基于快中子散射截面的气层评价方法及其应用  

Tight Gas Evaluation Method Based on Fast Neutron Cross Section and Its Applications

作　　者：揭志军 马晓静 蔡文浙 刘世伟[1] 石耀 邱飞 吕黎明 梁国武[1] JIE Zhijun;MA Xiaojing;CAI Wenzhe;LIU Shiwei;SHI Yao;QIU Fei;LYU Liming;LIANG Guowu(Well Tech Department,China Oilfield Services Limited,Hebei,Langfang 065201,China;China United Coalbed Methane Company,Beijing 100011,China)

机构地区：[1]中海油田服务股份有限公司油田技术事业部,河北廊坊065201 [2]中联煤层气有限责任公司,北京100011

出　　处：《测井技术》2025年第1期88-96,129,共10页Well Logging Technology

基　　金：中海油田服务股份有限公司科研项目“储层评价仪RET的工程化及应用”(E23215003)。

摘　　要：山西某地区致密砂岩气藏储层具有低孔隙度低渗透率的特点,其孔隙结构、电阻率与气和水之间的关系复杂,储层特性导致以传统电阻率测井为主的气层解释评价方法受到挑战,亟需寻求一种适应这种复杂储层、复杂井况的气层评价方法。该文基于小直径脉冲中子饱和度测井仪-储层评价仪(Reservoir Evaluation Tool,RET),采用快中子散射截面(Fast Neutron Cross Section,FNXS)方法来评价气层。利用了快中子散射截面值对气体敏感而对非气体不敏感的特征,在复杂的孔隙结构条件下通过蒙特卡罗数值模拟获取快中子散射截面表征公式,在标准刻度井中验证了快中子散射截面表征公式正确性,实现了储层含气饱和度的计算;并通过现场试气验证了该方法的准确性,同时通过对区块内多口井的数据分析,建立了适用于该区块的快中子散射截面表征泥质校正公式,进一步提升了含气饱和度计算精度,并形成了该区块初步气层评价标准。实践证明基于RET仪器采用快中子散射截面方法能够在复杂地层、复杂井况条件进行气层快速识别,经过泥质校正后快中子散射截面表征更加准确,含气饱和度计算精度更高,该研究有效指导了研究区块致密气的勘探与评价。对FNXS方法的深入研究表明该方法亦可在常规含气储层中推广使用。The tight sandstone gas reservoir in a certain area of Shanxi Province is characterized by low porosity and low permeability.The relationship between pore structure,resistivity and gas and water is complex.The reservoir characteristics pose challenges to the traditional gas layer interpretation and evaluation methods mainly based on resistivity logging.Therefore,it is urgent to seek a gas layer evaluation method that is suitable for such complex reservoirs and well conditions.This paper is based on the small-diameter pulsed neutron saturation logging tool-reservoir evaluation tool(RET),and uses the Fast Neutron Cross Section(FNXS)method to evaluate gas layers..Based on the feature that FNXS is sensitive to gas but not to non-gas,the FNXS value characterization formula is obtained through Monte Carlo numerical simulation under complex pore structure conditions.The correctness of the FNXS characterization formula is verified in the standard calibration well,and the gas saturation of the reservoir is calculated.The accuracy of this method is verified through field gas testing.Meanwhile,through the data analysis of multiple wells in the block,the FNXS value characterization formula for mudstone correction suitable for this block is established,further improving the accuracy of gas saturation calculation and forming the preliminary gas layer evaluation standard for this block.Practice has proved that the FNXS method based on the RET instrument can quickly identify gas layers under complex formation and well conditions.After slime emendation,the FNXS value characterization is more accurate and the calculation of gas saturation is more precise.This research effectively guides the exploration and evaluation of tight gas in the study block.In-depth research on the FNXS method shows that this method can also be popularized and applied in conventional gas-bearing reservoirs.

关 键 词：致密砂岩气 脉冲中子饱和度测井 快中子散射截面 气水评价 蒙特卡罗模拟 

分 类 号：P631.84[天文地球—地质矿产勘探]