用钻井地层异常压力参数标定逆断层的方法--以准噶尔盆地南部逆冲褶皱带为例

Calibration of thrust faults with abnormal formation pressure datatested during drilling——an example from the Southern fold-thrust belt in Junggar Baisn

准噶尔盆地南部逆冲褶皱带地表条件复杂,复杂的构造变形导致地震成像差,地震资料解释难度大。在解释横穿玛纳斯背斜构造二维或三维地震资料中,首先依据地表地质标定浅部已出露的地层和断层,利用常规钻井玛纳1井和玛纳002井的垂直地震测深(VSP)资料和声波测井资料进行地震-地质层位标定,再根据地震剖面反射特征标定出深部可能的断层。利用地层倾角测井资料,可识别出探井钻遇的一部分断层点。由于横穿玛纳斯背斜二维地震剖面上、中浅层地震反射杂乱,尤其逆冲断层沿古近系安集海河组泥岩、页岩滑脱,导致地层倾角测井无法识别构造增厚的安集海河地层中发育的逆冲断层断点。地震剖面上地震反射异常和玛纳1井、玛纳002井的断层断点井深对比表明,逆冲断层发育与钻井压力变化有关,因此利用钻井监测的地层异常压力以及地层压力系数变化的特点标定出一系列断点井深,并得到钻井地层压力图及邻井断点资料的相互佐证。这两口井的模块式地层动态测试器(MDT)实测地层数据均表明,在紫泥泉子组地层存在两套压力系统,分割两套压力系统的仍然为逆冲断层。最终,地震剖面的构造解释结果表明霍玛吐逆冲断裂是由一系列叠瓦扇断层组成。

The complex surface geology and intensive tectonic activities causes the poor seismic imaging in the southern fold-thrust belt,Junggar Basin,challenging structural interpretation.During the seismic interpretation of the Manas structure,we first projected the outcropped strata and faults onto the seismic lines with topographic data,then defined seismic horizons with the vertical seismic profile（VSP）and acoustic logging data of well Mana-1 and Mana-002,and finally fixed possible deep faults according to the seismic reflectance signatures.Some faults encountered during drilling can be identified by using dipmeter data.However,as chaotic seismic reflections exist in the middle-shallow layers on seismic reflection and thrust faults slipped along the shale and mudstone in the Paleogene Anjihai Formation,it is hard to identify the thrust faults in this structurally thickened formation by using dipmeter data.Correlation of seismic reflectance anomaly with fault depth in well Mana-1 and Mana-002 indicates that there is certain relationship between the thrust faults and the abnormal formation pressures tested during drilling.A series of the thrust fault points of the wells are identified by monitoring abnormal formation pressure and the pressure gradient during drilling,and they are verified by both the pressure data of wells and the fault points identified in the adjacent wells.The well formation pressure data tested with the Modular Dynamic Test（MDT）shows that two pressure systems exist in the Ziniquanzi Formation and are separate by a thrust fault.The final seismic structural interpretation demonstrates that the Horgos-Manas-Tugulu thrust belt is composed of a series of imbricate fans.