On separation of EOR /well stimulation effects with consideration of injection effect
This work discusses the problem of separation of effects from different EOR and well stimulation operations performed in the producing well and in the surrounding injection wells in the waterflooded development. Because of interference of effects, the true value of the main treatment might easily be overestimated, or on the contrary, underestimated. In such situations, estimate of base oil production comes to the forefront, however conventionally used draw-down curves and decline curve analysis (DCA) ignore effects from changes in bottomhole pressure before and after treatment and water injection rates. Model studies to calculate base oil production might be a good solution, however, because of the too long run time and rapid aging of data, prompt estimate is challenging and so are the responsive remedial in-field operations. Conventional approach to assess efficiency of stimulation treatment based on DCA is compared with the results of the numerical experiment using reservoir simulator. It has been shown that underestimation of injection wells’ effect while decline curve analysis results in considerable errors in calculation of incremental oil production. For a prompt assessment of separation of treatments’ effects, the authors suggest using capacitance-resistance models (CRM), which are analytical solutions of the material balance equations. It has been shown that CRM models can significantly improve the accuracy of assessment of treatment efficiency. Furthermore, the offered approach makes it possible to estimate efficiency of the conformance control operations taking into consideration the actual well interference coefficients.