Numerical Investigation of EOR Applications in Unconventional LiquidReservoirs through Surfactant-Assisted Spontaneous Imbibition SASI andGas Injection Following Primary Depletion

摘要

Surfactant-Assisted Spontaneous Imbibition(SASI)and gas injection have been proven to improveproduction from Unconventional Liquid Reservoirs(ULR).However,the novelty of the method has resultedin a few publications to date.This study utilizes numerical modeling to upscale laboratory data of SASIfor completion purposes and gas injection plus SASI for EOR.Novel gas and aqueous-phase injectionstrategies following primary depletion are designed based on actual completion and production data.Multiple sequencing configurations for both surfactant and gas injection are tested to propose the bestcombined-EOR scheme for ULR.Parameters related to the mechanism of SASI and gas injection are retrieved from CT-generated core-scale model of laboratory experiments.SASI and gas injection experimental results were upscaled to modelproduction response of a hydraulically fractured well with realistic fracture geometry and conductivity.Thecore-scale model was created to determine the diffusion coefficient,relative permeability,and capillarypressure curves by history-matching the laboratory data.The field-scale model was developed with a dual-porosity compositional model to predict production enhancement for various combined-EOR schemes inULR.Wettability and IFT alteration are the two primary mechanisms for SASI in enhancing production.Experimental studies revealed that surfactant solution recovered up to 30% OOIP,whereas water alone onlyrecovered approximately 10% OOIP.Capillary pressure and relative permeability constructed from scalinggroup analysis and core-scale numerical models showed that surfactant addition enhances the two curves.On the other hand,gas injection EOR was found to be driven by multi-contact miscibility and diffusion.Parameters related to both methods were applied to the field-scale model for multiple completion and EORschemes.Results demonstrate that the combination of SASI and gas injection possesses significant potentialin improving production rates and estimated ultimate recoveries(EUR)in ULR.Soak times,surfactantconcentration,injection pressure,duration of the cycle,and cumulative gas injection control the level ofenhancement.With a large number of control variables,specific customizations can be optimized to suitcriteria of different field applications.