In CSEM exploration, the receivers are generally located about three to five times the skin depth from the transmitter. In this paper, we study the effect of a conductor between the transmitter and the survey area on ...In CSEM exploration, the receivers are generally located about three to five times the skin depth from the transmitter. In this paper, we study the effect of a conductor between the transmitter and the survey area on the target conductor response using forward modeling and inversion. The 2D forward finite element calculations show that the conductor mainly affects the response at middle and low frequencies. The lower the resistivity and the larger the conductor, the larger the effect and the effect increases with decreasing frequency. The inversion results indicate that the calculated position of the target body can move towards the source, leading to an incorrect interpretation without considering the conductor. In order to reduce the effect of a conductor between the source and the survey area, CSEM acquisition should be conducted in three dimensions using multiple sources and 3D inversion should be used during interpretation.展开更多
The Controlled Source Electromagnetic Method (CSEM) is used for offshore hydrocarbon exploration. Hydrocarbon detection in seabed logging (SBL) is a very challenging task for deep hydrocarbon reservoirs. The electroma...The Controlled Source Electromagnetic Method (CSEM) is used for offshore hydrocarbon exploration. Hydrocarbon detection in seabed logging (SBL) is a very challenging task for deep hydrocarbon reservoirs. The electromagnetic field response of an antenna is unable to detect deep hydrocarbon reservoirs due to a weak electromagnetic signal response in the seabed logging environment. This work premise deals with the comparison of the electromagnetic signal strength of a new antenna with a straight antenna and the orientation of an antenna for deep target hydrocarbon exploration. Antenna position and orientation (Tx and Ty) was studied using Computer Simulation Technology software (CST) for deep targets in marine CSEM environments. The model area was assigned as (40 ′ 40 km) to replicate the real seabed environment. From the results, the new dipole antenna shows an 804% and 278% increase in electric and magnetic field strength than the straight antenna. An electric (E) and magnetic (H) field component study was done with and without the presence of a hydrocarbon reservoir. Ex and Hz field component responses with the new antenna at the1 kmtarget were measured in a deep water environment. It was analyzed that the antenna shows 53.10% (Ex) and 83.13% (Hz) field difference in deep water with and without a hydrocarbon reservoir at the30 mantenna position from the sea floor. From the antenna orientation results, it was observed that, the electric field Ex and magnetic field Hz responses decreased from 18% to 12% and 21% to 16%, respectively but was still able to detect the deep target hydrocarbon reservoir at the4 kmtarget depth. This EM antenna may open new frontiers for the oil and gas industry for deep target hydrocarbon detection (HC).展开更多
We present three-dimensional(3-D)modeling method of marine controlled-source electromagnetic(CSEM)fields in general anisotropic media using an adaptive finite element approach based on the vector-scalar potential.The ...We present three-dimensional(3-D)modeling method of marine controlled-source electromagnetic(CSEM)fields in general anisotropic media using an adaptive finite element approach based on the vector-scalar potential.The modeling is based on the governing Helmholtz equations in the vector-scalar potential system.Unstructured tetrahedral grids are employed,which can exactly simulate the terrain relief and complex electrical structures.Moreover,based on the gradient recovery technology,the adaptive finite element approach is used to drive the mesh refinement,and make the finite element solutions converge gradually to the exact solutions.The primary-secondary field approach is used to improve the numerical accuracy of CSEM fields near the source point,where the primary field is calculated by using the quasi-analytical formula.The accuracy of this approach is verified by a one-dimensional model.Two 3-D models are used to demonstrate the effectiveness of the adaptive mesh refinement and the influences of dipping anisotropy layer on the marine CSEM responses for both inline and broadside geometries.The complex synthetic model is simulated to show the capability and flexibility of the approach for geometrically complex situations.展开更多
文摘南黄海盆地构造层由陆相中、新生界和震旦系至中、下三叠统(青龙灰岩)海相碳酸盐岩沉积层构成,高速碳酸盐岩地层对地震波形成强屏蔽作用,导致地震反射成像不清晰,因而目前对南黄海中-古生界海相地层发育特征和结构认识还存在分歧.本文利用海洋可控源电磁(CSEM)探测技术对南黄海中部隆起区海相碳酸盐岩地层进行电阻率成像,分析与海水运动相关的电磁噪声特征,探讨海水运动对观测系统的影响.研究结果显示由海水运动造成的发射源方位变化可以解释电磁场振幅曲线的震荡现象.通过海洋CSEM数据二维反演获得了研究区电阻率结构,电阻率结构和地震反射剖面具有一致性,浅部低阻与第四系和新近系未固结沉积层以及破碎带的分布具有较好的对应关系;深部高阻可能揭示了海相碳酸岩盐地层的分布,结合地震、测井和电阻率反演结果,推测海相碳酸盐岩厚度超过6 km.
基金supported by the Project kzcx2-yw-113,kzcx2-yw-121 and kzcx1-yw-15-4,CAS
文摘In CSEM exploration, the receivers are generally located about three to five times the skin depth from the transmitter. In this paper, we study the effect of a conductor between the transmitter and the survey area on the target conductor response using forward modeling and inversion. The 2D forward finite element calculations show that the conductor mainly affects the response at middle and low frequencies. The lower the resistivity and the larger the conductor, the larger the effect and the effect increases with decreasing frequency. The inversion results indicate that the calculated position of the target body can move towards the source, leading to an incorrect interpretation without considering the conductor. In order to reduce the effect of a conductor between the source and the survey area, CSEM acquisition should be conducted in three dimensions using multiple sources and 3D inversion should be used during interpretation.
文摘The Controlled Source Electromagnetic Method (CSEM) is used for offshore hydrocarbon exploration. Hydrocarbon detection in seabed logging (SBL) is a very challenging task for deep hydrocarbon reservoirs. The electromagnetic field response of an antenna is unable to detect deep hydrocarbon reservoirs due to a weak electromagnetic signal response in the seabed logging environment. This work premise deals with the comparison of the electromagnetic signal strength of a new antenna with a straight antenna and the orientation of an antenna for deep target hydrocarbon exploration. Antenna position and orientation (Tx and Ty) was studied using Computer Simulation Technology software (CST) for deep targets in marine CSEM environments. The model area was assigned as (40 ′ 40 km) to replicate the real seabed environment. From the results, the new dipole antenna shows an 804% and 278% increase in electric and magnetic field strength than the straight antenna. An electric (E) and magnetic (H) field component study was done with and without the presence of a hydrocarbon reservoir. Ex and Hz field component responses with the new antenna at the1 kmtarget were measured in a deep water environment. It was analyzed that the antenna shows 53.10% (Ex) and 83.13% (Hz) field difference in deep water with and without a hydrocarbon reservoir at the30 mantenna position from the sea floor. From the antenna orientation results, it was observed that, the electric field Ex and magnetic field Hz responses decreased from 18% to 12% and 21% to 16%, respectively but was still able to detect the deep target hydrocarbon reservoir at the4 kmtarget depth. This EM antenna may open new frontiers for the oil and gas industry for deep target hydrocarbon detection (HC).
基金support from the Natural Science Foundation of Jiangxi Province,China(Nos.20202ACBL211006,20202BAB213017)the National Natural Science Foundation of China(Nos.41774078,41904075).
文摘We present three-dimensional(3-D)modeling method of marine controlled-source electromagnetic(CSEM)fields in general anisotropic media using an adaptive finite element approach based on the vector-scalar potential.The modeling is based on the governing Helmholtz equations in the vector-scalar potential system.Unstructured tetrahedral grids are employed,which can exactly simulate the terrain relief and complex electrical structures.Moreover,based on the gradient recovery technology,the adaptive finite element approach is used to drive the mesh refinement,and make the finite element solutions converge gradually to the exact solutions.The primary-secondary field approach is used to improve the numerical accuracy of CSEM fields near the source point,where the primary field is calculated by using the quasi-analytical formula.The accuracy of this approach is verified by a one-dimensional model.Two 3-D models are used to demonstrate the effectiveness of the adaptive mesh refinement and the influences of dipping anisotropy layer on the marine CSEM responses for both inline and broadside geometries.The complex synthetic model is simulated to show the capability and flexibility of the approach for geometrically complex situations.
