Water Blocking Research Articles

Evaluation of liquid nanofluid as fracturing fluid additive on enhanced oil recovery from low-permeability reservoirs

Hydraulic fracturing creates a complex fracture network that makes the oil production from low-permeability reservoirs economical. However, significant amount of water is likely lost into the rock matrix during hydraulic fracturing. This can cause formation damage due to multiphase flow, thus hindering the oil production rate. Surfactants can alter rock wettability and/or reduce oil-water interfacial tension (IFT), and it has been proposed to be used to mitigate such water blockage and enhance oil recovery. Among different approaches of using surfactants, forming liquid nanofluid (LNF) can minimize the adsorption of surfactants on rock surface, and it is likely to be one of the best options for low-permeability rocks with extensive surface area. In this study, the key properties of a well-screened LNF are evaluated, and then compared with a commercial flowback surfactant (CFS) that is widely used in the field. Pressure transmission test is further applied, which can determine the change of rock permeability due to different fluids and the potential formation damage due to multiphase flow. A systematic evaluation method is thus established to screen fracturing fluid additives to enhance oil production from low-permeability reservoirs both effectively and efficiently.

Self-fibering growth in the soot-templated CVD coating of silica on mesh for efficient oil/water separation

A comprehensive study of SiO2 grown by chemical vapor deposition is conducted on soot coated copper mesh, from which an excellent superhydrophobic-superoleophilic filter mesh is demonstrated using the structure of nano-fibered network. A dynamical model of “flow-guided dehydration” including the microscopic interplay between “flow-induced diffusion” and dehydration is presented. Furthermore, we present a device based on tubular separator to purify oily wastewater that is very much like tap-water delivering in daily life, which does not cause the problem of water blockage.

The Influence of the Ship's Speed and Distance to an Arbitrarily Shaped Bank on Bank Effects

In shallow and restricted waterways, the water displaced by a sailing ship is squeezed under and along its hull. These confinements result in increased velocities of the return flow along the hull and the induced pressure distribution on the hull causes a combination of forces and moments on the vessel. If generated because of asymmetric flow due to the presence of a bank, this combination of forces and moment is known as bank effects. A comprehensive experimental research program on bank effects has been carried out in the towing tank for maneuvers in shallow water (cooperation Flanders Hydraulics Research—Ghent University) at Flanders Hydraulics Research (FHR) in Antwerp, Belgium. The obtained data consist of more than 14,000 unique model test conditions. The relative position and distance between a ship and an arbitrarily shaped bank is ambiguous. Therefore, a definition for a dimensionless distance to the bank is introduced. In this way, the properties of a random cross section are taken into account without exaggerating the bathymetry at a distance far away from the ship or without underestimating the bank shape at close proximity to the ship. Also, a dimensionless velocity is introduced to take the influence of the water depth, forward speed, and blockage into account. The proposed mathematical model for bank effects, often described as a sway force and yaw moment, is instead decomposed in two sway forces at each perpendicular.

Effect of Soil Texture on Estimates of Soil‐Column Carbon Dioxide Flux Comparing Chamber and Gradient Methods

Core Ideas Carbon dioxide efflux from soil of different textures was compared. The dominant mechanism of CO2 efflux changed from coarse to fine soil. The gradient method should be used very carefully in coarse soils. A key component of the global C balance includes soil CO2 emissions. Both chamber‐ and gradient‐based methods have been effectively used for determination of soil CO2 efflux. The gradient‐based method, however, is installed belowground and requires assessment of the soil gas diffusion coefficient, which varies with soil properties such as soil texture. We hypothesized that the gradient and chamber methods would yield similar results when soil texture was appropriately accounted for. Our objective was to evaluate soil gas efflux by applying both methods in three different soil textures (loam, silty loam, and silty clay loam) packed in laboratory soil columns. Water was incrementally applied to soil surfaces while volumetric soil water contents (VWC) and CO2 concentrations were continually monitored at target locations in parallel with surface chamber measurements. The Soil Air Phase Individual Resistances (SAPHIR) model was used to determine the relative gas diffusion coefficients (DP/D0). The gradient‐based CO2 effluxes were compared with estimates derived from the CO2–efflux chamber. Soil CO2 effluxes estimated using the gradient method approximated those using the chamber for all three soil textures. The particle shape factor (p) in the SAPHIR model varied with silt content of the three soils. The SAPHIR model's water blockage factor (w) also varied with soil texture to a lesser extent. Under the repacked soil condition, these results confirm that the gradient method can provide consistent CO2 measurements in comparison with chamber‐based results from soils of varied texture when the diffusion coefficient takes into account the effects of soil texture. The gradient method should be used cautiously in coarse‐textured soils.

Well productivity enhancement by applying nanofluids for wettability alteration

Water blocking is a frequent cause for gas productivity decline in unconventional and conventional fields. It is a result of the capillary end effect near the wellbore vicinity. It creates significant formation damage and decreases gas well productivity. The alteration of the rock wettability by nanofluids is an effective way to reduce water blockage and enhance gas production. Presently, several types of surfactants and nanofluids are used in the industry for contact angle alteration. In this study, we developed an analytical model and analysed the sensitivity to several parameters. After the treatment, the porous medium in the well vicinity (or along the core) will have a stepwise constant contact angle profile. We derive analytical models for compressible steady-state two-phase linear and axi-symmetric flows, accounting for the piecewise-constant contact angle and contact-angle-dependent capillary pressure and relative permeability. The modelling reveals a complex interplay between the competing effects of compressibility, viscous and capillary forces, which influence the optimal contact angle for treatment. The optimal contact angle for treatment will depend on the initial wettability of the formation, the water cut and the capillary-viscous ratio.

The gas jet behavior in submerged Laval nozzle flow

The behavior of the combustion gas jet in a Laval nozzle flow is studied by numerical simulations. The Laval nozzle is installed in an engine and the combustion gas comes out of the engine through the nozzle and then injects into the surrounding environment. First, the jet injection into the air is simulated and the results are verified by the theoretical solutions of the 1-D isentropic flow. Then the behavior of the gas jet in a submerged Laval nozzle flow is simulated for various water depths. The stability of the jet and the jet evolution with a series of expansion waves and compression waves are analyzed, as well as the mechanism of the jet in a deep water depth. Finally, the numerical results are compared with existing experimental data and it is shown that the characteristics of the water blockage and the average values of the engine thrust are in good agreement and the unfixed engine in the experiment is the cause of the differences of the frequency and the amplitude of the oscillation.

Productivity index enhancement by wettability alteration in two-phase compressible flows

Water blocking due to the capillary end effect near the wellbore vicinity creates significant formation damage and decreases well productivity for oil and gas. The alteration of the rock wettability by a chemical well treatment is an effective way to reduce water blockage and enhance oil and gas production. Presently, several surfactants and nanofluids are used in the industry for contact angle alteration. After the treatment, the porous medium in the well vicinity (or along the core) has stepwise contact angle. The previous paper (Naik et al., 2015) develops analytical models for incompressible steady-state two-phase linear and axi-symmetric flows, accounting for the piecewise constant contact angle and contact-angle-dependent capillary pressure and relative permeability. The current paper adds the effect of compressibility, which is particularly important for high rate gas wells and wells in unconventional and tight-sand reservoirs. The obtained semi-analytical model has been validated by comparison with a set of laboratory coreflood tests. The modelling reveals a complex interplay between the competing effects of compressibility, viscous and capillary forces, yielding non-monotonic dependencies of well productivity on the wettability and the optimal contact angle. The model closely matches the productivity index data for two production wells from a field case before and after wettability treatment using surfactant.

Experimental studies on performances of flexible floating oil booms in coupled wave-current flow

Floating oil booms are commonly-adopted facility to collect spilled oil on sea surface, or to protect specific areas against oil slick spreading. In this study, 931 runs of laboratory test were carried out under wave-current coupling conditions to investigate hydrodynamic performances of the flexible floating oil boom. The tests first conducted a comparison on motion responses between the flexible floating boom and the rigid one to indicate the necessity of taking the flexibility of boom into consideration. Then a comprehensive analysis was carried out to investigate the effects of the ambient currents, waves and the boom characteristics of material stiffness, diameter of floater, length of skirt, and B/W (Buoyancy/Weight) ratio on the motion responses of the flexible floating booms. Finally, by taking the water blockage effect in front of the boom into consideration in the definition of boom effectiveness, the effective draft and freeboard were compared between the flexible boom and rigid one under fixed current and wave conditions. The effects of currents, waves, skirt lengths and B/W ratios on the effective draft and effective freeboard are assessed.

Toward a hydrocarbon-based chemical for wettability alteration of reservoir rocks to gas wetting condition: Implications to gas condensate reservoirs

Recently, wettability alteration has been much attended by researchers for studying well productivity improvement in gas condensate reservoirs. Previous studies in this area only utilized water/alcohol based chemicals for this purpose. While, hydrocarbon nature of the blocked condensate in retrograde gas reservoirs, may motivate application of hydrocarbon based chemical agents. In this study, a new hydrocarbon based wettability modifier is introduced to alter wettability of carbonate and sandstone rocks to preferentially gas wetting condition. Static and dynamic contact angle measurements, spontaneous imbibition and core flooding tests were conducted to investigate the effect of proposed chemical on surface wetting behavior, and fluid flow characteristics at core scale. SEM, EDX, EDX map and FTIR tests are used to characterize the adsorbed chemical layer and also to endorse the adsorption of fluorinated chemicals on both sandstone and carbonate rock surfaces. It is inferred from the results of contact angle hysteresis at different levels of tilt angle that the surface roughness increased as a result of treatment with the new chemical. Measurements of surface free energy of calcite thin section at different tilt angles, by means of dynamic contact angle method, showed a significance decrease due to treatment with the new chemical, the factor of reduction ranges from 0.24 to 0.03. The results of air-water and air-n-decane spontaneous imbibition tests showed remarkable decrease in the ultimate imbibed liquids by a factor of 0.14 and 0.34, respectively. Also, core flooding experiment results demonstrated improvement of liquid phase endpoint relative permeability by a factor of 1.73 as a result of treatment with the proposed chemical fluid. The proposed chemical is miscible with dropped out condensate and does not suffer from instability due to reservoir brine salinity. Effectiveness, as well as hydrocarbon base of the proposed chemical makes it an attractive candidate for possible applications to enhance condensate recovery due to both condensate and water blockage in gas reservoirs by wettability alteration technique.

An investigation into the effect of pressure source parameters and water depth on the wake wash wave generated by moving pressure source

In this study the effect of moving pressure source and channel parameters on the generated waves in a channel was numerically investigated. Draught, angle of attack and profile shape were investigated as parameters of pressure source and water depth and blockage factor as channel parameters on wave height. Firstly, the chosen Computational Fluid Dynamics (CFD) approach was validated with the experimental data over a range of speed. Then the CFD study was conducted for further investigations. It was shown that that by enlarging draught, angle of attack and beam of the pressure source, the wave height generated will be increased. Channel study showed that it is possible to increase the wave height generated by shallowing water for a given speed as long as the depth Froude number is subcritical and the wave height generated is independent of water depth for supercritical depth Froude numbers. The blockage factor has more influence at supercritical Froude depth values, while at subcritical Froude values is negligible compare with water depth.

Effectiveness and time variation of induced fracture volume: Lessons from water flowback analysis

Characterizing the induced fracture network is crucial for evaluating and optimizing fracturing operations and for forecasting hydrocarbon production. In our previous paper [1], we developed a closed-tank material balance model to estimate effective fracture volume using rates and pressure data measured during early-time water flowback. In this paper, we extend this model to an open-tank model to estimate fracture-matrix interface area using rates and pressure data measured during late-time water flowback. We verify the proposed model against a 2D numerical model solved by a commercial software, and demonstrate the application of the proposed model to an eight-well pad completed in the gas shales of the Horn River Basin. Finally, we conduct a comparative analysis to investigate the time variation of effective fracture volume during water flowback. The results show that up to 30% of the effective fracture volume is lost due to pressure depletion and fracture closure during early-time water flowback. The rate of fracture volume reduction decreases during late-time flowback when gas from the matrix kicks into the fracture network and provides sufficient pressure support. However, the estimated fracture-matrix interface area is relatively low and cannot be explained by the estimated fracture volume. This result suggests that although a large fracture network is created by hydraulic fracturing operations, only a small fraction of the fracture network receives gas influx from the matrix. Overall, the results suggest that a large fraction of the fractures induced in gas shales does not contribute to hydrocarbon production due to fracture closure, permeability jail effect, and water blockage.

Woody debris trapping phenomena evaluation in bridge piers: A Bayesian perspective

A flood occurs when water and other materials such as woody debris overflow dry areas. If there is infrastructure present, woody fragments could be transported downstream and eventually trapped, leading to increments in the hydrodynamic forces over, say, a bridge. Moreover, local scour can be developed in the structure piers. The purpose of this research is to investigate the bridge pier scour phenomena induced by woody debris from a probabilistic point of view. A Non Parametric Bayesian Belief Network comprising seven nodes has consequently been developed. They are: water level, Froude number, blockage amount, drag force, scour depth, damage and overturning. Through both Monte Carlo Simulation and data from a real structure, the nodes’ non parametric probability distributions have been established, an area that has, to date, received very little attention in the literature. By combining the variables under study, it was possible to determine their interaction and dependencies, showing that the depth of the approaching flow is correlated with two nodes: damage and overturning. The results are useful for bridge managers willing to rank investments in maintenance actions within the industry, and to develop optimal risk based strategies for efficiently employing the scarce resources used to that end.

Monitored Laser Grinding Using Real Time Nanobots Data: A Novel Mudcake Removal Approach

For ensuring casing and cementing quality, mud cake removal is essential. Various problems like stuck pipe take place because of the presence of mud cake. Mechanical methods of water jetting and chemical methods by means of acids, oxidizers, chelating agents, etc., are currently employed for mud cake removal. However, water jetting can cause water blockage problems and has detrimental effects on well productivity. Also, mud cakes of different permeability will not be removed by same intensity water jets. Acids and oxidizers are very reactive but nonspecific species, imposing several post perforation problems and formation damage. As an alternative, we propose a new method in this study with the usage of nanobots and laser grinding. The nanobots, placed in carrier, can be deployed in all directions into the targeted zone. These non-adherent and self-propelled nanobots will move through the vertical permeability of the mud filtrate and would interpret the petro physical properties of the mud filtrate. The sensors would then send this data to molecular processor and with the help of radio frequency transmitter and receiver, we could immediately interpret the real time data from every point in the zone of interest. This data would be used to change the intensity of the lasers in accordance with the petro physical properties. Lasers, lowered through wireline, would then vaporise the mud cake through spallation according to its thickness and will grind the mud cake by creating popped holes. This novel idea of real time laser grinding with the help of nanobots holds great potential in removing mud cake precisely and efficiently and could also be useful in multilateral and horizontal wells.

Determination of Hydraulic Properties of Unsaturated Soils Based on Nonequilibrium Multistep Outflow Experiments

AbstractIn this paper, a new procedure for rapidly determining the hydraulic properties of unsaturated soils is developed. The proposed procedure is used to characterize the evolution of the instant degree of saturation in an unsaturated soil during a multistep outflow experiment. By introducing the concept of capillary relaxation, a theoretical model is developed and adopted to describe the dynamic hydraulic properties of unsaturated soils under constant-volume conditions. A series of nonequilibrium multistep outflow experiments are performed on various types of unsaturated soils. It is shown that the evolution of the instant degree of saturation or the outflow mass generally follows an exponential law. Both experimental results and theoretical simulations illustrate that flow instability and water blockage can occur in the soil during multistep outflow experiments. The theoretical predictions are compared to the experimental results, showing that the proposed procedure can be effectively used to determi...

Stochastic microstructural modeling of fuel cell gas diffusion layers and numerical determination of transport properties in different liquid water saturation levels

Gas diffusion layer (GDL) materials in polymer electrolyte membrane fuel cells (PEMFCs) are commonly made hydrophobic to enhance water management by avoiding liquid water blockage of the pores and facilitating reactant gas transport to the adjacent catalyst layer. In this work, a stochastic microstructural modeling approach is developed to simulate the transport properties of a commercial carbon paper based GDL under a range of PTFE loadings and liquid water saturation levels. The proposed novel stochastic method mimics the GDL manufacturing process steps and resolves all relevant phases including fiber, binder, PTFE, liquid water, and gas. After thorough validation of the general microstructure with literature and in-house data, a comprehensive set of anisotropic transport properties is simulated for the reconstructed GDL in different PTFE loadings and liquid water saturation levels and validated through a comparison with in-house ex situ experimental data and empirical formulations. In general, the results show good agreement between simulated and measured data. Decreasing trends in porosity, gas diffusivity, and permeability is obtained by increasing the PTFE loading and liquid water content, while the thermal conductivity is found to increase with liquid water saturation. Using the validated model, new correlations for saturation dependent GDL properties are proposed.

Development of a novel water shut‐off test method: Experimental study of polymer gel in porous media with radial flow

Polymer gel treatment is an economic and effective method to reduce excessive water production in hydrocarbon reservoirs. However, there exist unsuccessful applications of polymer gel due to a mismatch of theoretical and experimental results in field conditions. In this study, a gel treatment experiment was implemented using a novel test method which includes a unique two‐dimensional coreflooding setup and a new procedure of simultaneous oil and water injection. To form the gel in situ, a Cr(III)‐acetate‐hydrolyze polyacrylamide (HPAM) gelant was used. The results showed that polymer gel could be successfully applied to water shut‐off (WSO) treatments in low‐permeable porous media with radial flow. The residual resistance factors for oil and water were 78.50 and 1.96, respectively. Polymer gel also showed disproportionate permeability reduction (DPR) behaviour in coreflooding experiments. The flow resistance to water was 40 times greater than that to oil. In gel treatment, high gel selectivity (DPR scale) of 0.83 was measured by simultaneous oil and water flow to the core, and the determined oil cut was much greater than the water cut, whereas a lower well production rate led to a higher water cut. In addition, a water blockage problem was examined in simultaneous injection at constant pressure. No observation of water in the outlet was reported, though water saturation through the sandpack was increased to 84 %. Finally, this paper suggests a new experimental test to increase the chances of successful WSO treatment under laboratory circumstances close to the field conditions.

Effects of Soil Bulk Density on Gas Transport Parameters and Pore‐Network Properties across a Sandy Field Site

The gas diffusion coefficient, air permeability, and their interrelations with air‐filled porosity are essential for characterization of diffusive and convective transport of gases in soils. Variations in soil bulk density can affect water retention, air‐filled pore space, and pore‐network connectivity and tortuosity and, thereby, control gas diffusion and air permeability. Considering 86 undisturbed core samples with variable bulk densities that were extracted on a 15 by 15 m grid from the top layer of a sandy field, the effects of soil bulk density on gas transport parameters and the soil water characteristic were investigated. Interactions with soil organic matter, sand, and clay fractions were also examined. To evaluate bulk density effects, two constitutive parameters were derived from each of the three measured relationships. The Campbell pore‐size distribution index (b) and the air‐entry matric potential (ψae) were derived from the soil water characteristic; the diffusive percolation threshold (εDPT), the air‐filled porosity where gas diffusivity ceases to almost zero because of interconnected water films creating isolated–inactive air content, and a pore‐network connectivity index (A2) were derived from the gas diffusivity curve, and the analogous parameters convective percolation threshold (εCPT) and convective pore‐network connectivity index (B2) from the air permeability curve. All six parameters showed significant negative correlations with bulk density. To further account for the effects of both bulk density and macroporosity in parametric gas transport models, a diffusive‐analog macroporosity–dependent model (DAMP) for gas diffusivity and a generalized Kawamoto et al. model (GK) for air permeability, which yielded improved predictive capabilities when compared with previous models, were developed. Both new models apply a reference point of prediction at −100 cm H2O matric potential (macroporosity drained), corresponding to the point where analysis of pore‐network tortuosity (T) and equivalent pore diameter for gas transport (dg) showed diminishing effects of water blockage on gas transport in the sandy soil.

Rate enhancement in unconventional gas reservoirs by wettability alteration

In unconventional water-wet gas reservoirs with extremely low permeability, water blockage due to the capillary end effect near the fracture face and in the wellbore vicinity is a severe obstacle to gas production. Wettability alteration of rock surface is discussed as an effective way to reduce water blockage and enhance gas production. It can also be applied to accelerating dewatering and preventing drilling and fracturing fluid leak-off. The current paper develops analytical models for steady-state two-phase linear and radial flows, accounting for the contact-angle-dependent capillary pressure and relative permeability. The model has been validated by comparison with laboratory test. Applications of the proposed model to porous media with constant and piecewise-constant contact angles are presented. The modelling shows that the competition between the viscous and capillary effects on productivity results in an optimal contact angle for the maximum well productivity indexes for water and gas. The productivity index increases with the capillary-viscous ratio and the altered zone length.

Control system of speed vector on mineral ventilation motor

Speed sensors of ventilation motor in mineral well are susceptible to various problems, such as water seepage and blockage as well as lack of feedback signals for entilators. As soon as they happen, the ventilation motor will not be controlled. These questions are mainly caused by the damp and dirty working environment. To solve the problems, control System of Speed Vector on ventilation Motor based on ARM (Advanced RISC Machine) is proposed, with IPM (Intelligent Power Module) PS21865 as inverter. The hardware design optimized system structure and expanded the controller memory and compatibility. Based on the optimized system structure, an estimation way of speed vector for the ventilation motor was given with main current control, auxiliaryvoltage control and speed-sensorless, The simulation results show that the adopted methods are correct and effective. With the rapid development of coal industry, a ventilator is widely used in safety production of coal mine because of its structure is solid and durable structure to prevent itself from moisture, explosion and low noise. And it has high efficiency and energy saving, too. But the environment in mineral well is wet and muddy. This environment often leads to water and blockage of speed sensorwithout feedback signal to ventilator. Once a ventilator has no feedback signal to be out of its control, causing poor ventilation, the gas concentration to increase and the temperature to rise in the well head. These conditions will result in gas poison or explosion. To address the problems, the estimation control of speed vector for the ventilation motor was proposed through a variety of transformations and based on the rotor field orientation with the equivalent principle of magnetic field. It used the actual speed of fan motor as the speed feedback signal by indirect calculation method, without speed detecting device. The core problem of the control strategy is accurate observation of the rotor flux and accurate esti- mation of motor speed. The current of motor stator coil can be directly detected, but magnetic flux and electromagnetic torque can not be measured, and we can use the decoupling method. The stator cur- rent vector can be divided into two components and they are mutually vertical and independent. Then a component is used to produce excitation flux, the other is used to generate the electromagnetic torque, This can approximately realize the indirect control of flux and torque. However, at high speed the speed estimation method on a ventilator can ignore the error influence. At low speed, the influence of magnetic

The Use of the Super Absorbent Polymer as Water Blocker in Concrete Structures

Adding super absorbent polymer to the concrete mix improves the performance of the concrete in its both stages; fresh concrete and hardened concrete. The super absorbent polymer has the ability to absorb relatively large amount of water and convert it into gel at the same time the volume increases proportionally. The new modified concrete has the ability to retain water in the form of gel which helps in the internal curing process of the concrete at its early stages and helps in blocking the water flow through voids and cracks in the mass of the concrete at its later stages. This study focuses on the ability of concrete to block the water flow through the concrete cracks. Several samples were prepared with different amount of super absorbent polymer added to the concrete mix expressed in percentage with respect to the weight of cement. Several cylindrical samples were prepared, but three different samples will be presented in this study. The samples were intentionally broken into two pieces. The two pieces are then put together forming artificially induced cracks in the samples. These samples were subjected to water pressure; falling head and constant head. The water flow through the induced crack in the sample is measured. The effect of the super absorbent polymer on the water flow is monitored and compared with the control samples, which is the sample prepared with no admixtures. The water tightness leading to complete water blockage is studied. The short term effect as well as the long term effect of the super absorbent polymer on the concrete water tightness is also studied. Several amounts of the super absorbent polymer expressed in terms of percentages of the cement weight are used in order to shed the light on the water tightness property of concrete. The increase of the amount of the super absorbent polymer in the concrete mix improves the internal curing properties of the concrete at the same generate more voids in the mass of the concrete which in turn reduces the strength of the concrete. Optimum amount of the superabsorbent polymer should be considered if the focus is the concrete strength. Also, the increase in the amount of the superabsorbent polymer in the concrete improves the water tightness of the concrete, which makes the concrete capable of blocking the water flow through the concrete cracks. There are several advantages of adding the super absorbent polymer to the concrete mix, including improving the concrete plasticity and workability at the same time improving the concrete mix stability and pump-ability.