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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]

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]

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]

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]

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 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]

Casing collapses are frequent events encountered in Iranian oil-producing wells. This phenomenon of casing collapse in wells can reduce and stop oil production. Among the oil fields that witnessed this problem, we have been to the Marun oil field in the southwest of Iran. In south Iran’s oil-rich regions, the Gachsaran Formation has the highest level of plasticity as it contains a large amount of salt units and also exhibits the largest frequency of casing collapse occurrence. The casing collapse occurrence phenomenon might result from the exertion of compression and shear stresses from the formation to the body of casing. In the case of inappropriate cementing, the mentioned stresses are applied in a nonuniform and anisotropic method to the casing. If the respective stresses can overcome the cement strength and then the casing strength, they will make the casing collapse. In the present study, the areas where casing collapse is most likely to happen was determined with the aid of an analytical geomechanical model and by comparing the maximal horizontal stresses against the cement and the casing strengths. Then, via 2-dimensional and numerical simulation of plastic Gachsaran Formation related to the well under analysis by means of the finite-element software ABAQUS, it was attempted to obtain the plastic properties of the formation as well as the numerical values and directions of stresses that might lead to casing collapse occurrence if exerted. The results of the numerical and analytical model indicate the high potential of the plastic Gachsaran Formation in creating a collapse phenomenon. Finally, it was observed that the maximum value of the numerical stresses resulting in the occurrence of casing collapse are along the direction of the maximum horizontal stresses and correspond to the Gachsaran Layer 4-2 possessing the highest salt content. [ABSTRACT FROM AUTHOR]

Aimed at serious casing damage problem during the process of oilfield development by injecting water, based on seepage mechanics, fluid mechanics and the theory of rock mechanics, the multi-physics coupling theory was also taken into account, the mathematical model for production of petroleum with water flooding was established, and the method to solve the coupling model was presented by combination of Abaqus and Eclipse software. The Q9G3 block in Jibei oilfield was taken for instance, the well log data and geological survey data were employed to build the numerical model of Q9G3 block, the method established above was applied to simulate the evolution of seepage and stress. The production data was imported into the model to conduct the history match work of the model, and the fitting accuracy of the model was quite good. The main mechanism of casing damage of the block was analyzed, and some wells with probable casing damage problem were pointed out, the displacement of the well wall matched very well with testing data of the filed. Finally, according to the simulation results, some useful measures for preventing casing damage in Jibei oilfield was proposed. [ABSTRACT FROM AUTHOR]

Most of the major oilfields in the North Sea, Persian Gulf and South China Sea are becoming very mature, with their assets exceeding their calculated design life. Severe corrosions on the metallic structures of oil wells consisting of the conductor and casings, combined with spalling of annular cement forming the barriers can result in catastrophic events leading to structural collapse and wellhead vertically dropping onto the platform deck. With the collected inspection records, a systematic approach is deemed essential to assess the in-place condition of these wells and to categorise them for life extension works. This paper presents a simplified screening method for the structural integrity assessment of platform conductors towards the end of their design life and the prioritisation which follows thereafter for life extension operations by bridging the gap between design data and inspection records. The deterministic and probabilistic integrated approach is taken to address this problem, by considering the information collected from the as-built design records to the in-place inspections, coupled with the operating and metocean loads. The pragmatic and novel conductor operating guideline curves are proposed and constructed to present the evaluated integrity states, which will enable operators to rapidly categorise conductors for rehabilitation. This screening method is applied to a group of 40-year old water injection wells, and is demonstrated to have the practical prospect, and can be automated to provide a robust and effective assessment technique. [ABSTRACT FROM AUTHOR]

Designs of petroleum wells involve many activities and technical areas. These areas cover various engineering aspects and can be solved with contributions from applied mathematics. This paper presents a new casing point optimization methodology. A novel mathematical formulation and procedure for optimization of casing string placement including geological uncertainty is developed. Determination of optimal casing point locations is a challenging task because many engineering and geologic variables affecting each other and are often uncertain and nonlinear. In this paper, the casing string placement problem was formulated as the optimization function under uncertainty. The geological uncertainty is modeled with considering different scenarios of geology. The Lingo software was used as the optimization tool. In order to find the optimum decisions for different risk attitudes, a utility framework that enables the assessment of the uncertainty of the casing string placement decisions is used. A large case study was undertaken to demonstrate the value of considering uncertainty in drilling decision-making. Numerical simulation was carried out with this selected case study to find optimum points under different risk attitudes in each section of drilling for different wells. Finally we show the application of that methodology has better performance to cost savings at least of 2.4–15.2% in the important drilling management. [ABSTRACT FROM AUTHOR]

Based on the statistics data extracted from underground hazards in 'A' region of Yuan Shi oilfield, and with casing failures as an example, engineering hazards, such as sand production, casing hazards, etc., in different geological structures are compared and distinguished. A detailed examination of their relationship is conducted in terms of mineral composition, sedimentary facies and other reservoir aspects. The triggering mechanism of engineering hazards is also theorized. Especially under water injection, the effect of geological structures on engineering hazards is illustrated. Finally, engineering hazards prevention and minimization measures are presented. The results show that in fluvial sediments, casing damage is mainly on the outside of the casing and casing bending. In a shallow lake environment, casing damage is chiefly of the leakage and rupture type. [ABSTRACT FROM AUTHOR]

The Suqiao gas storage of Huabei field is buried deep with high formation temperature, so the drilling and completion are difficult. According to the cementing difficulty of Suqiao gas storage, the technical countermeasures are proposed, such as optimizing wellbore scheme and technical casing depth, optimizing well plugging method, optimizing cementing technique, taking cyclone centralizer and cyclone generator, and taking the leading low density and low viscosity slurry with calcium resistance. So far, a part of the studied techniques have been applied in Well Su 4K-3X, and initial effect has been obtained. The study is directional to the following cementing process of Suqiao gas storage. [ABSTRACT FROM AUTHOR]

Engineering and geological factors such as casing defects and creep formation are the most sensitive factors among all of the factors that affect casing strength and loads. Based on the basic mechanical characteristics of the creep formation and casing materials, the viscoelastic and elastoplastic constitution equations were taken respectively to simulate their mechanical behaviors. The effect of casing wear on its burst strength and the external creep pressure load distribution of the casing with defects under complex conditions are illustrated. Further, the sensitivity to casing strength damage was analyzed. The numerical simulation results can provide theoretical guidance in investigations of casing behavior under complex engineering and geological conditions and are also very useful for casing design and its applications in oil fields. [ABSTRACT FROM AUTHOR]

Formation analysis from behind casing is gaining more relevance in assessing reservoirs, not only in aging fields but also in new wells completed either without the full complement of openhole petrophysical measurements or with openhole measurements of inadequate quality. Before this technology was available, formation evaluation in freshly drilled holes was dependent on the availability of openhole log measurements. This paper discusses field examples in which reservoirs were evaluated without a full suite of openhole log measurements. Examples from two sidetracks in a mature North Sea field supported by water injection are presented. The small hole size limited openhole data acquisition to resistivity and gamma ray (GR) measurements, which were acquired using logging-while-drilling (LWD) technology. In both cases, pulsed neutron (PN) measurements were recorded through casing to augment the existing data. Porosity and formation sigma (macroscopic thermal neutron capture cross section) measurements were obtained. Fluid saturations were computed using this porosity and the LWD resistivity. Saturations also were computed from the carbon/oxygen measurement, and these agreed with the resistivity-based answers. Lithology analysis was performed using elemental spectral capture yields and was reliable and consistent fieldwide. The results show that, in a mature oil field, PN measurements can provide a complete lithology and saturation analysis in circumstances in which insufficient openhole petrophysical measurements are available. [ABSTRACT FROM AUTHOR]

Casing tends to be put near the lower wellbore when cementing horizontal wells, in other words, the centralized degree is poor, so the cement thickness is unequal around the casing, resulting in poor cementing quality, and it restricts the advantages of horizontal wells severely. Centralizer is usually used to improve the casing centralized degree in the field, but conventional centralizers has some problems, such as large diameter, difficulties in tripping into the hole, and breaking wellbore. So the hydraulic centralizer for horizontal well cementing was developed. It has some advantages, such as small original diameter, safety in tripping into the hole and large diameter after expansion. It can improve the centralized degree significantly and make burbling effect in cementing. The quality of cementing is improved greatly with the hydraulic centralizer. The application of centralizer in fields is simple, and does not affect cementing process. The tool has been used in many wells in Shengli Oilfield with significant effect. [ABSTRACT FROM AUTHOR]