Deformation Processes in Reservoir Engineering of the Limestone and their Influence on the Engineering Calculations

Abstract

Abstract In the process of developing hydrocarbon deposits in terms of changing baric conditions, not only formation fluids are transformed, but also the rock itself, which possesses elastic properties and is capable of deforming. The article presents approaches to identifying, analyzing and interpreting the manifestations of deformation processes in the development of hydrocarbon deposits in the limestones of the Republic of Belarus. The article presents the methods for the justification and calculation of the values of critical pressures at which the deformation processes in the beds or formations appear. The main methods by which critical pressure values were determined were: a method for assessing of the critical bottomhole pressure based on the interpretation of well-test (change in productivity during the removal of PC); a method for determining the critical reservoir pressure, taking into account the construction of specific selection curves for closed deposits; a direct laboratory method for determining critical effective pressures, which significantly reduces permeability, which is associated with deformation processes (studies should be carried out at a constant sample crushing pressure and a variable pore pressure). Deformation processes significantly (by several orders of magnitude) reduce permeability and are not reversible. In this case, the presence of these processes is noted both in the test of individual wells, and in the process of developing the whole deposit. It is noted that according to the results of studies in 63% of cases, the decrease PI with increasing depression is associated with deformations in the bottomhole zone. Knowledge of these pressure values allows the correct application of the material balance method to assess hydrocarbon reserves and adapt hydrodynamic reservoir models, to plan efficiently and rationally the implementation and modernization of reservoir pressure maintenance systems and also to predict the change depending on the pressure of the productive characteristics of the wells. The new thing of this work is in identification and systematizing cases of deformation processes in the limestones of the Republic of Belarus, to justify simple methods for understanding and implementing methods for determining the critical values of pressures at which deformation of collectors occurs. A new method for estimating the reservoir type by the capacitive component is proposed, which evaluates the compressibility of the capacitance during the deformation process, as well as the capacitance volume susceptible to deformation.