弯线地震勘探技术应用中的若干问题

Some issues in applications of seismic crooked line

弯线地震勘探可以避开各种障碍物、因地制宜地优选激发与接收条件以提高采集资料品质,在复杂地区油气勘探中得到广泛应用。例如:①黄土塬区采用弯线地震勘探技术,沿沟谷布设炮、检点,避开巨厚黄土层对地震波激发和接收的影响;②在碎屑岩与碳酸盐岩交互出露地区,采用弯线避开裸露灰岩而选择在碎屑岩中进行激发、接收;③采用弯线布设可避开村镇、悬崖、水库等大型地表障碍物,有利于落实构造和施工安全;④弯线地震施工可以采用比较灵活的炮、检点分布,能大大提高施工效率和节约勘探成本。但另一方面,弯线施工中炮检中点分散,对共面元道的可叠加性和剖面的可信度构成威胁。本文从满足弯线共中心点面元叠加的时间、空间条件出发,从采集和处理两个环节分析控制炮检中点分散范围的具体方法,以便在充分发挥弯线地震勘探优点的同时,保证成果剖面的真实性。

Seismic crooked lines have been widely used for oil and gas or coal exploration in complex surfaces as they have obvious advantages,such as avoiding huge obstacles and improving data quality by means of choosing optimal source points and receiver locations.This work reviews the following solutions of crook line application from our field practices: ① In loess area,sources and receivers of crooked line are laid in the deep valley to avoid thick loess layer improve data quality;② In areas of clastic rock and carbonate rock alternately outcropping on the surface,crooked line should be lay out in clastic rock area avoiding shooting and receiving on carbonate outcropping surface;③ Crooked line can be lay out to keep away from large obstacles such as villages,cliffs,reservoirs and others for safe operation;④ Sources and receivers can be distributed more flexibly in order to cut down the operation cost.On the other hand,midpoints can be scattering to any direction with crooked line survey.This is a challenge for common midpoint bin gather stacking as well as the data credibility.In this paper,we propose a few specific measures for controlling midpoints scattering in data acquisition and processing from the spatio-temporal conditions of CMP's stacking to ensure authenticity of the final data.