bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reliable and Efficient Algorithms to Optimize Gas Well Intermittent Production Through Automatically Intelligent Control
Authors: Wu Qingxia , Han Guoqing , Yang Dingding , Zhu Zhiyong , Peng Long , Ma He , Liang Xingyuan 
Published: May 2024

Abstract
Liquid loading poses a prevalent challenge in gas well production. To maximize the gas production rate and reduce the cost of deliquification, intermittent production is often applied. However, optimization of operation parameters remains challenging due to the transient behavior of the reservoir-wellbore system. In this study, efficient algorithms are proposed to automatically optimize the parameters in real-time to remove the liquid efficiently and maintain gas production, through which the recovery factor can be extended.
Firstly, we build a comprehensive model that couples the reservoir transient behavior with wellbore dynamic characteristics. The coupling model lays out the fundamentals for reservoir-production system analysis. Then, two intelligent optimization algorithms, namely the Genetic Algorithm (GA) and Proximal Policy Optimization algorithm (PPO) are developed to obtain the optimal operation parameters, which are the key elements in intermittent production management. Finally, the optimal production system is determined by jointly controlling the gas production rate and bottom hole pressure in the coupled reservoir-wellbore model to adjust choke and open-shut intervals for obtaining the maximum cumulative gas production rate and drainage rate.
It is observed that the proposed reservoir-wellbore coupling model can characterize reservoir transient performance and capture the dynamic behavior of multiphase flow in the wellbore. The model facilitates the real-time analysis of the inflow-outflow system automatically, which can output optimal parameters to manage the operation. The global optimal solution of gas production rate and bottom hole pressure can be discerned from a set of combined parameters by using the GA algorithm. PPO algorithm can optimize the system by applying variable step size search and multivariable synchronous optimization depending on the environmental state, which can be a closed-loop optimization that allows automatic control/adjustment in the system. The simulation results indicate that intermittent production designed by two algorithms has higher cumulative gas production compared with continuous production scenarios, showing the significance of proper management in intermittent production. Additionally, it is noteworthy that GA and PPO exhibit no significant difference in gas cumulative production. Each algorithm has its special adaptability: the GA is suitable for the coupling model characterized by ideal homogeneity, whereas the PPO is more appropriate for the coupling model with complex heterogeneity, interference, transient response, and randomness.
This presented work demonstrates the ability of the GA and PPO optimization algorithms to optimize the coupled reservoir-wellbore model for solving the optimal operation parameters in intermittent production, which has great significance in avoiding the liquid loading phenomenon and improving gas recovery.
Recommended Practices and Lesson Learnt from High-Efficient Hydraulic Fracturing Towards China's Unconventional Resources Recovery
Authors: Tong Zheng , Zhang Shaolin , Li Shuai , Sun Qiang , Xue Jianjun , Qian Jie , Wang Xinzhong , Weng Dingwei 
Published: May 2024

Abstract
The latest research progress in the field of unconventional oil and gas reservoir hydraulic fracturing technology in China from the aspects of fracturing process optimization, electrification of fracturing equipment, upgrading of key devices, development of dissolvable materials, and R&D of downhole tools were proposed in this paper. Particularly since 2020, through a large amount of technical research and field trials, a comprehensive upgrade of the hydraulic fracturing technology system has been realized, supporting the confirmation of shale oil and gas geological reserves and the construction of scale benefits in the Sichuan Basin and Ordos Basin.
The electrification upgrade of fracturing equipment was continually on the way, in 2022, the number of electric driven fracturing operations by PetroChina reached 8,474, with an electricity replacement rate of 27.4%, saving 39,000 tons of diesel and reducing carbon emissions by 32,000 tons. Two types of dissolvable magnesium alloys were developed, with high-strength dissolvable magnesium alloy having a tensile strength of over 500MPa and a high elongation dissolvable magnesium alloy having an elongation rate of over 60%. The high-strength magnesium alloy was used as the core component of the delay mechanism in the delay toe sliding sleeve, ensuring the reliability of the toe sliding sleeve during the whole wellbore pressure test and sliding sleeve opening, improving the efficiency of the first section fracturing process in horizontal wells. The high-strength magnesium alloy was also used for the main body of bridge plug, and the high elongation rate dissolvable magnesium alloy was used as the sealing part, improving the sealing pressure performance from 70MPa to 90MPa and widening the temperature tolerance range to 20-200°C. In 2022, more than 20,000 sets of dissolvable bridge plugs were used by PetroChina. The composite low-density temporary plugging ball was developed, based on high-strength magnesium alloy with a hollow design wrapped in dissolvable rubber, allowing for variability in density and shape within a certain range, and field tests of temporary plugging fracturing showed an average pressure increase of 11.2MPa.
The comprehensive progress of domestic hydraulic fracturing technology systems from process to equipment, tools and materials has promoted the low-carbon and efficient utilization of unconventional resources and provided feasible technical ideas for the next step of high-quality development.
Unravelling the Tectonic History of the Oman Mountains Using Structural Restoration in the Emirate of Sharjah, UAE
Authors: Thurley Callum , Cowgill Mark , Stewart Donald , Kay Sarah , Cox Edward 
Published: May 2024

Abstract
The world-class outcrops of the MusandamPeninsula and Northern Oman Mountains have given valuable insight into the geological setting, history and genesis of the fold and thrust belt in the northern United Arab Emirates. This paper provides new insight into the tectonic evolution of the Northern Oman Mountains in the Emirate of Sharjah using state-of-the-art 3D seismic and reprocessed legacy 2D seismic via structural restoration.
Seismic interpretation has revealed that two thrust systems exist in the subsurface separated by a detachment which lies in Upper Cretaceous strata. A deep thrust system forms at Arabian Platform level (Lower Cretaceous and older) and a shallower thrust system within the Aruma Group (Upper Cretaceous and younger) is present as well. Throughout much of the thrust belt in Sharjah, the Aruma Group subcrops beneath the desert and outcrops along narrow ridges that protrude from it at present day. The thrust front is characterised by a series of en echelon pop-up structures which form a north-south trend across the Emirate. It is proposed that these transpressional features formed along pre-existing north-south trending lineaments. These are the most prospective hydrocarbon traps in the Northern Emirates and include the Sajaa, Moveiyed, Kahaif, Mahani, and Margham gas-condensate fields.
The area has been through a series of tectonic events, related to extension in the Permian, tectonic quiescence throughout much of the Mesozoic, an ophiolite obduction event in the late Cretaceous, and in line with the general view, a second compressional event in the Miocene related to the Zagros Orogeny. In the Miocene, the thrust front pop-up structures acted as buttresses and prevented the westward movement of the shallow thrust belt within the Aruma Group, which led to duplexing and intense imbrication to the east of the thrust front and to the west of the encroaching Semail Ophiolite.
The interrelationships between these events, stratigraphy, and basin evolution are discussed in this paper with a view to unravelling the tectonic history of the Northern Oman Mountains.
Unloading Gas Condensate from the Wellbore Using an Innovative Foamed System
Authors: Alsultan Sharefah , Karadkar Prasad , Harbi Bader , Shehri Tamim 
Published: May 2024

Abstract
Gas production can be enhanced by the unloading of liquid accumulated in the wellbore. These liquids can be either formation water or gas condensate. Conventionally, liquid loading is addressed by dropping soap sticks into gas well or nitrogen lifting operation without foaming. During this process, achieving a stable foam with condensate is a challenging task. In this paper, an advanced foaming system was developed to unload both formation water and condensate in addition to nitrogen lifting.
The novel foaming system consists of aqueous and hydrocarbon soluble foaming agents. The aqueous foaming agent is an amphoteric surfactant, whereas the hydrocarbon based foaming agent is a fluoro-polymeric surfactant. The test fluid was prepared by mixing foaming agent with synthetically prepared formation water and a condensate sample separately. The foamability of surfactants was assessed by using a static foam analyzer, measuring foam half-life. Liquid unloading phenomena was investigated using an in-house developed column flow test. Foam rheometer was used to measure stability under high-pressure high-temperature (HPHT) conditions.
The stability of foam greatly depends on ideal hydrophilic-lipophillic balance (HLB). This balance can be achieved by optimizing the foaming agents which significantly rely on liquid drainage, gas diffusion, and foam rupturing at high temperature. The aqueous foaming agent was analyzed from 0.5 to 1% (vol) using synthetically prepared formation water, whereas the hydrocarbon based foaming agent was optimized to 0.5% (vol) using actual condensate samples. The column flow test, which measures liquid unloading characteristics, was conducted to ensure liquid unloading from the glass column. Nitrogen gas was purged in the column from the bottom with 200 to 400 ml/min and the rate of foam displacement was measured. The stability of the foam prepared using an aqueous foaming agent with formation water was analyzed by foam viscosity at various qualities using N2 gas at different shear rate form 100-500 1/s at 1500 psi and 300°F. The effect pressure on foam viscosity was also studied to assess foam stability under HPHT conditions.
Liquid unloading using soap sticks is limited to liquids accumulated with aqueous fluids. In this paper, the advanced foaming system addresses both aqueous and hydrocarbon liquids accumulated in the wellbore that can be applicable for high temperature wells. These foaming systems can be injected with N2 with coiled tubing operation.
Extensive Study on the Influencing Parameters of Sc CO2 Foam Viscosity for Enhanced Oil Recovery and Carbon Sequestration: A Machine Learning Approach
Authors: Bashir Ahmed , Kasha Ahmed , Patil Shirish , Aljawad Murtada Saleh , Kamal Muhammad Shahzad 
Published: May 2024

Abstract
Foam flooding has been used to control gas mobility during oil displacement and CO2 sequestration processes in subsurface porous media, mitigating the negative impacts of low gas viscosity, reservoir heterogeneity, and gravity override. In this research, we study the application of machine learning (ML) to develop a data-driven prediction of the effective viscosity of supercritical CO2 foam (Sc-CO2) for enhanced oil recovery (EOR) and CO2 sequestration. The ML approach is used to overcome the challenge of using physical correlations to account for the effect of key experimental parameters on the viscosity of supercritical CO2 foam. The experimental data for evaluating the effective Sc-CO2 foam viscosity were measured using a high-pressure high-temperature foam rheometer (Model 8500) under different temperatures (50-110 °C), pressures (1000-3000 psi), foam qualities (30-90%), and surfactant concentrations (0.1-0.5 wt.%) at shear rates between 100-1450 s−1. A total of 5,552 data points were used as primary data for developing supervised ML regression models. Machine learning algorithms from the Scikit-learn library, such as K-Nearest Neighbors (KNN), Random Forest (RF), Gradient Boosting (GB), and AdaBoosting (AB), were used.
The results revealed that machine learning algorithms generated models for the effective viscosity of Sc-CO2 foam with predictive accuracies of 0.989, 0.987, 0.941, and 0.723 for RF, KNN, GB, and AB, respectively. The RF and KNN algorithm demonstrated superior performance among all the other algorithms, with RF being better in terms of accurate viscosity prediction across different viscosity values. This paper provides data-driven approach that can predict the effective foam viscosity under different reservoir conditions which leads to the design of an optimum injection strategy and effectively controls Sc-CO2 mobility for EOR and CO2 sequestration.
Crucial Factors for in-Situ CO2 Monitoring in CO2-EOR Projects Using Pulsed Neutron Well Logging
Authors: Kim Y. , Akang N. 
Published: May 2024

Abstract
Carbon dioxide (CO2) injection for enhanced oil recovery (EOR), also known as CO2-EOR, has become increasingly important due to the growing need for CO2 utilization and sequestration. CO2 monitoring is an integral part of the CO2- EOR process. Pulsed neutron (PN) well logging is an efficient and effective technology for understanding subsurface CO2 propagation and quantifying multiphase saturation. This paper discusses the critical factors—well conditions and reservoir properties—in designing a PN well logging program and analyzing PN data.
The Monte Carlo N-Particle (MCNP) simulation is a stochastic forward modeling method that generates PN tool responses under diverse well and formation conditions. With a series of MCNP models, including perturbations of various well logging environments, the characteristics of key PN measurements were delineated. This enabled the establishment of best practices in PN well logging operations and data analysis for in-situ CO2 profiling. The requirement for the PN tool is to be slim in terms of the outer diameter (i.e., 1.69 inches), allowing through-tubing deployment, and to have three scintillation gamma-ray detectors, enhancing the formation sensitivity compared to traditional dual detector-based PN tools.
We constructed MCNP models of time-spectra-based well logs; inelastic and thermal neutron capture logs were simulated considering several vital parameters—wellbore fluid, formation lithology, annular space materials, in-situ oil and CO2 densities, and reactions between CO2 and formation minerals and resident fluid. The type of wellbore fluid is water, CO2, or a mixture of the two depending on the well type—injection, monitoring, or production well. Although a water-filled wellbore is optimal for PN well logging, a CO2- filled wellbore does not adversely impact CO2 monitoring to a high degree if a sleeved-PN tool is used. As formation lithology types and water salinity influence inelastic and capture PN measurements differently, determining which PN log should be used for CO2 saturation analysis is essential. The impact of the shale volume and properties on the PN data is nonuniform, so this factor must also be carefully reviewed in conjunction with the lithology type. Furthermore, accurate estimation of oil and CO2 densities under downhole conditions minimizes the uncertainty of multiphase fluid saturation characterization. Finally, considering the effects of mineral alteration and formation dry-out is required when evaluating saturation in post-injection stages.
It is crucial to consider well- and formation- specific factors to ensure accurate monitoring of in-situ CO2 propagation and multiphase fluid volume variation with PN well logging. The best practices for PN well logging and data analysis were evaluated using a customized MCNP modeling technique. Furthermore, surveilling the behavior of injected CO2 on a well basis enables the optimization of CO2 injection parameters and the updating of reservoir models on a field-scale level.
Decarbonization of Gas Oil Separation Plants Through Automated Energy Balance
Authors: Alhamoud A. , Fallatah H. , Algady A. 
Published: May 2024

Abstract
In alignment with our commitment to decarbonization and sustainability, we prioritize energy optimization initiatives that continuously monitor and improve the energy efficiency of our assets. At Gas Oil Separation Plants, the primary assets identified as Significant Energy Users include multi-stage centrifugal pumps (utilized for water disposal and crude shipping) and centrifugal gas compressors. The energy consumption of these assets is contingent upon their optimal utilization, equipment performance, and settings A systematic data-driven energy balance using aggregated values is proposed as an effective way to monitor & optimize the performance of these assets, and linking of the energy consumption to actual production figures.
The energy balance is performed using available power meters or estimations based on first principles for assets without meters. Data is prepared in order to achieve adequate cleansing and time aggregated values are calculated per Significant Energy Users asset groups. The energy balance is then complemented with production values aggregates and KPls to relate actual consumption figures along with production records.
Aggregated values analysis provides a time-based approach to quantify deviations from optimum performance. Optimum performance for each facility depends on its design and particular configuration. The deviations can be due to a number of reasons such as operating more equipment than required for longer periods, equipment underperforming, non-optimum settings, instrumentation calibration requirements, etc. The periodic automated report of these deviations facilitates timely resolution and continuous usage of generated data for energy optimization.
The modeling tools used in this paper are self-service time-based data analytics solutions with built-in functions for modeling and prediction. It provides features to facilitate use case scalability across different facilities.
Enhancing Production in Carbonate Formations with Innovative Self-Supporting Lightweight Cement System to Isolate Water Zone Under Total Losses
Authors: Abdulqader Mustafa Sarbast , Imran Muhammad , Becharef Mohamed , Zanaty Omar El , Shahzad Kamil , Taher Sherwan 
Published: May 2024

Abstract
Addressing the compound issue of a placing a balanced cement plug to isolate the open hole section from 1026 m to 976 m in a workover well in northern Iraq. The Khurmala formation was experiencing total losses and increased water production issues. The plug also had to be accurately placed to avoid cementing the lower of perforation zone (956m - 965m). A cement slurry design had to be formulated to efficiently isolate the water zone under total losses.
Several fluid design approaches have been taken to design a successful slurry. First, to address the total losses condition of the open hole, the decision to use an 11 ppg slurry was mainly to reduce the hydrostatic pressure exerted by the cement column while introducing fluid loss control properties as well as optimizing the rheology. Furthermore, a specialized gelling agent was introduced to the design that enables the slurry develop a self-supporting characteristic as soon it is left in a static condition. As these were the key aspects of the design, more parameters and constraints that were identified and addressed will be discussed further in this paper.
As the job was executed, the success of the design was assessed according to industry standards. Initially contaminated cement was observed at surface while circulating out at the TOC indicating the presence of cement fluid at the intended interval. Subsequently, post the wait on cement period, the plug was tagged at the desired depth indicating that the water production zone has been successfully isolated in a single attempt, eliminating the need for excessive resources, solutions, time and cost that would otherwise be required for this kind of challenge and eventually the hydrocarbon production is increase significantly.
The novelty of this approach lies in designing a lightweight cement slurry with the key self-supporting characteristic while maintaining the required design parameters such API fluid loss, static gel strength, compressive strength development, and rheology.
Enhance the Transformation Effects of Hydraulic Fracturing in Casing Deformation Well
Authors: Zhang Shuo , Zhang Wei , Zeng Qijun , Jin Ningjing , Zhu Jianjun , He Zhenzhen 
Published: May 2024

Abstract
Casing deformation in shale gas wells poses a significant challenge to hydraulic fracturing operations, often leading to reduced efficiency and effectiveness in reservoir stimulation. This paper aims to enhance the transformation effects of hydraulic fracturing in wells afflicted by casing deformation through the introduction of novel techniques and materials. We present an integrated approach that includes the deployment of high expansion dissolvable plug tailored for restricted diameters, the use of spiral seal structures to ensure reliable anchoring within deformed wellbore sections. Finite element analysis and field trials are conducted to evaluate the performance of these solutions under varying downhole conditions. The outcomes demonstrate substantial improvements in the delivery and sustainability of fracturing pressures, leading to increased stimulated reservoir volumes and optimized hydrocarbon recovery rates. These results suggest that adopting such specialized interventions can significantly counteract the limitations imposed by casing deformations, thereby reviving the productivity of compromised wells and extending their operational lifespan.