bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental Investigation of Oil Displacement Caused by Fracturing Fluid Imbibition in Hydraulically Fractured Oil-Wet Shale Reservoirs
Authors: Jian Zhu , Fei Wang , Li Liu , Jiaxin Wang , Dong Xiong , Zhuo Dong , Herun Bi , Shicheng Zhang 
Published: February 2024

Abstract
Spontaneous imbibition (SI) has proven to be an effective method for enhancing oil recovery in water-wet shale reservoirs due to the capillary force. There are few articles that focus on the water imbibition and oil displacement for oil-wet reservoirs. However, we believe that the potential of oil displacement caused by water imbibition should not be neglected, since field observations from dozens of wells show strong positive relevance between initial oil production and post-fracturing well shut-in time in the oil-wet shale oil reservoir of Junggar Basin, China. In this paper, several experiments and numerical simulations are designed to shed light on the mechanism of oil displacement by fracturing fluid imbibition, including the driving force and the oil recovery of different pores. The real field fracturing fluid which is prepared by guar gel, anti-emulsifiers, anti-swelling, cleanup additives and gel breakers is used as the test fluid. Also, the oil-wet shale cores saturated with crude oil are used as the samples. Firstly, contact angle after different contact times and interfacial tension are measured to figure out the petrophysical properties of fracturing fluid and crude oil. Secondly, the SI experiments using the fracturing fluid made up of deuterium oxide as the imbibed fluid are conducted to discover the oil recovery of different sizes of pores with shale samples. The low-field nuclear magnetic resonance(LF-NMR) is used to describe the relative content of crude oil under different pores and different SI times. Finally, an experimental core model is established based on the above experimental results. The results show that wettability alteration appears in the oil-wet the core sample. As the contact time increases, the contact angle decreases continuously. The interfacial tension decreases from 72(water and crude oil) mN/m to 1.2(fracturing fluid and crude oil) mN/m. These two phenomena effectively explain the driving force of imbibition and displacement in oil-wet samples. The imbibition oil recovery is about 18.4% in the oil-wet core samples, which indicates that oil-wet cores have a certain oil displacement effect. The fracturing fluid enters the mesopore first because of the driving force produced by wettability alteration and the low frictional resistance, and the imbibition oil recovery in the mesopore is 35%, which is higher than that in micropore and small mesopore in oil-wet samples. This phenomenon and result show a sharp contrast with that of water-wet rock cores proved by previous studies. Finally, a new capillary force curve accounting for the effect of wettability alteration is fitted to characterize the oil displacement in oil-wet samples by the experimental core model simulation. This study aims to demonstrate the SI characteristics of oil-wet shale and helps to provide crucial theoretical foundations for developing oil-wet shale reservoirs.
Complexities in the Characterization and Index Measurements of the Unconventional Qusaiba Rock Member from Qassim Region, Saudi Arabia
Authors: Gramajo E. , Rached R. M. , Ghreizy A. E. , Maalouf E. , Ayranci K. 
Published: February 2024

Abstract
Unconventional shale reservoirs, notably Saudi Arabia's Qusaiba member, store a significant portion of the world's natural gas and tight oil reserves. The understanding and successful extraction of these reserves require a detailed comprehension of their complex geological, petrophysical, and geomechanical properties.
This research addresses the challenges faced during sample preparation and testing of standard rock mechanical properties of a shallow subsurface core from the Qalibah Formation (Sharawra and Qusaiba members), of the Qassim region in Central Saudi Arabia. Traditional methods faced limitations due to the shale's intricate heterogeneity, layered structure, and unique formation processes. However, microindentation testing helped solve most of these challenges.
With its expansive sampling capability, this method provided insights into the rock's strength and elasticity. By comparing the results of the micro-indentation tests against conventional measures, this study highlights the potential of innovative techniques in characterizing unconventional shale reservoirs, offering a promising avenue for future exploration and understanding.
The Design of Green Molecules for Demulsification
Authors: Ekoue-Kovi K. , Jakubowski W. 
Published: February 2024

Abstract
New chemistries are needed to address the negative environmental impact of currently used demulsifier (DMO) formulations especially when used offshore to separate water from crude oil emulsions. The goal of the study was to synthesize new eco-friendly molecules with targeted environmental profile, which behave as DMOs and develop a better understanding of chemical structure – biodegradation and toxicity relationships.
Different synthetic pathways were employed to assess the possibility of synthesizing molecules with specific biodegradation kinetics, acceptable toxicity as well as high demulsification performance. In the design of new DMO, we used highly biodegradable molecules as one of the building blocks of the final polymer. New DMO polymer biodegradability in seawater was evaluated by following the OECD guideline 306, and toxicity was tested against saltwater algae by measuring EC50 in 72 hours. The performance of the green DMO intermediates was tested in several crude oils in upstream and downstream applications using bottle test procedure and electrical desalting dehydration apparatus respectively.
New molecules demonstrated &gt; 60% biodegradability in 60 days and &gt;10 mg/L toxicity to seawater algae. Synthesized DMO intermediates showed higher biodegradation profiles compared to currently used DMOs, which are based on alkoxylated alcohols, phenolic resins and diepoxides that are not biodegradable due to high molecular weight and strong C-C and C-O-C bonds in their chemical structure. The connections of the newly synthesized highly biodegradable molecules were achieved with the bonds, which are prone to hydrolysis. In addition, the created polymer was functionalized with hydrophobic building blocks to tune the final DMO performance. The results showed that these new molecules were able to separate water from crude oil emulsions and showed optimal and similar performance to some of the currently used non-biodegradable DMO intermediates. The performance of new DMOs was strongly dependent on their chemical structure and composition. Clear correlations of relative solubility number to chemical structure and performance were observed.
Synthesized polymers exhibited a better biodegradation profile and better competitive performance to conventional non-biodegradable DMO products especially in terms of water drop during the bottle test evaluation. Due to systematic design of the synthesized polymers, this research led to a better understanding of chemical structure – biodegradation and toxicity relationships as well as performance of new DMO molecules.
Comparative Study of CO2 Mineral Trapping: A Numerical Investigation
Authors: Mouallem Johny , Arif Muhammad , Raza Arshad , Mahmoud Mohamed 
Published: February 2024

Abstract
During CO2 geo-storage, mineral dissolution is considered as the safest trapping technique but the longest and the most complicated as it includes different mechanisms: geo-chemical reactions, chemical reactions and physical mechanisms like diffusion and advection. Many factors also influence the mineral trapping capacity of the geological formation like mineralogy, temperature, pH, CO2 fugacity, pressure of CO2 and salinity of the brine. The scope of this study is to compare the mineral trapping of CO2 of sandstone and carbonate formations using a numerical simulation approach as a function of temperature, salinity and mineralogy of the subsurface systems.
Numerical simulation will be performed in this study using the geo-chemical, multi-component, non-isothermal, and multi-phase simulator CMG-GEM. 2D models will be used to study the mechanisms occurring during mineral trapping and how they affect its efficiency. Sensitivity analysis will be performed on the effect of temperature, mineralogy and brine salinity on CO2 mineralization tendency for both geological formations at the same conditions. The mineral composition, porosity and storage capacity will also be evaluated. It was found that dissolution and precipitation of minerals occurred during and post CO2 injection. The presence of small quantity of illite tends to decrease immensely the trapping capacity of CO2. Moreover, temperature and salinity tends to promote the mineral activity during CO2 storage.
This paper thus provides new insights into the dynamics of CO2 storage by mineral trapping pertinent to sandstones and carbonates. Furthermore, it will help in site selection evaluation for carbon geo-sequestration (CGS) projects. Extensive study of the parameters affecting the mineral trapping will be presented.
In Situ Characterization of Wettability in CO2-Brine-Rock System Based on X-Ray Microtomography
Authors: Chen Qian , Hou Jian , Wei Bei , Xue Yu , Du Qingjun , Liu Yongge 
Published: February 2024

Abstract
It is of great significance to evaluate wettability accurately because it controls the fluid distribution in the pores and throats. And the wettability is directly related to the safety of CO2 sequestration in aquifers. In this paper, in situ characterization of reservoir wettability based on micro-CT is investigated due to its repeatability and convenience. At first, a CT scanner is used to obtain the fluid distribution. Then, we use the artificial intelligence wizard segmentation method (AIWSM) to segment the images. The AIWSM combines threshold segmentation method with deep learning segmentation method to improve segmentation accuracy. After that, we measure CO2 contact angles and contact surface area between CO2 phase and rock phase to evaluate reservoir wettability, respectively. The measurements consider the influence of the roughness of the reservoir rock surface, which can better reflect the real situation of the reservoir. At last, we also study the influence of wettability on CO2 residual trapping. The results indicate that the images segmented by AIWSM is more accurate for each phase in CO2-brine-rock system. Subsequently, we consider the influence of salinity and surfactant concentration on CO2 contact angles and contact surface area between CO2 phase and rock phase. It shows that when salinity increases from 10,000 mg/L to 100,000 mg/L, CO2 contact angles decrease from 124.55° to 116.32° and contact surface area between CO2 phase and rock phase increases from 7.44×107 μm2 to 12.03×107 μm2 gradually. In addition, when surfactant concentration increases from 0 wt% to 0.5 wt%, CO2 contact angles increase from 124.55° to 137.88° and contact surface area between CO2 phase and rock phase decreases form 7.44×107 μm2 to 3.03×107 μm2 gradually. The results obtained by two wettability characterization methods are consistent: the reservoir hydrophilicity is weakened with the increase of salinity and enhanced with the increase of surfactant concentration. After we accurately characterize the reservoir wettability in situ, the influence of wettability on CO2 residual trapping can also be obtained. It shows that the more hydrophilic the rock is, the higher the CO2 residual trapping efficiency is. Accurate characterization of wettability in CO2-brine-rock system is essential for the long-term safety of CO2 sequestration. This can help better select the suitable CO2 sequestration locations for aquifers and provide reliable experimental data for CO2 sequestration simulation.
Changing The Status Quo: First Application of Utilizing Novel Tracer Technology for Monitoring Hydraulic Fracture Stage Contribution
Authors: Arshad W. , Brohi I. , Pooniwala S. 
Published: February 2024

Abstract
The ultimate goal of drilling and stimulating long horizontals wells is maximizing production with minimal economic investment to ensure a good return on investment. The costs associated with fracturing and stimulation are a significant portion of a well's completion cost. Considering that the number of stages and stage volumes have an almost linear relation with well completion costs, on a field scale optimizing the number of stages and fracturing treatments can have massive impact in budget optimizations.
Conventionally stage contribution in the field is estimated by running a PLT post fracturing. In long horizontals accessibility to TD could pose a challenge. Running a PLT also requires a wellbore cleared of isolation frac plugs or ball seats based on the completion type. In sub-hydrostatic pressured reservoirs, the debris created from the milling of plugs can be detrimental to the ultimate well performance. The results from PLTs’ provide a snapshot of well performance at a single point of time and not the dynamic response of the well over time.
In order to overcome the challenges of conventional PLTs’ for fracture stage contribution monitoring, various technologies were evaluated. It was decided to implement chemical tracers as an alternative monitoring technology due to the ease of deployment and some well monitoring benefits. The chemical tracer technology provides an intervention-less method to qualitatively measure stage by stage production which can be used to enable building a production profile for each stimulated stage. As the results can be observed with a quick turn-around time, production trends can be easily monitored over time by implementing a structured well surveillance plan.
Chemical tracers are applicable to Open Hole Multi-Stage Fracturing (OH-MSF) completions using ball operated frac sleeves and openhole packers and the "Perf & Plug" method of multi-stage fracturing in cemented completions. The examples presented in this paper include a 5-stage OH-MSF and 11-stage P&P stimulation scenarios.
Post-fracturing flowback in conjunction with chemical tracers provide interesting insights into the well clean-up operations and stage contributions from the heel to the toe of the well. Quite a few succinct conclusions can be made on the behavior of reservoirs and some unusual observations which highlight the persisting weaknesses in understanding complex reservoirs. The lessons learnt from some of the observations may help optimize the future hydraulic fracturing and post fracturing well clean-up strategy in the field.
This paper discusses the workflow of selecting the appropriate tracer technology, setting success criteria, and the field implementation of the technology.
Conveyance Options for Pipe Recovery in a Stuck Drill Pipe Scenario in Horizontal Wells
Authors: Kishore S. , Woods J. , Engel D. , Batyrkhanov K. 
Published: February 2024

Abstract
Recovery of stuck drill pipe is a challenge in deep horizontal wells. Typically, in a vertical or slightly deviated well, after attempts have been made for recovery of stuck drill pipe by working the pipe, the option to convey the pipe recovery tools with electric line is relatively simple due to gravity descent. However, in horizontal wells, the options to convey the recovery tools require electric line using tractor or pump-down techniques; alternatively, coiled tubing can be used for conveyance. Our study evaluates these three methods and compares the efficiency and effectiveness of these conveyance methodologies.
The application of these solutions each have their own advantages and some disadvantages, especially as the access within the drill pipe can be limited due to the presence of various types of restrictions such as debris or the variable diameter inside the pipe, which usually has an "internal upset" on the connections. These restrictions combined with the potential nonexistence of circulation will affect the maximum reach for the conveyance methods to differing degrees. The ability to reach the target may be limited in extended reach wells and the target cutting depth may not be feasible with some conveyance options. The presence of radioactive sources in the drilling assembly may also complicate the pipe recovery operation.
Three different conveyance options to perform the pipe recovery operation used on different operations in the Middle East are documented: e-line tractor, e-line pump-down, and coiled tubing conveyance. We compare the options and evaluate the results from the three conveyance methods for the pipe recovery tools to sever the stuck drill pipe. Each of the methodologies can be effective, and the ideal application depends on the existing downhole conditions present at the point the drill pipe becomes stuck.
Multivariate Sensitivity Analysis and Real-Time Algorithms in Data-Driven Coiled Tubing Cleanouts Turn Insights into Action
Authors: Tardy Philippe , Kotlyar Lev , Keong Azwan Hadi , Fonseca Santiago Hassig , Ramondenc Pierre , Segura Jordi , Spesivtsev Pavel 
Published: February 2024

Abstract
Depleted wells require underbalanced coiled tubing cleanouts (CTCO) in which natural production from the reservoir assists solids transport. Reservoir pressures are often uncertain in these subhydrostatic environments, making CTCO design conditions difficult to predict. Under these conditions, sustaining an efficient cleanout is challenging, and risks include undesired leakoff, damage to the wellbore, and stuck pipe. New physics-based algorithms and workflows consume real-time data and output actionable feedback to optimize design, execution, and evaluation of CTCOs.
A coiled tubing hydraulics (CTH) simulator with state-of-the-art flow and transport models improves CTCO design capabilities by sensitizing over every parameter, which generates a combinatorial number of scenarios. Once executed, this multivariate sensitivity analysis generates a large database of sensitized scenarios which delineate a safe and effective operational envelope. Meanwhile, a real-time execution advisor selects the sensitivity analysis scenario that best approximates actual conditions and guides coiled tubing (CT) operators to choose optimal liquid rates, nitrogen rates, and CT speed. This execution advisor is supported by an early inference algorithm (EIA), which assesses reservoir pressure during the run in hole (RIH), while surface testing flowmetering data are consumed by an annular velocity algorithm (AVA) to estimate solids transport efficiency, reservoir leakoff, and inflow in real time. EIA, AVA, and execution advisor run in real time to reduce operation time by up to 15% and nitrified fluid consumption by 10%, ultimately increasing hydrocarbon production by 50%. In addition to driving efficient workflows, the model reduces the risks of poor solids sweeping, formation damage due to reservoir leakoff, solids inflow from reservoir due to large drawdowns, and damage to the surface equipment.
This study demonstrates that by combining extensive multivariate sensitivity analysis, advanced flow models, surface and downhole measurements with real-time interpretation and inference algorithms, CTCO operators can quickly assess multiple metrics of job performance, such as downhole solids sweeping efficiency, reservoir leakoff and inflow, and drawdown, and react accordingly to significantly improve operational outcomes. This first use of these real-time execution advisors paves the way to a step change in the efficiency and safety of CT interventions worldwide.
Case Study: Automated Recommendations to Increase Run Life of the Electrical Submersible Pumps (ESPs) Using Machine Learning
Authors: Silvia Shejuti 
Published: February 2024

Abstract
Unplanned ESP shutdowns and failures result in deferred production, which can lead to significant revenue losses. Most operators rely on engineers to optimize hundreds of ESPs using traditional surveillance technologies. Due to inherent limitations of these technologies, identifying critical conditions and taking remedial actions is extremely time consuming. This case study demonstrates how automated field production solutions (AFPS) has helped a major operator in North America to increase ESP run life in two of its producing assets.
AFPS is an ensemble of machine learning (ML) and physics-based models that predicts critical conditions, estimates remaining useful life (RUL) and provides remedial recommendations to increase run-life of the ESP. ML models for predicting critical conditions were trained using historical timeseries sensor data, hand labeled by experts for various clinical conditions. Physics based models for detecting critical conditions were calibrated using well completions, fluid property, inflow performance, power, and correlations data. Recommendations models were trained using 5 years of event action logs data for 500+ ESPs installations in North America.
In this study, we demonstrate how AFPS increased run life of an ESP with gas interference and locking conditions. Since the first few months of run life, ESP1 experienced sudden fluctuation in motor current, and increase in intake pressure and motor temperature. Its production declined to outside of the minimum recommended flow range. AFPS was able to accurately identify these critical conditions and estimated reduced remaining life. Between May to Sept. 2023, ESP1 experienced severe gas interference/gas locking symptoms. AFPS automated recommendation was enabled and implemented with expert supervision. In Aug. 2023, experts carried out three recommendations provided by AFPS, which significantly improved the gas interference condition and reduced excessive cycling due to motor underload and high motor temperature.
AFPS is an innovative approach that combines ML and physics-based methods to automatically provide effective recommendations to increase ESP run-life. Unlike traditional surveillance approaches, AFPS leverages ML models to learn patterns in historical ESP operational data to reliably predict critical conditions, optimal remedial actions and remaining useful life. Thus, AFPS is scalable and robust to different operating conditions and requires minimal human interventions to avoid unplanned shutdowns and failures, resulting in deferred production.