Profile improvement during CO_2 flooding in ultra-low permeability reservoirs

Gas flooding such as CO2 flooding may be effectively applied to ultra-low permeability reservoirs, but gas channeling is inevitable due to low viscosity and high mobility of gas and formation heterogeneity. In order to mitigate or prevent gas channeling, ethylenediamine is chosen for permeability profile control. The reaction mechanism of ethylenediamine with CO2, injection performance, swept volume, and enhanced oil recovery were systematically evaluated. The reaction product of ethylenediamine and CO2 was a white solid or a light yellow viscous liquid, which would mitigate or prevent gas channeling. Also, ethylenediamine could be easily injected into ultra-low permeability cores at high temperature with protective ethanol slugs. The core was swept by injection of 0.3 PV ethylenediamine. Oil displacement tests performed on heterogeneous models with closed fractures, oil recovery was significantly enhanced with injection of ethylenediamine. Experimental results showed that using ethylenediamine to plug high permeability layers would provide a new research idea for the gas injection in fractured, heterogeneous and ultra-low permeability reservoirs. This technology has the potential to be widely applied in oilfields.

Review of permeability evolution model for fractured porous media

The ability to capture permeability of fractured porous media plays a significant role in several engineering applications, including reservoir, mining, petroleum and geotechnical engineering. In order to solve fluid flow and coupled flow-deformation problems encountered in these engineering applications,both empirical and theoretical models had been proposed in the past few decades. Some of them are simple but still work in certain circumstances; others are complex but also need some modifications to be applicable. Thus, the understanding of state-of-the-art permeability evolution model would help researchers and engineers solve engineering problems through an appropriate approach. This paper summarizes permeability evolution models proposed by earlier and recent researchers with emphasis on their characteristics and limitations.

Effect of heterogeneity on engineered water injection in carbonates using five-spot sector model:A numerical study

One of the promising and emerging enhanced oil recovery techniques in both sandstones and carbonates is engineered water injection(EWI).However,few studies discussed the field-scale applications of this technique in heterogeneous carbonate formations.This paper is an extension of our previous work of the EWI technology at core-scale.This research numerically investigates heterogeneity effect on EWI technique in carbonates at field-scale using five-spot models.Three synthetic five-spot sector models were considered including homogeneous,heterogeneous with permeability channeling,and heterogeneous with gravity underride.The results showed that EWI improves both volumetric and displacement sweep efficiencies compared to conventional formation water injection(FWI)for all models investigated.Also,tracer method is recommended for better estimation of volumetric sweep efficiency as opposed to fractional flow method.Moreover,secondary EWI outperforms other techniques including secondary FW and tertiary EWI.In addition,the observed delay in tertiary EWI can be reduced by increasing well injection pressure and sulfate concentration in the engineered water.An optimum sulfate concentration of 25,000 ppm is recommended for achieving the highest oil recovery by EWI.This study gives more insight into understanding the performance of the EWI technique at field-scale.Recommendations for boosting the performance of this technique have been discussed,which assure more certainty and lower risk.

Analytical investigation of laminar flow through expanding or contracting gaps with porous walls

Laminar,isothermal,incompressible and viscous flow in a rectangular domain bounded by two moving porous walls,w hich enable the fuid to enter or exit during successive expansions or contractions is investigated analytically using optimal homotopy asymptotic method(OHAM).OHAM is a powerful method for solving nonlinear problems without depending to the small parameter.The concept of this method is briefly introduced,and it's application for this problem is studied.Then,the results are compared with numerical results and the validity of these methods is shown.After this verification,we analyze the effects of some physical applicable parameters to show the efficiency of OHAM for this type of problems.Graphical results are presented to investigate the influence of the non-dimensional wall dilation rate(a)and pemeation Reynolds number(Re)on the velocity,normal pressure distribution and wall shear stress.The present problem for slowly expanding or contracting walls with weak permeability is a simple model for the transport of biological fuids through contracting or expanding vessels.