Reinjection Process Research Articles

Investigations of the Impact of Geothermal Water Reinjection on Water-Rock Interaction through Laboratory Experiments and Numerical Simulations

In the quest for sustainable geothermal energy production, the adoption of geothermal reinjection technology has become a crucial element in the development of geothermal resources. However, the processes of injection and extraction can lead to interactions between water and rock within the geothermal reservoir, resulting in pore blockage. This study focuses on the Kaifeng Zhenyu Garden geothermal field as a case study to examine the water-rock interactions that occur during geothermal reinjection, as well as the subsequent changes in mineral composition and porosity within the reservoir. The findings reveal that the primary minerals undergoing dissolution are dolomite and feldspar, with the precipitation of calcite and clay minerals following suit. Additionally, results from field simulations corroborate that dolomite and feldspar are the main minerals dissolving, accompanied by the precipitation of calcite and illite. Notably, significant changes in mineral dissolution and precipitation near the geothermal well have led to a slight reduction in the reservoir's porosity. This investigation provides valuable insights into the water-rock interactions involved in geothermal reinjection processes across various geothermal fields.

Experimental study on optimizing tailwater reinjection technology for weakly consolidated sandstone geothermal reservoirs

The difficulty of recharging the weakly consolidated sandstone geothermal reservoirs (WCSGR) is a macroscopic manifestation of the interplay of multiple factors associated with both fluids and formation properties. However, current studies predominantly focus on the influence mechanisms of individual factors on the reinjection of WCSGR. To address this limitation, a high temperature–pressure core flow experimental platform, combined with an orthogonal experimental design, is employed to investigate the dynamic reinjection process of WCSGR under the combined effects of multiple factors. The research indicates that high temperatures significantly impact the movement of 3 μm microspheres, leading to a rapid decrease in core permeability. Additionally, in experiments conducted at flow rates of 2 mL/min, 3 mL/min, and 4 mL/min, the pH stabilization time of the outflow solution decreased, while both the pH value and turbidity of the outflow solution increased, compared to the experiments conducted at flow rate of 0.5 mL/min and 1 mL/min. The permeability damage rate (%) was used as the experimental evaluation index. The primary and secondary order of influence of each factor on the permeability is: microsphere size > flow rate > turbidity > confining pressure > temperature. The optimal levels for each factor are 5 μm, 4 mL/min, 2 mg/L, 1.4 MPa, and 25 °C, respectively. Consequently, the reinjection technology of GT in WCSGR is optimized.

Assessment of carbon dioxide transcritical cycles for electrothermal energy storage with geological storage in salt cavities

Carbon capture, utilisation, and storage (CCUS) technologies are envisaged as critical actors in the energy transition and climate change mitigation framework. Despite the recent advances in CCUS implementation, there is still significant scope for their growth and improvement. On the other hand, developing new large-scale energy storage systems is a key factor for the massive deployment of renewable energy systems. Technologies such as the electrothermal energy storage system based on carbon dioxide transcritical cycles incorporating geological storage (CEEGS) can contribute to both fields. Preliminary studies have shown that the integrated storage system can operate with roundtrip efficiencies exceeding 50%, injecting over 1 million tons of captured carbon dioxide (CO2) annually. It is an early-stage technology with open challenges for successful development, such as an adequate balance between the high- and low-temperature thermal storage reservoirs or the operation definition between the electrothermal system and the carbon dioxide injection and recovery. Underground pressures will oscillate with the charge/discharge process, with operational implications and constraints. Advancing in the concept requires the definition of optimised operation. This work presents a novel analysis of the adaptation of CO2 transcritical cycles to include injection and production processes with the specific scenario of salt cavities. It considers new modifications to adapt the transcritical cycles in closed-mode operation to the conditions required by the salt cavities injection and production processes. Different case studies are evaluated, evaluating the impact of injection and geological storage, production and surface storage, and reinjection into the geological formation. The analyses show roundtrip efficiencies within the range of 49.1–73.0% when the injection, production, and reinjection processes are executed.

Study on the evolution of dissolved organic matter in the underground storage of mine water.

The water-rock interactions significantly affect the dissolution and release of dissolved organic matter (DOM) during the reinjection of mine water into the underground reservoir. In this study, the surface characteristics and chemical composition of the natural medium from the open-pit coal mine were characterized. The waste consists mainly of quartz-dominated sandstone (43.64%) and mudstone dominated by sanidine (76.36%). During the 35-day experiment, two protein-like, one humus-like, and one fulvic acid-like substances were identified by PARAFAC. It was observed that the type of aqueous medium significantly affected the variational trend of DOM. Compared to the artificial medium, the fluorescence intensity of waste materials in the waste dump increased significantly during the reinjection process. Therefore, a positive correlation was observed between the fraction of mudstone in the aqueous medium and the DOM composition, mainly due to the dissolution of polycyclic aromatic hydrocarbon substances from the mudstone. The results revealed that the natural water storage medium had a certain water storage feasibility when compared with the expensive artificial medium. However, the fraction of mudstone in the water storage medium should be controlled to minimize the release of organic matter into the environment.

EVALUASI SISTEM DAN DAMPAK LINGKUNGAN PENGELOLAAN AIR TERPRODUKSI PADA SUMUR X1 PT MGBI LAPANGAN WUNUT

PT Minarak Gas Brantas Inc.'s operations in the Wunut Field involve the production of waste in various forms, primarily liquid waste, with produced water being the most significant type. Proper management of this produced water waste is crucial to prevent environmental pollution and ensure economic and environmental sustainability. The company manages this waste by reinjecting it into the reservoir to prevent groundwater contamination. To ensure the effectiveness of this reinjection process, they have created a groundwater flow pattern map (flow net) at three locations near the injection well: LP1 in Keduung Boto Village, LP2 in Candi Pari Village, and LP3 in Candi Pari Village, all in Sidoarjo Regency. This helps in understanding the potential spread of pollutants in the soil and underground water, aiding in environmental pollution monitoring and managment.The groundwater from this area is used for various human activities like bathing, cooking, and washing. However, based on water quality standards outlined in Ministry of Health Regulation No. 2 of 2023, the produced water from Well X-1 in the Wunut Field does not meet the required TDS (Total Dissolved Solids) content standards due to a decline in hydrocarbon fluid production, resulting in a separator efficiency of 74,86%. Additionally, lab tests and flow net results indicate that the TDS levels in LP1, LP2, and LP3 do not meet the sanitation and hygiene water quality standards, suggesting potential seepage in these locations that could contaminate groundwater. Keywords: Oil; Gas Produced Water; Gas Separator Eficiency; Groundwater Flow

Stochastic 1-D reactive transport simulations to assess silica and carbonate phases during the CO2 reinjection process in metasediments

Stochastic 1-D reactive transport simulations to assess silica and carbonate phases during the CO2 reinjection process in metasediments

Molecular dynamics simulation on the displacement behaviour of crude oil by CO2/CH4 mixtures on a silica surface.

Produced gas re-injection is an effective and eco-friendly approach for enhancing oil recovery from shale oil reservoirs. However, the interactions between different gas phase components, and the oil phase and rocks are still unclear during the re-injection process. This study aims to investigate the potential of produced gas re-injection, particularly focusing on the effects of methane (CH4) content in the produced gas on shale oil displacement. Molecular dynamics simulations were employed to analyze the interactions between gas, oil, and matrix phases with different CH4 proportions (0%, 25%, 50%, and 100%), alkanes and under various burial depth. Results show that a 25% CH4 content in the produced gas achieves almost the same displacement effect as pure carbon dioxide (CO2) injection. However, when the CH4 content increases to 50% and 100%, the interaction between gas and quartz becomes insufficient to effectively isolate oil from quartz, causing only expansion and slight dispersion. Interestingly, the presence of CH4 has a synergistic effect on CO2, facilitating the diffusion of CO2 into the oil film. During the gas stripping process, CO2 is the main factor separating oil from quartz, while CH4 mainly contributes to oil expansion. In addition, for crude oil containing a large amount of light alkanes, extracting light components through mixed gas may be more effective than pure CO2. This study offers valuable insights for applications of produced gas re-injection to promote shale oil recovery.

Geo-temperature response to reinjection in sandstone geothermal reservoirs

To study the evolution rules and behaviors of heat transport in a sandstone geothermal reservoir caused by cooled water reinjection, this research focuses on the quantitative relationship among reinjection parameters and the thermal breakthrough time of production wells. The permeation, tracer, and reinjection tests were conducted in a simulation model using a large sand tank in conjunction with the numerical simulation method based on COMSOL Multiphysics. Subsequently, sensitivity analysis and nonlinear fitting were performed to investigate the effects of fluid viscosity and density on the reinjection process, and to analyze the impact of reinjection parameters on the thermal breakthrough time of production wells, along with their underlying mechanisms and law. The results indicate that the migration velocity of reinjection water is greater in coarse sand layer compared to that in medium sand layer, and the thermal breakthrough time t is linearly correlated with reinjection rate (Q) raised to the power of − 0.85, temperature difference (ΔT) raised to the power of − 0.21, and spacing between the production and reinjection wells (R) raised to the power of 1.4. The correlation equation and analysis show that when the temperature difference between production and reinjection ΔT is more than 30 ℃, the influence of ΔT on the thermal breakthrough time of production well becomes weak, because ΔT exerts an effect on the thermal breakthrough time of production well t by influencing the relative position of the 18.5 ℃ isotherm in the temperature transition region. The error in reinjecting high-temperature fluid into low-temperature fluid may be corrected by introducing a viscosity correction coefficient αμ.

Prospects of an Acid Gas Re-Injection Process into a Mature Reservoir

This study provides insights into the experience gained from the investigation of the dynamic behavior of a mature sour hydrocarbon reservoir modeling under an acid gas re-injection process production strategy. The primary objective was to analyze and evaluate the production behavior of proposed injection zones by assessing various injection scenarios and obtaining oil production over time. To achieve that, a workflow was developed to prioritize potential injection areas, select the optimal wells, determine the optimal operational parameters and optimize a pilot application design based on expected performance. Within this framework, the study encompasses diverse acid gas injection schemes on a pilot scale approach, including acid gas combined with waterflooding. The outcome of this analysis will eventually lead to the identification of the most promising and highest-performing injection scheme, elucidating the optimal range of operating parameters. This optimal combination forms the basis for the economic analysis of the venture and the subsequent detailed design of a full-scale application, where real-world implementation will validate the projected results.

A rapid optimization methodology of produced gas reinjection EOR in carbonate reservoirs

The Carboniferous carbonate reservoir of the Pre-Caspian basin has abundant oil and gas resources. The typical features of low porosity and low permeability and reservoir oil with high concentrations of H2S and CO2 and heavily dissolved gas-oil ratio allow produced gas reinjection as an effective and economic way to enhance oil recovery (EOR). However, the optimal design of injection/production parameters for gas injection processes is the premise for development scheme and technical decision. Compared to the conventional method of one-parameter-at-a-time approach with lack of interactions between various factors and tremendous challenge of main controlling factors identified, in this work we present a rapid optimization methodology to identify the main factors from numerous candidate parameters and obtain optimum levels of key factors. Our chosen methodology is a combination of experimental design with response surface method (RSM). Firstly, the two-level Plackett-Burman experimental design was used to screen and rank ten operational variables for the gas reinjection process. The top five significant parameters with the sum of their influencing weight greater than 94.3 % are bottomhole pressure for producers, reinjection ratio, injection period, injection gas timing and completion interval. Then the three-level Box-Behnken experimental design was employed to perform optimization exploration with the RSM. Regression models of the oil recovery factor (RF) were constructed by using these five key factors, which fits excellently with numerical simulation results. Finally, the optimal levels of controlling factors were determined to maximize oil recovery. This optimization procedure is very practical for reservoir engineers to guide a rapid evaluation of gas injection processes.

Investigating the Potential Impact on Shallow Groundwater Quality of Oily Wastewater Injection in Deep Petroleum Reservoirs: A Multidisciplinary Evaluation at the Val d’Agri Oilfield (Southern Italy)

The increase in oil production from petroleum reservoirs has led to studies examining the effects of these activities on groundwater quality. Oily wastewater associated with oil production is often reinjected through abandoned wells into the unproductive portions of the reservoir to avoid its discharge on the surface. The reinjection process is designed to be environmentally friendly and to exclude direct interactions between injected fluids and the surrounding groundwater; nevertheless, the evaluation of the compatibility between this process and the protection of the surrounding environment is of utmost importance when oilfields are located within sensitive and protected areas. The present work aimed to evaluate the impact of the oily wastewater reinjection into a long-term and high-rate disposal well in the Val d’Agri oilfield (Southern Italy). Previous preliminary investigations carried out at the study site led researchers to hypothesize the possible hydrocarbon contamination of the shallower aquifer caused by reinjection well integrity issues. Our strategy is based on an integrated and multidisciplinary approach involving isotopic (stable isotopes 2H and 18O), chemical, and microbiological (characterization of bacterial and archaeal communities) analyses. After a comprehensive and meticulous examination of the research data, it has been ascertained that significant discrepancies exist between the shallow and reinjection water systems. This allowed us to clarify the area’s complex flow dynamics and exclude hydrocarbon contamination of spring waters caused by the reinjection process.

Review of Chaotic Intermittency

Chaotic intermittency is characterized by a signal that alternates aleatory between long regular (pseudo-laminar) phases and irregular bursts (pseudo-turbulent or chaotic phases). This phenomenon has been found in physics, chemistry, engineering, medicine, neuroscience, economy, etc. As a control parameter increases, the number of chaotic phases also increases. Therefore, intermittency presents a continuous route from regular behavior to chaotic motion. In this paper, a review of different types of intermittency is carried out. In addition, the description of two recent formulations to evaluate the reinjection processes is developed. The new theoretical formulations have allowed us to explain several tests previously called pathological. The theoretical background also includes the noise effects in the reinjection mechanism.

Comparative study on properties of polypropylene-based composites reinforced with tobacco stalk fibers (unmodified / modified) from different parts of tobacco stalk

In this study, the effects of the three parts of the tobacco stalk: the xylem (TSX), husk (TSH), and core (TSC), on tobacco stalk fiber (TSF)/polypropylene (PP) composites were investigated. The effects of various types of interfacial modifiers and the number of recycled times on the properties of the composites were also explored. The results showed that the TSX reinforced PP composite exhibited better mechanical properties than those of TSH and TSC reinforced composites. The modifier improved the interfacial properties of the composites, and the tensile strengths of TSX/PP, TSH/PP and TSC/PP composites reached up to 32.8, 25.6 and 26.4 MPa in the presence of the modifier. The flexural strengths of TSX/PP, TSH/PP, and TSC/PP composites were 56.0, 46.1, and 48.7 MPa, respectively. Different parts of the tobacco stalk fiber had little effect on the thermal stability and crystallization properties of the compound material. After modification of the composites, their crystallization properties were improved, while there were no significant changes in their thermal stability. After four cycles of crushing and re-injection process, the composite material maintained good mechanical and thermal stability properties, and the interface of the compound material was tightly bonded, indicating that the prepared composites exhibited good reusability properties. Tobacco stalk fiber composite material can replace plastic or wood in decorative building materials, horticultural engineering materials, transportation packaging etc., which can obtain significant economic benefits by not only improving the broader utilization of agricultural and forestry waste but also reducing the use of plastics.

High-dimensional CFD optimization of a low-flow coefficient S–CO2 centrifugal compressor for enhanced oil recovery systems

The design of low-flow coefficient (∼0.01) centrifugal compressors with supercritical CO2 as working fluid is still a challenge for engineers due to its increased friction losses at the impeller. However, the reinjection pressure required for Enhanced Oil Recovery (EOR) systems is achieved by compression trains with stages of high-Pressure Ratios (PR > 3) which can only be obtained by lowering the flow coefficient of the equipment. The carbon dioxide mitigation, due to the reinjection process, also increases oil productivity and extraction lifetime. A four-staged compression system was considered and the preliminary geometry of its last stage was considered herein after a 1D optimization that decreased the total required power of the system. In order to further increase the systems' performance, a CFD model was developed and submitted to Sensitivity Analysis (SA) and parametric optimization procedure, considering polar angles, meridional profile and vaneless diffuser passage (25 variables). The assessment of the sequential SA using, Morris' screening method Design of Experiment (DoE) and SS-ANOVA for variable ranking and response surface training, has exposed the method's limitation in recognizing interaction between variables since low-quality Response Surfaces (RS) were trained. However, the Incremental Space Filler (ISF) sampling has complemented the sample space screening, guarantying adequate RS at a low computational cost. This indirect optimization strategy that increased the equipment's polytropic efficiency by 1.19%, diminishing total entropy generation by 8.5% can deliver important cost reductions to the operation of EOR compression systems. The ‘entropy-guided’ phenomenology analysis strategy combined with SA results, identified that the narrowing of the vaneless diffuser has extinguished the recirculation present in the original geometry's impeller/diffuser interface region, which was the largest difference in the entropy histogram. Moreover, the enlargement of the impeller's meridional profile has smoothed the fluid flow change of direction (from axial to radial) and displaced the swirl structures that restricted the fluid flow in the main passage.

Study on prevention and control measures of sandstone geothermal reinjection plugging.

In the process of geothermal tailwater reinjection of sandstone, the problem of plugging has been seriously restricting the continuous development of geothermal reinjection for many years, and the problems of plugging are complex and changeable. The plugging in the process of reinjection can be divided into physical plugging, chemical plugging, microbial plugging and gas plugging. Given these four types of blocking, according to the mechanism characteristics of the blocking caused by them, this paper puts forward corresponding blocking prevention measures and solves the current blocking problems by filtering, adding a scale inhibitor, intermittent reinjection, adding chlorine dioxide and regular lifting. In addition, the existing reinjection process and the equipment flow are relatively simple and cannot achieve the goal of efficient reinjection. Therefore, a complete set of reinjection processes is designed to ensure the efficient reinjection of sandstone geothermal tailwater.

Modelling reinjection of two-phase non-condensable gases and water in geothermal wells

Steam production from high enthalpy geothermal systems is frequently accompanied by the emission of non-condensable gases (NCGs), initially dissolved in the liquid phase or mixed in the vapour phase at depth in the reservoir. Capturing and reinjecting geothermal gases (CO2, CH4, NH3, H2S, H2, …) together with condensed steam leads to a significant improvement of the environmental profile of geothermal power systems and helps with reservoir recharge and pressure support. Nowadays, there are several ongoing projects targeting the minimalization of the environmental impact of geothermal exploitation through reinjection of the NCGs. For low NCG content, the gases can be fully dissolved into the condensed water and reinjected. However, for a high concentration of NCGs, the dissolution is only partial, and a two-phase mixture needs to be reinjected to achieve this goal. We present here the numerical results for the reinjection process in two different geothermal sites and for two different injection scenarios, focusing on the case of two-phase (liquid–gas) flows. Three commercial software (UniSim®, PIPESIM, and OLGA) and one in-house developed code (GWellFM) were used, and their results were compared. The injection should always take place inside a liquid column in the well to avoid degassing and accumulation of the NCGs. When targeting high pressure reservoirs or when injecting high ratios of water to NCGs flow rates, mixing of the two phases should take place on the surface. Whereas for low pressure reservoirs or for high gas contents mixing must occur deep in the well through one or several mixing points to ensure either complete dissolution of the gas or the downward flow of a two-phase mixture with minimum compression on the surface. The uncertainties of two-phase downward flows and water/NCGs mixtures characterisations introduce additional complexities in the modelling of the reinjection process.

含过氧化氢的气田水回注工艺过程安全风险评价

含过氧化氢的气田水回注工艺过程安全风险评价

Analysis of the Type V Intermittency Using the Perron-Frobenius Operator

A methodology to study the reinjection process in type V intermittency is introduced. The reinjection probability density function (RPD), and the probability density of the laminar lengths (RPDL) for type V intermittency are calculated. A family of maps with discontinuous and continuous RPD functions is analyzed. Several tests were performed, in which the proposed technique was compared with the classical theory of intermittency, the M function methodology, and numerical data. The analysis exposed that the new technique can accurately capture the numerical data. Therefore, the scheme presented herein is a useful tool to theoretically evaluate the statistical variables for type V intermittency.

Acid Gas Re-Injection System Design Using Machine Learning

An “energy evolution” is necessary to manifest an environmentally sustainable world while meeting global energy requirements, with natural gas being the most suitable transition fuel. Covering the ever-increasing demand requires exploiting lower value sour gas accumulations, which involves an acid gas treatment issue due to the greenhouse gas nature and toxicity of its constituents. Successful design of the process requires avoiding the formation of acid gas vapor which, in turn, requires time-consuming and complex phase behavior calculations to be repeated over the whole operating range. In this work, we propose classification models from the Machine Learning field, able to rapidly identify the problematic vapor/liquid encounters, as a tool to accelerate phase behavior calculations. To set up this model, a big number of acid gas instances are generated by perturbing pressure, temperature, and acid gas composition and offline solving the stability problem. The generated data are introduced to various classification models, selected based on their ability to provide rapid answers when trained. Results show that by integrating the resulting trained model into the gas reinjection process simulator, the simulation process is substantially accelerated, indicating that the proposed methodology can be readily utilized in all kinds of acid gas flow simulations.

Induced seismicity associated with geothermal fluids re-injection: Poroelastic stressing, thermoelastic stressing, or transient cooling-induced permeability enhancement?

Both field injectivity and induced seismicity were reported to be inversely correlated with the temperature of re-injected fluids at the Hellisheiði geothermal field in Iceland. This observation has led to a hypothesis that transient cooling-induced permeability enhancement is a novel mechanism for induced seismicity, in addition to elevated fluid pressure, poroelastic stressing, and thermoelastic stressing in geothermal environments. In this work, a 3D calibrated coupled THM model was developed to model the colder fluids re-injection process over a 1-year period and evaluate the potential for induced seismicity in terms of Coulomb stress changes at the Hellisheiði geothermal field. Three modelling scenarios taking into account respectively the poroelastic effect, thermoporoelastic effect, and thermoporoelastic effect with permeability enhancement, were examined and compared to identify the dominant mechanism for the recorded seismicity and examine the contribution from each individual mechanism. Results have shown that, under normal fluid re-injection pressure and temperature conditions, the permeability enhancement effect is the dominant mechanism for induced seismicity at the Hellisheiði geothermal field. Specifically, the contribution to Coulomb stress changes from the permeability enhancement effect is almost twice of that from the thermoelastic stressing, which is in turn two orders of magnitude larger than that from the poroelastic stressing. It has also been noted that, when reducing temperature of re-injected fluids from 120°C to 20°C, the temperature change is increased by 2.1 times at 1,000 m depth, while the amount of mass flow by around 4 times. Thus, the amount of heat transferred can be increased 8.4 times by lowering temperature of the injected fluids, which explains the high sensitivity of induced seismicity to temperature. Outcomes of this work suggest temperature control of injected fluids as a feasible regulation method to mitigate against injection-induced seismic risk in geothermal reservoirs.