This study defines and investigates the Hydraulic Interwell Connectivity (HIC) concept to characterize and estimate the reservoir connectivity. This approach is an integrated study of reservoir characterization, geostatistics, production performance and reservoir engineering. In this study HIC is quantitatively defined as the ratio of observed fluid flow rate to a maximum possible (ideal) flow rate between any combination of any two wells in the producing unit. The spatial distribution of HIC was determined for the net pay of a reservoir by geostatistics. It was used as a guide for selecting infill well locations to optimize waterflood infill drilling. A low permeability carbonate reservoir producing unit, J.L. Johnson "AB" was used to illustrate the application of HIC. In simulation study, three production wells 27, 107 and 109 were realigned according to HIC distribution which resulted in an additional 10% (10,000 STB) of waterflood oil recovery. Introduction Infill drilling can significantly improve waterflood recovery efficiency in most of the low permeability heterogeneous reservoirs. To maximize the economic return, we need a practical approach to design and implement an optimal infill drilling program. The well spacing reduction from infill drilling improves the reservoir connectivity between the wells, thereby enhances the oil recovery. Both well spacing and reservoir heterogeneity are the major controlling factors of reservoir connectivity. The profitability of infill drilling program is impacted by proper reservoir description and characterization. Study shows that reservoir description and characterization has a big influence on development strategies and reservoir management decisions. Reservoir description and characterization include the proper geological modeling of reservoir and determination of petrophysical properties by conventional and/or geostatistical approaches. Most of the reservoirs especially carbonate reservoirs are characterized by extreme heterogeneity of petrophysical properties, which require an integrated geological-engineering studies. The conventional geological approach of reservoir description uses interpolation technique based on the geometric distance of samples, while geostatistical technique is based on orientation and correlation. The geological environment models and reservoir parameters are controlling factors for accurate reservoir description and characterization. Reservoir connectivity was poorly defined in the literature. It was defined qualitatively, based on either the geological characteristics of the reservoir or the engineering aspect of the reservoir performance. This paper addresses the importance of interwell connectivity and a multidisciplinary approach to optimize waterflood infill drilling. It describes a new approach to define reservoir connectivity based on geological-engineering study. It uses the experimental semi-variograms to identify the variation of reservoir permeability and fits the variogram models to the experimental correlations. It uses conventional and geostatistical methods to obtain reservoir properties for simulation study. It uses HIC to determine the degree of communication between injectors and producers to determine the optimal locations for infill wells. P. 119^

This paper presents the use of hydraulic interwell connectivity concepts to characterize the reservoir for waterflood performance evaluation. These hydraulic interwell connectivity concepts are presented in terms of two indices: The Interwell Flow Capacity Index (IFCI) and the Hydraulic Interwell Connectivity Index (HICI). This approach utilizes the reservoir flow capacity and production/injection performance data to calculate the IFCI and HICI. The spatial distribution and correlations of these indices are useful to evaluate the reservoir characteristics for waterflood design and performance analysis. A Colombian (South America) sandstone reservoir in La Cira Field is used to illustrate the application of these concepts.

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This paper presents a new and practical methodology to identify the flow units in a mappable geological formation. This approach uses Interwell Flow Capacity Index (IFCI) to describe the flow unit. IFCI is defined as the ratio of actual flow rates (production or injection) in any two wells in a producing unit, with the higher fluid flow rate of the two wells in the denominator. The presented approach uses core, log and production-injection data to describe the variations in reservoir connectivity. The flow units are identified and described by the use of IFCI1. A flow unit is identified by the similarities between IFCI's calculated by using petrophysical and production-injection data. A Colombian (South America) sandstone, La Cira Field "C1C unit", is used to illustrate the application of IFCI to identify and describe flow units.

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