浅水条件下浅层气走航式海洋电阻率法探测结果模拟分析
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摘要
为分析海面走航式海洋电阻率探测技术对浅水条件下海底浅层气的探测能力,以舟山火山列岛海域浅层气分布区为研究区,根据电测井资料分别构建不同埋深和尺寸的气层、气囊地电模型进行正、反演计算,并对计算结果进行对比分析。计算结果显示,海面走航式电法探测剖面在一定条件下能够有效区分出浅层气的赋存形式,基于实测数据二次处理的电阻率变化比剖面能够有效反映层状浅层气的赋存状态及厚度、气囊尺寸的变化;当含气土与非含气土的电阻率变化比与含气层厚度值的1.2%相近时,其对应的等值线能够与含气区域良好吻合,可以有效判定含气区的底界埋深。
After the rock and soil inflated, the conductivity of the rock and soil will change accordingly. Based on this physical property change, the resistivity imaging technology has many applications in the detection and monitoring of shallow gas in the terrestrial area.In order to analyze the ability of asea surface navigated DC resistivity survey method to detect seabed shallow gas under shallow water, the shallow gas distribution area in the Zhoushan volcanic islands area was used as the research area.In this method, the electrode system is dragged on the tail of the ship and floats on the water.During the voyage, the supply electrode on the electrode system is continuously powered, and other potentials are simultaneously collected in parallel to realize resistivity profile measurement.According to the electric logging data of the research area, the geoelectric models of layered and saccate gas-bearing soil with different depths and sizes were constructed to carry out forward and inverse calculations. Through comparison and analysis, the calculation results show thatelectricity detection profile with a sea surface navigated DC resistivitysurvey method can effectively distinguish the shape of shallow gas, the resistivity change ratio based on the measured data with secondary processingcan effectively reflect the occurrence state, thickness of layered shallow gas,and the change in the size of the air sac. When the resistivity change ratio of gas-bearing soil and non-gas-bearing soil is close to 1.2% of the thickness of gas-bearing area, the corresponding isoline can well agree with the gas-bearing area, which can effectively determine the bottom boundary of the gas-bearing area.
After the rock and soil inflated, the conductivity of the rock and soil will change accordingly. Based on this physical property change, the resistivity imaging technology has many applications in the detection and monitoring of shallow gas in the terrestrial area.In order to analyze the ability of asea surface navigated DC resistivity survey method to detect seabed shallow gas under shallow water, the shallow gas distribution area in the Zhoushan volcanic islands area was used as the research area.In this method, the electrode system is dragged on the tail of the ship and floats on the water.During the voyage, the supply electrode on the electrode system is continuously powered, and other potentials are simultaneously collected in parallel to realize resistivity profile measurement.According to the electric logging data of the research area, the geoelectric models of layered and saccate gas-bearing soil with different depths and sizes were constructed to carry out forward and inverse calculations. Through comparison and analysis, the calculation results show thatelectricity detection profile with a sea surface navigated DC resistivitysurvey method can effectively distinguish the shape of shallow gas, the resistivity change ratio based on the measured data with secondary processingcan effectively reflect the occurrence state, thickness of layered shallow gas,and the change in the size of the air sac. When the resistivity change ratio of gas-bearing soil and non-gas-bearing soil is close to 1.2% of the thickness of gas-bearing area, the corresponding isoline can well agree with the gas-bearing area, which can effectively determine the bottom boundary of the gas-bearing area.
引文
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[16] Goto T,Kasaya T,Machiyama H,et al.A marinedeep-towed DC resistivity survey in a methane hydrate area,Japan Sea[J].Exploration Geophysics,2008,61(1):52-59.
[2] 陈俊仁,李廷桓.南海地质灾害类型与分布规律[J].地质学报,1993(1):76-85.Chen J R,Li T H.Types and distribution of geological hazards in the South China Sea[J].Acta Geologica Sinica,1993(1):76-85.
[3] 李萍,杜军,刘乐军,等.我国近海海底浅层气分布特征[J].中国地质灾害与防治学报,2010,21(1):69-74.Li P,Du J,Liu L J,et al.Distribution characteristics of the shallow gas in Chinese offshore seabed[J].The Chinese Journal of Geological Hazard and Control,2010,21(1):69-74.
[4] 金浩,张来斌,梁伟,等.天然气管道泄漏声源特性及传播机理数值模拟[J].石油学报,2014,35(1):172-177.Jin H,Zhang L B,Liang W,et al.Simulation research on leak source characteristics and propagation mechanism for natural gas pipeline[J].Acta Petrolei Sinica,2014,35(1):172-177.
[5] 侯志民,张异彪,蔡春麟,等.舟山东极岛东侧海底浅层气特征[J].海洋石油,2015,35(3):27-32.Hou Z M,Zhang Y B,Cai C L,et al.Characteristics of Sea Floor Shallow Gas in the Eastern Part of Zhoushan Dongji Island[J].Offshore Oil,2015,35(3):27-32.
[6] 尚可旭,郭秀军,吴景鑫,等.冷泉气体渗漏过程海洋多电极电阻率法探测效果模拟分析[J].海洋学报,2017,39(11):85-96.Shang K X,Guo X J,Wu J X,et al.Detecting cold spring gas leakage in seabed sediment with marine multi-electrode resistivity method;numerical simulation and experiment[J].Haiyang Xuebao,2017,39(11):85-96.
[7] Schütze C,Sauer U,Beyer K,et al.Natural analogues:a potential approach for developing reliable monitoring methods to understand subsurface CO2migration processes[J].Environmental Earth Sciences,2012,67(2):411-423.
[8] Terry N,Slater L,Comas X,et al.Free phase gas processes in a northern peatland inferred from autonomous field-scale resistivity imaging[J].Water Resources Research,10.1002/2015 WR018111.
[9] Breen S J,Carrigan C R,Labrecque D J,et al.Bench-scale experiments to evaluate electrical resistivity tomography as a monitoring tool for geologic CO2sequestration[J].International Journal of Greenhouse Gas Control,2012,9:484-494.
[10] Dunbar J A,Amidu S A,Allen P M.A Study of Seasonal Salinity Variation in Lake Whitney,Texas Using Continuous Resistivity Profiling[C].[s.1.]:Symposium on the Application of Geophysics to Engineering and Environmental Problems 2008,2008:805-815.
[11] Taylor R W.Continuous Electrical Resistivity Surveys Along the Lake Michigan and Green Bay Coastlines of Wisconsin[C].[s.1.]:Symposium on the Application of Geophysics to Engineering and Environmental Problems,1992:129-143.
[12] Snyder D D,Wightman W E.Application of Continuous Resistivity Profiling to Aquifer Characterization[C].[s.1.]:Symposium on the Application of Geophysics to Engineering and Environmental Problems,2002:GSL10-GSL10.
[13] Yang C H,You J I,Lin C P.Delineating lake bottom structure by resistivity image profiling on water surface[J].Terrestrial Atmospheric & Oceanic Sciences,2002,13(1):39-52.
[14] Belaval M,Lane J W,Lesmes D P,et al.Continuous-Resistivity Profiling for Coastal Ground-Water Investigations:Three Case Studies[C].[s.1.]:Symposium on the Application of Geophysics to Engineering and Environmental Problems,2003:432-445.
[15] 任广欣,郭秀军,蒋甫伟,等.走航式水下多道电阻率探测系统研制与应用[J].地球物理学进展,2015,30(3):1430-1436.Ren G X,Guo X J,Jiang F W,et al.A navigated underwater DC resistivity survey system developedand used in detecting[J].Progressin Geophysics,2015,30(3):1430-1436.
[16] Goto T,Kasaya T,Machiyama H,et al.A marinedeep-towed DC resistivity survey in a methane hydrate area,Japan Sea[J].Exploration Geophysics,2008,61(1):52-59.