论文详情
疏松的近地表介质对地震波的吸收衰减作用是导致地震记录分辨率降低的重要因素,准确求取近地表地层Q值可为地震波能量和频率的补偿处理提供确切参数。针对常规微测井近地表Q值估计时面临的激发与接收耦合的一致性、虚反射以及近场问题等,提出了一种深井激发、浅井和地面短排列联合接收的井地一体化测量的近地表Q值估算方法。该方法避免了低速层底部界面虚反射对子波的干涉,最大限度保证激发和接收的耦合一致性。大港探区实际应用结果表明,深井激发、浅井和地面短排列联合接收的井地一体化测量方法能获得稳定可靠的近地表低、降速层品质因子Q值,为近地表吸收衰减补偿处理奠定了基础。经补偿处理后的叠加剖面不仅拓宽了目的层频带,提高了地震资料分辨率,而且极大地增强了地震数据分辨薄互储层和特殊岩性边界的能力。
Seismic attenuation caused by a near-surface medium is an important factor that decreases the resolution of seismic data.Accurate measurements of the near-surface Q value play a fundamental role in enhancing seismic resolution via absorption compensation in the near-surface layer.Issues are encountered in conventional uphole surveys for Q estimations,such as those with the consistency between excitation and geophone coupling,ghost reflection,and near field effect.Given these issues,in the current study,a joint survey,combining surface and cross-hole seismic surveys,is proposed,where shooting is performed in a deep-hole and receiving is in a shallow-hole and short seismic arrangement in the ground.The proposed joint survey can avoid interference from a ghost reflection and maximize the coupling consistency of excitation and reception.Testing of an actual survey in the Dagang oilfield showed that the reliable quality factor,Q,of the weathering and sub-weathering layers was obtained,which can be used for near-surface absorption compensation.The resolution of the stack section was improved after absorption compensation.Moreover,the ability of seismic data to distinguish thin reservoirs and special lithologic boundaries was enhanced.The field data test results demonstrate the feasibility of the proposed joint survey.
国家重点基础研究发展计划(973计划)项目(2013CB228606)资助。