document preview

Abstract

The Opportunity Index Analysis is an intelligent method that uses numerical simulation models to identify zones with high potential of production, which with conventional reservoir engineering often represents a too complex and time consuming problem. This method reduces dramatically the required resources and the uncertainty to define these zones, being a practical tool to support the field development plan.

The producer potential of an area is calculated based on the basic rock and fluid properties, as well as the energy capacity associated with the reservoir pressure.  All those parameters are combined and normalized, to generate the “Opportunity Index” between 0 and 1, capable to identify the zones of greater potential.

In order to calculate this index, three main variables are considered. First, the flow capacity of the rock, which combines the thickness of the cell with its effective permeability (k*h); the second is the hydrocarbon pore volume mobile (HCPVm), associated to the rock-fluid system, and the third is the gradient pressure of the reservoir, defined as the difference between the reservoir and the abandonment pressures.  

One of the products of  the methodology are the time depending Opportunity Index Maps by layer, that represents a invaluable tool in the optimization of secondary recovery processes as well as to define unsweep zones due to the low volumetric sweep efficiency or pressure equilibrium between wells.  Those zones will be candidates for infill drilling, new wells geologically optimized or well production-injection patterns improvement.

The methodology was implemented with a commercial numerical simulator and applied in three mature reservoirs of the Neuquén Basin of Argentina. 3D maps were generated to identify sweet spots in the fields with time in order to define the most appropriate locations that may still have reserves to be produced, and a optimize exploitation plans were designed.

The Opportunity Index Analysis can play an important role in identifying new opportunities in mature fields and optimize the resources.  In this paper, the new methodology is introduced and its application in three mature fields was demonstrated.

Introduction

The Opportunity Index is a variable calculated as a function of the basic rock and fluid properties, as well as the energetic capacity derived from the reservoir pressure which combined can discover the zones of higher prospectivity to be exploited increasing the success in the design of the development plan. To reach this objective, it is necessary to rely on a numerical simulation model that allow to calculate the Opportunity Index for every time step which can go from the beginning of the reservoir exploitation, its development, forecasts up to his depletion. This method of calculation allows selecting and ranking the locations to drilling as well as determining the opportunities of recompletion of existing wells using maps in 2D and visualizations in 3D. The most important moment to implement this index is at the end of the history match or the forecast of production to design the immediate exploitation plan

The calculation of this index can be done for more than one sedimentary facie, block or regions for having different production mechanisms, abnormal pressures or other characteristics that define them as independent saturation regions, nevertheless the methodology will be explained based on a single saturation region, for a multiregional case the procedure can be repeated an many times as is required.