三维地震致密薄储层预测及水平井导向技术在苏里格气田中的应用

Application of technologies of tight thin reservoir prediction based on 3D seismic data and horizontal well geosteering in Sulige Gas Field

苏里格气田是中国已发现的陆上最大的整装“三低”气田,位于鄂尔多斯盆地伊陕斜坡西部宽缓西倾单斜上,整体上断裂和褶皱均不太发育。该气田的主力产气层是二叠系下石盒子组盒8段和山西组山1段河流相致密砂岩,砂体呈南北向带状展布,普遍呈纵向多期叠置、横向复合连片的特征,这给有效储层预测及水平井导向带来很大挑战。为此,利用三维地震数据,结合GeoEast解释系统中的特色模块,采用均方根振幅、单频体、高亮体等地震属性及叠前横波阻抗反演预测砂体展布;利用流体活动性、含气性检测技术、叠前弹性参数反演预测含气性;使用多信息融合技术优选甜点区;利用井约束高精度速度建场动态时深转换将地震预测成果从时间域转为深度域,实现了水平井整体部署、轨迹优化、随钻导向的地震技术全流程应用。GeoEast解释系统叠后地震属性、地震反演、油气检测、多信息融合等特色技术能较好地预测薄砂岩含气储层、优选有利目标区等,效果显著。

The Sulige Gas Field in the Ordos Basin is the largest onshore integral“three-low”gas field discovered in China.It is located on the wide and gentle west-dipping monocline in the west of the Yishan Slope in the basin,and on the whole,no faults or structures have developed in this gas field.The main gas-producing layers in this gas field are the tight sandstone reservoirs in fluvial facies in the He-8Member of the Permian Lower Shihezi Formation and the Shan-1 Member of the Shanxi Formation.The sand bodies distributed in a north-south zonal pattern are generally characterized by longitudinal multi-stage superposition and transverse composite linkage,posing great difficulty for effective seismic reservoir prediction and horizontal-well geosteering.For this reason,sand body distribution is predicted by availing 3Dseismic data,the characteristic modules in the GeoEast interpretation system,seismic attributes,such as rootmean-square amplitude,single-frequency volume,and highlight volume,and prestack shear wave impedance inversion.The fluid mobility,gas-bearing detection technology,and prestack elastic parameter inversion are used to predict gas bearing.Multi-information fusion technology is employed to select the sweet spot area.The seismic prediction results are converted into the depth domain by the dynamic time-depth conversion of well-constrained high-precision velocity field construction.The application of seismic technologies in the whole process of placement,trajectory optimization,and geosteering while drilling of horizontal wells is thereby achieved.The characteristic technologies of the GeoEast interpretation system for post-stack seismic attribute analysis,seismic inversion,oil and gas detection,and multi-information fusion can be used to predict thin gas-bearing sandstone reservoirs and select favorable target areas,and the results they deliver are remarkable.