Borehole Stablity Analysis Of Horizontal Well With Elasto-Plastic Seepage

With the increasing in energy demand, both at home and abroad, in the process of horizontal well technology developing, horizontal wells have become the preferred option. Horizontal wells are the advantages of oil wellbore and reservoir increases the direct contact area. For vertical wells, the reservoir thickness perforation limit its length; and horizontal wells in the length of horizontal plane only and reservoir distribution and technical conditions which are vertical wells perforation length several times, and in a well location on the Hirai saliva can be completed a few, so that an area of significant increase in oil spills.Firstly, the paper studies the role of seepage under the influence of horizontal wells in the surrounding stress, displacement and the gap of the analytical solution of pressure field. Saturated porous rock performance for compressible materials, follow Biot's law. In the Laplace space solution of the second category Bassel function, obtained the results of the analysis. The results reveal the entire scope of poroelastic coupling results, for further study on the stability and rock borehole shear rupture of the internal mechanics have provided the theoretical foundation.Finite element analysis has been made on elastoplastic deformation coupled with fluid flow of a horizontal wellbore. 4 set of numerical calculations were carried out in terms of variation of values of geostress components and variation of the relative position between axis of horizontal wellbore and direction of the maximum horizontal geostress components. 1) at a depth of 1088 meters along the horizontal well axis direction of maximum horizontal principal stress, 2) a depth of 1088 meters horizontal wells at the level of the axis along the smallest principal stress direction, 3) at a depth of 1760 meters horizontal wells along the maximum horizontal axis principal stress direction, 4) at a depth of 1760 meters along the smallest axis of horizontal wells in the level of principal stress direction. Besides, calculations were also carried out for the case of weakest material strength occurs in addition to the normal strength values. Principal results include: 1)Wellbore stability is better for a horizontal well with axial direction in the direction of maximum horizontal geostress component than that with axial direction in the direction of minimum geostress component direction. 2) Plastic region caused by pressure drawdown will increase with the depth of the horizontal wellbore. 3) At the weakest section of the horizontal well bore, plastic deformation could be serious, and consequently it is necessary to take special reinforcement measure to protect wellbore from potential instability.