Water Plugging Research Articles

Numerical simulation of in-depth profile control for dispersed particle gel in heterogeneous reservoirs

Introduction: As a new agent of enhancing oil recovery, the dispersed particle gel (DPG) has been gradually used for in-depth profile control in mature oilfields. Many researchers investigated the preparation, profile control mechanism and application of DPG based on a series of laboratory experiments. However, few numerical studies have been carried out on profile control mechanism of DPG.Methods: This paper proposes a novel mathematical model to proceed numerical simulation of profile control for DPG, considering DPG particles adsorption and weak shear thinning effects. The numerical codes are verified by the UTCHEM simulator.Results and discussion: The effects of the DPG viscosity, the DPG concentration, the water saturation of high permeable regions and the permeability ratio between high and low permeable regions on decreasing the water-cut of producing well are studied. Simultaneously, this paper also investigates the influence of different mobility ratios between high and low permeable regions on water shutoff of DPG. The numerical simulation results show that the effects of DPG profile control become better as the DPG solution viscosity, the suspension concentration and the permeability ratio increase. But the increased water saturation of high permeable regions is not helpful to improve oil recovery. Water plugging effect of DPG becomes worse with increasing mobility ratio between different regions. According to comparison results between DPG profile control and polymer flooding, it is found that DPG profile control is more suitable for heterogeneous reservoirs. These findings are of benefit to guide the efficient field application of DPG profile control in heterogeneous reservoirs.

Recent advances in enhanced polymer gels for profile control and water shutoff: A review.

Polymer gels have been effectively employed as a water management material for profile control and water shutoff treatments in low-middle temperature and low-middle salinity reservoirs. However, most polymer gel systems have limitations under high temperature and salinity reservoir conditions, such as short gelation time, poor strength, and long-term instability. Therefore, several researchers have developed enhanced polymer gels to satisfy the water control requirements in high temperature and salinity reservoirs. This work reviews the five main types of enhanced polymer gels that have been developed so far: nano silica-enhanced gel systems, cellulose-enhanced gel systems, graphite-enhanced gel systems, oily sludge-enhanced gel systems, and foam-enhanced polymer gel systems. Further, this article investigates the fundamental properties, strengthening and crosslinking mechanisms, reservoir application conditions, and field applications of several enhanced polymer systems. In this paper, it is found that the addition of strengthening materials can increase the bound water content in the gel network and significantly improve the temperature and salt resistance of polymer gel, so as to cope with the application of profile control and water plugging in high temperature and high salt reservoirs. Moreover, it also offers references and future research directions for enhanced polymer gel systems.

Research on Water Control and Production Enhancement Process in TY Gas Field

In order to solve the problem of water intrusion seriously affecting the development of each production well in TY gas field, a numerical model was established with reference to well X in TY gas field to study the characteristics of water intrusion in TY gas field, and four sets of water control and production increase experiments were completed, including elastic extraction experiment, water plugging experiment, side drilling experiment and combined water plugging and side drilling process experiment, which were verified by physical experiments on this basis. The results show that different water control and production enhancement measures have different effects, among which the combination of water plugging and lateral drilling process has the best effect, which can increase the gas production by 84.1%, and the error between the physical experiment results and the numerical simulation results is 7.7%.

Numerical Analysis of Dynamical Effects Associated with a Plugging String in a Horizontal Well

The finite element method has been applied to simulate the dynamics of a water plugging string in a complex horizontal well of a low-permeability oilfield. The force associated with the pipe string and the packer has been determined under the sucking action of the oil well pump. Such analysis has been conducted for a real drilling well, taking into account the process of lifting, lowering, unblocking and water plugging. Comparison between field measured data and simulation data indicates that the model is reliable and accurate. The packer creep effect under different pressure differences has also been investigated in the framework of the same model.

Research on Mesoscopic Characteristics of Limestone Grouting Diffusion Based on Discrete Fracture Network

The limestone stratum has well-developed rock fissures and abundant groundwater. Under extreme rainstorm conditions, tunnel surrounding rock seepage is serious especially. In order to reveal the grouting diffusion mechanism of karst fractured rock mass and realize effective water plugging, in this paper, the basic mechanical parameters of limestone are obtained by laboratory triaxial test, and the porosity distribution of rock mass is obtained by nuclear magnetic resonance test. The PFC2D discrete element software is used to simulate the mechanical characteristics of compressive deformation and fracture propagation pattern of the limestone and compared with the triaxial test results. Discrete fracture network theory is used to establish PFC2D numerical simulation of grouting diffusion model of fractured rock mass. And the filling diffusion mechanism and stress variation rule of cement slurry in fractured limestone under different grouting pressure are studied. The results show that (1) During the grouting process, the micro-cracks expand along the tip of the existing cracks, and extend to the surrounding cracks to finally form through cracks, so as to achieve the effect of grouting reinforcement. (2) With the increase of grouting pressure, the maximum displacement of particles increases continuously, but with the prolongation of grouting time, the maximum displacement of particles reaches a stable state and no longer increases. (3) During the grouting process of the fractured rock mass, with the increase of grouting time, the stress of the fractured rock mass finally reaches a stable state. This study provides an important reference for the setting of grouting parameters of limestone rock mass.

Evolution of pore structure and radon exhalation characterization of porous media grouting

Cracks and pores are considered as major sources of radon. Cement is widely used as a grouting material in mines, tunnels, and other projects for reinforcement, seepage prevention, and water plugging. This paper mainly experimentally studied the correlation between the radon exhalation rate of the porous medium after grouting and the sand grain diameter, grouting pressure, and slurry water-cement ratio. The pore characteristics of the samples before and after grouting were also studied based on the low field nuclear magnetic resonance (LF-NMR). The findings of the study show that the porosity of samples increases after the superfine cement solidification with an increase in the water-cement ratio, and the radon exhalation rate is proportional to porosity, the radon exhalation rate increases by 0.0005 Bq·m–2/s at W/C = 1.5, and by 0.0017 Bq·m−2/s at W/C = 2 increases, in comparison to the W/C = 1.The radon exhalation rate of porous media gradually increased after grouting in response to an increase in grouting pressure and the water-cement ratio. The radon exhalation rate of the porous media with larger pores was relatively higher and exhibited a positive correlation with the volume of micropores in porous media，the correlations of coarse, medium and fine media are 0.815, 0.826, and 0.859. The change in pore structure has an influence on radon exhalation. Although grouting changes the pore structure and reduces the connectivity between internal pores, the micropores generated after cement slurry solidification improves the radon exhalation rate by providing new channels, When the water-cement ratio is 1.5 and the grouting pressure is 1.5 MPa, the radon exhalation rate of porous media is 0.00273 Bq·m−2/s. The research results serve as a reference basis for the evaluation of the impact of rock masses on grouting reinforcement and pore sealing.

Preparation and Properties of Temperature-Sensitive P(NIPAM-AM) Nano–Microspheres in Enhanced Oil Recovery

As a new kind of water plugging and profile control agents, the polyacrylamide nano–microspheres have been experimentally applied and achieved satisfactory preliminary results in enhanced oil recovery, especially for low-permeability reservoirs. However, the larger swollen particle size and excessive hydrophilicity limit the effect at the oil–water interface. In order to further improve their profile control and flooding effect, the temperature-sensitive poly(N-isopropylacrylamide-acrylamide) nano–microspheres are prepared by inverse microemulsion polymerization. Based on the principle of conformation transition of PNIPAM triggered by simulated high temperature in reservoirs, the particle size and hydrophilicity of the microspheres are reduced, making it easier to reach the oil–water interface, reduce the oil–water interface tension, and enhance the structural disjoining pressure, which improves the spontaneous emulsification effect and removal effect of residual oil on rocks. The swelling properties, hydrophilicity, interfacial activity, and oil displacement properties of the nano–microspheres were also analyzed. The results show that the swelling ratio of the copolymerized nano–microspheres decreases to 1.5. At simulated reservoir temperature (65 °C), the water contact angle of copolymerized gel increases from 43 to 86°, indicating that its hydrophilicity decreases and shows a clear tendency to migrate to the water–oil interface. At 65 °C, 0.1 wt % PNIPAM-based microsphere emulsion (N3) reduces the oil–water interfacial tension from 17.8 to 0.9 mN m–1. The microscopic oil displacement experiment shows that the recovery efficiency of our designed temperature-sensitive nano–microspheres emulsion is increased by 7%, which is higher than that of the PAM polymer nanosphere. The PNIPAM-based temperature-sensitive nano–microspheres that can function at the oil–water interface have a potential development prospect in low-permeability reservoirs.

Preparation Method and Performance Evaluation of a Gel Based on AM/AMPS Copolymer.

Polymer gels have been widely used in high water cut oilfields for profile control and water plugging. It is urgent to develop a gel suitable for the Tahe Oilfield (Temperature: 130 °C, salinity: 2.2 × 105 mg/L) in China. A stable gel was prepared by using an acrylamide (AM)/2-acrylamide-2-methyl propanesulfonic acid (AMPS) copolymer crosslinked with urotropin (HMTA), hydroquinone (HQ), thiourea and Nano-SiO2. This paper covers a step-by-step process for designing gels based on experience with preparing gels. A wide range of combinations between polymers and crosslinking agents with and without stabilizers were investigated, and the results indicated that there is an optimal value of AMPS content of AM/AMPS copolymers in the preparation of gels. Increasing the mass fraction of copolymer and using stabilizer enhanced the performance of gel, but an excessive amount of crosslinking agent was not conducive to the stability of gel. The work optimized the formula of plugging agent suitable for the high temperature and high salt (HTHS) condition in the Tahe Oilfield. The gelling solution had a long gelation time of 20 h. The gel had high strength (Sydansk's gel-strength code of "G") with storage modulus of 12.9 Pa and could be stable for half a year at 130 °C and 2.2 × 105 mg/L of salinity. The plate model that could be heated and pressurized was used to simulate the oil flooding and profile modification under the condition of the Tahe Oilfield for the first time. The experiment results showed that the oil recovery could be increased by 13.22% by subsequent water flooding under heterogeneous formation condition. Therefore, it was fully confirmed that the plugging performance of AM/AMPS phenolic gel prepared in the work was excellent. The information provided in the study could be used as a reference for the design and evaluation of polymer gels in other HTHS reservoirs.

Optimization of Anti-Plugging Working Parameters for Alternating Injection Wells of Carbon Dioxide and Water

In the process of oilfield development, the use of CO2 can improve the degree of reservoir production. Usually, CO2 is injected alternately with water to expand the spread range of CO2, and CO2 presents a supercritical state in the formation conditions. In the process of alternating CO2 and water injection, wellbore freezing and plugging frequently occur. In order to determine the cause of freezing and plugging of injection wells, the supercritical CO2 flooding test area of YSL Oilfield in China is taken as an example to analyze the situation of freezing and plugging wells in the test area. The reasons for hydrate freezing and plugging are obtained, the distribution characteristics and sources of hydrate near the well are clarified, and a coupling model is established to calculate the limit injection velocity and limit shut-in time of CO2 and water alternate injection wells. The results show that the main reasons for freezing and plugging of supercritical CO2 water alternate injection wells are long time shut down after alternate injection, improper operation when stopping injection and starting and stopping pumps, and slow injection speed during alternate injection. In the process of supercritical CO2 water alternative injection, in the case of post-injection, the CO2 in the formation will reverse diffuse to the injection well end. With the continuous increase of daily water injection, the initial diffusion position and the time of CO2 diffusion to the perforated hole after well shut-in gradually increase. The time of CO2 reverse diffusion to the bottom of the well is 1.6–32.3 d, and the diffusion time in the perforated hole is 1.0–4.5 d. Therefore, the limit shut-in time following injection is 2.6–36.8 d. Following gas injection, the limit shut-in time of a waterproof compound can be divided into three stages according to the change of wellbore pressure: the pressure stabilization stage, pressure-drop stage and formation fluid-return stage. The limit shut-in time of a waterproof compound following gas injection is mainly affected by permeability, cumulative gas injection rate and formation depth. The limit shut-in time of a waterproof compound is 20.0~30.0 days. The research results provide technical support for the wide application of CO2 flooding.

Adaptation study on nitrogen foam flooding in thick reservoirs with high water cut and high permeability

Most of the oilfields in China are in high- or ultrahigh-water-cut stages, and the impacts of water flooding developments have declined due to the increase in reservoir heterogeneity, the rapid increase in the water cut and the discontinuous distribution of crude oil under these conditions. Based on this phenomenon, an experimental study of nitrogen foam flooding is conducted in this paper. The oil displacement characteristics of nitrogen foam in oil and water layers of thick, high-porosity and high-permeability reservoirs are studied through one-dimensional core tube experiments, and the mechanisms of profile control and water plugging are analyzed. Through two-dimensional visualization experiments, we observe the migration and diffusion patterns of nitrogen foam, analyze the effects of different degrees of vertical foam production on the residual oil after water flooding, clarify the production effect of gas overburden on the residual oil at the top of the reservoir, and summarize the mechanisms of nitrogen foam flooding involved in improving the recovery factor. The results show that in the core tube experiment, the recovery factor of the high-permeability core is 93.73%, the recovery factor of the low-permeability core is 71.33%, and the total recovery factor reaches 83.23% in the stage of nitrogen foam flooding, which is 28.96% higher than that of water flooding. In the visualization experiment, the recovery factor of the nitrogen foam flooding stage is 57.12%, which is 24.99% higher than that of water flooding. The recovery degrees of the layers are similar; by comparing the increase in the recovery degree of each layer before and after the two stages, it is found that the increase in recovery degree increases from the bottom to the top. The foam system exhibits a good selective plugging ability under the conditions of severe heterogeneity and low residual oil in the high-permeability zone. Nitrogen foam flooding can effectively improve the recovery factor in the late-stage reservoir development of the ultrahigh-water-cut stage, and it shows good adaptability to these types of reservoirs.

Overview of In-Situ Gelation Behavior of Gel Systems in Porous Media

Cross-linked polymer gel has been widely applied in profile control and water plugging due to its effective cost, wide suitability, excellent performance, and flexible gelation time. Previous research mainly focused on the bottle tests, reaction kinetics, and rheological properties of the gels, but the works of literature about the in situ gelations of gel placement in the porous media are relatively few. The study of the in-situ gelation behavior of gel systems is widely summarized in this paper, and the research tendency is proposed. The important practical questions, including the accurate lateral distance of gel placement, the variation of gel properties, and the injection pressure profile in the process of gel injection, should be resolved by laboratory and numerical research to enhance gel treatment success rate.

Mechanically robust and rapidly degradable hydrogels for temporary water plugging in oilfields

AbstractHydrogels have been widely used for in‐depth water control and water plugging in most mature oilfields; however, the poor mechanical properties as well as non‐degradable characteristics severely limit their applications. Herein, a multifunctional macromolecular cross‐linker (GA) based on a natural macromolecule, gelatin, is fabricated and used to prepare polyacrylamide hydrogels. Cross‐linking with GA leads to a special network involving physical entanglements that dissipate energy and topological cross‐links that distribute stress. Therefore, the hydrogels manifest remarkable mechanical strength, toughness and tear‐resistance. At the same time, GA can be readily degraded at high temperature, leading to disintegration of the hydrogels. The flow model in porous media reveals that the hydrogels present a significant ability of water plugging and rapid degradation, where the plugging ratio and degradation ratio reach 99% and 100%, respectively. Such mechanical properties and degradation performance enable the hydrogels to serve as a novel temporary water plugging agent for heterogeneous reservoirs of oilfield.

Development and Performance Evaluation of a Selective Plugging System for High-Temperature and High-Salinity Water-Bearing Gas Reservoir

In the development of natural gas reservoirs, the water produced in wells will cause a decline in gas well productivity. In this study, a selective frozen gel plugging agent system suitable for water plugging in gas reservoirs under conditions of high temperature and high salinity. The plugging capacity of the gel system was evaluated. The experimental results showed that: (1) the optimal experimental scheme of the frozen gelling system was as follows: 107 °C with 1.0% AM-AMPS +0.6% p-benzenediol +0.6% hexamethylenetetramine +0.2% thiourea. (2) The optimal injection volume of the system for water phase plugging was 0.5 PV, and the system has an excellent plugging effect at a permeability of 356–3118 mD. (3) The system could also effectively improve the degree of heterogeneity, and the smaller the degree of heterogeneity, the better the improvement effect. (4) The gel system had a good effect on different plugging methods, and the gas medium did not affect the plugging performance. This study provides a sufficient theoretical basis for the exploitation of high-temperature and high-salinity water-bearing gas reservoirs through experimental research, which is of great significance for improving production capacity.

Study and Application of Ultrafine Temperature-Resistant and Salt-Tolerant Swellable Particles in Low Permeability Reservoirs

Based on the characteristics of low-permeability oil and gas reservoirs and the requirements for profile control and water plugging and for water cut decrease and production increase in the high water cut stage of the middle and late exploitation periods, ultrafine temperature-resistant and salt-tolerant swellable particles DS-1 suitable for low permeability oilfields were prepared by introducing N,N-dimethylacrylamide(DMAA) monomers into the 2-acrylamido-2-methylpropanesulfonic acid (AMPS)/acrylamide(AM)/N,N-dimethylbisacrylamide ternary crosslinking system. The median of initial particle size was 22.00 μm, and is compatible with formation pore throats. A static water absorption experiment showed that the particles can still maintain a high swelling ratio after 15 days at a high temperature and high mineralization degree, so they have long-term stability. The physical and chemical properties of the particles were analyzed microscopically using the infrared spectrum method and the scanning electron microscope (SEM) method. A dynamic displacement experiment confirmed that the particles can effectively plug dominant channels of waterflooding, increase the injection pressure, and improve the interlayer and intralayer heterogeneity. In the field experiment, the swellable particles DS-1 were used as a main slug for water plugging operations, and a good water cut decrease and oil production increase effect was obtained.

Experimental Study and Numerical Simulation of Removing Water Blocking by Hot-Gas Injection in Tight Cores

Compared with oil, natural gas has been the focus of the energy industry in recent years. Renewable energy is the goal and trend of future developments, and it has made considerable progress; however, it has not reached the ideal popularization rate. Therefore, natural gas is still very important so far. In this paper, the influence of thermal gas injection and room temperature gas injection on gas reservoir recovery is analyzed, and the method of water plugging by hot gas injection in tight gas reservoir is put forward. Indoor simulation experiments were carried out to evaluate the effect of hot-gas injection in cut pore water and the degree of water blockage. On this basis, the numerical simulation of removing water blockage by hot-gas injection was carried out. The changes in core temperature and remaining water saturation were discussed by using simulation models. Results of this study can provide a theoretical basis for removing water blockage in actual oil and gas reservoirs.

Research on Soft Rocks for the Construction of Roadbeds for High-Speed Railroad: Effect of Water Soaking Environment

The strength of the roadbed composed of soft rock decreases following water immersion. Cement slurry is mixed with a soft rock to strengthen the soft rock roadbed to address this problem. The uniaxial compressive strength was determined, and the triaxial compression tests were conducted to analyze muddy sandstones mixed with different amounts of the cement slurry of the same composition. Some of the cured samples were soaked in water, and the samples were analyzed. The results were compared with the results obtained by analyzing unsoaked samples. The MIDAS/GTS NX software was used to develop a three-dimensional finite model to simulate the settlement patterns of roadbeds developed in the presence of natural water, saturated water, and muddy sandstone reinforcements. The experimental results have been presented and discussed. (1) When the filling rate corresponding to the cement slurry is 32%, the uniaxial compressive strength of muddy sandstone containing natural water reaches 3.32 MPa, which is approximately 5 times higher than the strength of muddy sandstone devoid of cement slurry. (2) The water absorption energy of the reinforced muddy sandstone was analyzed from the perspective of saturated water content. The water plugging effect observed after the addition of the cement slurry was studied, and the equations defining uniaxial compressive strength, elastic modulus, and free saturated water content were established. (3) An increase in the content of the cement slurry admixture resulted in a change in the nature of the partial stress–strain curves generated for muddy sandstone. The curve change from strain-hardening to strain-softening type and the deformation modulus and extent of cohesion realized increased exponentially with an increase in the cement slurry filling rate. A positive linear correlation was observed between the internal friction angle and the cement slurry filling rate. (4) An increase in the cement slurry filling rate corresponding to the saturated muddy sandstone resulted in an exponential decrease in the settlement deformation value. The vertical displacement decreased to 0.3497 mm when the grouting rate reached 32% under conditions of saturation. The deformation tended to converge and stabilize, indicating that the introduction of the admixture consisting of the cement slurry could help in effectively controlling the property of settlement deformation observed in the fully weathered muddy sandstone roadbed. The results helped in the scientific evaluation of the reinforcement effect. The reported results also helped develop a theoretical basis for the development of soft foundation reinforcement.

Molecular design and experiment of ion transport inhibitors towards concrete sustainability

Regulating the transmission of chloride medium in concrete is the primary research work to improve the durability and sustainability of concrete, effectively saving offshore buildings' maintenance costs. Inspired by the molecular design of drug delivery, this study designed an erosive solution-responsive ion transport inhibitors (ITI) to restrain the transport of erosive solution in calcium silicate hydrates (C–S–H) gel pores, which is expected to reduce the water absorption and chloride diffusion coefficient of concrete efficiently. In this investigation, molecular dynamics was applied to reveal the mechanism of ITI with different main-chain structures on the atomic scale, and an evaluation system of such polymers was proposed. When the main chain is the carboxylic group, the ITI is similar to the hinge of the door. Once the corrosion solution invades the gel channel, the hydrophobic group will be perpendicular to the surface of calcium silicate hydrates to prevent the transmission of the solution. However, when the main chain is alcohol amine, the ITI can gather at the front of the erosion solution to form a water plugging medium and complex with the eroded ions to inhibit the diffusion of ions. On this basis, the optimal ITI is evaluated through water adsorption and chloride ion diffusion tests and further applied in offshore engineering. The results show that they can effectively alleviate chloride ion erosion without sacrificing mechanical properties.

Preliminary Study on Double Lining Support Design for Water Plugging of Highway Tunnel under High Water Pressure in Mountain Area Based on Limited Drainage

In the water-rich karst regions, high water and mud outbursts are common geological disasters in tunnel construction. To ensure the safe and smooth construction of tunnel projects, it is necessary to consider anti-water pressure, water inrush prevention and geological disasters during the design of tunnels. Based on the Yongfutun Tunnel Project, this paper studies the application and effect of radial grouting and curtain grouting, which involves those in high-water-pressure tunnels under double-layer support conditions. To obtain the effects and parameters of radial grouting and curtain grouting, the influences of different grouting ranges on the tunnel’s surrounding rocks and supporting structures were analyzed and the finite difference method was adopted. The results show that the radial grouting of the surrounding rock can notably improve the initial support of the tunnel, but the impact is less obvious when the grouting range exceeds 4 m. The design of radial grouting is recommended to be 4.0 m to 4.5 m. Curtain grouting can effectively reduce the external water pressure of the tunnel lining. The external water pressure of the grouting area is 23% greater than that without curtain grouting. Curtain grouting can slow down the infiltration of external water pressure. This is beneficial to the stress of the tunnel lining structure, but the improvement in initial support force is slight. Moreover, curtain grouting improves the safety reserve of the secondary lining by strengthening the self-stability ability of the surrounding rock. Meanwhile, the double-layer primary support can effectively share the external water pressure and surrounding rock pressure. This study provides a certain reference for the lining design of high-water-pressure tunnels.

Physical simulation experiment method of water breakthrough mechanism and plugging effect of horizontal well in tight reservoir

Horizontal wells have become a key technology for the economical and effective development of tight reservoirs. In production, water cut increases rapidly, and even waterflooding is prominent. The mechanism of water breakthrough and the analysis of the water plugging effect are still tricky problems worldwide. Based on the reservoir characteristics of the typical tight oil area in Changqing oilfield, a physical simulation method of water breakthrough and plugging effect of segmented fractured horizontal wells was established based on the parallel connection of double cores and large-scale physical simulation system, and the mechanism of water breakthrough and water plugging effect of horizontal wells were studied. The results show that natural fractures or dynamic fractures are the main factors affecting the characteristics of water breakthrough. The end and waist of staged fractured horizontal wells are the main parts of water breakthrough. Water breakthrough points gradually increase in production, showing multi-direction. The overall water cut decreases after the water-prone area is plugged. Specifically, in this study, water plugging was implemented when the water cut of the horizontal well rose to 91%, and the water cut of a breakthrough part was reduced to about 60% after plugging, which played a good role in controlling the overall water cut. Oil displacement efficiency increased from 32.5% before plugging to 36% after plugging, rising by 4.5 percent. In addition, the duration of oil production increase in horizontal well after water plugging is not long, mainly because of the formation of water injection dominant channel between the injection well and horizontal well fracture before plugging. At this time, the resistance primarily exists in the water-affected area, and the Jamin effect caused by imbibition is the main factor of resistance; then, the swept volume is difficult to expand.

Study on Construction and Reinforcement Technology of Dolomite Sanding Tunnel

The No. 2 conduit of the Xiaopu Tunnel in the Yuxi section of central Yunnan’s water diversion project is taken as the research object, starting from the geological conditions along with the characteristics, formation mechanism and evolutionary model of dolomite sanding. This paper discusses the engineering problems of the project’s tunnels with dolomite sanding in the water-rich section, and its corresponding engineering reinforcement plan. It was found that in the tunnel section with normal level of dolomite sanding, there was no water seepage, where measures such as advanced small conduit, mechanical excavation, short grubbing and strong support could all be adopted for safe passage. Even in the water seepage section of the weak dolomite sanding tunnel, the surrounding rock was found in close interlock with strong self-stability. The excavation and support were implemented according to the category of normal surrounding rock. In the water-rich sections with strong and intense dolomite sanding, gushing of water and sand were quite frequent, with developed fissures, broken rock masses and rich waters. During the engineering operation, phosphoric acid and sodium silicate slurry in addition to urea formaldehyde resin and oxalic acid slurry plus Malisan and liquid catalyst slurry were first prepared for water plugging. Then, pure water slurry was used for surrounding rock reinforcement, which exerted an excellent effect. This method can provide reference for reinforcing tunnels of sandy dolomite in other areas of projects.