Evaluation of formation damages during filter cake deposition and removal process:The effect of primary damage on secondary damage

The properties of oil and gas formation could be significantly damaged during drilling and completion operations as a result of mud invasion,fluid incompatibility and interaction with rock minerals.This paper presents a systematic method for evaluating formation damage during filter cake deposition(primary damage)and removal process(secondary damage).The role of primary damage in the evolution of secondary damage was also investigated.The interaction of the filter cake solvent(chelating agent solution)with the rock samples was implemented through core flooding experiment.Nuclear Magnetic Resonance(NMR)was used to evaluate the properties of the rock sample,pre and post filter cake deposition and removal processes.The results show that secondary damaged is a strong function of the location and the intensity of the primary damage.The rock type and its pore structure also play important roles in both primary and secondary damage.The extent of secondary damage depends on the amount of barium sulphate deposited during primary damage.The chelating agent used to dissolve the barites in sandstones,deposited the barite in the small pores while it enlarges the bigger pores.In contrast,the chelating agent in the carbonate samples had multiple barite deposition points.

Statistical prediction of waterflooding performance by K-means clustering and empirical modeling

Statistical prediction is often required in reservoir simulation to quantify production uncertainty or assess potential risks.Most existing uncertainty quantification procedures aim to decompose the input random field to independent random variables,and may suffer from the curse of dimensionality if the correlation scale is small compared to the domain size.In this work,we develop and test a new approach,K-means clustering assisted empirical modeling,for efficiently estimating waterflooding performance for multiple geological realizations.This method performs single-phase flow simulations in a large number of realizations,and uses K-means clustering to select only a few representatives,on which the two-phase flow simulations are implemented.The empirical models are then adopted to describe the relation between the single-phase solutions and the two-phase solutions using these representatives.Finally,the two-phase solutions in all realizations can be predicted using the empirical models readily.The method is applied to both 2D and 3D synthetic models and is shown to perform well in the P10,P50 and P90 of production rates,as well as the probability distributions as illustrated by cumulative density functions.It is able to capture the ensemble statistics of the Monte Carlo simulation results with a large number of realizations,and the computational cost is significantly reduced.

Effect of ammonium based ionic liquids on the rheological behavior of the heavy crude oil for high pressure and high temperature conditions

Heavy crude oil(HCO)production,processing,and transportation forms several practical challenges to the oil and gas industry,due to its higher viscosity.Understanding the shear rheology of this HCO is highly important to tackle production and flow assurance.The environmental and economic viability of the conventional methods(thermal or dilution with organic solvents),force the industry to find an alternative.The present study was constructed to investigate the effect of eco-friendly ionic liquids(ILs)on the HCO's rheology,at high temperature and high pressure.Eight different alkyl ammonium ILs were screened for HCO's shear rheology at the temperatures of 25-100℃ and for pressures 0.1e10 MPa.The addition of ILs reduced the HCO's viscosity substantially from 25 to 33%from their original HCO viscosity.Also,it aids to reduce the yield stress to about 15-20%at all the studied experimental conditions.Furthermore,the viscoelastic property of the HCO was studied for both strain-sweep and frequencysweep and noticed the ILs helps to increase HCO's loss modulus(G00)by reducing storage modulus(G0),it leads to the reduction of the crossover point around 25-32%than the standard HCO.Mean the ILs addition with HCO converts its solid-like nature into liquid-like material.Besides,the effect ILs chain length was also studied and found the ILs which has lengthier chain length shows better efficiency on the flow-ability.Finally,the microscopic investigation of the HCO sample was analyzed with and without ILs and witnessed that these ILs help to fragment the flocculated HCO into smaller fractions.These findings indicate that the ILs could be considered as the better alternative for efficient oil production,processing,and transportation.

Red/NIR/SWIR multi-band persistent luminescent nanoparticles as ultrasensitive multi-channel tracers in water and crude oil/water emulsions

We report the use of CaTiO_(3):Pr^(3+)multiband persistent luminescent nanoparticles,which can simultaneously emit red(610 nm),near-infrared(893 nm),and short-wave infrared(1040 nm)photoluminescence and persistent luminescence,as the tracer nanoagents for water tracer sensing.By using a spectrofluorometer,an Si charge-coupled device(CCD)camera and an InGaAs array camera as the detection tools,we evaluated the sensing capabilities of the three emission bands of CaTiO_(3):Pr^(3+)nanoparticles in brine water solutions and crude oil/brine water emulsions in both photoluminescence mode and persistent luminescence mode.Among these different detection combinations,the persistent luminescence-based Si CCD camera imaging exhibits the best sensing performance with the detection limits being at a single-digit ppb level for the 610 and 893 nm bands and about 100–200 ppb for the 1040 nm band in both water solutions and crude oil/water emulsions,while the photoluminescencebased Si CCD camera imaging has a much higher detection limit of~10 ppm in water solutions and of~200 ppm in oil/water emulsions.The persistent luminescence-based InGaAs array camera imaging to the 1040 nm band has the worst performance with the detection limits higher than 200 ppm for both solutions.The sensing performances of the spectrofluorometer to photoluminescence signals and persistent luminescence signals in the two solutions are about the same,with the detection limits being around 100–200 ppm.

Oil-water interfacial tension, wettability alteration and foaming studies of natural surfactant extracted from Vernonia Amygdalina

Surfactant flooding is an enhanced oil recovery(EOR)method for recovering residual oil in the reservoir through mechanism of interfacial tension(IFT)reduction and wettability alteration.Due to toxicity and high cost associated with conventional surfactants,recent research has focussed on developing low-cost and environmentally benign surfactants.Herein,a low-cost green surfactant is extracted from Vernonia Amygdalina(VA)and appraised for EOR applications.The extracted surfactant was characterized using Fourier Transform Infrared(FTIR)and High-Pressure Liquid Chromatography(HPLC).The IFT of the synthesized surfactant at the oil-water interface was determined using Kruss tensiometer.Additionally,the foam stability of the synthesized surfactant was examined.Moreover,the wettability of the saponin based natural surfactant(SBNS)at the rock-fluid interface was analysed using Dataphysics drop shape analyser.Experimental result revealed that SBNS(1 wt%concentration)stabilized foam for longer periods with half-life of 1100 min.Furthermore,the synthesized surfactant was effective in lowering the IFT of oil-water interface from 18 mN/m to 0.97 mN/m.Finally,SBNS altered the wettability of sandstone cores to water-wetting condition by reducing the contact angle from 118.5° to 45.7°.Overall,SBNS exhibit excellent properties desirable for EOR and thereby recommended as supplementary alternative to conventional surfactants.

Impact of methane adsorption on tight rock permeability measurements using pulse-decay

The permeability of the rock is usually measured by the injection of gas using Darcy's flow model(pulse-decay).For oil formations,helium and nitrogen are the most common gases used to measure the permeability of the rock.However,recent approaches are based on the use of methane as it minimizes the properties difference between the testing fluid and reservoir fluid.This work focused on the latter approach to compute the correction of gas adsorption.The most widely used model is Cui et al.model that is based on Langmuir adsorption isotherm.In this work,we introduced a modified model that is based on Freundlich isotherm.This model also includes the correction for gas adsorption such as Freundlich isotherms proved to be more appropriate for the adsorption on intact reservoir rock.The model is based on gas and rock properties and reduced pressure and temperature were used to accommodate the gas compressibility.The modified model can also capture effective porosity of adsorption(a)that can correct the pulse-decay storage capacity parameters a and b.The permeability estimation of ultra-tight samples using the modified approach is enhanced owing to the correction in the storage volume and rock porosity.Including the proper adsorption isotherm enhanced the porosity estimation because Langmuir isotherm yielded 11%porosity and Freundlich isotherm yielded 12%porosity.Similar results were obtained in the permeability estimation,Langmuir isotherm resulted in a 1.5%error compared to zero error in the Freundlich isotherm estimation.