bluuebunny/crossref_metadata_2025_split huggingface dataset:
Annuli Material Pseudo-Density Estimation from Standard Integrity Logging Data
Authors: Merciu Ioan - Alexandru 
Published: March 2023

Abstract
Bonding to casing material characterization is a topic of interest in the context of well barrier evaluation. There is a consolidated need directed to log data interpreters to answer questions related to the type of material present in the casing annuli of a given well. The objective of this work is to explore the possibility to provide a complementary answer to current general acoustic impedance and attenuation practice.
We reiterate that knowledge about the density of the annuli material can reduce the well barrier evaluation uncertainty. We are describing and exemplifying a rapid method to estimate the "pseudo – density" of the material in the annuli at the time of data acquisition. We define "pseudo-density" as the ratio between estimated impedance (from ultrasonic pulse-echo) and annuli apparent velocities (from ultrasonic oblique incidence techniques). Resulting "pseudo-density" maps are constrained with prior information from geology, logging, and drilling data. This allows the interpreter to judge the uncertainty in the current interpretation practice and contextualization of the annuli material into the borehole reality.
The examples provided show that when the underlying physics principles are met, the results are clear and a robust interpretation at scale along the entire logged path is possible. The estimated complementary results are affected by inherent errors and uncertainty associated with acoustic impedance and velocity estimation. However, using prior knowledge information, intervals with high uncertainty (such as unusually high impedances or large errors in the velocity estimation) are flagged providing the interpreter with information background easy to be used for final delivery.
Along with standard applications, the proposed method includes the basic mandatory tool for evaluating, validating, and incorporating the forecasted growth based on nuclear integrity logging behind the casing evaluation techniques.
Automated Detection of Rig Events from Real-Time Surface Data Using Spectral Analysis and Machine Learning
Authors: Robinson Timothy S. , Revheim Olav 
Published: March 2023

Abstract
The authors present a method for automated, high-fidelity detection of rig events characterized by complex temporal signals, such as downlinking, or wave-induced heave affecting floating rigs. These can adversely impact other systems utilizing relevant data streams, for example downlinking via mud pulse telemetry can interfere with detection of pressure changes that might indicate hole cleaning problems. Identifying these events using classification techniques applied to time-domain data is difficult, hence spectral (frequency domain) techniques, combined with Machine Learning (ML), were applied to solving this problem. Surface measurements from a variety of wells, fields, regions, service companies and operators were used to develop and validate the detection methods. Data was preprocessed using time-frequency analysis, and then input to discriminative classifiers to identify rig events of interest.
For downlinking state detection, high recall and precision scores (both &gt;93%) were achieved on independent holdout well data, and thus false positive rates were low. Successful detection was demonstrated on wells separate from the training data, hence the method is expected to generalize to new well operations. The detection method enhances situational awareness, and can actively support other software in improved automated decision-making by providing operational context in real-time, such as suppression of false warnings from monitoring pressure or modelled ECD for detecting signs of poor hole cleaning. These techniques are not limited to downlinking or heave detection, and can be applied more generally to scenarios with complex periodic signals.
Improved Drilling Line Fatigue Model Reveals a Need for Revising Slip and Cut Procedures
Authors: Kyllingstad Åge , Hørsdal Rolf , Rajic Ivan 
Published: March 2023

Abstract
This paper presents a state-of-the-art bending fatigue model for wire ropes and applies it to optimize slip and cut intervals of drawworks drilling lines. The new model considers many parameters and variables, such as specific line tension, sheave-to-line diameter ratio, optional reverse bending, drum diameter, and excessive bending curvature at the crossover intervals of multilayer drums. The new model transforms block motion and hook load statistics into a high-resolution distribution of cumulative fatigue damage along the drilling line. In turn, the model justifies that the cut length and the energy transfer (in ton-miles) per cut length can be substantially increased relative to common practice today. The calculated fatigue damage distribution can also be used to pick peak fatigue damage line spots, most suited for focused inspection and optional strength testing after it is cut away.
Casing Design Implications of Managed Pressure Drilling and Cementing, and How to Consider Them in the Design of the Well and Operations
Authors: Gabaldon Oscar R , Suryanarayana P V , Gonzalez Luis Romar A , Cavalcanti de Sousa Pedro 
Published: March 2023

Abstract
Managed pressure drilling (MPD) and managed pressure cementing (MPC) typically use lighter fluids than in conventional drilling. One consequence of this is that the fluid behind the casing being run and cemented is lighter than would be the case with conventional drilling. This has implications to the casing design for two reasons: the burst loads on the casing are augmented due to the lower external density profile, and the annular pressure buildup (APB) loads are different. It is important to consider these design implications while performing the casing design, particularly for deepwater wells. Unfortunately, this is not common at present, since the MPD/MPC design work and the casing design work are often distinct and separate, both physically and temporally. When the lower density external fluid from MPD/MPC is considered in the casing design, it is possible that the casing in question has to be upgraded (increased weight and grade) to accommodate the loads post MPD/MPC. This paper presents such a case, where the consequence of having drilled the section using MPD and cementing the casing using MPC was to upgrade the casing. The paper further presents a solution to this problem- modifying the MPC procedures such that a heavier mud than that used during MPD can be placed above the top of the cement behind the casing, thus mitigating the loads and eliminating the need for a heavier or higher-grade casing. The authors show how this can be achieved, by managing the densities of the different fluids and cement during the MPC operation. The authors hope that this work highlights the interconnectedness of well design and MPD/MPC operations, and engenders more interaction between the two groups during well engineering.
Gas Migration in PMCD Operations: Instrumented Well Study Provides Fundamental Insights
Authors: Samdani Ganesh Arunkumar , Rao Sai Sashankh , Moganaradjou Yashwant , Almeida Mauricio A. , Kunju Mahendra K. , Upchurch Eric , Gupta Vishwas Paul 
Published: March 2023

Abstract
Significant discrepancy exists between the gas migration rates observed during the field applications of Pressurized Mud Cap Drilling (PMCD) and the widely used Taylor bubble velocity correlation. This impacts the fluid logistics planning and design of fluid properties for PMCD applications. Pilot-scale experiments and simulations have shown the importance of wellbore length-scale for estimating gas migration velocity (Samdani et al., 2021, 2022). Therefore, an industry-first well-scale study of gas migration in synthetic-based mud (SBM) was performed using a 5200-ft-deep vertical test-well (9-5/8″ × 2-7/8″ casing/tubing) located at Louisiana State University (LSU) well testing facilities. This test well is instrumented with 4 downhole pressure gauges and distributed temperature/acoustics sensing (DTS/DAS) fiber optic cables which were used to track the migrating gas and to determine its velocity. In a typical test, bottomhole pressure (BHP) was maintained, while gas migrated in a shut-in well. Tests were conducted by varying gas injection rate (10-250 gpm), total gas influx size (10-20 bbl), and BHP (2200-4500 psi). Gas migration rates indicated presence of Taylor bubbles at lower pressures (&lt;2000 psi) and relatively smaller cap-bubbles at higher pressures (&gt;2700 psi). The observation of pressure-dependent flow regime transition in a wellbore is one of the significant outcomes of this study. Changes in gas influx rate also influenced the gas migration velocity as it impacts the gas holdup and the rate at which gas can dissolve in comparison with the injection rate, under the prevailing flow regime. As a result, increase in influx rate led to higher gas migration velocity. A numerical model was also developed incorporating the experimentally observed relationship between pressure and transition of flow regime, to translate the test results into useful information and predictions for field PMCD. For example, the impact of reservoir gas solubility on gas migration rates was determined using this model while using the test-results based on nitrogen gas migration. The model results for reservoir gas migration rates in SBM showed a reasonable match with field-PMCD data under similar conditions.
Correlation of Borehole Images in Conductive and Non-Conductive Muds to Understand Carbonate Heterogeneity: Case Study from Sichuan Basin, China
Authors: Hou Kejun , Zhao Zuoan , Ni Gensheng , Sultan Gamal , Liu Bo , Zhang Tianhua 
Published: March 2023

Abstract
The heterogeneous carbonate reservoir is the most important exploration target in Sichuan basin. It is challenging to identify the potential flow units in the tight carbonate reservoir. High-resolution borehole resistivity image can reveal the dissolution features such as vugs or fractures in the pay zone. Operators in Sichuan Basin have acquired lots of borehole resistivity image using water-based mud imager in key exploration wells to identify potential reservoir. The oil-based mud has become increasingly popular in exploration and development because it reduces complex drilling practices reducing drilling costs. The new generation oil-based imager is used in these new wells. The borehole resistivity image can be obtained from both OBM (oil base mud) imager and WBM (water base mud) imagers. It is important to understand the response differences through the comparisons between different borehole imaging technologies in the same wellbore. The objective of this study is to understand the responses and refine the rule of oil-based mud borehole image interpretation in tight carbonate reservoir.
The operator has logged both WBM and OBM imager in the same wellbore at different times. The WBM resistivity image is acquired in water-base mud conditions in the beginning. Then drilling fluid system was changed to OBM, and 200 meters were drilled further in the borehole. Finally, the OBM imager was logged in the hole. A comparison between the WBM resistivity images and OBM resistivity images are carried out. Increased understandings of the image log responses in this vuggy or fractured carbonated reservoir were obtained.
The borehole resistivity image from WBM and OBM imager is highly correlatable over most of the logging interval as they both show similar resistivity response (bright / dark) on both images for the same geologic feature. The new generation OBM resistivity imager is proven to have similar applications as the WBM resistivity could offer. In fact, the OBM borehole images has higher resolution than the WBM borehole image in most of the intervals, especially in high resistivity formations. It was found that the responses of vugs or fractures can be interpreted slightly different in some intervals. Only the unfilled vug will have resistive response in OBM image while it will be very conductive in the WBM image because it was invaded by the resistive or conductive mud. The responses of induced fractures or natural fractures will be slightly different, which is influenced by formation conditions such as Rt/Rm. The induced fracture could be conductive or resistive under different logging conditions.
This case study improved the understandings of the OBM imager response in tight carbonate reservoirs. These observations can be used as a reference for borehole image interpretation in similar reservoirs.
Evaluation of Slickwater Refrac Treatments Utilizing Mechanical and Formation Diversion Techniques ao Extend Wells Productivity
Authors: Alnakhli Wafaa , Habiballah Zeyad , Baki Sohrat , Alzamil Abdullah , Rueda Jose , Alowaid Abdulrahman , Mechkak Karim 
Published: March 2023

Abstract
The objective of the paper is to evaluate the successful implementation of refrac treatment in unconventional wells with initial completion and stimulation practices. The implementation of refracturing treatment utilizing various diverter systems proved to be operationally feasible, increase productivity, and extend well life cycle.
Slick-water refrac practice relies on the combination of adding additional clusters through e-coil within previously stimulated clusters and utilizing mechanical or chemical diverters to plug dominant clusters, allowing the treatment to stimulate newly added or poorly contributing clusters. A fit-for-purpose criteria was developed for proper diverter selection, number and spacing of additional clusters, diverter drop systems, enhanced pumping schedules, and contingency plans.
The approach had been utilized in several wells, previously stimulated with various fluid systems and job volumes, completed with different completion types and sizes, and through numerous diverter types and drop systems, with notable success from operational and production point of view. Clear indications of effective diversion and stimulation were observed based on pressure response during diverter drop and treatment cycles, as well as an increased wells productivity. In conclusion, the application of refrac approach proved to be operationally feasible while allowing for an enhanced well performance post the refrac treatment.
The implemented combined approach of additional clusters, optimized diverter volumes, adjusted pumping schedules, and multiple diverter drop options offer several benefits in multiple categories: Operational (allowing for on-the-fly addition of diverters and continues cyclic pumping, and preventing the occurrence of screenouts during the refrac treatment), Technical (increasing the stimulated reservoir volume and contact with the formation), and Productivity (enhancing well performance and increasing well life cycle)
Impact of Permeability Heterogeneity Coupled with Well Placement Strategy on Underground Hydrogen Storage Reservoir Simulation
Authors: Alhotan Muhammad , Jia Cunqi , Alsousy Abdulhamid , Delshad Mojdeh , Sepehrnoori Kamy 
Published: March 2023

Abstract
The world is experiencing a transition from traditional to renewable and sustainable clean energy sources. One of the biggest hurdles for this transition is the storage of the excess electricity generated by wind or solar power. Hydrogen has been recognized as a clean-burning fuel that could overcome the barriers to meet this transition. However, there are many challenges associated with hydrogen energy since it requires vast storage volumes. Several new technologies have been proposed to store and produce hydrogen efficiently. One of the most promising storage technologies is Underground Hydrogen Storage (UHS). Reservoir simulation is a critical tool for understanding hydrogen behavior in geological porous media. This study examines the effect of permeability heterogeneity coupled with well placement strategy on several fundamental properties. The simulations are based on a 3D heterogeneous aquifer model with one well as injector/producer. Fifteen-permeability data sets were generated using the Gaussian sequential method using Dykstra-Parson's coefficients (VDP) of 0.3, 0.5, and 0.7, with several realizations. Additionally, the impacts of the well placement strategies in terms of orientations, such as vertical and horizontal configurations, and their locations are investigated. The properties examined are reservoir pressure, hydrogen volume in place and cumulative hydrogen volume recovered. The study uses a real field geological model and a compositional reservoir simulator to conduct these simulations. The published measured hydrogen properties and H2/water relative permeability and capillary pressure curves are incorporated in these simulations. Results indicate that reservoir pressure, the amount of hydrogen in place, and cumulatively produced hydrogen are highly dependent on the heterogeneity of the reservoir and the injection/production well placement. Models with less heterogeneity (i.e., relatively low VDP) show more consistent results on multiple realizations when the well location and orientation are kept constant. On the other hand, high VDP models showed significantly higher variations with different realizations. This paper provides new insights on how to model UHS projects to get the maximum return possible in terms of injected and recovered hydrogen.
An Engineer's Systematic Approach to Achieving Superior Safety Performances on Drilling Rigs
Authors: El-Shamouty Basma , Osisanya Samuel , Rahman Md Motiur , Ghosh Bisweswar , De Athe Mark , Al Jasmi Bekheet 
Published: March 2023

Abstract
Safety on the rig floor must be addressed habitually to avoid tragic fatalities and environmental crises. The objectives of this study were: (1) creating an engineer's system approach named "" to achieve a superior drilling rig safety performance by changing the Health Safety and Environment (HSE) culture and worksite behavior, (2) ensuring proper engagement and commitment of the workforce from the top to the bottom of the hierarchy and (3) to provide a tool that can be utilized on any rig floor. This tool assists in evaluating the risk from three different perspectives: People, Equipment, and Process (PEP). The research covered surveys of offshore oil companies in the Middle East. A total of 16 sites, which included four jack-ups, eight island rigs, and four service areas (mud and cementing units). The feedbacks from the surveys were used to create a risk model and a risk assessment tool, which evaluates the risk factor of hazards resulting from the interaction between people and equipment. Based on the risk factor value and each survey feedback, an episode is created to deliver a very attractive and methodical safety message for the rig-floor workforce. The crew's safety performance has been monitored on a monthly basis to test the impact on the company's’ HSE performance. The results show that had a significant positive impact. A total of 335 days of an injury-free environment was achieved in 2018 while delivering several wells with a lateral length of 25,000 feet in a total of 66 days.
Additionally, the number of incidents was reduced by 85% by the end of 2018. The survey data also show insightful analysis: 50% of the incidents are due to lack of situational awareness; the rig floor equipment that exhibits the highest risk are top drive, iron roughneck, manual tongs, air wench, and lifting gears. The humane factors that indicate the highest risk on the rig floor are people's attitude, awareness, communication, driller's influence, and green hands. The identified opportunity areas of major concern are the Red zone, functional Iron-Roughneck, and regular equipment maintenance. The six by four weeks’ work-leave rotation cycle results in more incidents compared to the four-by-four weeks’ rotation cycle.
Maximizing Productivity Index by Minimizing Fluid, Proppant and Additive Volumes
Authors: Rueda Jose , Alzamil Abdullah , Alowaid Abdulrahman , Valbuena Jose , Alnaimi Rashed 
Published: March 2023

Abstract
As part of the stimulation plan to obtain the optimum slickwater frac design in the main source rock play in Saudi Arabia, a series of systematic trials were carried out testing different frac design parameters, such as the proppant volumes and types, and fluid & additives volumes (friction reducers, spearhead acid etc.). These trials were carefully designed in several 4-well pads across the field, comparing different designs in wells next to each other in the same pad, to allow consistency in reservoir and geology conditions allowing the trials to be conclusive. Wells were flowed back for a relatively short period of time and different production analysis techniques were used to compare the different designs against the standard.
In this paper, the Normalized Initial Productivity Index of the wells was compared using the Gas, Gas Equivalent, Total Fluid Downhole Flow Rates Productivity Index (PI), and the Effective Fracture Lengths from rate transient analysis were used to help on selecting the optimum frac designs. In these trials, other important completion parameters were kept constant: the number of clusters per stage, cluster spacing, type of perforation guns, frac fluid and proppant type. The flowrates are measured using the three phase separators and the corresponding bottom-hole flowing pressures are estimated using multi-phase flow parameters, and the matched wellbore hydraulic models. The reservoir pressure is estimated from the pressure decline analysis of the frac stages along the lateral.
The results show that there was almost no change in the productivity results by lowering the proppant volumes 25%. The results also show that better wells are obtained by lowering fluid volumes by 33% and decreasing the additive volumes by more than 75%. Overall, the improved PI obtained with lower proppant and fluid volumes and less additive concentrations, provided an optimized frac design that is being carried into the development phase wells.
This paper helps in understanding and maximizing the productivity of the wells and optimizing the design including chemicals, to capitalize the value generation from the individual wells on the multi-well pads.