Dykstra Parsons Coefficients and Lorenz Coefficients calculated from core data are traditionally used as indicators of heterogeneity in a reservoir. Modified Lorenz (ML) plots serve as an indicator of heterogeneity and also depict the transmissivity versus the storativity of the payzone. In this work, ML plots are used to study the flow capacity versus the storage capacity of a reservoir, and to divide the reservoir into individual flow units. Production and injection profile logs were used to verify the depths at which CO2 was actually being injected or produced and compared to the depths where a high flow capacity was observed on the ML Plot. Premature production of CO2 and high GOR on producing wells in CO2 floods is attributed to the CO2 being injected and produced in high permeability zones as compared to low or no CO2 injection in low permeability zones. This study proposes a well completion technique using well core data to normalize CO2 injection across various ML defined zones, and thereby improve CO2 conformance and recovery.

High GOR in CO2 flooded reservoirs increases the net and gross utilization of CO2 and may also result in lower vertical sweep efficiency. Controlling the preferential entry of CO2 into high flow capacity regions, and selectively controlling the injection rate into the various flow units of the reservoir can minimize CO2 utilization, increase volumetric sweep efficiency and recovery. This paper presents a simple well completion technique to selectively control CO2 injection into the reservoir for various flow units. The area of flow open to CO2 is controlled by the perforation density. For most practical applications, the perforation density for a flow unit should be inversely proportional to the slope of the flow unit characterized using the ML plots.

You can access this article if you purchase or spend a download.