Consideração do repasse à modelagem do fechamento de poços verticais em rochas salinas

Abstract

One of the challenges in petroleum exploration in deep water is the presence of salt rocks during drilling, which implies possible operational complications during the drilling of wells. Due to their mobility, the salt rocks may cause problems such as the stuck pipe, high torques, casing collapse and closure of the well promoting enormous losses in different areas.The mud weight generates a hydrostatic pressure that serves as a counterpressure to the displacement of the salt, sometimes this measure is not sufficient, which leads to the backreaming operation. Thus,the diameter of the well is reconditioned to its original predicted state. Given the importance of backreaming during drilling operations in saltrocks, its incorporation into computational tools efficiently is necessary, since decision makingin the face of imminent event unwanted must be rapid. As the salt rocks have the viscoelastic behavior, the Double deformation mechanismis adopted to represent the deformability of the wall of the saline formation.Through theFinite Element Method, a program is developed to identify and simulate the effects of the backreaming in vertical Wells with the presence of salt layers.The simulation may be done by adoption of a one-dimensional axisymmetric layer with unit thickness or na association of one-dimensional multilayers through a coupling strategy between them. The effects of physical properties of the evaporite and the properties of the mesh are checked, as well as the performance of multilayers strategy when compared with a two-dimensional axisymmetric modeling of the problem of closing wells in the commercial software ABAQUS,for which fictitiouss cenários were generated. The comparison is based on the radial displacement histories of the multilayer strategy with and without the interaction consideration indicates similarity with ABAQUS for cases that consider interaction, while the curves of cases with out interaction exhibited a difference, mainly in zones near to material interfaces.