The application of the recent technique of creating lateral tunnels by acid jetting into the formation has been a topic of discussion in Petrobras because it is a reliable, fast an economic way to increase the well productivity index in complex geology carbonate reservoirs. In order to evaluate this technology, a pioneer intervention was carried out in the Garoupa field on a typical offshore well in Brazil. The objective was to simultaneously increase oil production and decrease water cut, by creating lateral tunnels at specific points in the well open hole section. The number of tunnels created as well as their positions were defined as a function of both, oil and water saturation profiles. Also mineralogical and geomechanical analysis were conducted as well as rock dissolution on different hydrochloric acid concentrations, in order to determine tunnel perforation rate and hole stability, The application of this technology has generated important incomes to the oil operator and the same technique could be also applied on other different scenarios. This paper illustrates the process from selecting the well candidate, premilary laboratory tests, treatment designs and field operation to after treatment well production results.

Stress reorientation is an important issue for the cuttings injection batching, refracturing design and stimulation candidate well selection. Long term production/injection causes the principal stresses to reorient. Temperature differences and pore pressure differentials induce thermal elastic stress and poroelastic stresses. These induced stresses are the fundamental reasons for the reorientation of the stress field. A model and numerical scheme are developed to study the effects of thermal differentials and pressure differentialss on stress reorientation. The model couples thermal diffusion and convection with hydraulic diffusion to obtain the temperature distribution reflecting the cumulative impact. The effective poro-elastic and thermo-elastic stresses result from the 1-D displacement equilibrium equations in a radial system. The 3-D in-situ analytical effective stress is superimposed on the 1-D solution. Application of this methodology simplifies the modeling of the 3-D stresses in a deviated borehole. The method makes it practical to obtain the stress distribution at any given injection/production time. The thermal stress and poro-elastic stress effects on the stress reorientation are compared and evaluated. Field examples are presented to show that in some cases the thermal stresses play an important role on stress reorientation. The quantified results of the model will give guidance on fracture treatments and well plans during injector or producer construction.