bluuebunny/crossref_metadata_2025_split huggingface dataset:
Naturally Fractured Basement Reservoir Characterization in a Mature Field
Authors: Akbar Muhammad Nur Ali 
Published: September 2021

Abstract
Characterizing the naturally fractured reservoir in a mature field is always a challenging task due to minimal subsurface data availability and the technology was not as advanced as nowadays. Therefore, this paper is proposed to provide an alternative solution to identify the presence of the fractures, classify them into the fractured quality related flowability, and distribute them vertically within the well interval and propose a lateral distribution method for reservoir modeling.
This research was conducted based on a case study of basement fractured carbonate reservoir in Hungary. I used more than twenty development wells which mainly drilled during 1980-2000's. The fractures presence is simply identified by using gamma-ray and density logs. The relative movement of density log to the defined fractured baselines was directed to classify the fracture quality within three groups of macro-fracture, micro-fracture, and host-rock. These groups were validated by core data and the acoustic image log from the newest drilled wells. Furthermore, I implemented the self-organizing map (SOM) for distributing the fracture group to other wells which having limited subsurface data.
Since the fracture classes were distributed along the well depth interval, then the well test (DST) results and production flow test data validated the flowability of them. As a result, the main flow contribution intervals of the fracture can be well-recognized. The macro-fracture consistently indicates the fracture class showing the main contribution of the liquid flowrate more than 10 m3/d along the perforated intervals. The rock properties of this class have porosity range around 1-2% with permeability dominantly more than 100 mD. In contrast, the host-rock class is defined as a protolith/non-fractured rock. The porosity and permeability are extremely low (tight rock). This class does not give any flow contribution due to the high content of the marl or clay, the absence of the fracture, or the fractures had been re-cemented by calcite or quartz minerals. Meanwhile, the micro-fracture denotes the group of rock with porosity range around 2-10% and permeability average between 1-10 mD. In general, the flowrate coming from this fracture class was lower than 10 m3/d of liquid during the flow-test.
As a novelty, this proposed approach with the machine learning of SOM-clustering effectively assists us to recognize the fracture presence and its quality along the well-depth interval from the absence of the advanced technologies of image logs and production logging (PLT) measurement. Also, the defined fracture class here can take a role as a fracture facies or rock typing in terms of 3D reservoir modeling and distributed laterally based on fault-likelihood attribute and fault zone defined by distance-to-fault.
Model Comparison for Esp Run-Life Prediction: Classic Statistics Vs. Machine Learning
Authors: Celemín Alejandro , Estupiñan Diego A. , Nieto Ricardo 
Published: September 2021

Abstract
Electrical Submersible Pumps reliability and run-life analysis has been extensively studied since its development. Current machine learning algorithms allow to correlate operational conditions to ESP run-life in order to generate predictions for active and new wells. Four machine learning models are compared to a linear proportional hazards model, used as a baseline for comparison purposes. Proper accuracy metrics for survival analysis problems are calculated on run-life predictions vs. actual values over training and validation data subsets. Results demonstrate that the baseline model is able to produce more consistent predictions with a slight reduction in its accuracy, compared to current machine learning models for small datasets. This study demonstrates that the quality of the date and it pre-processing supports the current shift from model-centric to data-centric approach to machine and deep learning problems.
Foam Generation in the Presence of Residual Oil in Porous Media
Authors: Almajid Muhammad , Kovscek Anthony 
Published: September 2021

Abstract
This paper studies the effect of trapped, emulsified oil on the requirement for the geometrical Roof snap-off for foam generation in a porous medium. We extend an existing hydrodynamic pore-level model to describe the liquid accumulation in an appropriately-sized pore in the presence of oil. The effect of oil is simulated by adjusting the pore shape to be asymmetrical as observed in microfluidic experiments with residual oil. We alter the boundary and initial conditions of the problem to test various scenarios. Specifically, four cases are presented. The liquid accumulation is presented when the amount of wetting liquid volume connected to the pore is altered through changing the boundary conditions (cases 1 and 2). Moreover, the effect of drier surrounding medium and/or drier pores is also tested by increasing either the capillary pressure surrounding the pore or the capillary pressure of the pore itself (cases 3 and 4). We find that the presence of residual oil affects the liquid accumulation times when there is no external liquid pressure gradient applied. Additionally, residual oil presence makes the Roof snap-off criterion for liquid accumulation stricter. To augment our pore-level study, we use a statistical pore network to observe the effect of the microscopic changes observed in our pore-level model macroscopically. Our results indicate that a stricter Roof snap-off criterion leads to fewer germination sites for lamellae generation. Our pore network analysis computes the generation rate constant to be as much as four times larger in the absence of oil than in its presence. Results suggest that changes to the shape of pore constrictions by emulsified oil reduce the effectiveness of foam generation.
Application of a Novel Analytical Technique to Monitor Corrosion Inhibitor Residual in Oilfield Samples
Authors: Jin Peng , Liu Zhengwei , Jani Jagrut , Murugesan Sankaran , Jackson Tracey , Liu Ya , Ramachandran Sunder , Wronska Malgorzata , Huang Lei 
Published: September 2021

Abstract
Accurate and in-time monitoring of corrosion inhibitor (CI) residual concentration is a key factor in asset integrity management for oil and gas operations. However, the natural variability of CI residual due to field conditions is usually convoluted with the error introduced by sampling and analytical techniques. In traditional analytical techniques, it is typical to encounter error of over 100%. Recently, a novel nanoscale technique (TrueDetect™, TD) was developed to accurately measure CI in the field. This technique is based on a proprietary spectrometry technique and allows quick and accurate analysis of CI residual at the ppm level. The portable instrument allows field samples to be analyzed on-site without the need for shipping them to a centralized laboratory. In the current study, the TD technique was applied to analyze field samples from various fields. Moreover, the TD technique was capable of analyzing CIs at low dosages and could be used as a method to qualify CI products in the lab and in the field.
A Curious Case of Addressing Well Integrity Issue with Production Logging
Authors: Agrawal Gaurav , Kumar Ajit , Verma Vibhor , Mishra Alok , Gualti Vikram , Mahajan Varun 
Published: September 2021

Abstract
The productive life of a well can be affected by deterioration of the well integrity which can be due to casing/tubing corrosion, casing damage during drilling/ work over, packer failure, plug failures, cement integrity issues etc.
Remedial measures can be executed if the nature of problem is diagnosed. One can receive early warning of a potential problem and obtain data for determining a specific restoration program by running well integrity diagnostic tools. There are various well integrity tools available to cater evaluation needs at present times with different working principles and targeting different well integrity problems such as casing/tubing and cement integrity. However, in challenging situation and complex environments, the tools may not provide complete diagnostics.
Production logging can be an effective tool in such scenarios by mapping the flow behaviour in the wellbore and can provide a better idea of the wellbore problems.
The well "A" is a development well which was drilled (max angle~ 27º) and completed in the interval X345-X349m and X362-X368m to exploit gas from the reservoir ABC. During initial testing it produced @ 1, 67,000 m3/d with FTHP of 2348psi. Later after acid job rate increased to 2,20,000 m3/d but later well had frequent water loading problem and required frequent activation / stimulation. The well has good reservoir zones as identified on the OH logs, hence, to diagnose the reason for water production, PLT was planned in the well in 2015. The well was producing 1,00,000 m3/d of gas at an FTHP of 1181psi during that time. Annulus pressure build-up was also observed in the well suggesting integrity issue with packer/tubing.
During the PL run, it was observed that the packer has fallen and settled across one the perforation and the flow was observed to be ongoing from inside as well as outside the packer element making the flow interpretation tricky.
A proper interpretation was carried out taking into consideration all available data and water entry point was confirmed. Based on the results, a well intervention was carried out and after the job, well started producing 1,50,000 m3/d of gas with 0% water cut whereas before it was producing 1,00,000 m3/d of gas with 1900 BPD of water. Thus, the intervention resulted in production enhancement by 50% and reduction in water cut by 100%.
This paper highlights the proper analysis of the recorded data for diagnosis of the flow condition in an adverse and complex scenario and finding out the water entry point for a proper remediation of the well integrity and production issue.
Mitigation of High Temperature Challenges in Limestone Acidizing through the use of Chelating Agents
Authors: Khan Mandeep , Qamruzzaman Mohammed , Roy Dhirendra Chandra , Raman Ravi 
Published: September 2021

Abstract
Acid jobs with conventional acid systems like hydrochloric acid in high temperature conditions is challenging on various fronts. Enhanced reactivity of strong acids results in poor penetration and severe face dissolution. Also, it aggravates the issue of corrosion of downhole equipment and may also result in sludge formation/asphaltene deposition. Worldwide, chelating agents has emerged as a standalone stimulation fluid for high temperature acidizing. Their unique attributes and properties have been proved very useful for acid jobs at elevated temperatures. However, the chelating agents-based formulations need to be carefully evaluated on various acidization parameters for a fruitful stimulation.
Mumbai Offshore field has been encountering the above-mentioned problems in acidizing of its high temperature (&gt;275°F) limestone reservoirs. The paper presents innovative solutions devised for high temperature matrix acidizing. Two chelating agents viz., EDTA (Ethylenediaminetetraceticacid) and GLDA (L-Glutamic Acid N, N-diacetic acid) were explored and evaluated with meticulous laboratory studies. The performance of the chelating agent-based stimulation fluid was compared with acetic acid. Slurry tests were performed to quantify the dissolving power of each acid. Consequently, core flooding tests were carried out to to find the optimum pH of the chelating agents from stimulation point of view. Core flooding studies were performed at anticipated injection rates on representative core samples from a payzone A, with BHT 275-290° F, from Mumbai Offshore. pH optimized formulations were tested against N-80 metallurgy coupons at reservoir temperature for corrosion potential estimation. Also, sludge, asphaltene and emulsion formation tendencies were analyzed with representative oil samples.
The results convey that both EDTA and GLDA were able to mitigate the challenges encountered at elevated temperatures. EDTA and GLDA were found to stimulate the cores with wormholes formed at wide pH range with no face dissolution observed. Chelating agents enjoyed good dissolving power with negligible corrosion rates, absence of sludge and asphaltene deposition, compatibility with formation fluid and excellent iron control properties.
Hydrocarbon Field Re-Development as Markov Decision Process
Authors: Sieberer Martin , Clemens Torsten 
Published: September 2021

Abstract
Hydrocarbon field (re-)development requires that a multitude of decisions are made under uncertainty. These decisions include the type and size of surface facilities, location, configuration and number of wells but also which data to acquire. Both types of decisions, which development to choose and which data to acquire, are strongly coupled. The aim of appraisal is to maximize value while minimizing data acquisition costs. These decisions have to be done under uncertainty owing to the inherent uncertainty of the subsurface but also of other costs and economic parameters. Conventional Value Of Information (VOI) evaluations can be used to determine how much can be spend to acquire data. However, VOI is very challenging to calculate for complex sequences of decisions with various costs and including the risk attitude of the decision maker.
We are using a fully observable Markov-Decision-Process (MDP) to determine the policy for the sequence and type of measurements and decisions to do. A fully observable MDP is characterised by the states (here: description of the system at a certain point in time), actions (here: measurements and development scenario), transition function (probabilities of transitioning from one state to the next), and rewards (costs for measurements, Expected Monetary Value (EMV) of development options). Solving the MDP gives the optimum policy, sequence of the decisions, the Probability Of Maturation (POM) of a project, the Expected Monetary Value (EMV), the expected loss, the expected appraisal costs, and the Probability of Economic Success (PES). These key performance indicators can then be used to select in a portfolio of projects the ones generating the highest expected reward for the company. Combining the production forecasts from numerical model ensembles with probabilistic capital and operating expenditures and economic parameters allows for quantitative decision making under uncertainty.
Retrospective Analysis of Geological Exploration 2010 - 2020
Authors: Mostovoy Pavel , Safarov Ildar , Tumanov Evgeniy , Zaytseva Maria , Aksenov Maksim , Vorobyev Vladimir 
Published: September 2021

Abstract
Oil and gas companies’ future production profile is shaped by their exploration strategy and resource base development. Gazprom Neft's production profile will include 40% of current exploration projects by 2030. Geological exploration, on the other hand, is a high-risk business because it involves a lot of uncertainty due to the geological complexity of the targets being explored, as well as a lot of risky capital.
Taking these factors into account, the Company will need to expand its exploration function as well as its approaches to managing exploration projects in order to meet its lofty aims. To determine the key areas of growth and a strategy for the exploration function development in the coming years, it was decided to first analyze the geological exploration activity in the Company in 2010 – 2020 period.
The knowledge of achievements, success stories, and development areas is the fulcrum for future victories. Therefore, retrospective analysis is an important tool for the development of any system of activity - individual, organization, or state.
Rate/Pressure Transient Analysis of a Variable Bottom Hole Pressure Multi-Well Horizontal Pad with Well Interference
Authors: Chu Hongyang , Liao Xinwei , Wei Cao , Lee John 
Published: September 2021

Abstract
Multi-well horizontal pads are common in unconventional reservoirs. With addition of infill wells and hydraulic fracturing, interference between multiple multi-fractured-horizontal wells (MFHWs) has become a serious issue. Current RTA workflows assume a single MFHW in the unconventional formation. This paper presents a new multi-MFHW solution and related analysis methodology to analyze targeted well rate performance in a multi-MFHW system.
In this work, a semi-analytical equation describing multi-well pad in the Laplace domain with well interference is proposed. The proposed semi-analytical model can simulate the rate performance of a multi-well horizontal pad with variable BHP for a targeted well in the pad and different initial production durations for the offset well. From the constant BHP condition and Laplace transforms, we obtained multi-MFHW solutions for transient flow. We used superposition of various constant BHP solutions to study interference among various fractures and MFHWs. The variable BHP of the targeted well is achieved by a variable dimensionless BHP function in the Laplace domain without any convolution or deconvolution calculations. A systematic validation for the proposed method is conducted using a commercial numerical simulator for cases of different initial production times for offset MFHWs, multi-MFHWs with variable BHP. Through the total material balance of the multi-MFHW system, we can analyze a target well in the pad with this multi-MFHW analysis. Interference by offset wells often appears after pseudo-radial flow in the target well's hydraulic fracture. It causes the pressure derivative curve during elliptical and infinite-acting radial flow (IARF) to rise, as does the RNP derivative. The inverse semi-log derivative has the opposite trend. Well interference also makes the rate/pressure drop functions to deviate from initial straight lines in later stages. Sensitivity analysis of well spacing shows that "transition flow" will change from elliptical to formation linear flow between wells as well spacing increases and it can show the transitional flow characteristics in more common cases.
Experimental and Modeling Studies on Pressure Gradient Prediction for Horizontal Gas Wells Based on Dimensionless Number Analysis
Authors: Luo Chengcheng , Wu Ning , Dong Sha , Liu Yonghui , Ye Changqing , Yang Jianying 
Published: September 2021

Abstract
Accurate prediction of pressure gradient in gas wells is the theoretical basis of gas well performance analysis, production optimization and deliquification technologies design. Experiment is the best access to characterize the flow behavior of gas wells. For low-pressure experimental investigation and gas wells, the most difference is the pressure (gas density), which could lead to totally different flow behavior. Dimensionless numbers are often used in the flow pattern maps to account for the flow similarities at different conditions, which means liquid holdup in the high pressure can be also predicted at low pressure conditions if we choose proper dimensionless numbers for pressure scaling up. However, no studies have focused on this point before. Besides, gas wells have high GLR, most empirical models were intended to developed for oil wells, which have greater weight in low GLR, decreasing the accuracy in gas wells.
In order to predict the pressure gradient in horizontal gas wells, an experimental investigation of gas-water flow has been conducted. The experimental test matrix was designed to cover all the flow patterns. The experiment was conducted in a 5-m long pipe. The liquid holdup and pressure gradient were measured. Subsequently, the effect of gas velocity, liquid velocity, pipe diameter, and inclined angle on liquid holdup was analyzed. Then the dimensionless numbers proposed in the literature have been investigated and analyzed for pressure scaling up. Finally, a comprehensive model was established, which is developed for prediction pressure drop in gas wells. Some field and experimental data were provided to evaluate the new model. The results show that the Duns-Ros dimensionless number was not proper for pressure scaling up while the Hewitt-Robert Number performs best. Compared to widely used pressure gradient models with field data, the new model with Hewitt-Robert Number performed best, which shows that it is capable of dealing with prediction of pressure gradient in gas wells.
Cementless Well Construction Opens the Full Control on Well Integrity for the Life of the Well
Authors: Teodoriu Catalin , Bello Opeyemi , Vasquez R. R. , Melander Ryan M. , Esquitin Yosafat 
Published: September 2021

Abstract
Well construction has relied on two main elements, casing and cement, to achieve the well goals while maintaining the highest possible well integrity. Can cementless well construction achieve similar goals? This paper is investigating the various well construction concepts proposed over the years and will analyze the cement's ability to withstand long term well loads.
First, a review of various well construction concepts such as slimhole, conventional, pre-salt and horizontal wells. We will normalize the casing to cement thickness ratio by validating and proposing a simple mathematical calculation for establishing this ratio. Our calculations have shown that in the case of slimhole well concept, the thin cement sheath cannot serve as a strong well barrier as defined by current standards, and thus a new solution might be necessary.
The second part will look at current new trends in wellbore construction that include external casing packers and other solutions such as metallic wellbore isolation solutions. Hydraulically expanded metal packers are a robust and reliable alternative to cement. They are each mounted to a casing joint and can be rotated while running in hole. They have a proven deployment track record of high diametrical expansion, conforming to the wellbore geometry, while isolating differential pressures more than 15,000psi. Exploration of load carrying capabilities will be completed using Finite Element Analysis (FEA), simulating the different well scenarios as described in the previous paragraph. This will enable us to establish which well types can use this novel technology for the replacement of cement.
The paper will conclude with one possible solution that could be used to mitigate cement problems by shifting the well construction concept to a cementless new era. Also, understanding that the cement manufacturing process is highly CO2 intensive, emissions per well could be reduced through the newly proposed concept.
The Use of Augmented Reality and 3D Visualization in Petroleum Engineering Education
Authors: Alyafei Nayef , Fadlelmula Mohamed , Sheharyar Ali , Idris Mohamed , Retnanto Albertus 
Published: September 2021

Abstract
The objective of this paper is to showcase the applications of augmented reality and 3D visualization to enhance the learning process of petroleum engineering concepts. In this study, an educational magazine covering various components of an offshore drilling rig with embedded 3D models is used. In addition, the magazine includes simplified text describing the definition and functionality of various drilling components.
The prototype of this magazine was sent to both current and former students of Texas A&M University at Qatar and was accompanied by a survey designed to evaluate the efficacy of the magazine. The participants showed a significant favor towards the use of augmented reality and 3D visualization in petroleum engineering education through the survey. Overall, the augmented reality experience provided has given the participants a new dimension in the interactive-learning field. Also, the magazine provides a unique experience to visualize petroleum engineering operations and concepts in the midst of COVID-19, where many trips and experiences are limited.