东海某凹陷大型砂体优势储层预测技术研究与应用

东海某凹陷中北部大型砂体发育,是油气勘探的重要地区之一。该砂体具有埋藏深、厚度大的特点,由于地震资料在深层频带变窄因而识别砂体厚度困难。同时,多期河道砂体叠置导致储层非均质性强、孔渗关系复杂。因此,有效刻画大型砂体的分布特征并预测优势储层发育区,是勘探开发亟需解决的问题。为此,提出了大型砂体岩性岩相分尺度地震预测技术。首先,在构造沉积研究的基础上,采用基于甚低频补偿的分频迭代反演方法,提高稀疏钻井条件下中深层窄频带的厚储层预测精度;然后,通过储层物性主控因素分析找到优势储层发育的有利岩相及其敏感弹性参数,利用改进的标准抛物线型三参数AVO方程,构建有利岩相敏感地震属性,以此作为约束条件实现相控反演,提高低信噪比条件下优势储层敏感弹性参数反演的分辨能力;最后,利用大型砂体分布特征刻画与有利岩相预测相结合,预测优势储层发育区。采用该技术在有效刻画东海某凹陷Z气田G1砂体厚度的基础上,基于沉积约束的分类岩相控制,结合横波反射率地震敏感属性预测了优势储层展布特征。预测结果表明,Z气田优势储层集中发育于辫状河近源主体部位,与区域沉积规律与认识吻合,证实了方法的有效性。

Large sand bodies can be found in the central and northern regions of a sag in the East China Sea,which represents an important target for oil and gas exploration.These bodies have a large burial depth and thickness,strong heterogeneity,and complex patterns of porosity and permeability,which result from the superposition of multi-stage channel-like sand bodies.To predict the distribution of these bodies and the location of favorable reservoirs,a seismic prediction technique at the lithology-lithofacies scale was proposed.A frequency-dependent iterative inversion method with ultralow frequency compensation was first implemented to predict the reservoir thickness from narrow-banded seismic data and sparse well log data.Then,the favorable lithofacies and the sensitive elastic parameters of the favorable reservoirs were identified by analyzing the reservoirs physical properties.An improved standard parabolic three-parameter amplitude variation with offset (AVO) equation was used to obtain the sensitive seismic attributes of the favorable lithofacies.These were employed to constrain the subsequent facies-guided inversion,so as to improve the resolution of the sensitive elastic parameters in the favorable reservoirs,which were inverted using seismic data with low signal to noise ratio (SNR).Finally,the information on the distribution of the large sand bodies and the predicted favorable lithofacies were combined to identify the favorable reservoirs.Tests on field data from the Z gas field in a sag in the East China Sea showed that the proposed technique can predict the thickness of the sand bodies and the distribution of the favorable reservoirs.In fact,the predicted locations were consistent with the existing regional sedimentary succession,confirming the effectiveness of the method.

国家科技重大专项(2016ZX05027-002)资助。