Impact of Injection Water Quality on Injectivity - A Lab Study

摘要

Waterflooding is commonly performed in oil wells for pressure support and increased oil production.Different sources of injection water can be used for waterflooding,such as aquifer water,seawater orproduced water.Each of these water sources contain particulates in them that deposit at the injection pointforming both an external filter cake on the reservoir face and an internal cake inside the rock surface.The properties of the external and internal filter cake negatively affect injectivity.In order to identify theoptimum water filtration specs prior to injection,the contribution of different solid particle types present inthe injected water on filter cake properties and injectivity need to be understood.A lab study has been undertaken to gauge the contribution of different solid types,solid sizes,andthe presence of oil droplets on filter cake properties and water injectivity.The solid types tested weresilica/quartz,clay,iron oxide,barium sulfate and calcium carbonate,with and without oil contamination.Membrane tests were conducted to understand the correlation between the porosity and the permeability ofthe external filter cake that forms at the formation face for each particulate type.A heavy slurry of selectedsolid particulate was mixed in brine and was compressed into a membrane under different applied pressures,and the porosity and the permeability of the cake was calculated at each stage.Core tests were designed tolook at the combined effects of the external and internal filter cake on reduction in injectivity.Outcrop cores,representative of the field cores,with similar pore throat size,porosity and permeability were used in thecore tests,as particle bridging at pore throats is a function of the comparison between the injected particlesize and the pore throat size distribution of the reservoir.A slurry of the selected solid particulates in brinewas injected into the core system and the permeability drop across the core was monitored as a function ofinjected water pore volumes.Both types of tests were repeated in the presence of oil contamination in theinjected water.The test data from the membrane tests and the core tests were used in the numerical modelto obtain the permeability reduction function for the internal and external filter cake.