RESEARCH ON OPTIMAL OPERATION OF WATER PRODUCING SYSTEM

Basing on a viewpoint of all sided water producing system,a comprehensive analysis of the operation status and the relationship between each working unit in water producing system,including coagulation,sedimentation and filtration etc.was made.By investigating the influence of backwashing consumption,the amount of sludge ejected from sedimentation tank and coagulant ratio upon the cost,the cost effective function of the system was presented.Afterwards,the solution was found out and the corresponding computer program was developed.When applied with real world data,it proved that this method significantly reduced the water producing cost.

Purification of Produced Water from a Sour Oilfield in South Kuwait. 2. Oil-Water Separation and Crystallization of Calcium Carbonate

Oil-water separation for produced water (PW) originating from an oil extraction site in South Kuwait was carried out using bleached, esterified cellulosic material from used coffee grounds. Thereafter, earth-alkaline metal ions, specifically calcium ions, of the de-oiled PW were removed by precipitation with sodium carbonate to give access to pure sodium chloride as industrial salt from the remaining PW. While the purity of the precipitated calcium carbonate (CaCO3) depends on the precipitation conditions, CaCO3 of up to 95.48% purity can be obtained, which makes it a salable product. The precipitation of CaCO3 decreases the amount of calcium ions in PW from 11,300 ppm to 84 ppm.

Purification of Produced Water from a Sour Oilfield in South Kuwait. 1. Oil-Water Separation and Industrial Salt Production

Produced water from an oil extraction site in South Kuwait was sampled after primary oil – water separation had been carried out. The produced water was filtered through a mixture of activated charcoal and esterified cellulosic material gained from spent coffee grounds as a tertiary adsorption treatment. The earth-alkaline metal ions and heavy metals were separated from the de-oiled produced water by addition of either sodium or potassium hydroxide in the presence of carbon dioxide or by direct addition of solid sodium carbonate. The resulting filtrate gave salt of industrial purity upon selective crystallization on evaporation.

Variability in Quantity and Salinity of Produced Water from an Oil Production in South Kuwait

Produced water (PW) is the largest waste stream in the oil and gas industry. Water remains trapped for millions of years in the reservoir with oil and gas. When a hydrocarbon reservoir is infiltrated by a production well, the produced fluids commonly contain water. The understanding of this water’s constituents and volumes is vital for the sustainable continuity of production operations, as PW has a number of negative impacts on the infrastructure integrity of the operation. On the other hand, PW can be an alternative source of irrigation water as well as of industrial salt. Interestingly, both the quantity as well as the quality of PW do not remain constant but can vary, both progressively and erratically, even over short periods of time. This paper discusses such a situation of variable PW in an oil and gas operation in the State of Kuwait.

Kinetic Performance of Oil-field Produced Water Treatment by Biological Aerated Filter

The biological aerated filter （BAF） was used to treat the oil-field produced water. The removal efficiency for oil, COD, BOD and suspended solids （SS） was 76.3%-80.3%, 31.6%-57.9%, 8.6.3%-96.3% and76.4%--82.7%, respectively when the hydraulic loading rates varied from 016m·h^-1 to 1.4m·h^-1. The greatest partof removal, for example more than 80% of COD removal, occurred on the top 100cm of the media in BAF. The kinetic .performance of BAF indicated that the relationship of BOD removal efficiency with the hydraulic loadingrates, in biological aerated filters could be described by c1/c1=l-exp（-2.44/L^0.59）. This equation could be used topredict the B OD.removal efficiency at different hydraulic loading rates.

Flux enhancement during ultrafiltration of produced water using turbulence promoter

Concentration polarization and membrane fouling remain one of the major hurdles for the implementation of ultrafiltration of produced water. Although many applications for ultrafiltration were already suggested, only few were implemented on an industrial scale. Among those techniques, turbulence promoter can be more simple and effective in overcoming membrane fouling and enhancing membrane flux. As for the result that turbulence promoter increase fluid velocity, wall shear rates and produce secondary flows or instabilities, the influence of turbulence promoter was investigated on permeate flux during produced water ultrafiltration and the potential application of this arrangement for an industrial development. Experimental investigations were performed on 100 KDa molecular weight cut-off PVDF single-channel tubular membrane module using four kinds of turbulence promoters. It is observed that the significant flux enhancement in the range of 83%--164% was achieved while the hydraulic dissipated power per unit volume of permeate decreased from 31%--42%, which indicated that the using of turbulence promoter is more efficient than operation without the turbulence promoter. The effects of transmembrane pressure and cross-flow velocity with and without turbulence promoter were studied as well. Among the four kinds of turbulence promoters, winding inserts with 20.0 mm pitch and 1.0 mm wire diameter showed better performances than the others did.

Influences of water treatment agents on oil-water interfacial properties of oilfield produced water

The emulsion stability of oilfield produced water is related to the oil-water interfacial film strength and the zeta potential of the oil droplets. We investigated the effects of water treatment agents （corrosion inhibitor SL-2, scale inhibitor HEDP, germicide 1227, and flocculant polyaluminium chloride PAC） on the stability of oilfield produced water. The influence of these treatment agents on oil-water interfacial properties and the mechanism of these agents acting on the oilfield produced water were studied by measuring the interfacial shear viscosity, interfacial tension and zeta electric potential. The results indicated that the scale inhibitor HEDP could increase the oil-water interfacial film strength, and it could also increase the absolute value of the zeta potential of oil droplets. HEDP played an important role in the stability of the emulsion. Polyaluminum chloride （PAC） reduced the stability of the emulsion by considerably decreasing the absolute value of the zeta potential of oil droplets. Corrosion inhibitor SL-2 and germicide 1227 could decrease the oil-water interfacial tension, whereas they had little influence on oil-water interfacial shear viscosity and oil-water interfacial electricity properties.

Geochemical Characters of Water Coproduced with Coalbed Gas and Shallow Groundwater in Liulin Coalfield of China

To reveal the geochemical characters of water coproduced with coalbed gas and shallow groundwater,water samples were collected from 12 wells of coalbed methane and 7 wells of shallow groundwater.The pH,CODMn,fCO2,total dissolved solids （TDS）,total hardness,and concentrations of metasilicic acid,sodium and kalium,calcium ion,magnesium ion,ammonium iron,bicarbonate ion,carbonate,chloride,sulfate ion,nitrate ion,fluoride,lithium,zinc,nickel,manganese,iron,boron,barium,etc.of the samples were measured.Research results showed the following：（1） Concentrations of TDS,chloride,fluoride,sodium and kalium,ammonium,iron,and barium in the water coproduced with coalbed gas exceeded the national standards of China; however,physical,chemical,and biological properties of shallow groundwater could meet the national standard.（2） The water produced from coalbed contained mainly Na-Cl·HCO3,with average TDS of 4588.5 ppm,whereas shallow groundwater contained a mixture of chemicals including Na.Mg.Ca-HCO3·SO4 and Na.Mg-HCO3·SO4,with average TDS of 663.8 ppm.（3） In general,it was observed that bicarbonate and sodium accumulated in a reducing environment and deeper system,while depletion of hydrogen ions and dissolution of sulfate,calcium,and magnesium occurred in a redox environment and shallow system.（4） Sodium and kalium,ammonium,chloride,and bicarbonate ions were the main ions found in the study area.

Bioflocculant Produced by Klebsiella sp. MYC and Its Appli-cation in the Treatment of Oil-field Produced Water

Seventy-nine strains of bioflocculant-producing bacteria were isolated from 3 activated sludge samples. Among them, strain MYC was found to have the highest and stable flocculating rate for both kaolin clay suspension and oil-field produced water. The bacterial strain was identified as Klebsiella sp. MYC according to its morphological and biochemical characteristics and 16SrDNA sequence. The optimal medium for bioflocculant production by this bacterial strain was composed of cane sugar 20 g L^-1, KH2PO4 2 g L^-1, K2HPO4 5 g L^- 1, （ NH4）2SO4 0.2 g L^-1, urea 0.5 g L^- 1 and yeast extract 0.5 g L^- 1, the initial pH being 5.5. When the suspension of kaolin clay was treated with0.5% of Klebsiella sp. MYC culture broth, the flocculating rate reached more than 90.0% in the presence of 500mg L^-1 CaCI2, while the flocculating rate for oil-field produced water was near 80.0% in a pH range of 7.0 - 9.0 with the separation of oil and suspended particles from the oil-field produced water under similar conditions. The environment-friendly nature of the bioflocculant and high flocculating rate of the strain make the bioflocculant produced by Klebsiella sp. MYC an attractive bioflocculant in oil-field produced water treatment.

Oilfield produced water treatment in internal-loop airlift reactor using electrocoagulation/flotation technique

Oilfield produced water is large quantities of salty water trapped in underground formations and subsisted under high temperatures and pressures that are brought to the surface along with oil during production. Produced water(PW) contains a lot of pollutants such as hydrocarbons and metals, this water must be treated before disposal. Therefore, different techniques are being used to treat produced water. Electrocoagulation is an efficient treatment technique involving the dissolution of anodes and formation of electro-coagulants, while the simultaneous generation of H_2 bubbles at the cathode leads to the pollutant removal by flotation. Electrocoagulation(EC)method is one of the most promising and widely used processes to treat oilfield produced water. In the present work, a conventional internal-loop(draught tube) airlift reactor was utilized as electrocoagulation/flotation cell for PW treatment by inserting two aluminum electrodes in the riser section of the airlift reactor. The EC airlift reactor was operated in a batch mode for the liquid phase. Different experimental parameters were studied on the oil and turbidity removal efficiencies such as current density, initial pH, electrocoagulation time, and air injection.The experimental results showed that mixing of the oil droplets in the PW was accomplished using only the liquid recirculation resulted by H_2 microbubbles generated by EC process which enhanced the oil removal. The experimental results further showed that the EC time required achieving ≥ 90% oil removal efficiency decreases from 46 to 15 min when operating current density increases from 6.8 to 45.5 mA·cm^(-2). This reactor type was found to be highly efficient and less energy consuming compared to conventional existing electrochemical cells which used mechanical agitation.

Progression of injectivity damage with oily waste water in linear flow

Numerous laboratory experiments and field cases show that even very small amount of oil in injected water can cause severe injectivity damage. Although injectivity decline caused by oil droplets has been studied experimentally, there is still lack of an easy-to-use and widely accepted model to predict the decline behavior. In this work, we developed an analytical model to predict the time-dependent progress of the water permeability reduction in linear flow by analyzing experimental data obtained from linear core flooding. The model considers mass transfer of the oil phase from the produced water to the rock due capture effects by dispersion, advection and adsorption inside the rock. As the captured oil saturation increases, permeability reduces following the relative permeability drainage relationship. The reduction stabilizes when the oil saturation comes to an equilibrium value controlled by oil droplet size and injection velocity. The model is calibrated using published experimental data from prolonged core floods with oil- contaminated waste water. Theoretical runs of the model replicate all the effects known from experimental observations. Resulting from the model is a distributed change of permeability vs. time and distance from the point of injection that can be converted to the overall injectivity damage.

Characteristics of dissolved inorganic carbon in produced water from coalbed methane wells and its geological significance

Based on long-term dynamic tracing of dissolved inorganic carbon(DIC)and stable carbon isotope(δ13CDIC)in produced water from 20 coalbed methane(CBM)wells in western Guizhou,the spatial-temporal dynamic variations ofδ13CDIC of the GP well group produced in multi-layer commingled manner were analyzed,and the relationship between the value ofδ13CDIC and CBM productivity was examined.The produced water samples of typical wells in the GP well group were amplified and sequenced using 16S rDNA,and a geological response model ofδ13CDIC in produced water from CBM wells with multi-coal seams was put forward.The research shows that:δ13CDIC in produced water from medium-rank coal seams commonly show positive anomalies,the produced water contains more than 15 species of methanogens,and Methanobacterium is the dominant genus.The dominant methanogens sequence numbers in the produced water are positively correlated withδ13CDIC,and the positive anomaly of v is caused by reduction of methanogens,and especially hydrogenotrophic methanogens.Vertical segmentation of sedimentary facies and lithology in stratum with multi-coal seams will result in permeability and water cut segmentation,which will lead to the segmentation ofδ13CDIC and archaea community in produced water,so in the strata with better permeability and high water cut,theδ13CDIC of the produced water is abnormally enriched,and the dominant archaea is mainly Methanobacterium.In the strata with weak permeability and low water cut,theδ13CDIC of the produced water is small,and the microbial action is weak.The shallow layer close to the coal seam outcrop is likely to be affected by meteoric precipitation,so theδ13CDIC of the produced water is smaller.The geological response model ofδ13CDIC in produced water from multi-coal seams CBM wells in the medium-rank coal reveals the geological mechanism and microbial action mechanism of theδ13CDIC difference in the produced water from the multi-coal seams CBM wells.It also provides effective geochemical evidence for the superimposed fluid system controlled by sedimentary facies,and can also be used for the contribution analysis of the produced gas and water by the multi-layer CBM wells.

Produced Water from Oil and Gas Exploration—Problems, Solutions and Opportunities

Large volumes of water are generated in gas- and oil-production. This includes the water that is present originally in the reservoirs, but also water that is injected into the wells. While currently much of the produced water is either reinjected or disposed of after treatment, treated produced water is increasingly seen as an interesting resource, especially in water-scarce regions. This review looks at different PW treatment methods available, with an emphasis on the management of PW in oil- and gas production on the Arabian Peninsula.

Quantifying Spatiotemporal Change in Landuse and Land Cover and Accessing Water Quality: A Case Study of Missouri Watershed James Sub-Region, North Dakota

Spatial causal effects on water quality are essential in identification of vulnerable watersheds. Modelling landuse variables is an effective method of projecting localized impairment. This study presents an integrated index, designed to gauge the ability of an 8-digit Hydrologic Unit Code watershed in its ability to produce clean water. This index, IAPCW, can be successfully applied on a geospatial platform. In this study we utilized IAPCW to address forest cover dynamics of an impaired watershed, that is, Missouri Watershed James Sub-region in North Dakota. Specific parametric functions were analysed and combined within a customized GIS interface to provide a multi-faceted structured technique to derive IAPCW. These included ambient forest cover, housing density, agricultural land, soil erodibility and road density;it can be lucidly ascertained that where a prevailing forest cover undergoes conversion processes, the secondary effect may spur an exponential increase in water treatment costs. These parameters when projected statistically validated temporal and spatial relations of landuse/land cover dynamics to nutrient concentrations especially those that would be noted at the mouth of the watershed. In this study, we found that the levels of Total Dissolved Solids (TDS) were much higher for the years 2014 to 2016 with a discernible increased alkalizing effect within the watershed. When IAPCW was compared to Annualized Agricultural Nonpoint Source (AnnAGNPS), the spatial distribution generated by the AnnAGNPS study showed that fallow areas produced significant amounts of sediment loads from the sub-watershed. These same locations in this study generated a low IAPCW.

Perikinetics and sludge study for the decontamination of petroleum produced water(PW) using novel mucuna seed extract

In this study, Mucuna flagellipes seed extract was applied in the coagulation-flocculation of produced water （PW）. Process parameters such as pH, dosage, and settling time were investigated. Process kinetics was also studied. Instrumental characterization of mucuna seed （MS）, mucuna seed coagulant （MSC）, and post effluent treatment settled sludge （PTSS） were carried out. The optimum decontamination efficiency of 95 % was obtained at 1 g/L MSC dosage, PW pH of 2, and rate constant of 0.0001 （L/g/s）. Characterization results indicated that MS, MSC, and PTSS were of network structure, primitive lat- tice, and thermally stable. It could be concluded that MSC would be potential biomass for the treatment of produced water under the experimental conditions.

Removal of ions from produced water using Powder River Basin coal

In addition to being used as an energy source,coal also has significant potential for other,more sustainable uses including water treatment.In this study,we present a simple approach to treat water that was produced during oil production and contained a total dissolved solids(TDS)content of over 150 g/L using Powder River Basin(PRB)coal.PRB coal used as packing material in a flow-through column effectively removed 60%–80%of the cations and anions simultaneously.Additionally,71%–92%of the total organic carbon in the produced water was removed as was all of the total suspended solids.The removal mechanisms of both cations and anions were investigated.Cations were removed by ion exchange with protons from oxygen-containing functional groups such as carboxylic and phenolic hydroxyl groups.Anions,mainly Cl−1,appeared to be removed through either the formation of resonance structures as a result of delocalization of electrons within coal molecules or through ion–πinteractions.We propose that coal is a“pseudo-amphoteric”exchange material that can remove cations and anions simultaneously by exchanging ions with both ionized and non-ionized acids that are ubiquitous in coal structure or resonance effect.

Corrosion Behavior of Pipeline Steel in Oilfield Produced Water under Dynamic Corrosion System

In order to predict the corrosion trendency of X100 pipeline steel in flowing oilfield produced water,the effect of flow rate on the corrosion behavior of X100 pipeline steel was studied under general dynamic condition and simulated real working condition at the flow rate of 0.2,0.4,and 0.6 m·s^(-1).Potentiodynamic polarization curves and electrochemical impedance spectroscopy were used to study the corrosion behavior of X100 steel.Energy dispersive spectroscopy,X-ray diffraction and scanning electron microscopy were used to analyze corrosion product composition and micromorphology.The experimental results show that the corrosion is more serious under simulated real working conditions than that under the general dynamic conditions.In any case the corrosion current density increases with the increase of the flow rate,and the total impedance value decreases.The corrosion products include Fe_(3)O_(4),Fe_(2)O_(3),and FeOOH.The mass transfer and electrochemistry were simulated by flow coupled in COMSOL software.The multiphysical field coupling simulation results are closer to the engineering practice than the single flow field simulation,and similar results from the experiments were obtained.Both experimental and simulation results reveal that the higher flow rate is,the more serious corrosion appear and the more corrosion products accumulate.By combining experimental and COMSOL simulation data,the corrosion process model of X100 steel was proposed.

Temporal variations in geochemistry of hydraulic fracturing fluid and flowback water in a tight oil reservoir

Hydraulic fracturing facilitates the development and exploitation of unconventional reservoirs.In this study,the injected hydraulic fracturing fluid(HFF)and flowback and produced water(FPW)in tight oil reservoirs of the Lucaogou Formation in the Junggar Basin are temporally sampled from day 1 to day 64.Freshwater is used for fracturing,and HFF is obtained.The chemical and isotopic parameters(including the water type,total salinity,total dissolved solids(TDS),pH,concentrations of Na^(+),Cl^(-),Ba^(+),K^(+),Fe^(2+)+Fe^(3+),and CO_(3)^(2-),dD,and δ^(18)O)are experimentally obtained,and their variations with time are systematically analyzed based on the flowback water.The results show that the water type,Na/Cl ratio,total salinity,and TDS of the FPW change periodically primarily due to the HFF mixing with formation water,thus causing δD and δ^(18)O to deviate from the meteoric water line of Xinjiang.Because of watererock interaction(WRI),the concentrations of Fe^(2+)+Fe^(3+)and CO_(3)^(2-)of the FPW increase over time,with the solution pH becoming more alkaline.Furthermore,based on the significant changes observed in the geochemistry of the FPW,three separate time intervals of flowback time are identified:Stage Ⅰ(<10 days),where the FPW is dominated by the HFF and the changes in ions and isotopes are mainly caused by the WRI;Stage Ⅱ(10-37 days),where the FPW is dominated by the addition of formation water to the HFF and the WRI is weakened;and finally,Stage Ⅲ(>37 days),where the FPW is dominated by the chemistry of the formation water.The methodology implemented in this study can provide critical support for the source identification of formation water.

Treatment of ASP produced water with hydrophilic fibre ball filtration

The conventional treatment process cannot meet the need for treatment of produced water from alka- line/surfactant/polymer flooding（ ASP produced water） in Daqing oilfield. In this study, a new type of hydro- philic fibre ball medium was developed through surface modification method. The hydrophilic property of the surface modified fibre ball was tested with ASP produced liquid at laboratory. The results showed that this fibre hall had higher oll degreasing efficiency, The surface components were also observed by Scanning Electron Microscope and X-ray Photoelectron Spectroscopy, the result showed that the hydrophilic fibre＇ s surface was covered by sulfonic group. Using hydrophilic fibre ball as filter medium, a new type of filter was designed to treat ASP produced water in pilot-scale experiments. The obtained results indicated that this type of filter had high capability and efficiency for the treatment of ASP produced water. This filter should have a better application prospect in oilfield produced water treatment.

Effects of the Produced Water from a Sour Oilfield in South Kuwait on the Production Tubing

Kuwaiti oil production faces a growing challenge in the increasing quantities of produced water generated in the production of oil. The high water cut of the produced fluid from the wells and the high salinity of the produced water lead to significant degradation of subsurface equipment, specifically the production tubing. Debris generated through the degradation of the inner part of the tubing becomes a constituent of the scaling that deposits in the tubing and blocks the flow of the production fluid, inducing higher maintenance costs. This paper looks at the characteristics of the scaling in regard to the produced water and outlines the economic impact of the produced water induced degradation of the tubing structure.