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用恩迪科特油田西北部两块重叠的三维地震资料确定的断层位置出现了明显的不一致性,在地震剖面上横向归位偏差高达1000英尺(300米)。对断层位置的解释存在这么大的不可靠性,给布井带来了极大的风险。为了定量表述并校正地震归位误差,本文用射线追踪模拟方法建立起三维速度模型。产生的横向归位误差图揭示出在恩迪科特油田范围内归位偏差存在明显变化,这主要是永冻层厚度的横向变化所致。将归位误差图用于校正地震成果图件上特征构造的位置,使得在紧靠主断层处成功地打出了几口开发井。而在进行此项研究之前,这几口为优化开采而定的井位被认为是风险太大不能接受。对地震资料采用最终确定的速度模型进行了三维叠后深度偏移,给出了与射线追踪预测结果一致的重新归位图象。此外,还采用常规方法来提高地震图象的质量,从而改善了剖面的可解释性,实现了恩迪科特油田外围赛格三角洲北区油藏的重新构图及其后的成功开发。
Significant inconsistencies in the location of the fault, as identified by the two overlapping 3D seismic data in the northwestern Endicott field, have lateral homing deviations up to 1,000 feet (300 meters) above the seismic profile. The interpretation of the fault location is so unreliable that it poses a great risk to wells. In order to quantitatively describe and correct the earthquake homing error, a three-dimensional velocity model is established by ray tracing simulation. The resulting horizontal homing error map reveals a significant change in homing bias within the Endicott field, mainly due to lateral variations in the thickness of the permafrost. The homing error map is used to correct the location of the feature on the seismic results map so that several development wells are successfully shot in close proximity to the main fault. Before proceeding with the study, these well positions for optimizing mining were considered too risky to accept. Three-dimensional post-stack depth migration was performed on the seismic data using the finally determined velocity model, and the relocated images consistent with the ray tracing prediction results were given. In addition, conventional methods were used to improve the quality of seismic images, thereby improving the interpretability of the profiles and enabling the reconstruction and subsequent successful development of reservoirs in the northern area of Endicott Field.