“两宽一高”地震采集技术在鄂东缘致密砂岩气藏勘探中的应用

Broadband,wide-azimuth and high-density seismic acquisition for the tight sand gas exploration in the east margin of Ordos Basin

鄂尔多斯盆地东缘蕴含丰富的致密砂岩气资源,主要赋存于二叠系河道砂体中,砂体厚度横向变化大,提高薄砂体识别及其含气性预测的精度是该区地震勘探的关键;该区表层为典型的黄土山地地貌,地表起伏剧烈,地震资料信噪比低,因此提高原始采集资料品质,为叠前反演提供可靠基础资料,是极具挑战的技术难题。东方地球物理公司近年在该区三维地震勘探中,引入"两宽一高"(宽频、宽方位和高密度)的勘探理念和技术,采取提高激发子波频宽、应用低频单点检波器拓展地震资料频宽,通过宽方位观测满足OVT处理要求以提高叠前道集精度,通过高覆盖采集提高资料信噪比等措施,探索形成了适用于黄土山地的"两宽一高"地震采集技术系列,包括面向致密砂岩气储层的观测系统设计技术、基于高清航片的激发因素优选和宽频激发/接收技术等。该系列技术在鄂东缘的应用结果表明,所采集三维地震资料频带得到拓宽,低频信息更加丰富,信噪比显著提高,砂体识别及其含气性预测的精度大幅提高,促成该区致密砂岩气藏勘探取得突破。

There are abundant tight sand gas resources in the east margin of Ordos Basin.However,the thickness of Permian channel sand bodies there varies greatly.The thin sand identification and the gas-bearing prediction are challenges for the seismic exploration.On the other hand,the surface is a typical loess mountainous landform and the signalto-noise ratio(SNR)of previous seismic data is very low.To overcome these difficulties,some broadband,wide-azimuth,and high-density(BWH)3 Dseismic surveys were conducted by BGP in the eastern margin of the basin.The acquired BWH seismic data possesses much more broadband,wideazimuth information with higher SNR,which is very suitable for the offset vector tile(OVT)processing and prestack depth imaging.The practice proves that this kind of seismic data provides a solid foundation for thin-sand identification and gasbearing prediction,which has made great contribution of the tight-sand gas exploration and development in the area.