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The study analyses the oil well blowout that took place at the Baghjan oil field in Assam, India, on 27 May 2020. This incident escalated into a massive fire on 9th June that lasted more than 5 months. The tragedy degraded the environment and inflicted substantial problems on the area's inhabitants. The present study employs the analytical case study approach and various data sources to unfold the disaster and its causes, impact, and response. It also examines the local inhabitants and environmental impact and tries to analyze the event comprehensively. The incident resulted from technical malfunctions and human errors, leading to the relocation of the adjacent settlement to refugee camps amidst the global COVID-19 epidemic. However, it is essential to mention that many households received adequate compensation for their damages. The incident has resulted in the contamination of the air, noise, soil, and water, causing significant damage to the fragile ecosystem and its rare species. The research employs the Normalized Difference Vegetation Index to quantify changes in vegetation cover resulting from the blowout, thus showing the extensive damage to the affected region. The incident shed light on legal and regulatory deficiencies alongside a lack of accountability and transparency within the Oil India Limited sector. Despite the numerous proposals for environmental restoration, it appears challenging to revert to the previous state swiftly. The present study reflects the collective and collaborative action to protect and preserve the environment. [ABSTRACT FROM AUTHOR]

The use of simulation software applicable to the various stages of petroleum engineering facilitates decision-making and, at the same time, minimizes possible failures, problems, and incidents during each well intervention. In addition, a computer tool provides the user with instant and accurate results that can be used during personnel training and higher education. The objective of the present work was to develop an open-source computational tool with a graphical, numerical, and schematic interface to facilitate the teaching and learning of operations related to primary cementing. The tool considers four sections: (a) wellbore diagram, (b) identification of the relation between volumetry and the geometric design of the well, (c) integration of the mechanical state with the number of intervals, slurry design, and operating characteristics of the pumps, and (d) the wellbore diagram integrated by drilling, displacement and slurry fluids, according to each of the cementing stages. Among the results, it was combined programming with specialized technical and scientific material, considering academic and field experience characteristics. The program is a versatile tool that integrates the general mechanical state and each of the five stages with a maximum depth of 5,000 m. [ABSTRACT FROM AUTHOR]

The evaluation of well integrity in double-casing wells is critical for ensuring well stability, preventing oil and gas leaks, avoiding pollution, and ensuring safety throughout well development and production. However, the current predominant method of assessing cementing quality primarily focuses on single-casing wells, with limited work conducted on double-casing wells. This study introduces a novel approach for evaluating the cementing quality using the Inception module of convolutional neural networks. First, the finite-difference method is employed to generate borehole sonic data corresponding to a variety of model configurations, which are used to train a neural network that learns spatial features from the borehole sonic data to reconstruct the slowness model. By adjusting the network architecture and parameters, it is discovered that a neural network with two blocks and 4096 nodes in the fully connected layer demonstrated the best imaging results and exhibited strong anti-noise capabilities. The proposed method is validated using practical wellbore size models, demonstrating excellent results and offering a more effective means of evaluating wellbore integrity in double-casing wells. In addition, dipole acoustic logging data are used to conduct slowness model imaging of the compressional (P-) wave and shear (S-) wave in double-casing wells to verify the feasibility of cementing quality evaluation. The developed method contributes to more accurate evaluations of wellbore integrity for the oil and gas industry, leading to improved safety and environmental outcomes. [ABSTRACT FROM AUTHOR]

Copyright of Iraqi Journal of Chemical & Petroleum Engineering is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Within this article the importance of the optical light microscopy for the investigation of cement clinker is illustrated by three examples: (a) Ono's method plays an important role in the case of the production of oil well clinker where the reactivity of alite and additionally the melting phase influences strongly the properties of the later cement; (b) the use of secondary fuels can lead to unexpected phenomena in the clinker matrix accompanied by strange changes in colour; (c) for the interpretation of CSA clinkers, the combination of light and scanning electron microscopy can give important information about the formation of clinker phases depending on the burning conditions which can hardly be detected by other methods. However, in case of CSA clinker, there is still little knowledge about the relationship between production and hydraulic properties of the clinker and therefore no systematic documentation is available. [ABSTRACT FROM AUTHOR]

This study focuses on the modelling wellbore compartmentalization techniques for downhole flow control in both homogeneous and heterogeneous oil reservoirs. The objective was to achieve fluid inflow equalization to address variable productivity effects (VPE) in heterogeneous multilayered reservoirs and to ensure flow uniformity across horizontal intervals in homogeneous reservoirs, mitigating the heel-to-toe effect (THE) caused by frictional pressure drop in horizontal well completions. The compartmentalization along the wellbore was achieved using swellable packers, ensuring each well compartment had uniform productivity before equalization. Inflow equalization across compartments was accomplished using inflow control devices (ICDs). Analytical models for ICDs were developed based on fundamental fluid flow equations, including Darcy's and Bernoulli's equations. Simulation of the developed model was conducted using MATLAB 2014Rb. Three simulation cases were explored: Case 1 studied variable pressure effects in homogeneous reservoirs where pressure and permeability influenced inflow inequality; Case 2 examined variable pressure effects considering pressure, permeability, and skin as factors for inflow variation; Case 3 simulated inflow equalization in horizontal homogeneous reservoirs to counteract the heel-to-toe effects. The results demonstrated successful equalization in all cases: Case 1 achieved a target well production rate of 7500 stb/d; Case 2 resulted in a total target well inflow rate of 6250 stb/d; Case 3 achieved a composite well inflow rate of 15000 stb/d. Implementation of variable ICDs in the horizontal well segment prevented early water/gas breakthrough due to THE, enhancing well longevity and recovery efficiency, thereby improving total well recovery. [ABSTRACT FROM AUTHOR]

In order to solve the high shut-in pressure (close to or exceeding 90 MPa) that sulfur-containing wells will face, while not increasing operating costs and changing the wellbore structure, this article combines domestic and foreign standards, 110ksi in oilfield evaluation and on-site use, as well as 125ksi material indoor evaluation and other oilfield field applications, and designs two types of high internal pressure strength (all greater than 140 MPa) production casings under different sulfur-containing conditions to solve the above problems. [ABSTRACT FROM AUTHOR]

In order to solve the problem of external corrosion of deep well casing in oil and gas fields, a new type of high-temperature-resistant zinc alloy sacrificial anode material was used. The temperature and corrosion resistance of the new anode material and TP140 casing were investigated by simulating the high-temperature working conditions of a deep well in an oil field using high-temperature and high-pressure corrosion tests and electrochemical tests. The results showed that at 100–120 °C, the corrosion rate of TP140 protected by a sacrificial anode was only one-tenth of that under unprotected conditions, and the minimum corrosion rate of TP140 protected by a sacrificial anode at 100 °C was 0.0089 mm/a. The results of the dynamic potential polarization curve showed that the corresponding corrosion current density of TP140 first increased and then decreased with the increase in temperature. The self-corrosion potential in sacrificial anode materials first increased and then decreased with the increase in temperature, and the potential difference with TP140 gradually decreased. [ABSTRACT FROM AUTHOR]

During the multistage fracturing in shale oil and gas wells with tieback and liner, one of the major challenges is the wellbore temperature variation due to the high-rate fracturing. In such a case, the axial shrinkage trend of the casing string could be caused due to the sudden drop in temperature, but the actual axial length of the casing string would not change due to the cement constraints. Therefore, this could lead to cementation damage between the casing and cement due to excessive load from the casing string. A wellbore seal that is out of control often leads to irreversible consequences, even well abandonment. In order to study the mechanism of casing deformation in shale oil and gas wells with tieback and liner quantitatively, in this paper, take LS1 well (a typical shale oil and gas well with tieback and liner, and casing deformation is caused) for example, the transient changes of temperature and pressure in the whole wellbore during multistage fracturing are studied. Moreover, the cementing strength test of the interface between casing and cement is also tested. Then, the testing results are carried out and extended to model the finite element (FE) model with the whole vertical section casing string with tieback and liner. The model is used to simulate the internal force changes under fracturing conditions with different stages of fracturing. Meanwhile, the casing deformation mechanism in LS1 well is analyzed and studied in detail. Our simulation results indicated the failure process and mechanism of cementation between casing and cement in shale oil and gas wells with tieback and liner. Our work can provide a detailed theoretical reference and a basis for field application. [ABSTRACT FROM AUTHOR]

This technology obtains the casing contour and inner wall information by using multi-frequency ultrasonic scanning with more abundant data than traditional single frequency ultrasonic testing. On the basis of high-precision measurement and imaging obtained by multi-frequency ultrasonic scanning equipment, the casing contour features and image features are combined. The radial damage and axial damage of oil and gas well casing are considered at the same time. It can effectively improve the visualization and identification of casing damage area of oil and gas wells in borehole. Firstly, according to the conventional oil and gas well casing damage characteristics, the mapping relationship between ultrasonic scanning signal and damage characteristics is proposed. Then, based on the oil and gas well casing visualization of profile and surface features, a 3 D visualization model of oil and gas well casing is constructed, and a 3 D reconstruction system of oil and gas well casing is formed with simultaneous consideration of profile features and image features. Finally, through the verification and analysis of the technical method combined with the actual project, the feasibility and intuitiveness of the technology are verified. This technology can greatly improve the detection efficiency and precision of oil and gas well casing in borehole. [ABSTRACT FROM AUTHOR]

The failure of managed-pressure running casing in oil and gas wells may lead to complex accidents such as overflow or leakage. The technique of using multi-density gradient drilling fluids in wellbores with negative pressure windows (NPWs) is often used to deal with this situation. Therefore, it is vital to analyze the dynamic slurry column structure and calculate the wellbore pressure during casing running. For this issue, the model of transient surge pressure is established during casing running. The calculation equation of the model is proposed, and the calculations of the wellbore pressure are carried out with the exploration of Well LT-X1, located in the Xinjiang oil field. A circulation scheme is designed as follows: Circulate 125 m3 of drilling fluid with a density of 2.45 g/cm3 and 155 m3 of drilling fluid with a density of 2.35 g/cm3 at a depth of 3560 m. From there, circulate 164 m3 of drilling fluid with a density of 2.35 g/cm3 at a depth of 5900 m. Finally, at a depth of 7050 m, circulate 250 m3 of drilling fluid with a density of 2.30 g/cm3. The casing running speeds and back-pressure values were designed as follows for the respective well sections: 0–1523 m: 0.160 m/s casing speed, 0 MPa back pressure; 1523–3560 m: 0.160 m/s casing speed, 1.641 MPa back pressure; 3560–5900 m: 0.145 m/s casing speed, 2.427 MPa back pressure; 5900–6674 m: 0.137 m/s casing speed, 4.041 MPa back pressure; 6674–7050 m: 0.124 m/s casing speed, 4.457 MPa back pressure. The results show that optimizing structure of the multi-density gradient drilling fluid with different densities and applying annular back pressure in stages, with the accurate calculation of wellbore pressure, can achieve the goals of leak-proofing and pressure-stabilization. It is concluded that this result may serve as the foundation for managed-pressure running casing technology. [ABSTRACT FROM AUTHOR]

Pitting corrosion often occurs due to the presence of various corrosive substances, such as CO2 and H2S, in the pipe service environment. As a result of this process, the residual strength of oil pipes is reduced and this can compromise the integrity of the entire pipe string. In the present work, a model is introduced on the basis of the API579 standard to determine the so-called stress concentration coefficient. The model accounts for pitting corrosion shapes such as shallow semi-circles, semi-circles, and deep semi-circles. The relationship between the corrosion pit depth and opening diameter and the residual strength of the oil casing is obtained. The results show that the influence of the pit opening diameter on the stress concentration coefficient is smaller than that of the pit depth. For a constant pit opening diameter, the coefficient increases gradually with increasing the pit depth. The compressive strength and internal pressure strength of the carbon steel oil casing decrease accordingly. When the depth of the corrosion pit is relatively small, the growth of the coefficient is slower; when the depth of the corrosion pit increases to a certain value, the increase in stress concentration coefficient becomes obvious. [ABSTRACT FROM AUTHOR]

A large amount of casing deformation has occurred in shale gas wells during the complex fracturing process, which affects the fracturing construction and single well production. Based on the statistical analysis of casing deformation wells and caliper logging interpretation, the main mechanism of casing deformation of shale gas wells is revealed as formation slip. By comprehensively considering the rotating speed under casing running condition, the cement solidification heat release under cementing condition, and the fracturing fluid temperature drop under fracturing condition, the safe service margin of the casing is large. Moreover, simply increasing the casing steel grade and wall thickness has no obvious effect on casing deformation prevention, so full wellbore casing deformation prevention measures should be considered. By using the method of unconventional oil and gas well casing string simulation test and numerical simulation, the mechanical response of wellbore and the mechanism of bridge plug resistance are analyzed. By analyzing the influence of elastic modulus and wall thickness of cement on the casing minimum drift diameter after shear deformation, an analytical model of the minimum drift diameter of shale gas casing under the effect of fracture slip is established and verified, which provides technical support for parameter selection of cement and measures to prevent casing deformation. [ABSTRACT FROM AUTHOR]

The casing leakage phenomenon seriously affects the safety and economic problems of oil and gas production and transportation. In this paper, the numerical simulation study of the casing's micro-leakage flow field and acoustic field is carried out by taking the oil and gas well casing as the research object. The CFD numerical model of the casing micro-leakage is established, and the influence of the size of the leakage hole, the shape of the leakage hole, and the pressure difference between the inside and outside the casing on the microleakage flow field is analyzed. An acoustic-vibroacoustic coupling calculation model based on Fluent and LMS Virtual LAB is established, and the sound pressure value and distribution at different frequencies are calculated. The results show that the flow rate of the leakage hole increases with the pressure difference between the inside and the outside leakage hole and the area of the leakage hole. Moreover, the flow rate of the circular leakage hole is higher for the same leakage hole area. The simulation model based on the equivalent sound source can be used to calculate and analyze the sound field in the tubing. By sound field computation based on the near-field equivalent sound source, when the frequency is 32,000 Hz, the amplitude of sound pressure is maximum. In addition, the sound pressure is greatly reduced once the sound wave passes through the tubing pipeline. Lastly, the sound pressure is higher at the position facing the leakage hole in the tubing, making detecting the leakage sound field signal easier. The results can provide a reference for further research on oil casing microleakage detection technology. [ABSTRACT FROM AUTHOR]

The Yanchang Eastern Oilfield of Ordos Basin is a typical ultra-low permeability shallow reservoir. Because of the relatively low vertical pressure, horizontal artificial fractures are prone to take place in the case of oil well fracturing. Given the bigger contact surface between the horizontal fracture and the waterflood front of the water injection well, the oil well may be flooded fast in a short time, leading to a low mobilization degree of the reservoir. According to the characteristics of waterflooding of horizontal fractures, the development mode of waterflooding at the bottom of oil reservoirs was proposed. Through core sample displacement experiments and nuclear magnetic resonance online tests, combined with numerical simulation of reservoirs, field tracer test, and other comprehensive methods, the heterogeneity of reservoirs and the limit of waterflooding parameters were optimized. The research results show that the waterflooding effect is the best when the variation coefficient of permeability is less than 0.5, the permeability rush coefficient is less than 1.5, the permeability contrast is less than 5, the waterflooding rate is 0.06 mL/min, and the waterflooding pressure is 7 MPa. Through field practice, the daily oil production of a single well in the test well group increased from 0.054 t/d before the test to 0.179 t/d, the water cut decreased from 15% before the test to 10%, the formation pressure increased by 0.18 MPa, and it is predicted that the final recovery would increase by 2%. This study provides an experimental and theoretical basis for water injection development of ultra-low permeability shallow reservoirs with horizontal fracture, and also plays a good demonstration role for high-efficiency water injection development of shallow reservoirs. [ABSTRACT FROM AUTHOR]

The effects of expansion deformation on the mechanical properties and corrosion resistance of an AISI 304 stainless steel (SS) tube with dimensions of ϕ 108 mm × 6 mm were studied with a full-scale test, a mechanical property test, microstructural analysis and a corrosion property test in order to explore the feasibility of using AISI 304 SS tubes as solid expandable tubes in repairing damaged well casings. The results showed that the AISI 304 SS tube had good expansion performance, suitable strength after expansion and excellent corrosion resistance, and it met the technical requirements for repairing the casings of common oil wells. After ~11% radial expansion, the internal pressure strength and collapsing strength of the tube were 71 and 32 MPa, respectively. The increase in dislocations, and in the formation of strain-induced martensite and twinning stimulated by plastic deformation, led to the yield strength of the AISI 304 SS tube increasing from 249 to 539 MPa; however, the corrosion resistance of the AISI 304 SS tube was somewhat worsened because of the increase in dislocations and strain-induced martensite caused by expansion deformation. However, the corrosion resistance of the AISI 304 SS tube was still much better than that of conventional casings. [ABSTRACT FROM AUTHOR]

In this article, we address the problem of synthesized magnetic field focusing (SMF) of the pulsed eddy-current (PEC) technology for the non-destructive testing (NDT) of oil and gas well casing pipes. The electromagnetic response excited by multiple transmitters was derived using the signal model of downhole PEC system. The magnetic field was shown to be adjustable by modifying the currents of the multiple transmitting array. Based on this property, magnetic fields were synthesized with the mean squared error (MMSE) criterion to be focused on the center of the transmitting array, and a weighted MMSE (WMMSE)-based SMF was also proposed to achieve an optimal synthetic magnetic field. Furthermore, the primal-dual interior-point method was used to solve the WMMSE optimization problem with the total and single transmit power constraints for the practical application. Simulations and experimental results showed that the SMF with the PEC array effectively focuses the eddy-current field on the center of the transmitting array. [ABSTRACT FROM AUTHOR]

Copyright of Oil Drilling & Production Technology / Shiyou Zuancai Gongyi is the property of Shiyou Zuancai Gongyi Bianjibu and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A theoretical investigation of the radial temperature distributions in the upward and downward flows of fluid in the borehole of a production well has been performed. The radial differences between the temperatures at the axis and wall of such a well in the cases of water and oil flows in it were determined. [ABSTRACT FROM AUTHOR]

In the past decade, rapid advances in distributed optical fibre sensing technologies have made it possible to record various geophysical data (e.g. strain, temperature and pressure) continuously in both time and space along the fibre, providing an unprecedented quantity and spatial density of data compared to traditional geophysical measurements as well as reducing data acquisition cost. To date, no distributed fibre‐based electromagnetic field sensing system has been implemented although electromagnetic sensing could have a broad range of applications to geophysical imaging and monitoring in borehole environments. The goal of this paper is to provide a theoretical feasibility study regarding the design and use of an electromagnetic sensing optical fibre for geophysical applications. First, we present the sensitivity analysis of a 'hypothetical' optical fibre coated with polyvinylidene fluoride, a polymer that provides relatively high piezoelectric properties, yet unlike ceramics, is flexible. Using a two‐dimensional electromagnetic modelling algorithm, we simulate the earth electric‐field‐to‐fibre‐strain transfer function and estimate the theoretical sensitivity of the optical fibre to electric fields. Given the state‐of‐the‐art distributed acoustic sensing strain sensitivities in the picometres strain range, our numerical modelling analysis suggests that a perfectly coupled polyvinylidene fluoride–coated optical fibre can measure electric field values in the mV/m to V/m amplitude range. We then apply a cylindrically symmetric modelling algorithm to simulate numerical models demonstrating the applicability of such a fibre in an oilfield environment. Scenarios investigated employ an electric field source and suggest that the measurements can be used to distinguish the oil versus water ratio with a fibre mounted inside a producing steel cased oil well as well as distinguishing between brine and hydrocarbon filled reservoir zones with a fibre located outside of the casing. [ABSTRACT FROM AUTHOR]

In the process of thermal recovery of heavy oil, the casing in oil production wells is subjected to complex stress conditions, which may cause potential damage and affect the lifecycle of the casing. The factors influencing the casing instability and the mechanism of the process in thermal production wells need to be comprehensively researched, particularly in the case where oil extraction is accompanied by sand production. In this paper, the authors have applied the three-dimensional finite element method to simulate the casing instability characteristics in the sand production section of a thermal recovery well. We have also analyzed the effect of sand production, perforation parameters, and the casing strength parameters on the axial and circumferential instability of the casing. The results show that sand production can cause a significant decrease in the lateral support of the casing and greatly reduce the buckling resistance of the casing in a thermal horizontal well. With increase in perforation diameter and perforation density, the critical buckling load of the casing decreases. On the other hand, the buckling load is less affected by the perforation phase. When the combination of the perforation density and perforation phase angle results in a bigger number of perforation holes in the row, it can significantly reduce the casing collapse strength and increase the risk of circumferential instability. The research results provide a theoretical basis in the design of casing in horizontal sections of thermal production wells. [ABSTRACT FROM AUTHOR]

Risk assessment and management objective is to maximize the probability of a project's success by identifying, analysing, mitigating and controlling the risks. The goals of the drilling management engineers team is to work with drilling clients to significantly reduce cost, time and non productive time through integration of planning and real time drilling solutions. During drilling, deformation occurred to 9 5/8" casing in Well AG-1, Well AG-2 and Well AG-3 in Abu Ghirab oilfield. Casing deformation was discovered while running Bottom Hole Assembly (BHA) and tools in the hole as they got an obstruction and stuck due to 9% inch casing deformation in Lower Fars formation This study includes an investigation, analysis and designing new specifications of 9% inch casing using Landmark software. Results of investigations showed poor in cement evaluation practices. Formation integrity tests (FIT) and Casing Integrity Tests (CIT) has not been implemented and Cement Bond Log (CBL) or Segmented Bond Tool (SBT) log has not been running in the hole. The proposed new casing design; increase casing weight, change casing grade, change casing thread type and increase casing design safety factor of collapse and burst load, can avoid the impact of salt creeping on 9 5/8 casing. Applying best available technology and drilling risk management to reduce drilling cost and minimize time by mitigating or preventing drilling problems. [ABSTRACT FROM AUTHOR]

CO2–basalt–water interaction safely converts CO2 into carbonate minerals within a short period, which has been verified by the CarbFix project in Iceland. However, the neo-formed secondary silicates as well as carbonate readily fill the fluid paths in the basalt, preventing the CO2 from passing through the rocks, thereby greatly reducing the storage efficiency and increasing the storage costs. This is especially the case if the permeability of the original reservoir is low. To address this problem, we propose the use of hydraulic fracturing to enhance the permeability of the basalt reservoir, increase the sequestration space, and prolong the reservoir life. In this study, the basalt formation in the Xujiaweizi area in northeastern China was chosen as the research target due to its enormous CO2 sequestration potential (about 357 × 108 tons). First, the reservoir was investigated using actual geological, laboratory, and logging data. Second, reservoir stimulation was investigated using laboratory experiments and numerical simulations. Finally, a 10-year simulation of the CO2–basalt–water interaction was performed in the enhanced basalt reservoir to determine the difference in the physical and chemical behavior in the zones with different permeability. The results showed that the permeability of the fractured zone with good percolation conditions only decreased by 4.5% in 10 years, and CO2 sequestration capacity in this zone was as high as 1.19 kg/m3. [ABSTRACT FROM AUTHOR]

Copyright of Exacta is the property of Exacta - Engenharia de Producao and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Delivering efficient and cost-effective drilled and excavated holes require effective prediction of instability along the hole profile. Most drilled and excavated hole stability analyses in the literature are performed for a given zone without considering the influence of depth. This study focused on determining the influence of depth on induced geo-mechanical, chemical, and thermal stresses and strains in drilled or excavated holes. To this end, a new porochemothermoelastic model was developed based on extended poroelastic theory, and the developed model was employed in determining induced strains and stresses for an oil and gas well case study, using data from the literature. The study delineated the different significance levels of geo-thermal-, chemical-, and thermal-induced strains and stresses as depth increased. From the results obtained, it was clear that at shallow depths, chemically induced strains and stress were the most significant formation perturbations responsible for instability of drilled and excavated holes. On the other hand, at deeper depths, geo-mechanical-induced strains and stress were the most predominant. Comparatively, thermally induced strains and stresses were found to be the least significant formation perturbations responsible for instability of drilled and excavated holes. For this case study, the results indicated that chemical strains and stresses were more prominent at depths below 170 m, accounting for more than 50% of the total stresses and strains. At 170 m, both chemical and geo-mechanical stress and strain had equal contributions to the overall stress and strain. However, as depth increased, the percentage contribution of the geo-mechanical component increased and accounted for about 80% of the total strains and stresses at 1000 m, which increased to 98.48% at depths of 6000 m and beyond. The findings of this study will provide guide for future studies on the application of extended poroelasticity theory in solving instability problems of drilled and excavated holes. [ABSTRACT FROM AUTHOR]

This study explores the distribution of stress and deformation on casings in heavy oil recovery wells and the distribution of stress in the thaw bulb in permafrost areas. Considering the expansion of the thaw bulb, the simulation analysis method is used to explore the internal mechanisms of vertical settlement displacement development and stress redistribution within thawed soil and casing. Calculation results show the following: (a) The maximum settlement of the thawed soil and the casing was positively correlated with the expansion of the thaw bulb. Although the settlement of the thawed soil was greater than that of the casing, the initial increase in maximum settlement difference between the thawed soil and the casing eventually tended to be constant due to stabilization of the thaw bulb's expansion. (b) The size of the thaw bulb directly affects the redistribution of internal stress in thawed soil, leading to different distribution rules for the vertical displacement of thawed soil and casing with depth. (c) Beyond a certain formation depth, the vertical stress of thawed soil gradually transits from a tensile stress state to a compressive stress state. The depth of a soil layer whose horizontal stress value is initially greater than its vertical stress value will gradually deepen with an increase in thaw bulb radius. (d) There is no significant negative friction on the lateral wall of casing in yield state, but significant negative friction exists on the lateral wall of casing in elastic state. The vertical stress of casing in elastic state increased gradually with the increase of casing depth, due to the existence of continuous negative friction and dead weight. [ABSTRACT FROM AUTHOR]

Abandoned wells may act as conduits for the contamination of groundwater by oil field brines and other pollutants. The steel casings of abandoned wells eventually develop leaks, which if not properly plugged, can allow pollutants to reach freshwater aquifers that supply drinking water. Resistivity surveys were conducted in the vicinity of five abandoned oil wells in order to characterize the near-surface geology and to determine the effects of the steel casings and potential leakage. The arrays consisted of dipole-dipole (DD) and inverse Schlumberger (SLB) arrays. The effects from steel cased wells can manifest as low resistivity anomalies in the vicinity of the casings, depending on proximity of the line to the well, well location along the line, and the specific array used. These features appear as vertical, circular, elliptical, and bell-like anomalies. However, in some instances with the SLB array, the data appear not to be affected by the presence of steel casings. This observation is significant because resistivity surveys utilizing the SLB array can provide reliable information on near-surface geology next to abandoned wells, and horizontal and vertical extension of brine impacted areas due to leaking abandoned oil wells. The DD array, on the other hand, is better at locating potentially hidden abandoned wells but interpreting subsurface structure or contamination with the array is more difficult. [ABSTRACT FROM AUTHOR]

This paper deals with oil well cementing flash setting problem definition, interpretation and localization via PABM (phenomenon analysis-based method) and Swiss cheese model investigation. Cementing is the most critical job throughout the well realization process; it presents the face of the well during production or abandonment. Within cement job some, problems come out and could lead to lose the well objectives, and it can be classified as cementing program's awkward or operational hitches. This work is oriented toward operational stage, even if cement program and preparation seem in the rules of the art, the execution stage can interrupt the smooth running of cement job. Flash setting is one of the most critical problems that could be occurred, and it can be recognized by the prior increases in pressure to reach unpumpable stage. Identifying flash setting phenomenon and distinguishing them from other operational comportment stay hard task and present the heart of this work. Consequences could be varied from simple cement left inside casing to total free pipe of the annulus. PABM together with cheese model is proposed to be used for deep analysis of flash setting problems and points out the real causes, if they exist, rather than flash setting. The method proposed includes five steps, description of the operation, phenomenon, assumptions, cheese model and conclusion. The three first steps construct operation scrutiny, and the fourth step represents PABM. In this latter method, assumptions will pass through a selective process made from operation facts, and only the adequate assumption reaches the last layer of the model. Practical cases have been detailed to point out the merit of this method and distinguishing flash setting from other related cement problems. [ABSTRACT FROM AUTHOR]

Oil Country Tubular Goods (OCTG) steels are used in the form of tubes in the casing column of the oil well walls and exhibit tempered martensitic structure after quenching and tempering. In these steels, due to the high cost of chromium, nickel and molybdenum, an alternative is the replacement of these elements by boron, which increases the hardenability. In order to maintain the efficiency of boron in solution during the quenching, it is necessary to add titanium to form titanium nitrides (TiN), which inhibit austenitic grain growth and avoid the formation of boron nitride. Another factor is to evaluate the effect of heat treatment on the mechanical properties of this steel. In the present study were evaluated the microstructure, hardness and tensile properties of a microalloyed hot rolled steel containing boron and titanium after heat treatments. Samples of a coil were quenched at 850 and 1050°C and then tempered at 200 and 600°C. The results show that the hardness, yield stress and tensile strength after austenitization temperature at 1050°C are smaller, due to the formation of auto-tempering martensite in the quenching. [ABSTRACT FROM AUTHOR]

• The electrical current through oil dramatically increases with atmospheric humidity. • Available model predicts magnitude of electrical conductivity except at high humidity. • Change in electrostatic atomization (EA) with high humidity pretreatment is not much. • Pretreated cases show detrimental effect on EA with random spikes in electric current. In this work, the effect of the atmospheric humidity on the electrical conductivity of oil as well as its implications in the case of electrostatic atomizers are studied. It was observed that the electrical current through oil increased by at least two orders of magnitude when the relative humidity changed from ∼10% to ∼85%. A comparison of these results is made with the available model for the electrical conductivity of organic liquids. Additional experiments with oil previously subjected to elevated relative humidity were conducted to evaluate its performance in electrostatic atomizer. No improvement of electrostatic atomization was detected, rather a detrimental effect to the steady operation was introduced. [ABSTRACT FROM AUTHOR]

The failure of a 5″ casing hanger at an oil well led to costly workover operations and lost production. The brittle failure was due to the instantaneous propagation of a circumferential fracture, initiated at a geometrical stress raiser. Combined operation stresses from internal pressure, casing weight and tightening torque were close to the yield strength of the material. If the material had sufficient ductility, plastic deformation would have led to stress relaxation and redistribution. But a SAE/AISI 4140 steel with a low forging ratio, plus a poor heat treatment and incomplete quenching, led to a banded microstructure with both low strength and toughness, and a consequent limited capacity for plastic deformation. Geometric discontinuities due to elongated inclusions and other microestructural defects justify crack propagation at the reported service loads. Quality assurance failed to prevent unacceptable pieces. Some recommendations are provided to reduce the likelihood of recurrence in new hangers: an appropriate microstructure must be assured, controlling the forging stages and heat treatment parameters. The representativeness of test coupons used for quality control must be ensured. Re -evaluating the geometry of the casing hanger and switching to a steel with higher hardenability would lead to more defect - tolerant components. • The failure of a 5" casing hanger at an oil well led to costly workover operations and lost production. • The brittle failure was due to the instantaneous propagation of a circumferential fracture, initiated at a geometrical stress raiser. • Geometric discontinuities due to elongated inclusions and other microstructural defects justify crack propagation at the reported service loads. • Quality assurance failed to prevent unacceptable pieces. [ABSTRACT FROM AUTHOR]

Metallic structures such as oil well casings in contact with soil or submerged under water are subject to corrosion. Leaks that develop in the casing of a well, constitute a serious problem and are expensive to repair. Cathodic protection (CP) is the cost‐effective control of external well casing corrosion. There are certain methods to ensure that the applied CP should meet the required criteria. In CP of well casings, monitoring of potential values is often based on surface E‐log I measurement which is a cost‐ and time‐consuming method. Simulation software and numerical methods often have been used to address this issue. In this paper, simulation of CP has been done by means of a computer software with finite element capability (ANSYS 11). Potential profiles were obtained by selecting different soil electrical conductivities (single‐ and multi‐layered media) and by changing applied current density values. Experimental procedure was established to determine the accuracy of simulation data. The results showed good agreement, especially in the single‐layered medium and at higher values of applied current. [ABSTRACT FROM AUTHOR]

Pulse current cathodic protection had obvious advantages over traditional DC cathodic protection, but when square-wave pulse current was used for cathodic protection of oil well casing, the influence of pulse protection parameters on potential distribution was not very clear. Therefore, according to the current situation of oil fields in China, the typical formation characteristic structure of oil wells was selected and the cathodic protection model of pulse current for oil well casing was established. Based on the established model, the effects of pulse current parameters (frequency and duty cycle) and anode distance on the cathodic protection effect of square-wave pulse current were studied. The results showed that better protection effect could be obtained by choosing appropriate anode distance, high frequency, and moderate duty cycle. [ABSTRACT FROM AUTHOR]

Abstract Casing failures have been systematically encountered during multi-stage hydraulic fracturing of horizontal wells in some unconventional reservoirs of China. Such failures usually manifest themselves as excessive localized radial deformation of the casing after some fracturing stages, which prevent the bridge plugs of subsequent stages from being installed to the design depths, or even result in abandonment of all remaining fracturing stages. In this paper, aiming at clarifying the casing failure mechanism during hydraulic fracturing, we performed an integrated investigation of tight-oil wells in northwest China, by analyzing the field-gained data and modeling possible mechanisms responsible for the casing failure. The investigation results show that, radial deformation of the casing due to alteration of in-situ stresses, even jointly with poor cement sheath, is far smaller than that observed in the field which could reach the order of magnitude of 1–3 cm. In contrast, we find that shear slips of pre-existing fractures/faults crossing the casing can deform the casing to the observed magnitude, justifying a conclusion that casing failure is due to the shear of pre-existing fractures/faults. This modeling-derived conclusion is supported by the records of micro-seismic events. In addition, lead impression blocks have also run for determining the deformed shape of the casing, and the results match the modeling results for the casing sheared by activated fractures/faults. Effect of fracturing pressure, in-situ stresses, length and orientation of pre-existing fractures/faults on the slippage of the fractures/faults and thus the deformation of the casing are demonstrated by a series of sensitivity studies. Additionally, some insights are derived for mitigating the casing failure in future fracturing jobs in similar unconventional reservoirs. Highlights • A statistical analysis of casing failure during multi-stage hydraulic fracturing was performed. • The reduction of casing diameter was adopted as the casing-failure criterion. • The reactivation of pre-existing fracture/faults may be the primary reason for casing failure during hydraulic fracturing. [ABSTRACT FROM AUTHOR]

From the perspective of acoustics, two layers of medium including cementing agent and sand grains exist between the casing and cement sheath of adhering sand casing well, which can impact the acoustic waveform received by the receiver on the borehole center axis. If the cementing quality of adhering sand casing well is evaluated according to existing standards, wrong interpretation can be generated, which will impair the oil field development effect. To solve this problem, an acoustic logging simulation experiment was designed to observe characteristics of full waveform received, and respectively calculate the relative amplitude of casing waves of casing well and adhering sand casing well. Besides, the relative amplitude of casing well was regarded as the benchmark to work out correction factors of relative amplitude under different cementing conditions of adhering sand casing well, and establish acoustic logging evaluation standards for cementing quality of adhering sand casing well. It's hoped that these can serve as a guide for cementing quality evaluation and enhance the interpretation accuracy for the cementing quality of adhering sand casing well. [ABSTRACT FROM AUTHOR]

Abstract In Tarim oilfield of China, the true vertical depth (TVD) is >6000 m, non-API 140 casings are often used as the intermediate and production casing. No industry standard has been established for such high grade casing, although there are some obvious shortcomings, such as sensitivity to defects and service environment, so that the fracture failure accidents of non-API 140 casing in Tarim oilfield happens frequently. Hence, this paper presents a discussion on the technical specifications of non-API 140 casing. Firstly, the system test and analysis of physical and chemical performance of non-API 140 casing material from various manufacturers have been conducted, including chemical composition, tensile properties, impact toughness, hardness, metallographic structure. Secondly, the analysis method of required minimum transverse impact toughness (CVN min) to resist cracking for pipe body and coupling of non-API casing has been presented, by which the effects of effective thickness and non-destructive examination level (defect depth) on CVN min to resist cracking of pipe body and coupling under diffenrent internal pressure have been analyzed.Thirdly, the full-scale ductile burst test of non-API 140 casing has been performed based on API 5CT standard. Finally, based on experimental data and analysis, the technical specifications for non-API 140 casing are proposed. Cases Analysis of Tarim field shows no fracture failure occurs during the subsequent service after adopting those technical specifications. Highlights • Physical/chemical performance of non-API 140 casing from three manufacturers is obtained. • Analysis method of required impact toughness to resist cracking has been presented. • Full-scale ductile burst test of non-API 140 casing has been performed. • Technical specifications for application of non-API 140 casing are proposed. [ABSTRACT FROM AUTHOR]

Abstract Wellbores are comprised by a steel casing surrounded by a cement sheath. The microannulus is the typically very small annular or degraded space that may develop between cement and casing that has been identified as a common leakage pathway in wellbore systems. Although data regarding the actual size and character of wellbore microannuli are limited, the hydraulic aperture of the microannulus can be estimated from pressure build up or flow measurements at the wellhead. Such information can be misleading, however, as it represents microannuli as uniform annular gaps along the wellbore. This study aims to provide a quantitative measure of the variability of the microannuli. We generated wellbore-based samples with microannuli between the steel casing and cement, and calculated their hydraulic aperture and permeability by flowing gas through the microannuli. We then injected dyed epoxy into the microannuli, cut the specimens into five circumferential sections per sample, and used microphotographs to measure microannulus aperture size and contact between the steel and the cement to generate microannulus profiles for each section. These measurements are unique as they provide a quantitative measure of the variability of the microannulus with a resolution as low as 3 μm. Aperture sizes were fitted to different statistical distributions, most frequently lognormal and gamma. Capillary entry pressure (CEP) for gas displacing brine in the microannulus was estimated from measured aperture size. CEP estimated from actual aperture size was generally much greater than that estimated from the hydraulic aperture of the entire specimen, resulting in a wide range of values. Measured aperture sizes were used to evaluate possible microannulus repair by estimating the penetration of cementitious materials. The data showed that the repair using cementitious materials is unlikely to be effective for microannuli with a hydraulic aperture <50 μm. Highlights • Microannuli have apertures that vary orders of magnitude in a circumferential section. • Flow through microannuli deviates from the typical parallel plate assumption. • Hydraulic aperture is inappropriate for describing microannuli for some applications. • Cementitious material will not penetrate microannuli with hydraulic apertures <50 μm. [ABSTRACT FROM AUTHOR]

• Purpose of the current article is to describe casing and tubing pipelines' corrosion failures and their control. • CO 2 and H 2 S cause sweet and sour corrosion and enormously contribute to internal pipeline failure (≈ 60%). • The use of corrosion inhibitors is the most cost-effective way to prevent casing and tubing corrosion. • Mechanism of sweet and sour corrosion and formation of corrosion products depends upon various parameters. • The main input parameters are pH, temperature, P CO2 , P H2S , etc. Casing and tubing for oil and gas wells are frequently made of steel alloys. Many corrosive gases, organic acids, salts, and other contaminants are present in the fluids of oil and gas wells, which hurt their productivity, efficiency, and continuous production. The common corrosive species include carbon dioxide (CO 2), hydrogen sulfide (H 2 S), water (H 2 O), organic acids (HCOOH, CH 3 COOH etc.) and salts (NaCl, CaCl 2 , MgCl 2 , NH 4 Cl etc.) that can cause the corrosion of metals at any stage of production, purification, storage and transportation processes. The purpose of the current article is to cover the corrosion of oil and gas well casing and tubing and corrosion mitigation techniques. Numerous factors influence the corrosion rate in these wells, and various management techniques and procedures have been implemented to address corrosion-related problems in oil and gas wells. Corrosion-resistant materials are one of the most popular and frequently used techniques. To prevent internal pipeline corrosion, anti-corrosive and wear-resistance coatings are also utilized. Another frequent method against corrosion is using scavengers, primarily for H 2 S and O 2 , to lessen the corrosivity of the well fluids. The most popular H 2 S-scavenging technique uses alkaline solutions and activated carbon. Triazine and aldehydes are the most common and efficient non-generative H 2 S scavengers. The use of corrosion inhibitors is one of the most practical and cost-effective ways to prevent corrosion in well casing and tubing. The corrosion inhibitors adsorb at the point where corrosive fluids and internal pipelines interface, preventing the corrosive attack. [Display omitted] [ABSTRACT FROM AUTHOR]

Taking a composite system of casing-cement sheath-formation in a high temperature and high pressure oil well as the research object,a thermo-structural coupling model is constructed and its theoretical solution is obtained by considering contact,continuity and boundary conditions. The theoretical solution is very accurate in comparison with FEM solution. Comparing the theoretical solutions with thermo-structural coupling effects and without thermal load,it is indicated that thermal load has much greater influence on the equivalent stress. Failure coefficient,which is used to analyze structure integrity,is defined by Mises,Drucker-Prager and Mohr-Coulomb yield criteria. The factors of elastic modulus,Poisson's ratio,nonuniform in-situ stress coefficient,formation temperature and casing pressure are discussed by considering the failure coefficient distribution of casing-cement sheath formation. The results show that the above factors have great effect on the failure coefficient distribution. The failure coefficient of the 1st cementation plane is greater than that of other planes and its influence on wellbore integrity is large.