复杂区分层约束近地表建模方法及应用

随着油气勘探程度的不断深入，岩性和低幅度构造越来越重要。就低幅度构造而言，除地层岩性固有因素外，长波长静校正是影响低幅度构造描述的关键因素。产生长波长静校正的主要原因是复杂地表区近地表速度结构建立的精度不够及降速层底界面的空间形态刻画不准。因此，采用分层约束的建模思路，首先用微测井资料建立低速层模型，然后用小折射、VSP资料联合建立降速层模型，获得全局寻优非线性层析反演的初始模型，进行分层约束层析反演近地表建模，建立高精度的近地表速度结构。基于VSP及实测井深约束，采用协克里金方法优化降速层底界面的空间形态。通过以上2种策略，很好地解决了复杂地表区长波长静校正问题，在准噶尔盆地玛湖凹陷X地区岩性油气藏勘探中取得了很好的应用实效。

Stratified constrained near-surface model building method and its application in complex surface area

With the development of petroleum exploration,lithologic and low-relief structure reservoirs become more and more important. For low-relief structure,besides the inherent factor of stratigraphic lithology,the key factor that influences low-relief structures is the long-wavelength statics. The main reasons resulting in the longwavelength statics are the relative low precision of the near-surface velocity model and the inaccurate space depiction of low-velocity bottom interface in complex surface area. The near-surface velocity model was built using stratified constrained model building method. Firstly,the accurate low-velocity layer model was built using micrologging data,and then the descending-velocity layer model was built using short-refraction and vertical seismic profile(VSP) data,so as to obtain the initial model of global optimization nonlinear near-surface tomography. Nearsurface velocity model with high precision can be built by using the stratified constrained tomography method. Based on the VSP and measured well depth constraints,the space morphology of the interface of the descending-velocity layer was optimized by cokriging method. Through the above two strategies,the long-wavelength static correc tion problems in complex surface area were well solved,and good application results were achieved in litho-logic reservoir exploration in X area of Mahu Sag,Junggar Basin.