Carbon nanotube enhanced water-based drilling fluid for high temperature and high salinity deep resource development

Drilling fluids face failure during drilling deep reservoir with high temperature and high salt.The experimental results show that high temperature and salinity reduce the negative charge on the surface of bentonite in the drilling fluid and cause the coalescence of bentonite particles.As a result,the particles coalesce,the grid structure is destroyed,and the rheological properties,rock-carrying capacity and filtration properties are lost.To resolve the foregoing,in this study,0.05-wt%carbon nanotubes are introduced into a 4%bentonite drilling fluid under conditions where the temperature and concentration of added Na Cl reach 180°C and 10 wt%,respectively.The carbon nanotubes adsorb on the bentonite surface and increase the space among bentonite particles.The steric hindrance prevents the coalescence of bentonite in high temperature and high salt environment.Thus bentonite maintains the small size distribution of bentonite and supports the bentonite grid structure in the drilling fluid.As a result,the rock-carrying capacity of the drilling fluid increases by 85.1%.Moreover,the mud cake formed by the accumulation of small-sized bentonite particles is dense;consequently,the filtration of bentonite drilling fluid reduced by 30.2%.

Singlet oxygen-dominated peroxymonosulfate activation by layered crednerite for organic pollutants degradation in high salinity wastewater

Advanced oxidation processes have been widely studied for organic pollutants treatment in water,but the degradation performance of radical-dominated pathway was severely inhibited by the side reactions between the anions and radicals,especially in high salinity conditions.Here,a singlet oxygen(^(1)O_(2))-dominated non-radical process was developed for organic pollutants degradation in high salinity wastewater,with layered crednerite(CuMnO_(2))as catalysts and peroxymonosulfate(PMS)as oxidant.Based on the experiments and density functional theory calculations,^(1)O_(2)was the dominating reactive species and the constructed Cu-O-Mn with electron-deficient Mn captured electron from PMS promoting the generation of^(1)O_(2).The rapid degradation of bisphenol A(BPA)was achieved by CuMnO_(2)/PMS system,which was 5-fold and 21-fold higher than that in Mn_(2)O_(3)/PMS system and Cu_(2)O/PMS system.The CuMnO_(2)/PMS system shown prominent BPA removal performance under high salinity conditions,prominent PMS utilization efficiency,outstanding total organic carbon removal rate,wide range of applicable pH and good stability.This work unveiled that the^(1)O_(2)-dominated non-radical process of CuMnO_(2)/PMS system overcame the inhibitory effect of anions in high salinity conditions,which provided a promising technique to remove organic pollutants from high saline wastewater.

Investigation of Electrical Parameters of Fresh Water and Produced Mixed Injection in High-Salinity Reservoirs

Assuming a reservoir with a typical salt-lake background in the Qaidam Basin as a testbed,in this study the var-iation law of the rock electrical parameters has been determined through water displacement experiments with different salinities.As made evident by the results,the saturation index increases with the degree of water injec-tion.When the salinity of the injected water is lower than 80000 ppm,the resistivity of the rock samplefirst decreases,then it remains almost constant in an intermediate stage,andfinally it grows,thereby giving rise to a‘U’profile behavior.As the salinity decreases,the water saturation corresponding to the inflection point of the resistivity becomes lower,thereby leading to a wider‘U’type range and a higher terminal resistivity.For dif-ferent samples,higher initial resistivity of the sample in the oil-bearing state,and higher resistivity after low-sali-nity water washing are obtained when a thicker lithology is considered.

Effect of six kinds of scale inhibitors on calcium carbonate precipitation in high salinity wastewater at high temperatures

Precipitation of calcium carbonate （CaCOs） scale on heat transfer surfaces is a serious and expensive problem widely occurring in numerous industrial processes. In this study, we compared the scale inhibition effect of six kinds of commercial scale inhibitors and screened out the best one （scale inhibitor SQ-1211） to investigate its scale inhibition performance in highly saline conditions at high temperature through static scale inhibition tests. The influences of scale inhibitor dosage, temperature, heating time and pH on the inhibition efficiency of the optimal scale inhibitor were investigated. The morphologies and crystal structures of the precipitates were characterized by Scanning Electron Microscopy and X-ray Diffraction analysis. Results showed that the scale inhibition efficiency of the optimal scale inhibitor decreased with the increase of the reaction temperature. When the concentration of Ca^2＋ was 1600 mg/L, the scale inhibition rate could reach 90.7% at 80℃ at pH 8. The optimal scale inhibitor could effectively retard scaling at high temperature. In the presence of the optimal scale inhibitor, the main crystal structure of CaCOs changed from calcite to aragonite.

Low-tension gas process in high-salinity and low-permeability reservoirs

Polymer-based EOR methods in low-permeability reservoirs face injectivity issues and increased fracturing due to near wellbore plugging,as well as high-pressure gradients in these reservoirs.Polymer may cause pore blockage and undergo shear degradation and even oxidative degradation at high temperatures in the presence of very hard brine.Low-tension gas(LTG) flooding has the potential to be applied successfully for low-permeability carbonate reservoirs even in the presence of high formation brine salinity.In LTG flooding,the interfacial tension between oil and water is reduced to ultra-low values(10^-3 dyne/cm) by injecting an optimized surfactant formulation to maximize mobilization of residual oil post-waterflood.Gas(nitrogen,hydrocarbon gases or C02) is co-injected along with the surfactant slug to generate in situ foam which reduces the mobility ratio between the displaced(oil) and displacing phases,thus improving the displacement efficiency of the oil.In this work,the mechanism governing LTG flooding in low-permeability,high-salinity reservoirs was studied at a microscopic level using microemulsion properties and on a macroscopic scale by laboratory-scale coreflooding experiments.The main injection parameters studied were injected slug salinity and the interrelation between surfactant concentration and injected foam quality,and how they influence oil mobilization and displacement efficiency.Qualitative assessment of the results was performed by studying oil recovery,oil fractional flow,oil bank breakthrough and effluent salinity and pressure drop characteristics.

A novel polymer gel with high-temperature and high-salinity resistance for conformance control in carbonate reservoirs

Plugging agents have been widely used to enhance oil recovery in fractured-vuggy carbonate reservoirs.However,the harsh conditions of fractured-vuggy carbonate reservoirs yield a significant challenge in maintaining a long-term stabilization of plugging agents.In this work,we developed an anti-hightemperature and high-salinity polymer gel(APG)with excellent resistance to high temperature(140℃)and ultra-high salinity(240000 mg/L).The rheology and microstructure of APG were characterized before and after gelation.Core plugging tests on fractured cubic cores were conducted to quantify the plugging performance of the gel system.Experimental results showed that the Sclerglucan and Cobalt(Ⅱ)Chloride Hexahydrate filled the three-dimensional(3-D)network with various morphologies,providing extra protection to the cross-linking points of the 3D network structure of APG and thus,leading to a prolongation of the dehydration time.The dehydration rate of APG was only 5%within 30days,and the strength of APG could be maintained at a rigid or near-rigid level over 150 days.Moreover,APG exhibited satisfactory shear and scour resistance.Core plugging tests showed that APG could achieve a plugging rate of 90%and demonstrate ignorable minor damage to the substrate.Our results indicate that APG can serve as a great candidate in channel plugging in fractured-vuggy carbonate reservoirs where fractures are fully developed.

Enhanced Biodegradation of High-Salinity and Low- Temperature Crude-Oil Wastewater by Immobilized Crude-Oil Biodegrading Microbiota

High salt and low temperature are the bottlenecks for the remove of oil contaminants by enriched crude-oil degrading microbiota in Liaohe Estuarine Wetland(LEW),China.To improve the performance of crude-oil removal,microbiota was further immobilized by two methods,i.e.,sodium alginate(SA),and polyvinyl alcohol and sodium alginate(PVA+SA).Results showed that the crude oil was effectively removed by the enrichment with an average degrading ratio of 19.42-31.45 mg(L d)^(−1).The optimal inoculum size for the n-alkanes removal was 10%and 99.89%.Some members of genera Acinetobacter,Actinophytocola,Aquabac-terium,Dysgonomonas,Frigidibacter,Sphingobium,Serpens,and Pseudomonas dominated in crude-oil degrading microflora.Though the removal efficiency was lower than free bacteria when the temperature was 15℃,SA and PVA+SA immobilization im-proved the resistance to salinity.The composite crude-oil degrading microbiota in this study demonstrated a perspective potential for crude oil removal from surface water under high salinity and low temperature conditions.

Discrepancy in photosynthetic responses of the red alga Pyropia yezoensis to dehydration stresses under exposure to desiccation,high salinity,and high mannitol concentration

Macroalgae that inhabit intertidal zones are exposed to the air for several hours during low tide and must endure desiccation and high variations in temperature, light intensity, and salinity. Pyropia yezoensis (Rhodophyta, Bangiales), a typical intertidal red macroalga that is commercially cultivated in the northwestern Pacific Ocean, was investigated under different dehydration stresses of desiccation, high salinity, and high mannitol concentration. Using chlorophyll fluorescence imaging, photosynthetic activities of P. yezoensis thalli were analyzed using six parameters derived from quenching curves and rapid light curves. A distinct discrepancy was revealed in photosynthetic responses to different dehydration stresses. Dehydration caused by exposure to air resulted in rapid decreases in photosynthetic activities, which were always lower than two other stresses at the same water loss (WL) level. High salinity only reduced photosynthesis significantly at its maximum WL of 40% but maintained a relatively stable maximum quantum yield of photosystem II (PSII) (Fv/Fm). High mannitol concentration induced maximum WL of 20% for a longer time (60 min) than the other two treatments and caused no adverse influences on the six parameters at different WL except for a significant decrease in non-photochemical quenching (NPQ) at 20% WL. Illustrated by chlorophyll fluorescence images, severe spatial heterogeneities were induced by desiccation with lower values in the upper parts than the middle or basal parts of the thalli. The NPQ and rETRmax (maximum relative electron transport rate) demonstrated clear distinctions for evaluating photosynthetic responses, indicating their sensitivity and applicability. The findings of this study indicated that the natural dehydration of exposure to air results in stronger and more heterogeneous effects than those of high salinity or high mannitol concentration.

Highly Efficient Power Conversion from Salinity Gradients with Ion-Selective Polymeric Nanopores

A polymeric nanopore membrane with selective ionic transport has been proposed as a potential device to convert the chemical potential energy in salinity gradients to electrical power. However, its energy conversion efficiency and power density are often limited due to the challenge in reliably controlling the size of the nanopores with the conventional chemical etching method. Here we report that without chemical etching, polyimide （PI） membranes irradiated with GeV heavy ions have negatively charged nanopores, showing nearly perfect selectivity for cations over anions, and they can generate electrical power from salinity gradients. We further demonstrate that the power generation efficiency of the PI membrane approaches the theoretical limit, and the maximum power density reaches 130m W/m2 with a modified etching method, outperforming the previous energy conversion device that was made of polymeric nanopore membranes.

Diagenesis of the Paleogene Sandstones in the DN2 Gas Field,Kuqa Foreland Basin and its Link to Tectonics

We investigated diagenesis of the sandstones from the DN2 Gas Field of the Kuqa Foreland Basin(KFB),in order to infer the timing of fluid migration and discuss the linkage between fluids and tectonics.The textures and chemical composition of authigenic minerals,fluid evidence from fluid inclusions and formation water measurements were all used to fulfill this aim.Eodiagenesis occurred with the participation of meteoric water and connate water.Mesodiagenesis is related to high salinity fluids,which were attributed as originating from the overlying Neogene Jidike Formation evaporite(principal minerals including halite,anhydrite,glauberite,carnallite and thenardite).The onset of high salinity fluid migration is inferred to occur during the late Miocene(12.4-9.2 Ma)through the use of homogenization temperatures measured in the present study and K-Ar dating of authigenetic illites from previous work.This period is consistent with the crucial phase(13-10 Ma)that witnessed the rapid uplift of the southern Tianshan Mts and the stage when calcite and anhydrite veins formed in the studied strata.We thus argue that diagenesis related to high salinity fluids occurred as a response to the Tianshan Mts'rapid uplift and related tectonic processes.The flow of high salinity fluids was probably driven by a density gradient and channeled and focused by fractures formed contemporaneously.

新型缔合聚合物AP调剖体系研制及矿场应用(英文)

A new polymer system, referred to simply as the AP-P4 polymer system, aims at solving the problems of high temperature, high salinity and the poor shearing resistance, all of which are encountered by conventional polymers (such as polyacrylamide) used in profile control, profile performance improvement and EOR operations in the Zhongyuan Oilfield, Sinopec. This system has been developed on the basis of the specific molecular structure and the better properties of high temperature resistance, high salinity resistance and strong shearing resistance of the new type of AP-P4 association polymer. Acidity modifying agents and cross-linking agents (MZ-YL, MZ-BE, MZ-XS), compatible with the new polymer system, are selected. Results of performance tests have shown that the new polymer system has excellent thickening, high temperature, high salinity and shearing resistance and anti-dehydrating properties. In 2003, it underwent its first pilot test in 26 wells in China, with remarkable effects in increasing oil production and decreasing water production. The newly developed polymer system and its application technology described in this paper may play a guiding role in polymer profile control operations in the oil reservoirs of high temperature and high salinity.

Temperature effect on performance of nanoparticle/surfactant flooding in enhanced heavy oil recovery

Recently,nanoparticles have been used along with surfactants for enhancing oil recovery.Although the recent studies show that oil recovery is enhanced using nanoparticle/surfactant solutions,some effective parameters and mechanisms involved in the oil recovery have not yet been investigated.Therefore,the temperature effect on the stability of nanoparticle/surfactant solutions and ultimate oil recovery has been studied in this work,and the optimal concentrations of both SiO2 nanoparticle and surfactant(sodium dodecyl sulfate)have been determined by the Central Composite Design method.In addition,the simultaneous effects of parameters and their interactions have been investigated.Study of the stability of the injected solutions indicates that the nanoparticle concentration is the most important factor affecting the solution stability.The surfactant makes the solution more stable if used in appropriate concentrations below the CMC.According to the micromodel flooding results,the most effective factor for enhancing oil recovery is temperature compared to the nanoparticle and surfactant concentrations.Therefore,in floodings with higher porous medium temperature,the oil viscosity reduction is considerable,and more oil is recovered.In addition,the surfactant concentration plays a more effective role in reservoirs with higher temperatures.In other words,at a surfactant concentration of 250 ppm,the ultimate oil recovery is improved about 20%with a temperature increase of 20°C.However,when the surfactant concentration is equal to 750 ppm,the temperature increase enhances the ultimate oil recovery by only about 7%.Finally,the nanoparticle and surfactant optimum concentrations determined by Design-Expert software were equal to 46 and 159 ppm,respectively.It is worthy to note that obtained results are validated by the confirmation test.

Soil respiration in typical plant communities in the wetland surrounding the high-salinity Ebinur Lake

Soil respiration in wetlands surrounding lakes is a vital component of the soil carbon cycle in arid regions. However, information remains limited on the soil respiration around highly saline lakes during the plant growing season. Here, we aimed to evaluate diurnal and seasonal variation in soil respiration to elucidate the controlling factors in the wetland of Ebinur Lake, Xinjiang Uygur Autonomous Region, western China. We used a soil carbon flux automatic analyzer （LI-840A） to measure soil respiration rates during the growing season （April to November） in two fields covered by reeds and tamarisk and one field with no vegetation （bare soil） from 2015 to 2016. The results showed a single peak in the diurnal pattern of soil respiration from 11：00 to 17：00 for plots covered in reeds, tamarisk, and bare soil, with minimum values being detected from 03：00 to 07：00. During the growing season, the soil respiration of reeds and tamarisk peaked during the thriving period （4.16 and 3.75 μmol.m-2.s-1, respectively）, while that of bare soil peaked during the intermediate growth period （0.74 pmol-m-2-s-1）. The soil respiration in all three plots was lowest during the wintering period （0.08, 0.09, and -0.87 μmol.m-2.s-1, respectively）. Air temperature and relative humidity significantly influenced soil respiration. A significant linear relationship was detected between soil respiration and soil temperature for reeds, tamarisk, and bare soil. The average Q10 of reeds and tamarisk were larger than that of bare soil. However, soil moisture content was not the main factor controlling soil respiration. Soil respiration was negatively correlated with soil pH and soil salinity in all three plot types. In contrast, soil respiration was positively correlated with organic carbon. Overall,CO2 emissions and greenhouse gases had a relatively weak effect on the wetlands surrounding the highly saline Ebinur Lake.

Enhancement of a foaming formulation with a zwitterionic surfactant for gas mobility control in harsh reservoir conditions

This work presents the design of a robust foam formulation that tolerates harsh reservoir conditions(high salinity,high divalent ion concentration,high temperature,light oil,and hydrocarbon injection gas)in a sandstone reservoir.For this,we selected anionic Alpha Olefin Sulfonate(AOS)surfactants and studied their synergistic effects in mixtures with zwitterionic betaines to enhance foam performance.The laboratory workflow used to define the best formulation followed a de-risking approach in three consecutive phases.First,(phase 1)the main surfactant(AOS)was selected among a series of commercial candidates in static conditions.Then,(phase 2)the betaine booster to be combined with the previously selected AOS was chosen and their ratio optimized in static conditions.Subsequently,(phase 3)the surfactant/booster ratio was optimized under dynamic conditions in a porous medium in the absence and the presence of oil.As a result of this study,a mixture of an AOS C14-C16 and cocamidopropyl hydroxysultaine(CAPHS)was selected as the one having the best performance.The designed formulation was proven to be robust in a wide range of conditions.It generated a strong and stable foam at reservoir conditions,overcoming variations in salinity and foam quality,and tolerated the presence of oil.

Microbial electrosynthesis of acetate from CO_(2)under hypersaline conditions

Microbial electrosynthesis(MES)enables the bioproduction of multicarbon compounds from CO_(2)using electricity as the driver.Although high salinity can improve the energetic performance of bioelectrochemical systems,acetogenic processes under elevated salinity are poorly known.Here MES under 35e60 g L^(-1)salinity was evaluated.Acetate production in two-chamber MES systems at 35 g L^(-1)salinity(seawater composition)gradually decreased within 60 days,both under-1.2 V cathode potential(vs.Ag/AgCl)and^(-1).56 A m^(-2)reductive current.Carbonate precipitation on cathodes(mostly CaCO3)likely declined the production through inhibiting CO_(2)supply,the direct electrode contact for acetogens and H2 production.Upon decreasing Ca2t and Mg2t levels in three-chamber reactors,acetate was stably produced over 137 days along with a low cathode apparent resistance at 1.9±0.6 mU m^(2)and an average production rate at 3.80±0.21 g m^(-2)d^(-1).Increasing the salinity step-wise from 35 to 60 g L^(-1)gave the most efficient acetate production at 40 g L^(-1)salinity with average rates of acetate production and CO_(2)consumption at 4.56±3.09 and 7.02±4.75 g m^(-2)d^(-1),respectively.The instantaneous coulombic efficiency for VFA averaged 55.1±31.4%.Acetate production dropped at higher salinity likely due to the inhibited CO_(2)dissolution and acetogenic metabolism.Acetobacterium up to 78%was enriched on cathodes as the main acetogen at 35 g L^(-1).Under high-salinity selection,96.5%Acetobacterium dominated on the cathode along with 34.0%Sphaerochaeta in catholyte.This research provides a first proof of concept that MES starting from CO_(2)reduction can be achieved at elevated salinity.

Pilot test of polymer microsphere alternate surfactant flood(PMAS)with mixtures of anionic-cationic surfactants under harsh conditions in a sandstone reservoir

The first pilot test of polyacrylamide microsphere alternate surfactant flood(PMAS)with mixtures of anionic-cationic surfactants(Sa/c)was carried out for a high-temperature,high-salinity,and highhardness sandstone reservoir to demonstrate the potential of this novel technique to improve oil recovery.A critical micelle concentration(CMC)of 4.82 mg/L,an ultralow interfacial tension(IFT)of 8104 mN/m,and a high oil solubilization of 22 were obtained.Static and dynamic adsorptions of Sa/c on natural core containing 15 wt%clay were reduced to about 2.20 and 0.30 mg/g-core,respectively,with the addition of adsorption inhibitor(AI).Since June 2014,the pilot test of PMAS was carried out in a Sinopec reservoir with a temperature of 87C,a salinity of 260,393 mg/L,and a hardness of 6,401 mg/L.Twelve cycles of alternative injection of 0.0125 PV Sa/c with a concentration of 0.1%and 0.0125 PV polyacrylamide microsphere with a concentration of 0.2%were conducted at an injection rate of 0.1 PV/yr,for a total of 0.3 PV chemical injection.As a result,the net daily oil production increased from 0 t to 6.5 t,and the water cut decreased from 96.3%to 93.8%,leading to an ultimate improved oil recovery of 6.3%original oil-in-place.

Siderophore-Producing Rhizobacteria as a Promising Tool for Empowering Plants to Cope with Iron Limitation in Saline Soils:A Review

Iron(Fe) bioavailability to plants is reduced in saline soils;however, the exact mechanisms underlying this effect are not yet completely understood. Siderophore-expressing rhizobacteria may represent a promising alternative to chemical fertilizers by simultaneously tackling salt-stress effects and Fe limitation in saline soils. In addition to draught, plants growing in arid soils face two other major challenges: high salinity and Fe deficiency. Salinity attenuates growth, affects plant physiology, and causes nutrient imbalance,which is, in fact, one of the major consequences of saline stress. Iron is a micronutrient essential for plant development, and it is required by several metalloenzymes involved in photosynthesis and respiration. Iron deficiency is associated with chlorosis and low crop productivity. The role of microbial siderophores in Fe supply to plants and the effect of plant growth-promoting rhizobacteria(PGPR) on the mitigation of saline stress in crop culture are well documented. However, the dual effect of siderophore-producing PGPR, both on salt stress and Fe limitation, is still poorly explored. This review provides a critical overview of the combined effects of Fe limitation and soil salinization as challenges to modern agriculture and intends to summarize some indirect evidence that argues in favour of siderophore-producing PGPR as biofertilization agents in salinized soils. Recent developments and future perspectives on the use of PGPR are discussed as clues to sustainable agricultural practices in the context of present and future climate change scenarios.

Ectopic Expression of a Bacterium NhaD-type Na^+/H^+ Antiporter Leads to Increased Tolerance to Combined Salt/Alkali Stresses

AaNhaD, a gene isolated from the soda lake alkaliphile Alkalimonas amylolytica, encodes a Na＋/H＋ antiporter crucial for the bacterium＇s resistance to salt/alkali stresses. However, it remains unknown whether this type of bacterial gene may be able to increase the tolerance of flowering plants to salt/alkali stresses. To investigate the use of extremophile genetic resources in higher plants, transgenic tobacco BY-2 cells and plants harboring AaNhaDwere generated and their stress tolerance was evaluated. Ectopic expression of AaNhaD enhanced the salt tolerance of the transgenic BY-2 cells in a pH-dependent manner. Compared to wild-type controls, the transgenic cells exhibited increased Na＋ concentrations and pH levels in the vacuoles. Subcellular localization analysis indicated that AaNhaD-GFP fusion proteins were primarily localized in the tonoplasts. Similar to the transgenic BY-2 cells, AaNhaD.overexpressing tobacco plants displayed enhanced stress tolerance when grown in saline-alkali soil. These results indicate that AaNhaD functions as a pH-dependent tonoplast Na＋/H＋ antiporter in plant cells, thus presenting a new avenue for the genetic improvement of salinity/alkalinity tolerance.

Optimization of the O_(3)/H_(2)O_(2) process with response surface methodology for pretreatment of mother liquor of gas field wastewater

The present study reports the use of the O_(3)/H_(2)O_(2) process in the pretreatment of the mother liquor of gas field wastewater(ML-GFW),obtained from the multi-effect distillation treatment of the gas field wastewater.The range of optimal operation conditions was obtained by single-factor experiments.Response surface methodology(RSM)based on the central composite design(CCD)was used for the optimization procedure.A regression model with Total organic carbon(TOC)removal efficiency as the response value was established(R^(2)=0.9865).The three key factors were arranged according to their significance as:pH>H_(2)O_(2) dosage>ozone flow rate.The model predicted that the best operation conditions could be obtained at a pH of 10.9,an ozone flow rate of 0.8 L/min,and H_(2)O_(2) dosage of 6.2 mL.The dosing ratio of ozone was calculated to be 9.84 mg O3/mg TOC.The maximum removal efficiency predicted was 75.9%,while the measured value was 72.3%.The relative deviation was found to be in an acceptable range.The ozone utilization and free radical quenching experiments showed that the addition of H_(2)O_(2) promoted the decomposition of ozone to produce hydroxyl radicals(·OH).This also improved the ozone utilization efficiency.Gas chromatography-mass spectrometry(GC-MS)analysis showed that most of the organic matters in ML-GFW were degraded,while some residuals needed further treatment.This study provided the data and the necessary technical supports for further research on the treatment of ML-GFW.