Increase In Differential Pressure Research Articles

Study on the Spatial Damage Characteristics of Working Fluid in a Sandstone Reservoir and an Unplugged Fluid System.

Due to its good physical properties and low pressure coefficient, the K75 reservoir is prone to leakage and intrusion of drilling and completion fluids during well construction, resulting in plugging of the borehole throat, which will inevitably affect the injection and recovery capacity of the gas well. In order to ensure the strong injection and production capacity of the K75 reservoir, this paper clarifies the reservoir space damage characteristics under different pressure differences and different entry fluids by establishing physical simulation of the damage, selecting the optimal system of the decongestant, and conducting dynamic flow decongestion experiments, as well as combining with the characterization means of the continuous scanning system of the core and the permeability test of the gas measurement. The test results show that the degree of damage of the same working fluid increases with the increase of differential pressure of repulsion, and the degree of damage of sequential working fluids (drilling fluid, completion fluid, and perforating fluid) is greater than that of drilling fluid damage under the same differential pressure of repulsion. In order to relieve the damage of wellbore working fluids, a set of multifunctional, low-corrosion composite acid system formulas was selected through rock powder, mud cake dissolution experiments, and dynamic flow unblocking experiments; the permeability recovery rate of this acid system after unblocking was more than 90%, which is widely applicable, and it is useful for the acidizing and unblocking practice in similar reservoirs.

Modeling of High Pressure Loss (Head Loss) in a Flow Measurement Unit with Various Pipe Network Manifold Openings

The head loss in water flowing through pipes often turns out to be different from what we assume, which is the occurrence of incompressible flow. However, this assumption is not always true because the flow pattern inside the pipe is not visible and can only be measured with precise equipment. The presence of water in the pipes can only be tested on a clear scale, especially when it is part of the network within a multi-story building. Determining the need for a pipe network within a building is not an easy calculation due to differences in length, diameter, and bends. Hydraulic experts often overlook these differences, which can become a problem when clogs occur during the flow process. To find a solution to this problem, it is necessary to conduct tests using a device called a Water Measurement Unit. This is rarely done in laboratories. Testing the water pressure with this device requires various instruments and a variety of valve openings supplied with pressurized water by a pump at a certain capacity. To analyze the flow rates resulting from the tests with different valve openings, researchers test and measure the flow rate capacity for each opening, starting with openings of 0.5, 0.75, 1.00, and so on. They read the instrument, move the copper from one height to another, and create a graph of the test results in the form of a pair of connectors. The researchers test the device and its openings three times for each opening, recording and mapping the pressure values and the time it takes on the measuring instrument. Subsequently, the results of the pressure test (Head Loss) are recommended to provide information to water pipe installation planners that the test results with various valve openings under certain conditions have different pressure values and travel times. It turns out that in the placement of hose or copper number 2, stability is observed with pressure, and there is no significant differential pressure increase. In the experiment with hose or copper number 2, it can be said that everything is stable enough to conclude that there is no head loss, and it is recommended to be safe for modeling.

The measurement of deformation rate of flexible container based on constant conductance element in molecular regime

An innovative method using constant conductance element to measure the deformation rate of flexible container was proposed based on the theoretical model of dynamic micro-flow detection. The measurement system of dynamic deformation rate was built by using the semi-flexible container encapsulated with polyimide film, and a constant conductance element was installed between the flexible container and the pressure stabilizing chamber to provide a constant micro-flow rate. The dynamic differential pressure variation between the inlet and the outlet of the constant conductance element was measured and then the deformation rate of flexible container could be obtained through the iterative calculation of the measured differential pressure change over time. The results show that the deformation rate gradually decreases with the increase of differential pressure. In addition, Boyle's law was used to verify the experimental results of dynamic micro-flow detection method, and it is revealed that the measurement error is less than 11%. Finally, a standard leak element was applied to simulate the leak source of flexible container. The conductance of standard leak element and the leak rate of flexible container have been successfully predicted by using the measured deformation rate.

Performance Analysis of the Cylinder Gas Film Seal between Dual-Rotor Reverse Shafts Considering Lubrication and Centrifugal Expansion Effects

The cylinder gas film seal between dual-rotor reverse shafts is a new method for sealing aircraft engines that has excellent developmental prospects. We propose a novel method for determining if the sealing ring is fully fluid-lubricated using the average Reynolds equation. Considering surface roughness and centrifugal expansion, we calculated the dynamic pressure, gas film force and friction power consumption with and without inlet pressure differences for each of the four rotation modes. The gas film’s dynamic pressure effects were weakest when the dual rotors rotated in a reverse direction (Mode 3), with or without differences in inlet pressure, since solid contact is most likely to occur under counter-rotation. When the dual rotors were in counter-rotation with an inlet differential pressure of 80 kPa and fixed inner and outer rotor speeds (e.g., 3000 rpm), we calculated the minimum sealing ring film thickness, leakage rate, friction power consumption and gas film force. Changes in outer rotor speed greatly influenced the minimum film thickness and the sealing ring’s performance. Meanwhile, changes in the inner rotor speed had little influence on the minimum film thickness and sealing ring’s lubrication performance. When the speed difference was fixed and the sealing ring was fully fluid-lubricated, lubrication performance changes were mainly affected by changes in centrifugal expansion caused by the outer rotor speed. Given a fixed rotor speed and under dual-rotor counter-rotation, we calculated the effects of inlet differential pressure changes on minimum gas film thickness, leakage rate, friction power consumption, gas film force and other sealing performance variables. Leakage rate and the friction power consumption increase as inlet differential pressure increases. Our results provide a theoretical reference for avoiding solid contact of the cylinder seal between dual-rotor reverse shafts.

Inhibitor-Resistant Calcites Causing Solids Fouling Identified, Studied

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 209475, “Unraveling the Mystery of Inhibitor-Resistant Calcite Affecting Onshore and Offshore Operations,” by Hugh M. Bourne, SPE, Adil A. Abbasov, and Ben E. Smith, BP. The paper has not been peer reviewed. _ Magnesian calcite has been identified as the main constituent of solids fouling in several of an operator’s facilities in the North Sea and Azerbaijan and in partner operations in other locations. These solids were, for many years, thought to be calcite scale. The complete paper describes how this “pseudoscale” was detected and its prevalence, using field case examples. The Discovery: Case 1 Soon after the start of operations in May 2017, fouling of the rundown coolers was observed on a North Sea floating production, storage, and offloading vessel. The increase in differential pressure across the coolers was believed to be the result of wax deposition. The cooler performance, however, progressively deteriorated with every dewaxing cycle to a point at which running the cooler without cooling medium had no effect on the differential pressure. One of the rundown coolers was removed and returned to the manufacturer for inspection and cleaning. This revealed that hard, scale-like solids were filling the space between the plates completely (Fig. 1). The retrieved solids dissolved in acid, were calcium-rich, and appeared visually and mechanically to be a scale; thus, they were assumed initially to be calcium carbonate. The first analysis of solids from the rundown cooler and other parts of the plant suggested that up to 33% of the composition of these solids was calcium, which would be equivalent to greater than 80% of these solids being calcium carbonate. Scaling in the rundown cooler was not expected and raised concerns about uncontrolled scaling in other parts of the plant. A wider review of plant performance was initiated, and more-detailed analysis of the solids collected in the rundown coolers was undertaken using X-ray diffraction spectroscopy (XRD). The rundown cooler solids analysis revealed an inorganic crystalline compound consisting of magnesian calcite (calcium/magnesium carbonate) that had the appearance of a compacted transported solid. The dewaxing frequency was increased to prevent this accumulation, which ultimately proved an effective mitigation strategy. The wider review of plant performance identified frequent fouling of the produced water-pump suction strainers and a gradual decrease in the performance of the crude-oil heaters. Analysis of the solids fouling the produced-water-pump suction strainers also was dominated by magnesian calcite, suggesting that the reservoir fines were transported in both the oil and the produced-water streams. Reservoir solids fouling is not uncommon, but, by the beginning of 2018, the decrease in the differential pressure trend across the crude-oil heaters became more prominent. By the end of the first quarter of 2018, the degradation was limiting the ability of the plant to meet temperature set points in the separators, potentially limiting production rates.

Pressure effects on the anisotropic electrical conductivity of artificial porous rocks with aligned fractures

ABSTRACTUnderstanding the electrical properties of reservoir rocks has important applications in oil and gas exploration. Small‐scale fractures that are widely existing in reservoir rocks are usually aligned along a certain preferential direction due to reasons such as tectonic movement, making the electrical conductivity of the rocks anisotropic. Since all rocks are experiencing geological pressure, it is theoretically and practically important to study the influence of pressure on the fractures and its control on the anisotropic conductivity of reservoir rocks. We first prepared artificial porous sandstone samples with and without penny‐shaped fractures and experimentally measured the anisotropic conductivity of the samples under differential pressure (the difference between confining pressure and pore fluid pressure). Then, we inverted from the experimental data for the fracture porosity and fracture aspect ratio at each differential pressure. The variation of the fracture parameters caused by the differential pressure and their influence on the anisotropic electrical conductivity of the rocks were further analysed theoretically. The results show that as the differential pressure increases, the measured anisotropic conductivity of the artificial samples with and without fractures all decreases exponentially. We also show that both the inverted fracture porosity and fracture aspect ratio decrease exponentially with the increase of differential pressure, and the fracture porosity and fracture aspect ratio are linearly correlated as an implicit function of differential pressure. The modelling results show that the differential pressure‐induced decrease in the fracture porosity reduces the electrical conductivity in all directions, and the conductivity reduction in the rock parallel to the direction of the fractures is most significant. Comparing with the influence of the fracture porosity resulting from the applied differential pressure, the pressure‐caused variation in the fracture aspect ratio was shown to play a secondary role on affecting the pressure‐dependent anisotropic electrical properties.

Interfacial dynamics of gas–water displacement in fractured porous media under high pressure

To deeply understand the dynamics of gas–water displacement in fractured porous media, especially under extreme high-pressure conditions, is essential to prevent water invasion in natural gas reservoirs. To this end, we presented an experimental study on the interfacial dynamics of gas–water displacement in a microfluidic device with fractured porous media, in which the displacement pressure could reach as high as 25 MPa. We found that, under the condition of quasi-static imbibition (i.e., at quite low differential pressure), water preferentially invaded the matrix instead of the fracture. In contrast, invasive water tended to permeate the fracture under high differential pressure; as a consequence, a conical front edge was formed at the gas–water displacing interface. More importantly, the interfacial front in different fractures contacted at the cross junctions and led to the formation of trapped gas in the matrix, due to the velocity of gas–water interface in the fracture being higher than that in the matrix. Besides, with increase in differential pressure and fracture number, the difference in the interfacial velocity between fractures and the matrix increased and hence the gas in the matrix was more easily trapped. Finally, we established a theoretical model to predict the interfacial velocity of gas–water displacement in fractured porous media under high pressure, which was able to well reproduce experimental data.

Two-phase pressure drop analysis of swirl tube in one-side high heat load condition for plasma facing component application

In this study, the two-phase pressure drop of a one-side heated swirl tube (twist ratio = 3, 5) was experimentally studied. If the a heat flux is gradually increased, the vapor blocks the flow path, thus leading to an increase in the differential pressure. As the inset sub-cooling and mass flow rate increase, the vapor is removed by condensation more rapidly, and thus, the rate of increase of differential pressure is reduced. From the evaluation of the prediction performance of the existing two-phase pressure drop correlations, it was found that the mean error rates of all correlations exceeded 50%. This is because most of the existing correlations were not developed based on the microchannel, but they were not focused on the swirl tube. Therefore, the authors developed a new two-phase pressure drop multiplier correlation for a one-side heated swirl tube that reflects the effect of the twist tape by modifying the Manglick single-phase swirl tube pressure drop correlation using the AI regression method.

Numerical investigation on sealing performance of drainage pipeline inspection gauge crossing pipeline elbows

AbstractA pipeline inspection gauge (PIG) is routinely passed throughout the long‐distance oil and gas pipelines by pipeline operators to clean the pipeline. Sealing performance is a significant evaluation index for PIG's safety operation. To comprehensively evaluate the PIG's seal performance, nonlinear finite element models were developed, and parametric analysis was conducted in this study. The accuracy of simulation model was validated from numerical and experimental results reported in the literature. The results show that comparing with the pigging in straight pipes, the sealing rubber cups of PIGs can be more easily detached from the pipe wall when passing through elbows, causing smaller sealing areas. For a typical elbow (with curvature radius equals to six times of pipe diameter) widely used in pipeline industry, the minimum sealing area of rubber cup is only 8.07% during common operation conditions. The sealing ability of rubber cups can be obviously enhanced by increasing the curvature radius for the pigging operation of small curvature elbow. Elbow radius slightly affects the cup's sealing behavior when the curvature radius is over six times of pipe's outer diameter. An increment in sealing cup interference can increase the contact area between cup and pipe wall, and the blockage risk of PIGs will be reduced due to the good sealing ability and sufficient driving force. The minimum interference required for the cups is 4% under a most common operation condition; that is, the sealing cup thickness, fluid pressure difference, and friction coefficient are 35 mm, 0.02 MPa, and 0.3, respectively. A proper decrease in sealing cup thickness will reduce the stiffness of rubber cups, indicating that the cups with a smaller thickness are more prone to deformation. Thus, an increase in differential pressure over PIG can enhance the sealing performance of cups when the cups are separated from pipe wall. A large friction coefficient is risky for a safe pigging due to the decrease in sealing region with the increase in friction coefficient. In engineering practice, proper measures should be taken to reduce friction force. Above all, the results obtained in this study provide a reference for the structural design of PIGs.

Differentiation and grouping of complex-structured oil reservoirs in carbonate reservoirs in development management problems solving

The article presents the developed algorithm and the results of carried out differentiation and grouping of oil deposits in the carbonate reservoirs of the Volga-Ural oil and gas province, both under development and out of exploration, according to geological parameters, the determination of which is possible at the stage of geological exploration. A method for selecting an analogue deposit, which has been in development for a long time has been worked out for a deposit coming out of exploration in order to use the experience of developing an analogue deposit in the conditions of a deposit being put into development. The comparison of the selected groups of objects by geological parameters is carried out, the characteristics of the features of each of them are given, the main differences in the geological structure are revealed. It has been established that the features of the geological structure of various groups of objects are mostly determined by their tectonic-stratigraphic confinement. Keywords: free-flow production; increase of differential pressure; field-scale experiment; well pattern; well interference; oil flow paths.

Justification of necessity to consider well interference in the process of well

The paper discusses results of the unique field-scale experiment on halving of active wells and increase of pressure differential at bottomholes of active wells in the Bavlinskoye oil field. With a view to assess the effect of well interference between shut-in and active wells, two scenarios of oil flow lines in the reservoir, shut-in scenario and do-nothing scenario, were modeled. The numerical computation demonstrated that increase of pressure differential at an early stage of development can maintain the obtained level of production with a less number of free-flowing wells. It was also found that an optimal well pattern has to be used at an early stage of development. In this case, oil losses are lower vs. infill drilling at the late stage of development. In the latter case, high water cut challenges economic production, which was the case with half of re-entry experimental wells. Keywords: free-flow production; increase of differential pressure; field-scale experiment; well pattern; well interference; oil flow paths.

Study Investigates Factors Affecting Coefficient of Discharge in Stimulation

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 200612, “The Role of Backpressure and Perforation-Hole Erosion on the Magnitude of the Coefficient of Discharge in Hydraulic Fracturing Stimulation,” by Davood M. Yosefnejad, Bernd Fricke, and Joern Loehken, DynaEnergetics Europe, et al., prepared for the 2020 SPE Virtual Europec Conference, 1–3 December. The paper has not been peer reviewed. One of the important factors affecting the near-wellbore-fluid pressure drop is the coefficient of discharge (Cd). In the complete paper, the authors investigate some of the factors that can affect Cd, such as the erosion of the perforated hole and the backpressure given by the fracture. The paper studies the effect of perforation hole size, geometry, and shape on the Cd value at ambient conditions and with backpressure, before and after sand erosion. Setup Specifications and Materials For this study, a high-pressure, high-flow setup was built for Cd measurements, as well as a second setup in which the holes can be eroded by proppant-laden slurries. The test cell was the same for both setups. The holders of the plates were stainless steel and connected to 7-in. pipes approximately 4 ft long on each side. In all the experiments, the flow rate and inlet and outlet pressure data were recorded simultaneously vs. injection time by high-precision sensors. All experiments were carried out at an ambient temperature of 15–28°C. For these flow-test experiments, only water was used, circulated with different pressure differentials to determine the effect of pressure on Cd magnitude. In addition, backpressure was applied through the needle valve to simulate real reservoir conditions and to compare the Cd value with the tests under ambient conditions. The flow rate range of the pump was 1–7 bbl/min at maximum pressures of approximately 2,000 psi. Erosion tests have been performed for 30 minutes with a near-constant flow rate (approximately 1 bbl/min), constant pressure (approximately 200 psi), and constant sand concentration. For the erosion test, a viscosity of approximately 10 cp was used. The sand concentration was kept at 1 to 2 lbm/gal to keep the erosion rate low, which would allow distinguishing between shape-driven changes in Cd and changes caused by an increase of the hole size. The study used machined holes and holes created by differently shaped charges, which also differed in size and geometry. A description of these holes, and associated shaped-charge tests, is provided in the complete paper. Experimental Results and Discussion Generic Holes. In the first sets of experiments, generic holes with different entrance-hole diameters were used. The experiment began with the lowest inlet pressure, which gradually was increased to the maximum pressure. The outlet pressure was kept constant at an ambient pressure. The flow rate increased because of the increase in differential pressure. After reaching the maximum pressure, the inlet pressure was kept constant and the choke on the outlet side was closed step by step to establish a backpressure, which led to a decrease in differential pressure. Surprisingly, the flow rate stayed constant until the differential pressure surpassed 700 psi.

Effects of release pressure on the transportation characteristics in pipeline and the diffusion behaviors in enclosure space of typical gas extinguishing agent

Reducing the release pressure of fire extinguishing systems can decrease potential safety hazards in large transport airplanes. To explore whether reducing the release pressure can achieve the release effect required by the airworthiness standards or not, the transportation characteristics in the pipeline and diffusion behaviors in the enclosure space of a typical fire extinguishing agent (Halon 1301) were investigated under five release pressures in the present study. The effects of the release pressure on the degree of superheat, injection duration, jet structure, and concentration distribution of Halon 1301 were analyzed. The results show that both of the degree of superheat and the injection duration decrease with an increase in the release pressure. The supplement of bubble expansion in the fire extinguishing agent can slow down the pressure decrease in the vessel. Both of the maximum and mean values of the pipeline differential pressure increase with an increase in release pressure. The maximum value of the jet angle decreases linearly with the increase in release pressure, and the jet deflects upward owing to the effects of buoyancy. The maximum concentration value decreases with an increase in the distance from the nozzle. The maximum concentration values in the near field from the nozzle increase with an increase in the release pressure. Under five release pressures, the concentration and holding time (duration above 6% volume concentration) of Halon 1301 on the centerline of the jet meet the requirements of airworthiness provisions.

Effect of Water Distribution on Spontaneous Imbibition of Tight Rocks: A Fractal Approach

The original water distribution characteristic plays an important role in the fracturing liquid retention in actual tight reservoirs. In this paper, an analytical model was proposed to characterize the water distribution and its effect on the spontaneous imbibition, based on the capillary tube model and fractal theory. Furthermore, the effect of the water film and the non-piston-like front related to the pore size are included in our model. The proposed model was successfully validated with the experimental results of core imbibition tests. Our work demonstrates that water distribution is influenced by displacement pressure and pore structure. For a small differential pressure, the porous media with richer large pores usually possesses a lower water saturation, and this difference will decrease with the increase of differential pressure. Moreover, compared with previous studies, the proposed imbibition model can not only distinguish the valid pores and invalid pores for imbibition but it can also predict the initial imbibition rate and equilibrium time of tight porous media with different water saturation. The results show that the equilibrium time is controlled by the minimum effective pore radius while the initial imbibition rate is mainly controlled by the large pores. Both of these two parameters will decrease with an increase of water saturation; the former is more sensitive to a low water saturation, while the latter decreases more quickly for a middle-high water saturation.

Cell biophysical stimuli in lobopodium formation: a computer based approach

Different cell migration modes have been identified in 3D environments, e.g., modes incorporating lamellopodia or blebs. Recently, a new type of cellular migration has been investigated: lobopodia-based migration, which appears only in three-dimensional matrices under certain conditions. The cell creates a protrusion through which the nucleus slips, dividing the cell into two parts (front and rear) with different hydrostatic pressures. In this work, we elucidate the mechanical conditions that favour this type of migration. One of the hypotheses about this type of migration is that it depends on the mechanical properties of the extracellular matrix. That is, lobopodia-based migration is dependent on whether the extracellular matrix is linearly elastic or non-linearly elastic. To determine whether the mechanical properties of the extracellular matrix are crucial in the choice of cell migration mode and which mechanotransduction mechanism the cell might use, we develop a finite element model. From our simulations, we identify two different possible mechanotransduction mechanisms that could regulate the cell to switch from a lobopodial to a lamellipodial migration mode. The first relies on a differential pressure increase inside the cytoplasm while the cell contracts, and the second relies on a change in the fluid flow direction in non-linearly elastic extracellular matrices but not in linearly elastic matrices. The biphasic nature of the cell has been determined to mediate this mechanism and the different behaviours of cells in linearly elastic and non-linearly elastic matrices.

Performance Evaluation of a Novel Thermal Power Plant Process with Low-Temperature Selective Catalytic Reduction

We present the concept of a novel thermal power plant process in conjunction with low-temperature selective catalytic reduction (SCR). This process can be employed to achieve modern standards for NOx emissions and solve problems related to post-gas cleaning processes, such as thermal fatigue, catalyst damage, and an increase in differential pressure in the boiler. Therefore, this study is aimed at evaluating the performance of a novel flue-gas cleaning process for use in a thermal power plant, where a low-temperature SCR is implemented, along with the existing SCR. We developed a process model for a large-scale power plant, in which the thermal power plant was divided into a series of heat exchanger block models. The mass and energy balances were solved by considering the heat transfer interaction between the hot and cold sides to obtain the properties of each material flow. Using the process model, we performed a simulation of the new process. New optimal operating conditions were derived, and the effects that the new facilities have on the existing process were evaluated. The results show that the new process is feasible in terms of operating stability and cost, as well as showing an increase in the boiler thermal efficiency of up to 1.3%.

Effects of Reservoir Parameters on Separation Behaviors of the Spiral Separator for Purifying Natural Gas Hydrate

The spiral separator is an important tool for desanding in natural gas hydrate production, and the change of hydrate reservoir parameters has a great impact on spiral separator behavior. Mastering the influence law is helpful to improve the separation performance. Until now, there was still no detailed analysis of the effect mechanism between reservoir parameters and spiral separator behavior. In this paper, a downhole spiral separator was designed. Then, the effects of reservoir parameters (particle size, hydrate, volume fraction, and sand volume fraction) on separation performance (discrete phase distribution, separation efficiency, and differential pressure) with different flow rates were investigated by numerical simulation method Fluent 18.0. The results show that effects degree of reservoir parameters is in order from large to small: sand phase volume fraction, particle size, hydrate volume fraction. As the particle size increases, the separation performance is improved. When the sand volume fraction increases, the natural gas hydrate (NGH) recovery efficiency and differential pressure both increase, but the sand removal efficiency decreases. When the hydrate fraction increases, the separation performance change law is opposite to that when the sand volume fraction increases. In addition, with increasing the flow rate, the efficiency and differential pressure increase. Therefore, reservoir saturation and porosity can balance NGH recovery efficiency and sand removal efficiency. Furthermore, the spiral separator has good performance under the change of reservoir parameters. The performance of the NGH spiral separator can be also maintained by increasing the flow rate.

A mechanistic experimental study on the combined effect of Mg2+, Ca2+, and SO42- ions and a cationic surfactant in improving the surface properties of oil/water/rock system

More than half of the discovered hydrocarbon reservoirs in the world are the oil-wet carbonates. Enhanced oil recovery (EOR) from these reservoirs is challenging because of their tendency to retain oil at the rock surface. The use of low salinity (LS) water injection to recover more oil from these types of oil reservoirs has been recommended by several researchers. There are possible mechanisms concerning LS water flooding that have been introduced in the literature; a distinct lack of experimental investigation to enhancing the efficiency of this method is still felt. In this work, a detailed and comprehensive study was carried out on using LS + surfactant (LSS) to improve the surface and interface properties of oil + water + calcite rock samples. In the first step, the point of zero charge of the rock sample was determined. Then, the effect of different salts including MgCl2, CaCl2, and Na2SO4 at different concentrations on improving the oil-water interfacial tension and wettability alteration of the rock surfaces was investigated in the presence and absence of a cationic surfactant, cetyl methylammonium bromide (CTAB), in the operational range of pH. Emulsion formation and adsorption measurement tests were performed for a deep investigation of the performance of the cationic surfactant in the presence of different salts. Finally, waterflooding experiments were carried out and the water/oil relative permeabilities, amount of recovery and wettability alteration were thoroughly investigated for three different injection scenarios.The results showed that the co-presence of magnesium, calcium and sulfate ions all in the presence and absence of CTAB surfactant causes a significant reduction in IFT and contact angle values, especially at the lower ranges of salinity. The addition of divalent cations, i.e., Mg2+ and Ca2+, could reduce the amount of surfactant adsorbed on the calcite rock surfaces, especially in the low ranges of salinities. Also, in flooding tests, an increase in differential pressure between the inlet and outlet faces of the core samples from about 2.9 MPa for LS to about 4.7 MPa for LSS flooding, at the breakthrough time, was observed which was related to the formation of water in oil emulsions during LSS flooding. Comparison of the ratio of the residual to initial oil saturation (Sor/Soi) for different flooding scenarios (i.e., injection of saline water (SW), LS and LSS solutions) indicates that as the salinity of water reduces, the efficiency of CTAB surfactant in improving oil recovery increases.

Clay-Free Drilling Fluid with Anti-Water Locking and Low Damage Performance Used in the Changbei Block

Continuous mass production of wells in Changbei Block has led to formation pressure attenuation, differential pressure increase and formation damage by drilling fluids. Therefore, the damage mechanism of reservoir has been studied. After doing so, the G311 water-locking removal agent and other agents were implemented, so as to form a clay-free drilling fluid with anti-water locking and lower damage performance, and it is suitable for the Changbei Block depleted reservoir. Compared with the clay-free low damage drilling fluid, its filtrate has a surface tension reduction rate of 77.8%, a linear expansion rate of 22.6%, and a core damage rate of lower than 15.0%. It has the advantage of water-locking removal, water sensitivity inhibition and remarkable reservoir protection effect. The new drilling fluid has been tested in 2 wells of the Changbei Phase II project, and no downhole failure occurred during the drilling process. The trip operation was smooth, and the wellbore maintained a well cleaned state. Among them, the average ROP of Well CX-5 increased by 12.1%, the open hole completion and direct gas lifting production were used in this well, and the production reached 70×104 m3/d, higher than the expected gas production. The research results showed that the clay-free drilling fluid with anti-water locking and lower damage performance could meet the requirement of drilling safety and reservoir protection, suitable for long horizontal section drilling in pressure attenuated formation of Changbei Phase II.

Rapid Clogging of High-Efficiency Particulate Air Filters During In-Cell Solvent Fires at Reprocessing Facilities

Recent Japanese nuclear regulations have focused on the hazards of in-cell solvent fires at reprocessing facilities. In this work, a mixture of tributyl phosphate and dodecane-based solvents was burned to generate an aerosol composed of soot and unburned solvent that was then loaded onto a high-efficiency particulate air filter simulating the ventilation system of reprocessing facilities. A radical increase of differential pressure occurred in the filters during these tests after the dodecane burned out from the solvent in a phenomenon we named as rapid clogging, likely caused by the burnout of dodecane. This relationship provides valuable insight into the establishment of new regulations for reprocessing facilities. Moreover, an analysis of the aerosol revealed an increase in unburned solvent content and aerosol particle size generated during the rapid clogging. As such, the rapid clogging may be caused by the unburned solvent release or interactions between the soot and unburned solvent vapor. Overall, this work indicates that clogging of ventilation filters during solvent fires may occur more rapidly than previously estimated.