Water Plugging Research Articles

Experimental Study on Water-Plugging Performance of Silicon Dioxide/Polystyrene Hydrophobic Insoluble Microsphere Particle Flooded by High-Water-Cut Oil–Water Mixture

Abstract Water plugging was an important but difficult process close to high-water-cut production wells. The injected water-plugging materials were usually liquid and typically had been evaluated by conventional water-flooding experiments. In this study, silicon dioxide (SiO2)/polystyrene hydrophobic insoluble microsphere particles were introduced as a selective water shutoff agent, and the water-saturated core was flooded with a high-water-cut oil–water mixture. Indexes such as modified oil-coning time, water-cut fluctuation, and cumulative water cut were proposed to evaluate water-plugging capability. A parametric study was conducted to evaluate the influence of particle composition (A, SiO2/polystyrene particle; B, complete polystyrene particle), water cut of the injected oil–water mixture, and preheating temperature of the insoluble particles on water-plugging performance. The results from the index analysis and relative permeability curve showed that the proposed indexes could be used to compare water-plugging performance during oil–water mixture drive; both particles had better water-plugging performance when the injected mixture was not an ultrahigh water cut (fw < 90%). Particle B had larger lipophilicity and stronger capacity for decreasing the water cut (about 0.55–1.28%) at a conventional temperature when the oil–water mixture of the injected fluid had a water cut of 90%. Particle A had lower capacity to decrease the water cut (by about −0.94–0.26%), but it was resistant to reservoir temperature because of its dense structure and the addition of SiO2. These results provided suggestions for the application of hydrophobic insoluble microsphere particles in water plugging in production wells.

Column Penetration and Diffusion Mechanism of Bingham Fluid Considering Displacement Effect

The diffusion progress of grout is hindered by groundwater, which means the diffusion distance cannot reach the designed values required in engineering for water plugging or reinforcement. In this study, based on the generalized Darcy’s law and the continuity equation of steady column penetration, a column diffusion mechanism for Bingham fluid, considering the displacement effect of grout on groundwater, is proposed. This diffusion mechanism is then validated by the penetration grouting experiments that have been previously performed. The influences of the grouting pressure, groundwater pressure, water–cement ratio and penetration coefficient of porous media on the diffusion radius are analyzed. Based on the Comsol Multiphysics platform, a three-dimensional numerical simulation program for this mechanism is developed using computer programming technology. Numerical simulations of the penetration and diffusion morphology of Bingham cement grout in porous media are then carried out. The results show that the theoretical calculation values of diffusion radius obtained from this mechanism are closer to the experimental values than those obtained from the column penetration grouting theory of Bingham fluid, without considering the displacement effect. The results of this study can provide theoretical support for practical grouting engineering.

Investigation on the water-coning control by CO2 injection in strong bottom water reservoir

The crestal CO2 injection can be used to control the flow of water in a strong bottom water reservoir. Pressure-Volume-Temperature and relative permeability studies were done under formation circumstances (50 MPa, 110 °C) to elucidate the mechanism of water-coning regulation. The findings of the PVT test demonstrated that CO2 might shift the water phase downward, so regulating water-coning and lowering the viscosity of the oil, thereby preventing water break. The results of the relative permeability test indicated that CO2 could reduce the relative permeability of brine, increase the relative flow capacity of crude oil, form a CO2-oil miscible bank concurrently, increase the efficiency of oil displacement by water flooding, and inhibit the formation of water-coning. An appropriate strong bottom-water block was chosen as a trial location for evaluating the water-coning control by CO2 injection. The results suggested that crestal CO2 injection was more successful in reducing water cut than the basic gravity effect. The results also indicated that CO2 injection is a more effective method of controlling water-coning than water plugging.

Fractal Statistical Study on the Strength of Jointed Rock Mass

The failure probability and strength of jointed and fractured rock mass under water pressure action place important constraints on the safety and stability of rock mass engineering. In this study, two strength calculation models for rock mass joint rupture failure and shear slip failure are established according to different relative sizes and working conditions, and the effects of fractal dimension, water pressure, and number of cracks on the strength and failure probability of rock mass are analyzed. The most unfavorable dip angle under shear-slip conditions is calculated. The proposed models accurately reflect the failure probability and strength of jointed rock mass, and different strength calculation methods should be selected according to the specific working conditions. The effect of water pressure on the strength of jointed rock mass is sensitive to the failure mode. Reasonable drainage should be carried out according to the different failure modes when constructing tunnels with abundant groundwater, and certain drainage or water plugging construction schemes are not necessarily applicable to all cases. The dip angle at which joint fissures are most prone to shear slip is given as π/4 + φ/2, where φ is the jointed rock mass strength parameter. An increase in the fractal dimensions, external stress, and number of fractures will enhance the rock mass failure probability regardless of failure mode. Controlled blasting and advanced grouting reinforcement measures are recommended when a tunnel traverses through a joint fissure zone to reduce the number of cracks generated in the surrounding rock and thus improve its strength and stability.

Experimental research on the mechanisms of improving water flooding in fractured-vuggy reservoirs

Fractured-vuggy reservoirs have extremely complex reservoir characteristics, leading to a large amount of remaining oil not being recovered after water flooding. In order to solve the problem of the low recovery in fractured-vuggy reservoirs, we utilized 3D printing technology to fabricate two-dimensional and three-dimensional experimental models based on the typical reservoir structure. A series of experiments with different models on improving water flooding is conducted to study the production improvement effect. The difference in oil-water distribution or oil saturation distribution before and after improved water flooding is also compared, and the mechanism is analyzed. The results show that the oil-water gravity differentiation is the most critical factor affecting the remaining oil distribution, and changing the injected pressure or its propagation direction is the root of improving water injection. Reversing injection-production wells, increasing injection strength, water plugging, and cyclic water injection can effectively increase the sweeping scope or displacement efficiency. The attic oil, residual oil in filling medium, bypass remaining oil, and water cone remaining oil can be produced by one or more improving water flooding methods. This paper provides effective measures and mechanisms for the efficient and rapid development of fractured-vuggy reservoirs.

Experimental Study on Stimulation of Horizontal Wells Filled with Film-Coated Gravel in Deep-Sea Bottom-Water Gas Reservoirs.

Large gas reservoirs such as Yacheng and Lingshen have been discovered in the exploration of deep-sea gas reservoirs in the South China Sea in recent years. However, the existence of bottom-water and sufficient water energy in deep-sea gas reservoirs seriously affects the development effect of gas reservoirs. In order to effectively control water development of deep-seabed water gas reservoirs, it is proposed to fill water-resistant and breathable coated gravel outside horizontal wells for mining. Based on the preparation of modified coated gravel, this paper studies the resistance of coated gravel to friction damage, temperature damage, acid damage, pressure damage, and water-resistant performance of coated gravel. The results show that (1) the coated gravel coating has good resistance to friction erosion and acidification corrosion. The upper limit of temperature resistance is 250°, and the pressure resistance is 90.4 MPa. (2) The water resistance of the film-coated gravel packing layer decreases with the increase of packing layer permeability. (3) The film-coated gravel pack can reduce the water-phase flow ability of reservoirs, delay the bottom water ridging speed, increase the waterless gas development time of gas wells, and improve the final recovery of bottom-water gas reservoirs. The coated gravel has permeability and water resistance properties and can be used to voluntarily select water plugging in the coated gravel pack. This technology can develop a new technical idea for water control of deep-seabed water gas reservoirs.

Experimental investigation on plugging performance of nanospheres in low-permeability reservoir with bottom water

The oil production rate decreases rapidly after a short period of high yield from acidizing or fracturing in low-permeability reservoirs. In this paper, nanospheres are applied before the fracturing step, which possess the ability to absorb water and expand in the water layer, reducing the flow capacity of bottom water and finally enhancing the oil recovery. The plugging performance is investigated by nanosphere displacement experiments in cores and sand-packs, which explores the plugging effect in the oil layer, the oil-water transition zones, the water layer and the fracturing zones. In addition, a nuclear magnetic resonance experiment is conducted to study the flow mechanism of nanospheres and determine the plugging rates, which can characterize the plugging performance of nanospheres in porous media. The results show that the plugging rate is 85.84% and 78.65% on the water layer and oil-water transition zone, respectively, and 94.36% in the fracturing zone. Meanwhile, the nanospheres cannot plug the oil layer. The formation pressure has a less considerable effect on the plugging performance of nanospheres. The nanospheres have good injectivity, and the intensity variations in small, medium and large pores account for 34.46%, 13.22% and 52.32%, respectively. Overall, this paper explores the feasibility of applying nanospheres for water plugging and enhanced oil recovery. Cited as: Tang, M., Wang, C., Deng, X., Yang, H., Lu, J., Yu, H. Experimental investigation on plugging performance of nanospheres in low-permeability reservoir with bottom water. Advances in Geo-Energy Research, 2022, 6(2): 95-103. https://doi.org/10.46690/ager.2022.02.02

Conjoined-network induced highly tough hydrogels by using copolymer and nano-cellulose for oilfield water plugging

Hydrogels have been widely adopted for in-depth water control in mature oilfields, however, the poor mechanical properties limit their application. Herein, a conjoined-network induced hydrogel was prepared through the in-situ free radical copolymerization of acrylamide (AM), Acrylic acid (AA) and N,N′-methylenebis(acrylamide) (MBA) in the presence of nano-cellulose (CNF/ACNF), and the coordination effect between aluminium ion and carboxyl. The results showed that a small amount of nano-cellulose (0.2 %) increased the compressive strength of the hydrogel by 7 times. The presence of nano-cellulose endowed the hydrogel with excellent thermal stability and high shearing elasticity, at the same time, could effectively reduced the swelling rate that hindered its disintegration in practical application. The evaluation of sand-pack plugging suggested that the double cross-linked nano-cellulose hydrogel presented a significant capacity for efficient water plugging, where the breakthrough pressure gradient was as high as 23.73 MPa, the plugging rate reached 99.9%, and the maximum residual resistance factor was 3902.06. This work provided a novel design of hydrogel with high compressive strength and satisfactory stability for water shutoff and conformance control in heterogeneous oil reservoirs.

A Study of the Thin Film-Coated Swelling Retarding Particles in Fractured Carbonate Reservoirs for Water Plugging and Profile Control

T oilfield is the fractured-vuggy carbonate reservoir at a temperature of around 130 °C, with salinity of up to 22 × 104 mg/L. In order to solve the problem of the high water cut in the late development stage of T oilfield, we selected XN-T from 27 kinds of swelling retarding particles by testing their swelling capacity, and coated a thin film to improve its retarding swelling capacity. The mechanisms of strong water absorption and water-holding abilities of particles were analyzed by infrared spectrometry and SEM. In the core flow experiment, the plugging rate was found to be 98.42%. Finally, the injection parameters of the coated particles were optimized to maximize the water plugging and profile control ability, resulting in an optimal particle size of 0.4–0.6 mm and a mass fraction of 10%.

Physical simulation study on grouting water plugging of flexible isolation layer in coal seam mining

Deep coal seam mining often leads to water resource loss due to bedrock water entering the workings of the mine and is discharged adjacent to the mining area. Using the geological conditions of the Maiduoshan coal mine, this paper applied a physical simulation experiment. The specified rock above the coal seam was hydraulically fractured in advance to form a postmining grouted fracture network, followed by grouting to construct a flexible isolation layer that blocked the infiltration of groundwater from the aquifer into the water-conducting fracture zone. Stress sensors, flow sensors and strata displacement monitoring technology were deployed inside the experimental material to study the spatial distribution characteristics and evolution law of the water-conducting fracture zone in the overlying rocks. Analysis of the water-conducting fracture zone development law, stress variation, overburden evolution characteristics, fracturing and grouting sequence of the flexible isolation layer and the effect of postmining grouting on the water barrier was conducted. These experiments verified the feasibility of fracture and grouting of the flexible isolation layer. These research results will provide practical guidance for the transition from the current safe and efficient mining methods to safe and green mining methods of deep coal mining in the western mining areas of China.

Study on the Mix of Slurry Membrane for Soil Conditioning of EPB Shield and Its Application Effect in Water‐Rich Gravel Strata

The water inrush and large surface settlement encountered by EPB shield crossing water‐rich gravel layer have attracted much attention. Based on the section tunnel engineering of the Inner Mongolia University South Campus Station‐Xilin Park Station of line 2 of Hohhot Rail Transit, the optimum mix proportion of bentonite slurry and foam diluent for forming slurry membrane in water‐rich gravel stratum was studied in this study at first. The characteristics of conditioned soil were analyzed in combination with slag soil. The water plugging effect and surface settlement with or without slurry membrane were investigated with numerical simulation. The numerical model has been effectively verified by comparing the field monitoring and numerical simulation of surface settlement value. Further, the water shutoff mechanism of the slurry membrane is revealed. The setting of the slurry membrane exhibited a good water plugging effect and effectively decreased the surface settlement. The construction method of “water plugging with a slurry membrane” proposed in this study could powerfully combine the respective advantages of EPB shield and slurry balance shield, ensuring the safety, high quality, and high efficiency of tunnel construction.

Study on selective plugging characteristics and oil displacement mechanism of microsphere in porous media

Microspheres are widely used as profile control and water plugging products at present. However, the current research on microspheres is mainly focused on oil displacement experiments. In order to solve this problem, based on the Bohai sea in the BZ of inhomogeneous reservoir conditions, this article has done the matching study on particle size and hole roar and the seepage research in porous medium by means of particle size analysis, pressure tests, single-phase block experiments, and the double tube parallel oil displacement experiments, revealing the characteristics of oil & water selective plugging and the mechanism of oil displacement in porous media. The results show that the average particle size of the microspheres increases from 4.857μm to 24.53μm, and the maximum expansion factor reaches 5.03 times after 72h of swelling in BZ25 oilfield water at 75 C. In the two-pipe parallel oil flooding experiment with the permeability of 1000mD and 3000mD respectively, the comprehensive recovery rate after the first water flooding is 28.06%, and the two-pipe average recovery rate is increased by 1.58% after the injection of 2000ppm microsphere with 0.3PV, and there is no significant increase in oil displacement efficiency. The comprehensive recovery rate reached 38.6% and increased by 8.99% after 4PV of subsequent water flooding, indicating that microsphere flooding effectively improved the water sweep efficiency of subsequent injection.

Prediction of critical liquid loading time for water-producing gas wells: Effect of liquid drop rotation

After more than 20 years of continuous development, part of the wells in the Moxilei-1 gas reservoir located at the Sichuan Basin have entered the middle–later production stage. With the continuous decline in formation pressure and production rates, some of the gas wells have entered the potential period of liquid loading, while some have already suffered water plugging. Currently, the field engineers usually carry out some corresponding drainage measures after the occurrence of liquid loading in the gas well, which will first affect the production progress of the gas field, then increase the difficulty in drainage and reduce the drainage effect afterward. On the basis of Pan’s model for evaluating critical liquid-carrying flow rate, the influence of liquid drop rotation was considered in the new model. Further, combined with the Arps production decline equation, a prediction model of liquid loading timing was deduced. Taking a typical well in the Moxilei-1 gas reservoir as an example, based on the early-stage production data of the gas well, the model was used to predict the liquid loading timing accurately. The model can predict the possibility and timing of liquid loading in gas wells at different production stages. It can check the gas wells with potential liquid loading, so as to reduce the workload for field workers. Furthermore, it can predict the potential liquid accumulation and its timing in advance, so as to guide the field workers to prepare for drainage in advance.

Experimental Study on Physical and Mechanical Properties of Sandy Cobble Strata of Beijing Subway

The aquifers of θ cobble stratum,⑦ cobble stratum and ⑨ cobble stratum are the main shallow aquifers affecting the construction of Beijing subway, and water inrush accidents often occur in the process of construction of Beijing subway. In addition, Beijing is located in a semi-arid area, the per capita water resources are less. In order to ensure the safety and protection of underground water resources in the construction of Beijing subway engineering, the typical soil samples of Beijing sandy cobble quifer were used for grain size distribution test, water content test and consolidation test. The results showed that the cobble accounted for 64.77% of the weight of the soil sample, the uniformity coefficient Cu=30.06 and the curvity coefficient Cc=0.32, which indicated that the soil was poorly graded; the water content of sand soil was 4.00%; the compression modulus of sand was 2.5~520 kPa. The test results can provide a scientific basis for remodeling the sandy cobble aquifers in Beijing subway and the simulation test of grouting water plugging and reinforcement the aquifers, and can also provide a reference for the evaluation of aquifers’ grouting effect.

Thermally stable poly (acrylic acid‐acrylamide‐biomass‐fly ash) composites with improved temperature resistance and salt resistance

AbstractEngineering functional materials from biomass and industrial waste is of great significance for sustainable chemistry and engineering. Bio‐based poly (acrylic acid‐acrylamide‐biomass‐fly ash) (PAABF) composites with appropriate densities were designed. Graft copolymer composites were prepared for the first time by combining biomass and fly ash as graft materials with acrylic acid and acrylamide as monomers. The results showed that PAABF composites have a three‐dimensional network structure. Cellulosic biomass (sodium carboxymethyl cellulose, cattail cellulose) and fly ash improved the thermal stability, water absorption, water retention, temperature resistance, and salt resistance of the composites. PAABF composites can be used as water plugging profile control agent for oilfield with high‐salinity and deep burial.

High‐temperature performance and cross‐linking mechanism of different types of gel systems in saline environment

AbstractProfile modification of injection wells or water plugging of production wells are the most common ways to improve oil recovery with the continuous development of oil reservoirs. For high temperature and high‐salt oil and gas reservoirs, the plugging agent is required to have certain stability under high temperature and high‐salt conditions. Polymer gel is one of the commonly used plugging agents in oil fields. This article conducted detailed experimental research and mechanism analysis on six gel systems composed by two types of polymer (hydrolyzed polyacrylamide [HPAM] and terpolymer L‐1) and three types of cross‐linker systems (phenol/hexamethylenetetramine [HMTA], resorcinol/HMTA and bisphenol‐A/HMTA). The mechanisms of cross‐linker systems and polymer were studied, and the experimental researches were done on their gelation process, long‐term thermal stability, salt resistance, microstructure observation, rheological properties, and so on. The number of high‐temperature resistant cross‐linking points determines the performance of the gel system formed by cross‐linker systems with the polymer. The cross‐linker systems of bisphenol‐A/HMTA have four high‐temperature resistant cross‐linking points, and its performance was the best. Due to the introduction of ATBS and NVP groups on the polymer chain, the performance of gel system formed by the terpolymer L‐1 was significantly more stable than that of formed by HPAM. This study shows that the bisphenol‐A/HMTA‐L‐1 gel has excellent long‐term thermal stability and salt tolerance, and can be used in ultrahigh temperature (150°C) and high‐salt oil and gas reservoirs to improve oil recovery.

Study on Water Plugging Technology Outside Drivepipe of Oil Well

A new chemical water shutoff agent was developed to solve the problem of casing water flowing out of production wells in Liaohe Oilfield. Under the specific process conditions, the new chemical water shutoff agent can be injected into the position where the water goes out of the casing. The solidified water plugging agent can form a high strength, high temperature resistant and impermeable barrier laye.t can achieve the purpose of secondary cementing and casing protection. The water plugging agent has been applied in the field and has achieved good effect of oil increase and precipitation.

Analysis of potential tapping and efficiency increasing measures of reservoir measures in late stage of oilfield development

In the process of oilfield development, with the continuous development of resource exploitation and oil transportation, the later exploitation is likely to reduce the potential energy of the oilfield, which has a serious impact on the oil exploitation. In order to make our oilfield development efficiency has been significantly improved, and effectively improve the comprehensive development and utilization efficiency of our oilfield, we must continue to use the oilfield potential enhancement technology. In the actual production process, we need to combine a variety of technologies, such as hydraulic transmission pressure fracture, water plugging, acidification and other technologies. Through the comprehensive utilization of these technologies, we can reduce the water content of comprehensive oil wells in the oilfield, effectively improve the production of the oilfield, bring greater economic benefits to the society, and promote the long-term, stable and healthy development of China’s oilfield.

A review of key tools for oil pipe blockage operation in gas wells under pressure

Blockage in tubing is an important guarantee for gas wells under pressure. The internal blockage is to close the channel inside the tubing through a sealing device, the pipe string can be lifted and lowered under pressure. In order to prevent natural gas from leaking through the tubing channel during well completion and string lifting operations, a plugging tool in the tubing is required to block the tubing channel, and the blockage is removed after the operation is completed to effectively control the pressure in the well. This article starts with the key tools related to internal plugging operations in Snubbing operation, introduces the basic principles of setting the internal plugging barriers when running the tubing string in completion operations, and introduces the key tools for internal plugging when the tubing runs in completion operations. The internal plugging method of the pipe string under pressure is introduced. The key tools (bridge plugs) and setting methods that have been matured or formed at home and abroad when the pipe string is lifted in workover are introduced. Well technology and key tool selection provide reference. Finally, we analyze and think about the domestically developed self-developed internal plugging tools for pressurized operations in my country. It is believed that internal clogging is not an isolated process of oil, gas, and water plugging, but is usually a process of multi-system construction processes working together. The key domestic tools and equipment also need to further improve their autonomous capabilities in terms of overall performance and stability, as well as intelligence.

Grouting Mechanism in Water-Bearing Fractured Rock Based on Two-Phase Flow

Grouting is always used in mine water plugging, reinforcement, and other disaster prevention projects. The diffusion mechanism of slurry in fractured rock is affected by geological environment and slurry performance, which should be revealed and characterized better. Based on the two-phase flow diffusion theory, a slurry diffusion model considering flowing water condition was established for a blocking area of a fracture zone in one case from China. The feasibility of two-phase flow model in grouting diffusion calculation was analyzed. The diffusion model in dynamic water environment was studied, and the diffusion range varying with time in the grouting area of Zhangji Coal Mine was explored. The optimization method of multi grouting holes was put forward, and the influence of water flowing was discussed. The results show that the slurry diffusion calculated by the two-phase flow model was feasible and consistent with the experimental study. The dynamic water can change the conventional circular diffusion state of slurry, but its pattern was oval and leaf type. There were different penetration distances in directions, and typical grouting voids were made on the side and upstream. When the single-hole grouting was carried out, the predetermined value can be achieved in the height range, but it was only about 15 m on the side because of the water flowing, which cannot meet the requirements. The optimization scheme of grouting was put forward, which adopted multiple grouting holes in the long side, and grouting in different directions and periods to avoid the possible problems of multihole intersection. The rationality and effectiveness of the proposed optimization method were verified through the calculation of water yield and analysis of cement composition from the drilling core in the grouted zone. In the grouting process, the water flowing has double effects, which has a significant role in promoting and scouring along the flow direction, but there is a significant weakness in the side diffusion. It is very important to realize the rational use of the dynamic water through the optimization scheme. This study is an important basic work of grouting mechanism, and it is expected to promote the development of grouting technology and application of two-phase fluid-solid coupling theory.