Study On The Stability Of Wellbore In Tight Oil Formation In Jimsar Sag

Wellbore instability is a complex downhole problem that is common in the global drilling process.Since the 1980 s,wellbore instability has been plaguing the safety and rapid development of drilling.Especially with the gradual expansion of the oilfield exploration area,the drilling encounters are becoming more and more complex,and the problem of shaft wall instability is becoming increasingly prominent.Over the years,the complicated downhole conditions and accident losses caused by the instability of the wellbore are quite serious,which not only affects the drilling speed and reduces the quality of logging and cementing,but also has an adverse impact on the development and protection of oil and gas layers.The direct economic losses caused by the instability amount to hundreds of millions of dollars.Therefore,maintaining the stability of the borehole wall has become a worldwide common problem in drilling engineering,which has attracted great attention from the drilling community.Many research scholars at home and abroad have been engaged in this research.The object of this paper is the tight oil formation in Jimsar Sag located in the hilly tectonic belt of Taipei Sag.The tight oil formation in Jimsar Sag is an important area for natural gas production succession in Tuha Oilfield.Its well location is concentrated in the piedmont structural belt.This area has the characteristics of harsh geological conditions,complex structure,and deep reservoir burial.Due to the large dip angle of the formation 1.The fault is developed and the problem of borehole instability is outstanding.Therefore,in order to achieve high-quality fast and safe drilling of tight oil formations in Jimsar Sag and prevent the occurrence of complex accidents,this paper aims at the geological characteristics of tight oil formations in Jimsar Sag,and establishes the dynamic rock mechanics of the whole vertical section through logging data Parameter model;through the rock mechanics experiment,the static parameters of the core at the core level are obtained,and fitted with the dynamic rock mechanical parameters of the corresponding well depth,the static rock mechanical parameter model of the longitudinal full well section is established,and the continuous formation rock is established The distribution of mechanical parameters was determined to determine the distribution law;through the study of the stress state of the tight oil formation in Jimsar Sag,an appropriate in-situ stress model was selected,and the stress model of the tight oil formation in Jimsar Sag was established to master Jimsar Distribution of in-situ stress in tight oil formations in the sag;selecting the Mohr Coulomb criterion to establish the model of formation collapse pressure and fracture pressure in this area,thus determining the distribution law of formation collapse and fracture pressure in this area,and determining the tight oil formation area in Jimsar Sag Safe drilling fluid tightness during drilling Window.It provides a scientific basis for formulating reasonable wellbore structure,drilling fluid density,optimizing drilling fluid performance,and formulating reasonable drilling process measures in the area,avoidingthe occurrence of downhole complex conditions such as collapse,jamming,and leakage during drilling,and ensuring drilling safety.