bluuebunny/crossref_metadata_2025_split huggingface dataset:
Optimization of Interval Pumping System for Oil Wells Under New Energy Self-Consumption Scenarios
Authors: Xu Jianguo , Fan Chuanlei , Song Kecong , Yang Qinghai , Zhang Hao 
Published: October 2024

Abstract
Intermittent production can significantly enhance system efficiency and reduce lifting power consumption in low-production oil wells located in low-permeability reservoirs. The original determination of pumping shut-in duration of intermittent pumping oil well was mainly based on experience, which led to the inappropriate setting of shut-in time, affecting the economic benefits of oil wells. The determination of intermittent pumping well shut-in period is based on the principle of peak cutting and valley filling. The participation of photovoltaic(PV) power generation in energy supply changes the peak and valley of electricity price. If the oil well runs according to the original system, the photovoltaic power output will exceed and the power will be abandoned during the peak period. This study proposes an optimization methodology tailored for interval pumping systems under new energy self-consumption scenarios, integrating PV power generation. Liquid level recovery tests during shutdown periods were conducted to analyze recovery patterns and identify optimal shutdown durations based on the recovery speed "inflection point". Real-time electricity price curves, incorporating both PV generation and grid consumption, facilitated the determination of rational shutdown periods aligned with electricity pricing dynamics. Implemented in Block X of the Jilin Oilfield, the study found that traditional shutdown periods of 8 to 10 hours were suboptimal. Following on-site fluid level recovery tests, shut-in periods of 4 to 6 hours were identified, corresponding to a recovery rate showing an "inflection point," thus determining a reasonable shut-in duration. Previously scheduled shutdown periods were from 9:00 to 11:30 and 15:30 to 19:00. Considering PV generation, the peak electricity pricing period from 16:00 to 21:00 was identified as the optimal shut-in period. Comparative analysis pre- and post-optimization demonstrated a reduction in abandonment rates from 7.2% to 0% and a 12% decrease in lifting electricity costs. The study highlights the effectiveness of optimizing shutdown durations based on liquid level recovery characteristics and aligning them with PV power generation, effectively mitigating surplus electricity and abandonment issues. This approach underscores its adaptability for low-yield interval pumping wells in evolving energy consumption landscapes.
Rapid Screening and Optimization of CO2 Enhanced Oil Recovery Process in Unconventional Reservoirs Using Interpretable Random Forests
Authors: Wei Bing , Wen Shuqin , You Junyu , He Yujiao , Wu Runnan , Chen Yongqiang , Lu Jun 
Published: October 2024

Abstract
Rapid screening and optimization of CO2 enhanced oil recovery (EOR) process in unconventional reservoirs is urgently needed but challenging due to the complexity of this process and poor understanding of seepage in multiscale porous media. To address this issue, an interpretable model with high interpretability was developed to evaluate the response of CO2-EOR processes using random forest (RF) to maximize performance. The feature importance and interaction analyses were conducted to enhance the interpretability of RF model from global to local levels. The genetic algorithm (GA) was used to optimize the CO2-EOR response, and select operational parameters with a minimum CO2 injection and maximum incremental oil recovery. To validate the reliability of the method, the results of the GA-RF model were compared with numerical simulation results under the same conditions, yielding an average relative error of 5.3%. The feature importance analyses show that geological parameters such as Φ and SO have a greater impact on the oil recovery compared to operational parameters. This work represents a pioneering advancement in the rapid optimization of the CO2-EOR process in unconventional reservoirs. The developed workflow offers an efficient process for optimizing the most suitable CO2-EOR process for various types of reservoirs and provides valuable time and resource savings in the optimization.
Rock Dry-Out and Fines Migration During CO2 Storage: Laboratory and Mathematical Modelling
Authors: Nguyen C. , Loi G. , Keykhosravi A. , Russell T. , Yang Y. , Zulkifli N. N. , Amir M. I. Mahamad , Manap A. A. Abdul , Shafian S. R. Mohd , Badalyan A. , Bedrikovetsky P. , Zeinijahromi A. 
Published: October 2024

Abstract
The work comprises the set of lab corefloods of the displacement of water by CO2 from sandstone cores. Previous experimental studies investigated the effects of water evaporation, Rock Dry-out, viscous fingering and Fines Migration with respect to permeability damage during CO2 injection. However, the synergy of those physics mechanisms, their simultaneous occurrence and mutual interactions haven't been studied in necessary details. We performed 8 corefloods in 5 Berea cores, creating secondary and tertiary core re-saturations by brine after complete drying during CO2 flood. To study detachment of fines during different stages of rock drying, we modelled forces and torques exerting the attached clay particles by the by-passing CO2 flow. It allows formulating the mobilisation criteria for attached clays. The main phenomena observed encompass intensive viscous fingering, rock sweep by isolated fingers under high water saturation, uniform timely drying of the rock by injected CO2 during hundreds of thousands of PVI, abrupt rock permeability increase under joining the isolated viscous fingers into a united gas-conductive network, and fines production during the overall drying period. The micro-scale mechanical-equilibrium modelling of fines detachment accords to the fact of fines production during the total displacement period.
Methane Pyrolysis to Produce Hydrogen and Carbon Solids Using Thermocatalytic Pathway
Authors: Chai I. C. H. , Chan Y. H. , Nikulainen K. , Laukka J. , Ishak M. A. 
Published: October 2024

Thermo-catalytic decomposition (TCD) of natural gas is a suitable technology to provide clean hydrogen (H2). This TCD process directly splits hydrocarbons, mainly methane (CH4), into H2 and carbon as illustrated in Equation 1. [Equation 1]CH4(g)→C(s)+2H2(g)ΔH∘=74 kJ/mol
In TCD process, H2 is produced as a gas while carbon is generated in solid form. Though the reaction can occur with heat energy alone, the use of a catalyst significantly reduces the required reaction temperature, making the process less energy-intensive. Various reactor designs are used for TCD to pyrolyze CH4, including fluidized/packed bed reactor, moving bed reactor, bubble column reactor (using molten metal or salt), and plug flow reactor. This paper elucidates ROTOBOOST's bubble column reactor, which utilizes a specific molten metal alloy as TCD catalyst. Although methane pyrolysis demonstration has started since the 1950s, the development and understanding of liquid catalyst in bubble column has gained more momentum since the 2000s. This stems from the benefit of lowering the reaction temperature to below 1000°C, making the process less energy-intensive, mitigating coking issues and subsequent deactivation of solid catalysts, and allowing better control and tuning of solid carbon quality Von Wald et al. (2020) reported that methane pyrolysis using the bubble column technology with liquid metal catalyst is a suitable process for reducing CO2 emissions in the short term.
In TCD process with bubble column reactor, pre-treated natural gas or methane is continuously fed to the bottom of the reactor, allowing it to travel upward through the molten catalytic alloy, which is heated to the reaction temperature. The catalytic alloy, with high heat capacity, provides a homogenous heat supply directly to each hydrocarbon gas molecule. As the bubbles burst at the upper interface of the liquid media, H2 and carbon are released. Since the density of carbon is much lower than that of the molten media, the produced carbon rises with the bubbles, floating at top of the liquid surface, and finally deposits at the surface of the liquid column. Therefore, the produced carbon does not affect the reaction zone on the inside/surface of the bubbles as they rise through the molten media, ensuring the bubble surface is a continuously renewed catalyst. The main advantage of liquid bubble column reactors is the continuous carbon removal from the liquid media due to density differences, preventing reactor blockage or contamination from carbon accumulation.
Skidding Rig and Introduction of Batch Drilling System Increased Drilling Operation Efficiency in Onshore UAE Unconventional Project Saving 70mm $
Authors: Elzeky Moataz Mohamed Fahmy , Varma Esha Narendra , Elhusseiny Mahmoud , Anwar Mohamed , Al Shamisi Eisa Daban , Hamdy Ibrahim 
Published: October 2024

Abstract
Batch drilling is not a new concept to Oil and Gas Industry, however thorough studies and analysis were conducted to adopt Batch vs Standard drilling methodology in unconventional wells project. The application of batch drilling resulted in huge cost saving up to 30% of total well cost. Thus, enhancing the sustainability by reducing the Footprint Impact by re-using same mud in each section for the clusters and reducing the rig flat time.
Unconventional Pad wells consists of 10 wells with 10m spacing in a single row,identical for unconventional reservoir.The wells were drilled in 3batches.This was achieved by spudding on well A and drilling and cementing the first section 16" Hole.The rig is then skid to well B to start drilling the first section again,meanwhile in well A is nipple down the Diverter,install wellhead section offline.This operation is repeated till well #10 in the last corner, optimizing the materials/services and applying the lessons learned from each section, improving the operations well by well. The wells were completed with 30% improvement of well performance.
Applying Batch drilling technique in Unconventional Pad wells has had great savings up to 13% of cost and 7% of duration per well that will finally save the cost of 1 complete well from the 10 wells in the cluster, more savings were achieved by recycling same mud system for each section to be used for the next well requiring treatment only, additional many operations can be shifted offline as: - Pickup and makeup drill string and BHA - Nipple up diverter - Nipple wellhead sections/ Christmas tree - Run mutli-shot gyro survey - Rigless Cementing The Batch drilling aimed to optimize time and learning curve for the drilling team at site for the same section drilled.Several Simultaneous Operation (SIMOP) between drilling and Fraccing is decided from the very beginning.Utilization of triple catwalk helped improve performance in tripping by 50% and the rig setback area was sufficient to skid with pipes on the rack, thus eliminating the tripping time. This technique has also showed a huge impact by reducing CO2 emissions due to less resources required, compared with standard rig move. This concept was transferred to all the fields resulting in savings of 70MM$ across 10 batches.
First time implemented in Onshore Abu Dhabi UNCONVENTIONAL wells, In terms of HSE, reduce crew exposure to high-risk operations such as pickup and laydown drill string, lifting heavy equipment during the moving and minimizing rig footprint impact owing to the reduction of CO2 emissions
Advanced 4D Drilling Dynamics Model Simulates Downhole Vibration and Helps to Optimize in Preventing Drill String Failure
Authors: Zhang Jiawei , Wang Qing , Du Shiliang , Zhuo Lubin , Liu Wei , Ling Bo 
Published: October 2024

Abstract
Downhole vibration, such as backward or chaotic whirling, is one of the primary causes for drill string failure during drilling operation. Understanding drilling dynamics is crucial for determining the mechanism of vibration and fatigue accumulation so as to mitigate risk of drill string failure. Drilling dynamics or vibration data can either be obtained from real-time measurement or simulation based on dynamics model, which plays a crucial role for drilling optimization in pre-drill planning phase.
An advanced 4D drilling dynamics model, which considers the interaction between drill bit and formation, impact and friction between drill string and wellbore, constraints exerted on drill string and drill bit, is proposed to simulate the distribution and variation of 3D displacement, velocity, acceleration as well as the stress state of entire drill string within specified time period. This time domain model allows exploration of the full range of dynamics response under different drilling scenarios, which helps to optimize the performance and reliability of BHA as well as WOB/RPM selection. Moreover, drill string fatigue life prediction can also be achieved by combing simulated stress state and fatigue accumulation theory.
Simulation shows that BHA with smaller- sized drill collar or fewer stabilizers are more susceptible to backward and even chaotic whirling while drilling. Also, inappropriate WOB/RPM combinations such as low WOB with high RPM could also cause the onset of severe lateral vibration. High frequency bending stress, mainly concentrated on BHA and caused by lateral vibration, is the main reason for rapid fatigue accumulation and continuous severe vibration could even result in drill string fatigue failure within hours. These findings helped to justify the 5 consecutive BHA failure and 1 washout while drilling the 171/2" wellbore with 7621 ft length of an ultra-deep well. Simulation also showed that downhole lateral vibration severity was significantly reduced after optimizing drill bit design, adopting BHA with larger stiffness and optimizing drilling parameters, which guaranteed the successful drilling of a new 171/2" wellbore with 4659 ft length of another offset well without downhole accident.
This 4D drilling dynamics model could be used to conduct comparative analysis of dynamics responses based on specific criteria to identify the optimum BHA design and drilling parameters, which shows great potential in drill string fatigue failure prevention and drilling optimization.
Stability of Perforation During CO2 Injection
Authors: Younessi A. 
Published: October 2024

Abstract
The injected CO2 in geological storage layers has lower downhole temperature compared to the storage formation. This induces cooling effects in the formation rocks surrounding the injection wells and their perforations. The stability of the perforations is affected by the cooling. Perforation stability is investigated for different reservoir pressures, bottom hole pressures and temperatures. The tendency for shear failure at the perforation wall is investigated through a series of customized finite element simulations, while the risk of tensile failure in the perforations is modelled using an analytical approach. The tensile failure analysis is done for two major time steps at the start and at the end of the CO2 injection. The tendency for shear failure is quantified by the plastic strain magnitude calculated around the perforation tunnel in the numerical simulations. The perforations oriented to the side of the well are more unstable compared to the perforations oriented to the top of the well for the selected normal-faulting stress regime. As expected from the theory of thermo-elasticity, the perforations are more stable with greater cooling. The plastic strain increases with higher drawdown, while less plastic strain is calculated in overbalance-injection scenarios. The cooling effect reduces the fracture initiation pressure, i.e. increases the risk of tensile failure. The fracture initiation pressure is compared against the planned highest bottom hole pressure for individual cases to ensure the stability of the perforations. Overall, injecting CO2 with a temperature lower than the formation temperature does not induce excessive compressional or shear stresses, and is unlikely to cause collapse of the perforation. The risk of shear failure tends to be higher during the early stages of injection when the reservoirs are fully depleted. The cooling effect from CO2 injection may induce tensile fractures in the perforation tunnels, which requires a case-by-case detailed investigation.
Study on CO2 Potential Damage to Fracture Conductivity and Matrix Permeability in Shale Reservoirs
Authors: Tao Jiaping , Meng Siwei , Li Dongxu , Liang Lihao 
Published: October 2024

Abstract
CO2 fracturing is a promising unconventional reservoir fracturing technology that can effectively increase fracture complexity and supplement formation energy, thus improving oil production. However, during the development of continental shale reservoirs, some of the CO2 fracturing field tests were not as effective as expected. Therefore, targeted analysis is needed to clarify the CO2 potential damage to shale oil production.
Based on nanoindentation experiments, the effect of CO2 treatment on the micro mechanical properties of the shale fracture surface is explored. Then, the effect of mechanical properties changes on the embedding of proppants is clarified. Based on physical simulation experiments, the damage law of fracture conductivity before and after CO2 treatment is analyzed. Finally, through the porosity and permeability analysis, the differential evolution law of shale porosity and permeability around the fractures is clarified.
The results show that there is a significant effect of CO2 on the micro mechanical properties of the shale fracture surface. After CO2 treatment, the average hardness of the shale surface is reduced by 22.54%. This leads to a significant increase in the indentation depth of the indenter on the shale surface under the same load. The CO2 treatment can increase the average indentation depth by 15.83%, which will lead to a deeper embedding of the proppants under formation pressure, and consequently lead to a significant decrease in the fracture conductivity. Analysis of porosity and permeability shows that near the fracture areas, the permeability of the shale matrix is improved. However, in the deeper area, the permeability of the shale matrix shows significant damage, with permeability loss of up to more than 70% after CO2 treatment.
Based on laboratory experiments, the effect of CO2 on the micromechanical properties of shale fracture surface is explored, the resulting damage to fracture conductivity by proppant embedment is elucidated, and the matrix permeability damage that exists around the fractures is clarified. Therefore, the possible formation damage of CO2 fracturing should be carefully considered in the development of high clay shale reservoirs.
Exploration and Understanding of Intermittent Water-Flooding in Low-Permeability Reservoirs Supported by New Energy Supply
Authors: Xu Jianguo , Liu Yazhen , Shen Qiaochu , Huang Hui , Yang Qinghai , Xu Gege , Han Yingda , Liu Kexin, 
Published: October 2024

Abstract
The expansion of new energy construction, characterized by its scalability and cost-effectiveness, is increasingly integrated into the oil and gas industry, albeit still in the exploratory phase. Chinese oil fields predominantly employ continuous water injection methods, which incur substantial electricity consumption and costs. Embracing new energy sources for supply promises substantial reductions in electricity costs. However, the intermittent and unpredictable nature of wind and solar power generation does not align with the consistent and stable electricity demand required for continuous water injection, necessitating the exploration of novel water injection models compatible with new energy supplies.
In pursuit of minimizing water injection electricity costs, this study proposes an intermittent water injection model grounded in the distinctive characteristics of new energy supply. During peaks of green electricity output surpassing production demand, "increased injection" is implemented, while during troughs of green electricity output falling below production demand, "reduced or halted injection" strategies are adopted. Insights derived from well test interpretations using shut-in pressure drop data guide the fine-tuning of water injection parameters. This transition shifts the water injection regime from the conventional "24-hour stable flow continuous water injection" to an "X hours injection/ 24-X hours shut-in intermittent water injection" approach. The feasibility of this model is comprehensively evaluated through real-time monitoring, engineering tests, and well test interpretations, assessing injection capacity, water absorption efficiency, reservoir characteristics, and productivity across the project lifecycle.
A 5-month intermittent water injection trial was conducted across two injection-production well pairs in the low-permeability reservoirs of the Jilin oilfield. Three distinct intermittent water injection protocols were designed: "15 hours injection/ 9 hours shut-in", "13.3 hours injection/ 10.7 hours shut-in", and "12 hours injection/ 12 hours shut-in". The injection rates, set at 1.6 times, 1.8 times, and 2.0 times the rate of continuous water injection, respectively, were determined by these protocols. Trial outcomes demonstrate reasonable high-speed injection pressures, satisfactory injection volumes, intact reservoir conditions, a 2.5 % reduction in water cut, and a delay of over 1.5 % in natural decline. Calculations based on new energy generation costs reveal a reduction of over 60% in daily electricity expenses compared to continuous water injection methods.
The successful field trial validates the feasibility of intermittent technology in low-permeability reservoirs, showcasing substantial savings in electricity costs and offering robust technical underpinning for the efficient development of such reservoirs.