New Approach to Estimate Reservoir Complexity Index for West Siberian Fields

Abstract

The main purpose of this project became a creation of the reservoir complexity index calculation method. This index should integrate the whole complex of geological characteristics which work on the reservoir engineering complexity in one value. The article describes the approach to calculation the reservoir complexity index based on the Gaspromneft Company's assets using simplified simulation. This index allows you to conduct an express assessment of the field potential and is useful in the process of benchmarking the fields of the Company or the region. We analyzed widespread available approaches of figuring the complexity index (RCI) in which RCI acts as a function of a number of parameters affecting the Recovery Factor (RF). Then based on results of analysis a new advanced approach was submitted that takes into account, in addition to the main geological characteristics of the formation, the indices of layered and lateral inhomogeneity expressed in numerical form During the next stage was realized the multivariate statistical modelling with 2D-simulator on the stream-line that is necessary for obtaining real function connection RF=f(RCI). For the simulation, statistical data of the fields of Western Siberia (Gazprom Neft Company) were used. Then with use of gradient method were matched weighing coefficients of equation linear regression expressing RCI as a function of its parameters. As a result, a set of equations (linear regressions) with a different number of variables and different weight coefficients was obtained. These equations make it possible to calculate the field complexity factor for different sets of input data, as well as for different methods and development systems, operating conditions for the deposit, well completion types, field development periods, etc. RCI for the company's fields was evaluated and noted the high convergence of project RF data with theoretical dependence found out earlier. At the same time, it was noted that for a number of Company's fields with a high index of complexity, the values of project RF could be unjustly uprate. This approach was used for the benchmarking of the Company's fields and proved to be a good express method for assessing the field potential. The aspects considered in the article are related to the new and quite unknown area in Russian speaking segment of OnePetro library. The novelty of the approach is to use a set of simplified simulation models to obtain the linear regression equation, and also to take into account in this equation the indices of reservoir heterogeneity in numerical form. It is also a point of interest to apply this approach in conditions of deposits in Western Siberia.