resistivity reservoirs in Wenchang Oilfield of South China Sea, NMR logging while drilling provides porosity, permeability and other parameters in a safe and efficient logging way, and plays a key role in qualitative identification of light oil. In order to further improve the application value of NMR logging while drilling in fluid identification of low resistivity reservoir in Wenchang Oilfield, starting from two influencing factors which is pore structure and fluid properties, T2spectrum oil-bearing characteristic index was proposed, and pure water spectrum reconstruction was introduced to carry out fluid quantitative identification. The T2spectrum oil-bearing characteristics index method was based on eliminating the influence of pore structure, and by using the transverse relaxation time difference between light oil and water to extract the real tail phenomenon of light oil, so as to achieve the purpose of quantitative identification of fluid.The water spectrum reconstruction method used the spherical tube model and the normal distribution model to construct the bound water spectrum and the movable water spectrum respectively, which the sum of the two spectrum is pure water spectrum. The information of fluid properties is extracted by comparing with the actual measured NMR T2spectrum, so as to identify the fluid properties. The two methods have good applications to the fluid identification of low resistivity reservoirs in Wenchang Oilfield.These two methods can play important roles in the quantitative identification of reservoir fluids such as low resistivity reservoirs and water flooded reservoirs.