四川盆地中部侏罗系沙溪庙组致密砂岩气藏地震一体化描述技术

Integrated seismic description technology for tight sandstone gas reservoir of Jurassic Shaximiao Formation in the central Sichuan Basin

四川盆地中部中侏罗统沙溪庙组砂体具有“期次多、分布广、宽度窄、厚度薄”的地质特征,砂岩储层致密,非均质性较强,砂岩地震识别及精细刻画、储层预测及含气性预测配套技术不成熟,制约了该区致密气勘探开发进程和效果。为此,通过地震处理、解释联合攻关,研究形成了适用于沙溪庙组致密砂岩气藏的地震一体化描述技术。研究结果表明:①面向沙溪庙组目的层的保真、保幅、宽频、高分辨率地震处理技术,可以有效地提高河道砂体地震资料纵横向分辨率及地震成像,砂体特征更突出,断层成像更清晰,道集质量明显提高,为后续叠前地震储层及含气性检测提供了可靠数据;②在明确砂体地震反射特征的前提下,通过河道砂组地震层序划分及砂体精细雕刻技术,可以确定沙溪庙组河道砂体空间期次、重点砂体及单河道横向展布,岩性预测吻合率100%;③形成针对重点河道致密砂岩储层及含气性预测的有效技术手段及高产井部署地震模式,定量预测储层厚度、孔隙度及含气性的误差均小于10%,高产井模式有效地指导了水平井部署。结论认为,形成的沙溪庙组致密砂岩气藏地震一体化描述技术经实际应用证明较为成熟,获气井成功率大幅提升,单井产气量不断获得新突破,该技术有效地支撑了致密砂岩气藏的勘探开发成效显著。

The sandbodies of Shaximiao Formation of Middle Jurassic in the central Sichuan Basin are geologically characterized by multiple stages, wide distribution, narrow width and small thickness, and the sandstone reservoirs are tight with stronger heterogeneity.In addition, the support technologies for seismic identification and fine description of sandstone, reservoir prediction and gas content prediction are not mature, which restricts the process and effect of tight gas exploration and development in this area. By researching seismic data processing and interpretation jointly, this paper develops an integrated seismic description technology which is applicable to the tight sandstone gas reservoir of Shaximiao Formation. And the following research results are obtained. First, the seismic data processing technology of fidelity, preserved amplitude, wideband and high resolution which is developed for the target layer of Shaximiao Formation can effectively improve the vertical and horizontal resolution of seismic data and the seismic imaging of channel sand bodies, so the characteristics of sand bodies are more prominent, fault imaging is clearer, the quality of the trace gather is improved greatly, which provides reliable data for the subsequent pre-stack seismic reservoir and gas content detection. Second, while the seismic reflection characteristics of sand bodies are clarified, the spatial period of Shaximiao Formation channel sand bodies and the lateral distribution of key sand bodies and single channels can be figured out by means of seismic sequence division of channel sand body and fine description of sand body,and the coincidence rate of lithology prediction is 100%. Third, the effective technical method for the prediction of key channel tight sandstone reservoir and its gas content and the seismic mode for the deployment of high-yield well are developed, which ensure the quantitative prediction error of reservoir thickness, porosity and gas content less than 10% and provide effective guidance for the deployment of horizontal wells. In conclusion, practical application shows that the integrated seismic description technology for the tight sandstone gas reservoir of Shaximiao Formation is relatively mature, which improves the success ratio of production tests greatly and realizes new breakthroughs in single-well gas production continuously. This technology effectively supports the exploration and development of tight sandstone gas reservoirs, and the achievements are remarkable.