Quantitative Study On The Tectonic Reformation Effect Of Clastic Reservoirs In The Yingdong Area,Qaidam Basin

Tectonic stress has important reformation effects on the physical properties and distribution of clastic reservoirs.This is one of the hot issues in the geological theory research of clastic rock diagenesis and reservoir formation in recent years.The Qaidam Basin continues to be in the background of tectonic stress field of the uplift of the Qinghai-Tibet Plateau,and this procession has begun since the basin formation during the Cenozoic.The effect of tectonic stress on the reformation of clastic reservoirs is very significant.However,there has been no systematic and quantitative research work currently.Because of no systematic and quantitative research work,this study is based on theNo.1 structure located in the eastern section of the Yingxiongling ridge rich oil and gas tectonic belt in the Qaidam Basin?referred to as the Yingdong area?.I summarize that the maximum principal stress of the footwall of Youshashan fault in the study area is75 MPa and the maximum principal stress of the hangingwall of Youshashan fault is 71MPa by experimental study on rock acoustic emission.Through the direction of the long axis of the anticline and the regional fault trend,the maximum principal stress direction in this area is southwest-northeast and it is perpendicular to the Kunlun Mountains.Based on the Ansys finite element software which is most widely used in the stress field simulation,this study performed three-dimensional numerical simulation experiments of the paleo-tectonic stress field of N₂¹ reservoir in the late Pliocene to early Quaternary?N₂³-Q period?,and obtained the distribution of maximum principal stress and effective stress in the study area.It can be seen from the map that the paleo-tectonic stress in this area shows a gradually increasing distribution from northwest to southeast,and the plane distribution law of tectonic stress also has a certain correlation with the tectonic form.By combining the paleo-tectonic stress simulation results with the statistics of a largenumber of casting thin sections,I write 4 quantitative prediction formulas.Using the formulas,I can get the average 0.6%reduction of the porosity due to the tectonic compression within a certain range in the hangingwall of the Youshashan fault in the N₂¹ reservoir in the study area.The horizontal maximum tectonic compression principal stress difference is about 5MPa,and the tectonic compression porosity reduction rate is about 0.12%/MPa.We can predicte the amount of porosity reduction in the hangingwall and the footwall of the Youshashan fault in the study area due to tectonic compression based on the simulated distribution of maximum principal stress by analogy analysis.Strong tectonic compression also produces granule crushing cracks in the study area.The development of this micro-cracks is mainly controlled by four factors:tectonic stress intensity,initial porosity,particle size,interstitial content.The contribution of the granule crushing cracks in the N₂¹ reservoir in the hangingwall and the footwall of the Youshashan fault in the study area is 2%.I predicte the distribution of the micro-cracks in the study area based on the simulated distribution of effective stress.