Reduce Water Production Research Articles

Application of Horizontal Wells to Reduce Water Production during Gel Treatment

It is well known that gel treatment has outstanding potential to delay water breakthrough and reduce water production. However, it causes the decrease of oil production by permeability reduction, even though it is not as much as reduction of water production. For this reason, to improve oil production with substantial reduction of water production, performances of gel treatments through the combination of horizontal and/or vertical wells were assessed and compared. An extensive numerical simulation was executed for four different well configurations under gel treatment associated with waterflood to accomplish the purpose of this study. Performances were compared according to cumulative oil recovery and water-oil ratio at the production well for different systems. Though all of well configurations considered in this study effectively decreased the water production compared with waterflood, applications of horizontal wells led to much higher oil recovery than vertical well because of improved sweep efficiency. Based on these results, the potential of horizontal wells was examined through different scenarios in combinations of injection and production wells. Furthermore, various well lengths of injectors or producers were assessed for horizontal wells. Because cross-flow between layers dominates performance of gel treatment, effects of vertical permeability were also investigated in application of gel treatment with horizontal well. Longer wells and higher cross-flow results in better performance. This study represents that effectiveness of horizontal wells for gel treatment even for reservoirs having dominant cross-flow.

Study on Performance Evaluation of Dispersed Particle Gel for Improved Oil Recovery

This work investigates the performance of dispersed particle gel (DPG) by core flow tests including injectivity, selective plugging, thermal stability, and improved oil recovery (IOR). Results showed that the resistance factor is small when DPG was injected, but obviously became larger while turning into brine water flooding. Both the oil and water relative permeability were reduced and greater reduction appeared in water relative permeability. DPG could block water flow without affecting oil flow, and oil–water segregated flow mechanism was proposed to explain this selective plugging. The injection pressure increases, caused by strong plugging due to the DPG aggregation aging in high temperature, which was consistent with the observation of atomic force microscope (AFM) photos. The DPG could effectively block high permeability zone and produce oil from low permeability zone, which could provide a practical way to enhance hydrocarbon recovery while reducing water production for extremely heterogeneous reservoirs.

Electrodialytic removal of NaCl from water: Impacts of using pulsed electric potential on ion transport and water dissociation phenomena

Applying pulsation to an electrodialysis (ED) system helps to minimise some limitations such as water dissociation and power efficiency losses, encountered due to concentration polarization (CP). Further, ED directly powered by fluctuating renewable energy has great potential to be used in remote locations. In this paper, desalination tests were carried out under both constant and pulsed voltages at feed of 5g/L NaCl. The impacts of applying pulsed voltage on ED performance were investigated over a wide range of voltages (15–50V DC), frequencies (0.05–10Hz) and duty cycles (20–80%). In the sub-limiting regime, CP had a negligible impact on ED performance and thus applying pulsed voltage led to significantly reduced water production. However, the energy efficiency of the process was similar to that of the conventional process at constant potential, suggesting that ED is an energetically robust system to be directly coupled with fluctuating energy sources. In the limiting current region, both water dissociation and desalination time decreased noticeably with increased frequency. By optimizing the duty cycle significant water dissociation was prevented from occurring. When desalinating a brackish feed salinity of 5g/L NaCl at 2L/min and at voltages of 30 and 50V, experimental findings showed negligible water dissociation at optimum frequency of 5Hz and duty cycles below 50 and 40%, respectively. Thus, by using an optimally selected pulse regime, it is possible to safely operate above the limiting current density (LCD), obtain higher water production with negligible water splitting, and at only slightly higher energetic cost. The increase in the energy consumption was solely due to operating at higher voltages and independent of the mode of operation.

Replacing Fallow with Continuous Cropping Reduces Crop Water Productivity of Semiarid Wheat

Water supply frequently limits crop yield in semiarid cropping systems; water deficits can restrict yields in drought‐affected subhumid regions. In semiarid wheat (Triticum aestivum L.)‐based cropping systems, replacing an uncropped fallow period with a crop can increase precipitation use efficiency but reduce wheat productivity. Our objective was to analyze crop sequence and environmental effects on water use, components of water productivity, and net returns of winter wheat (WW) in a semiarid region. A field study was established to evaluate eight 3‐yr crop sequences, including a wheat phase followed by a feed grain phase (corn [Zea mays L.] or grain sorghum [Sorghum bicolor (L.) Moench]) and an oilseed phase (OS; spring canola [Brassica napus L.], soybean [Glycine max (L.) Merr.], sunflower [Helianthus annuus L.], or none [fallow]). Standard measurements included crop water use (WU), canopy leaf area index at anthesis, biomass, grain yield, and yield components. Net return (NR) was calculated as the difference between crop revenue and total operating costs. Replacing an uncropped fallow period with an OS crop reduced water productivity responses of WW (biomass, grain yield, and NR) by 18, 31, and 56%, respectively, relative to that of WW grown after fallow. These responses to continuous cropping corresponded to reductions in all components of a water‐limiting yield production function. The modest water productivity observed (0.28–0.62 kg m−3), relative to a reported global range of 0.6 to 1.7 kg m−3, indicates opportunity to improve wheat water productivity through management and genetic gain.

Effects of membrane properties on water production cost in small scale membrane distillation systems

Membrane distillation (MD) has shown potential as a desalination process. As a thermally driven membrane technology which runs at relatively low pressure and can tolerate high salinity feed, MD may be useful for desalination under condition for which reverse osmosis is not a good option. However, improved energy utilization and reduced water production cost in MD systems remains an important technical challenge. In this paper, we examine how optimization of the heat and mass transfer properties of the MD membrane can raise water flux and reduce unit energy consumption. Numerical modeling tools and factorial analysis are used to examine the effect of five MD membrane characteristics: porosity, tortuosity, thermal conductivity, pore diameter, and thickness. The water production cost (in USD/m3 of purified water) is calculated as a function of these parameters for a small-scale, single-stage MD process driven by waste heat. Two MD configurations were considered: Direct Contact MD (DCMD) and Air Gap MD (AGMD). All five membrane properties examined were found to have a significant effect on water production cost, although the magnitude of this effect was greatly dependent on the MD configuration.

Effect of polymer solution structure on displacement efficiency

In this paper, a series of experiments, including atomic force microscope (AFM), environmental scanning electron microscope (ESEM), and core displacement tests were conducted to investigate the effect of polymer solution structure on solution properties and oil displacement efficiency. The results show that in the HPAM solution polymer coils were formed and then aggregated into a loose structure, while the HAP2010 solution formed a strong network structure, which would significantly improve the solution viscosity and flow resistance so as to upgrade the capacity of piston-like oil displacement in highly permeable porous media. Meanwhile, the retention of the HAP2010 solution at pore throats were also enhanced, which could reduce water production during subsequent water flooding and enlarge the swept volume during polymer flooding. Therefore, enhancing the interaction among polymer molecules is an effective way to improve the displacement efficiency of polymer solutions in heavy oil reservoirs with high permeability.

Experimental study of the interaction between surfactants and super absorbent polymer gel

This work investigates the interaction between negatively charged super absorbent gel, also called preformed particle gel (PPG), and six surfactants: two cationic, two anionic, and two neutral. Results showed that the swelling of PPG in surfactant solution could increase the concentration of anionic and neutral surfactants in their free aqueous phase but decrease cationic surfactant concentration. Rheology measurement showed that surfactant could significantly reduce the strength of PPG, which was consistent with the injection pressure measurement results from the experiment of PPG extrusion through fractured model that was designed. This work and other ongoing lab experiments is a first step to establish hybrid technique of PPG and surfactant which could provide a practical way to enhance hydrocarbon recovery while reducing water production for extremely heterogeneous mature reservoirs.

Conformance Control with Polymer Gels: What it Takes to be Successful

Whenever water production exceeds economic limits of a given oil or gas field, the need arises for a process by which produced water is reduced. Published data indicate that the petroleum industry spends $40 billion every year to process excessive produced water. Water also causes corrosion, scale and requires the construction of larger downstream handling facilities. Polymer gels, due to their versatile nature, are deemed suitable for reducing water production from oil and gas fields. Treatments utilizing these materials are generally referred to as conformance improvement treatments (CITs). Depending on the type of the crosslinker used, polymer gels can be classified as inorganically crosslinked or organically crosslinked. Examples on each type highlighting their capabilities and shortcomings are provided. Polymer thermal stability, compatibility with mixing waters, correct identification of the water production mechanism and gelation time are all key parameters for successful polymer-gel CITs. We will present an overview of the polymer gels technology available up-to-date with practical examples on key parameters for successful CITs. This paper will serve as a guide for scientists and engineers on the use of polymer gels for water control.

Evaluation of Aquifer Diversion After Large Polymer-Gel Water-Shutoff Treatments

This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper SPE 132978, ’Quantitative Evaluation of Aquifer Diversion to Surrounding Wells After Multiple Large Polymer Gel Water Shutoff Treatments,’ by Ben Turner, SPE, Tiorco, and Jude Nwaozo, SPE, and Brad Funston, SPE, Marathon Oil Company, originally prepared for the 2010 SPE Production and Operations Conference and Exhibition, Tunis, Tunisia, 8-10 June. The paper has not been peer reviewed. From April through August of 2009, seven producing wells in the Spring Creek field in the Big Horn basin of Wyoming were treated with chromium-acetate-crosslinked polyacrylamide in an attempt to reduce water production, lower fluid levels, and achieve greater drawdown, resulting in improved oil production. The wells were chosen because of their high productivity, high water cut, suboptimal operation because of pump limitations, and in some cases, marginal economics. Introduction The Spring Creek field is on the west flank of the Big Horn basin in Park County, Wyoming. Structurally, Spring Creek forms an asymmetrical anticline. The main oil reservoirs in Spring Creek are the Tensleep sandstone (Pennsylvanian) and the Phosphoria formation (Permian). Both the Phosphoria and the Tensleep are connected to prolific aquifers that supply reservoir energy, but also supply a high rate of water. In most wells in the field, both formations are produced and commingled, but in many wells, the Tensleep is so productive that the well is limited in lifting capacity and the Phosporia has not been perforated. The well spacing in the field averages approximately 5 acres. Strategy The operator has an extensive history of shutting off water production by use of chromium-crosslinked polyacrylamide gels. By using chromium acetate as a delayed crosslinker for partially hydrolyzed polyacrylamide, a large volume (as much as 11,500 bbl in this case) can be injected and then allowed to cure for a week. When the gel cures, it reduces the permeability of the fracture and is able to withstand a high differential pressure such as that seen in the near-wellbore region of a producing well. The gel is bullheaded through tubing, with a packer set above the productive formations. Because of the large permeability difference between the fractures and the formation matrix, the gel will penetrate the fractures and significantly reduce the permeability, reducing the water production and fluid level, thus allowing the well to be pumped off and oil production to be increased. This technique has been used quite successfully in several hundred applications throughout the USA.

Production optimisation and water control in oil/water producing wells using horizontal downhole water sink technology

Water breakthrough and the flow of water towards the perforations of a producing well increase production operation costs and influence overall recovery efficiency. To control water production, a downhole water sink can be used in which a well is completed in both oil and water zones. Water is produced from an interval in water zone, which can result in the same pressure drop below water oil contact (WOC) as the pressure drop created by oil or gas production. This system can reduce water production through oil zone perforations. Water produced from water zone perforations can then be injected in deeper aquifers intervals. This technology can also be implemented in horizontal and multi-lateral wells to further increase hydrocarbon recovery with fewer water problems. This study examines the use of horizontal downhole water sink technology to increase oil recovery. Numerical simulation is performed to optimise oil production and water control in a multi-layered oil reservoir, by optimising the direction of drilling and the downhole water sink method. Different scenarios of drilling direction and horizontal down-hole water sink method are examined to identify the option that provides maximum oil recovery. The simulation results showed that drilling horizontal wells in a north–south direction resulted in higher well productivity, and that wells with significantly more water production problems can be controlled using a horizontal downhole water sink.

Using Screening Test Results to Predict the Effective Viscosity of Swollen Superabsorbent Polymer Particles Extrusion through an Open Fracture

Superabsorbent polymer particles, also called preformed particle gels (PPGs), have been successfully applied to reduce water production and enhance oil production in mature reservoirs with fractures or super-high-permeability streaks/channels. The applied particles usually range in size from a few hundred micrometers to a few millimeters and are irregular in shape, which make it impossible to measure their rheology behavior using a traditional rheometer. A simple method, a screen model test, was designed to evaluate the rheological behavior of the swollen PPG. The results show that a swollen PPG is a shear-thinning material with properties that can be expressed using a power-law equation from which an apparent consistency constant and an apparent flow index can be obtained. Considering the shear-thinning properties, we first developed a theoretical mathematical model using a general power-law equation to predict the pressure gradient of a swollen PPG during its extrusion through a fracture. Then, we modified the model by correlating screen test results with fracture experiment results so that the apparent consistency constant and the apparent flow index obtained from the screen tests were introduced to replace the consistency constant and flow index from the general power-law equation. These equations correlated effective viscosity with flow rate, fracture width, apparent consistency constant, and apparent flow index together. The newly developed correlations were validated, and the results showed that a single group of screen test measurements can be applied to determine the effective viscosity of a PPG in a fracture with limited errors.

Smart-Well Production Optimization Using an Ensemble-Based Method

Summary Ensemble methods have been applied successfully in assisted history matching and in production optimization. In history matching, the ensemble Kalman filter (EnKF) has been used to estimate the values of hundreds of thousands of variables from various types of data. In production optimization, an ensemble-based method has been used to estimate optimal control settings for problems with thousands of control variables. In both cases, relatively small numbers of random realizations are used to compute update directions for improving estimates. In this paper, we illustrate the application of the ensemble-based optimization on two fairly complex problems that would be difficult to handle by other methods. In the first example, we show its application to optimize inflow-control-valve (ICV) settings on two horizontal wells in a sector model of 200,000 cells. One hundred layers were used in the reservoir model to capture geological heterogeneity. The two wells were drilled parallel to the edgewater boundary. The optimization objective in this example is to minimize cumulative water production over a 10-year production period while maintaining a constant liquid-production rate. Results after only five optimization iterations with improved control-valve settings showed a 50% reduction in cumulative water production. The fully automated optimization process was completed within a few hours under a parallel-computing environment. The ensemble-based method was also applied successfully to a 3D case consisting of 10 multilateral wells with ICVs installed at each lateral junction. The interaction of various laterals is difficult to visualize, but the optimization algorithm was again successful in reducing water production. In this example, we demonstrate that proper choice of control variables can be important to the success of the optimization.

Experimental and Modeling Study of the Transport of Chromium Acetate Solutions Through Carbonate Rocks

Summary Gelled polymer systems are applied to oil reservoirs to reduce water production and to increase sweep efficiencies in recovery processes. A common system consists of hydrolyzed polyacrylamide with a chromium (III) crosslinker. Transport of these chemicals through the reservoir rock is essential for a successful treatment. In carbonate reservoirs, dissolution of the carbonate raises the pH of the gelant to levels where chromium precipitates, robbing the gelant of crosslinker. The transport of chromium acetate solutions through dolomite rock material was studied by injecting various solutions through short cores and measuring Cr, Mg, and Ca concentrations and pH in the effluent. Chromium retention in the cores caused by precipitation was a rate-controlled process. A mathematical model was developed that described convection, dispersion, kinetic reactions of carbonate dissolution and chromium precipitation, and chemical equilibrium for reactions between aqueous components. Experimental data from this work and taken from literature were simulated by the model. One rate equation with one set of parameters described the steady-state values of chromium concentration exiting the cores after the breakthrough of the injected solutions.

Inflow-Control Devices for Reducing Water Production

This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper SPE 124154, ’Practical Consideration of an Inflow Control Device Application for Reducing Water Production,’ by Liang-Biao Ouyang, SPE, Chevron Energy Technology Company, originally prepared for the 2009 SPE Annual Technical Conference and Exhibition, New Orleans, 4-7 October. Inflow-control devices (ICDs) have been developed to improve well performance and enhance reservoir management by mitigating undesired water and/or gas breakthroughs that often occur as a result of a variety of factors, including reservoir-permeability heterogeneity, heel/toe effects, and different reservoir pressures in different regions penetrated by a well. Success of an ICD completion relies heavily on appropriate completion design. The full-length paper identifies several key issues that should be addressed in designing an ICD completion and discusses their effects on performance of a well equipped with ICDs. Introduction Despite their superiority in production and recovery to conventional wells by maximizing reservoir contact, horizontal and multilateral completions are more prone to water and/or gas coning toward the heel of the well as a result of frictional pressure drop from toe to heel and/or breakthrough anywhere in the well because of permeability variation along the well and proximity of water traps. ICDs, a choking device installed as part of sandface completion hardware, were proposed in the early 1990s as a solution to the difficulties particularly associated with horizontal and multilateral wells. An ICD completion offers a number of potential unique benefits: Optimize production Delay water progress Minimize /eliminate annular flow and thus reduce the risk of sand production behind screen and subsequent plugging or erosion “hot spots” Mitigate the nonuniform production profile across the horizontal hole, especially in highly heterogeneous and fractured reservoirs that may result in premature water production, bypassed oil, and lower ultimate recovery Improve well cleanup and reduce the effect of formation damage caused by drilling of the well For sandstone, the application of ICDs should reduce the effect of heel/toe effects and high-permeability intervals, defer water/gas breakthrough, and improve well cleanup and sweep efficiency. For carbonate, the application of ICDs should help to control inflow from high-permeability intervals and limit production from each compartment based on lateral offset from gas/oil and oil/water contact to prevent premature gas and/or water breakthrough. ICDs have gained increasing popularity and increasingly are being applied to a wide range of reservoir types.

Compaction, Permeability, and Fluid Flow in Brent-Type Reservoirs Under Depletion and Pressure Blowdown

Compaction-induced permeability reduction in a producing reservoir rock/soil can be significant, but neverthe- less is often neglected or overly simplified in reservoir simulations. Provided examples show that the commonly used compaction models in reservoir simulators are not capable of capturing the actual spatial variation of the compaction, which generally is more complex than the simplified models predict. The only way to compute a reliable compaction state is by rock mechanics simulation. The computing time can be considerably reduced by an accurate and efficient procedure, which has been used to do the compaction modeling and study the effects of permeability reduction on fluid flow and production. Weak, moderate, and strong materials behave differently when loaded, such that large contrasts in initial permeability can be reduced by increasing load (depletion), resulting in more homogeneous flow. It is demonstrated how this can be util- ized to achieve better sweep efficiency, reduced water production and increased oil recovery. The effects are especially pronounced when the pressure reduction is considerable (pressure blowdown). The data used are from Brent-type reser- voirs, but the results also apply to a wider range of reservoirs.

A Depletion Strategy for an Active Bottom-Water Drive Reservoir Using Analytical and Numerical Models—Field Case Study

Water coning is one of the most serious problems encountered in active bottom-water drive reservoir. It increases the cost of production operations, reduces the efficiency of the depletion mechanism, and decreases the overall oil recovery. Therefore, preventive measures to curtail water coning damaging effects should be well delineated at the early stages of reservoir depletion. Production rate, mobility ratio, well completion design, and reservoir anisotropy are few of the major parameters influencing and promoting water coning. The objective of this paper is to develop a depletion strategy for an active bottom-water drive reservoir that would improve oil recovery, reduce water production due to coning, delay water breakthrough time, and pre-identify wells that are candidates to excessive water production. The proposed depletion strategy does not only take into consideration the reservoir conditions, but also the currently available surface production facilities and future development plan. Analytical methods are first used to obtain preliminary estimates of critical production rate and water breakthrough time, then comprehensive numerical investigation of the relevant parameters affecting water coning behavior is conducted using a single well 3D radial reservoir simulation model.

Versatile Swellable Packer Tool Provides Reliable and Economical Zonal Isolation

Technology Update A simple observation of the expansion of a child's toy snake in water by a lateral-thinking Shell R&D technologist a few years ago has led to an emerging revolution in the oil and gas industry—swellable-elastomer packers. Following rapid industry acceptance, the technology now can be found downhole in wells in every producing region of the world, and the technology recently won a major international award for applied innovation. Versatile, Highly Reliable Technology The underlying objective of using swellable-elastomer packers, most of the time, is to reduce water production and increase oil and gas production proportionally. Swellable packers combine the advantages of mechanical and inflatable packers, without the inherent complications associated with the traditional technologies. Swellable packers adhere to the profile of the formation in a reliable and efficient manner, and like conventional packers, they create a pressure-holding seal within the wellbore. However, unlike traditional methods of zonal isolation, swellable packers always have something in reserve in the event of a future washout or water break-through. In such cases, the packer will swell further and adapt to the new structure until a seal is re-established (Fig. 1). The packers themselves are thin sections of swellable rubber that are vulcanized directly on to standard tubing. The rubber swells when it comes into contact with the appropriate fluid, water or oil. The basic principle is natural and very simple. Add water or oil to an appropriate rubber-based compound, and it will swell as it absorbs the liquid. There are no moving parts to fail, and as long as the application is correctly engineered and deployed, there is very little that can go wrong. However, the key factor is engineering it properly in the first place. The simplicity of swellables belies the science and vast body of research behind the technology. Literally thousands of tests have been conducted on a multitude of compounds, under different oilfield conditions, to make sure that the swellable elastomers will perform exactly as they should downhole. Swellable packers are not a one-type-fits-all technology. Elastomer compounds numbering in the hundreds are needed to meet a vast range of downhole requirements. An exhaustive testing program by Swellfix has found that various characteristics of particular crudes, different oil/water mixtures, and other specific well factors all affect how various swellable compounds perform. A comprehensive understanding of the relationship between packer composition, well fluids, and swelling enables selection of the appropriate compounds for best performance. In 5,000 swellable-packer deployments by Swellfix, no failures have yet resulted. Water- and Oil-Swellable Packers Water-swellable elastomers work on the principle of osmosis, a process that encourages the movement of water particles across a semipermeable membrane, where there is a salinity difference on either side of the membrane. Effectively, the water is drawn into the elastomer and retained because of the salinity gradient across the surface of the elastomer. This causes it to swell, increasing its size to fill a void.

Efficacy of mulching, irrigation and nitrogen applications on bottle gourd and okra for yield improvement and crop diversification

An on-farm irrigation trial conducted on the upland of Chitwan valley of Nepal evaluated the amount and frequency of irrigation as well as the effect of nitrogen fertilizer and straw mulch applications on the performance of bottle gourd and okra vegetables. The experiment was laid out on split-split-plot design with fertilizer as main-plot factor, frequencies of irrigation as sub-plot factor, and amount of irrigation as sub-sub-plot factor. Data analysis revealed that frequency and amount of irrigation had a significant interaction effect on the number of nodes that emerge before the opening of the first flower in bottle gourd. Likewise, a significant effect of mulching was observed on the number of primary branches (P = 0.05). Number of nodes and primary branches both contributed to higher production of bottle gourd. Results also indicated that frequent application of higher amount of irrigation to bottle gourd could lead to reduced water productivity and suffer from yield losses. In the case of okra, low level of nitrogen application (30 kg N ha−1) with low but daily watering had significantly higher yield (1,365 g plot−1) than from higher level of nitrogen application (90 kg ha−1) (P = 0.01). Interaction effect of all factors was also significant (P = 0.05) on the fruit yield of okra which implied greater value of smaller irrigation to contribute to increased returns to farmers by improving production level of okra in this area of Nepal

A laboratory investigation of water abatement chemicals for potential use in the Wanaea field

The disadvantages of water influx into a producing well include reduced relative permeability to hydrocarbon and increased expenses for both water handling and corrosion control. An effective water control technique is, therefore, highly desirable. One potential solution for reducing excessive water production is the injection of “Relative Permeability Modifier” (RPM) chemicals into producing wells. The work described in this paper is concerned with finding a highly selective chemical to reduce water production without affecting oil production. Presented herein are results of laboratory tests using relative permeability modifiers in conjunction with core samples from the Wanaea field. The oil producing Wanaea field is operated by Woodside Energy. This field is in offshore Western Australian waters. Some of the wells suffer from high water cut, therefore the introduction of a relative permeability modifier (RPM) has been considered. Four RPM chemicals were tested with core plugs taken from Unit II of well Wanaea-3 (core depth 2832.00 to 2844.50 m). Laboratory experiments were conducted on 4 reservoir core plugs, with air permeabilities ranging from 158 to 334 md and porosities from 16.4 to 19.9%. The objective of the tests was to assess the effectiveness of selected RPM's in selectively reducing water production. The experimental results demonstrated that the chemicals were variably effective in reducing the relative permeability to the water phase, but they also variably affected the relative permeability to the oil phase.

Performance analysis of a trihybrid NF/RO/MSF desalination plant

The Saline Water Desalination Research Institute (SWDRI) of the Saline Water Conversion Corporation (SWCC), Saudi Arabia has been actively involved in developing the application of nanofiltration (NF) pretreatment to both seawater reverse osmosis (SWRO) and multistage flash (MSF) desalination processes. Full integration of NF, SWRO and MSF processes would result in enhancing the reliability, flexibility, plant productivity and ultimately reduce water production cost. Extensive experimental studies on a pilot-scale were conducted recently by SWDRI to establish the operational boundaries and constraints of the trihybrid NF/RO/MSF desalination system. The system was configured in such a way that the NF unit received seawater feed from the heat rejection of the MSF pilot plant and was able to operate at a fairly constant temperature of about 33°C which produced NF permeate (NFP) at a recovery ratio of about 64%. The SWRO unit which received the NFP as a feed yielded a permeate recovery of about 47%. Average chemical analysis of the RO reject (ROR) revealed that the sulphate and calcium concentrations were only 124 and 281 ppm, respectively, and was subsequently used as a make-up to the MSF pilot plant. The very low concentration of the sulphate and calcium ions in the brine recycle which were below the saturation limits enabled to operate the MSF unit safely up to a top brine temperature of 130°C (unit temperature design limit) and water recovery ratio of about 69%. In this paper, the operational performance of the trihybrid NF/RO/MSF desalination pilot plant will be presented. The established optimum operating conditions can be used as a guide to assess the techno-economic viability of the trihybrid desalination scheme.