Numerical simulation of present-day stress field on the top surface of Ordovician Wufeng Formation shale in the Shilongxia anticline area,Southeast Sichuan,China
In recent years,significant breakthroughs have been made in shale gas exploration in the Southeast Sichuan area,and the exploration field has further advanced to the deep and ultra-deep layers.Under the influence of multi-phase tectonic movement and multiple sets of sliding layers,the Southeast Sichuan area shows a complex tectonic style with multi-layer sliding,and the present distribution characteristics of the geostress in the deep layer are controversial,and the orientation change of the local stress field is still unclear,which brings a great challenge to the development of deep shale gas.In this paper,based on the drilling and logging data and high-precision 3D seismic data,a geological model of Shilongxia anticline is established,the mechanical model of the study area is determined according to the rock mechanical parameters and boundary conditions,and the distribution of the present stress field in the top interface of Ordovician Wufeng Formation shale in the Shilongxia anticline area is simulated using the 2D finite element numerical simulation method.On this basis,the reasonableness of the simulation results is verified by combining the actual drilling data of SY1 well in the study area.The results show that:1)the distribution of the present stress field in the Shilongxia anticline area is affected by the pre-existing tectonic structure,rock mechanical variability and other factors.The simulation results show that around the fault zone,especially at the turning end and the end of the fault zone,there is a stress concentration phenomenon,and the stress value in this area is high,with a distribution range of-81.85～-80.95 MPa;while the fault zone itself is in a broken state,with a low stress value,with a distribution range of-77.8～-49.74 MPa.The core of the anticline is an area of strong dryness and is in a state of stress concentration with higher stress values and the stress distribution ranges from-113.2～-81.85 MPa.2)The present maximum principal stress of the top interface of Ordovician Wufeng Formation of Shilongxia anticline is spreading in a near-north-south direction,which is mainly controlled by the influence of extrusion from the direction of Daloushan Mountain in the late stage.The stress field in Southeast Sichuan is superimposed by several periods of tectonic effects,and the Early Yanshan Period is mainly controlled by the thrusting and overturning effects of the Xuefengshan Mountain arc tectonic belt in the east,forming the tectonic morphology of the Shilongxia anticline.Nowadays,the distribution of the stress field is mainly controlled by the thrusting and overturning of the southern Daloushan Mountain during the Late Yanshan and Himalayan periods,which makes the direction of the maximum principal stresses in the study area nowadays nearly north-south.
Southeast SichuanShilongxia anticlineOrdovician Wufeng FormationPresent-day stress fieldFinite element numerical simulation
万方数据
维普
