Accurately determining the gas and water production contributions of each pay zone in a gas well is fundamental for developing rational production allocation schemes， preventing and controlling water invasion， and enhancing gas recovery in the development of offshore gas fields. However， restricted by the nature of point measurement， operational risks and economic costs， conventional production logging is difficult to deliver real-time， continuous and full-wellbore monitoring. As an emerging monitoring technology in recent years， optical fiber enables real-time monitoring of downhole fluid dynamics and provides strong technical support for production profile analysis. This study proposes a quantitative interpretation method for gas production profiles in gas wells by comprehensively utilizing data of distributed acoustic sensing （DAS） and distributed temperature sensing （DTS）， and systematically constructs a complete analysis workflow from data processing and operation condition identification to production profile quantitative inversion. The method identifies pay zones and calculates relative production rates through DAS frequency band energy （FBE） analysis. A thermodynamic model was constructed and combined with DTS temperature and pressure data to invert absolute gas/water production rates. DAS results were applied to DTS inversion for consistency constraints and verification. Finally， an integrated joint interpretation workflow was developed. Compared with the single DAS or DTS methods， the DAS quantification-constrained DTS inversion significantly improves the consistency of pay zone identification and the accuracy of production calculation. Comprehensive interpretation of the case well， an offshore gas well， shows that Zone A2 is the main gas producer with a gas production rate of approximately 2.86×10⁴ m³/d and no water production； Zone A1， a secondary gas producer with low water production， presenting a gas production rate of about 1.45×10⁴ m³/d and a water production rate of about 1.50 m³/d； Zone A3， a water producer with certain gas production. Comparison of interpretation with the actual well production state indicates that the proposed method not only realizes the quantitative interpretation of gas production profiles but also effectively identifies anomalies like interlayer crossflow， representing improved reliability of interpretation results. The proposed method provides strong technical support for offshore gas well monitoring and production optimization.

Gas kick early warning in deepwater drilling is challenged by weak precursors and multi-source noise, which can delay detection and increase false alarms under conventional single-signal thresholds. This narrative review synthesizes recent advances in gas kick early warning methods based on machine learning and organizes the evidence with a decision-oriented framework that links sensing observability, feature construction, model design, evaluation metrics, and well control actions. Three themes recur: multi-source fusion across surface, riser, and downhole channels; a shift from shallow statistical learners to deep and hybrid architectures; and increasing emphasis on estimating influx volume and rate within operational workflows. Engineering evidence indicates that a developing gas influx produces distributed, time-shifted signatures along the wellbore that may emerge first in downhole, riser, or surface measurements depending on circulation and operating conditions. These considerations motivate an integrated monitoring layout that combines topside mud logging streams, riser acoustics, and annular pressure while drilling (APWD) or other while-drilling measurements. This review clarifies how monitoring outputs can be integrated into managed pressure drilling workflows to close the loop from detection and tiered alerts to operational adjustments. An illustrative offshore test case is included solely to demonstrate reporting schema and deployment context; the cited trial reports an earlier alert on the order of 12–15 min relative to conventional mud-logging surveillance. Overall, the review provides comparative, evidence-based, and deployment-oriented guidance to support earlier and more reliable gas-kick early warning in deepwater operations.

During drilling operations, variations in well deviation angle and azimuth with depth readily induce drill string eccentricity, leading to changes in the annular two-phase gas-liquid flow pattern during gas invasion, which in turn affect the accuracy of electromagnetic flow measurement. Addressing the issue that the annular electromagnetic flow measurement sensor (AEFMS) accuracy is affected by the eccentric distribution of the annular gas-liquid two-phase flow pattern, this paper first derives the AEFMS weight function during the eccentric process and in the presence of the gas phase through theoretical modeling. Subsequently, finite element simulation analyses the response variations of the output weighting function for eccentric AEFMS under different eccentricity orientations, alongside the influence patterns of the gas phase on the virtual current density of eccentric AEFMS. Finally, an experimental simulation platform was established. By incorporating instrument correction factors for different flow patterns, equations relating the electromotive force response of the eccentric AEFMS to gas void fraction were derived. The eccentric AEFMS maintained measurement deviations of +/- 15 % for gas and liquid phase velocities. Under annular air bubble flow conditions, the corresponding absolute mean percentage deviation was 7.858 %, with an absolute mean deviation value of 0.042 m/s. These findings help mitigate interference from annular eccentric gas-liquid two-phase flow on annular electromagnetic flow sensor measurements, providing novel measurement strategies for early annular overflow monitoring in downhole applications.

This study employed a full-scale cement sheath quality evaluation apparatus, along with a high-precision distributed fiber optic temperature sensing system, to perform real-time, continuous monitoring of the temperature change throughout the cement hydration process. The results of the cement annulus and cement bond defect monitoring during the hydration process indicated that the distributed fiber optic temperature data enabled centimeter-level resolution in defect identification. Defective regions exhibited significantly reduced temperature fluctuation amplitudes, and an inversion in temperature change at the early hydration stage, detected at the cement–defect boundary, facilitated the early detection of defect locations. The distributed fiber optic system was capable of conducting continuous and comprehensive monitoring of the sequential hydration temperature peaks of cement stages injected into the annulus. The results revealed the interdependence among different cement stages, as well as a phenomenon whereby an elevated annular temperature accelerates the progression of cement hydration. The experimental findings provide a reference for identifying the characteristic signals in distributed fiber optic monitoring of well-cementing operations, thereby establishing a foundation for the optimal and effective use of distributed fiber optics in assessing well-cementing quality.

The riserless drilling system offers superior well control, aiding in the prevention of drilling accidents and compliance with environmental standards in the polar cold sea. Predicting the temperature and pressure in such systems is crucial for operational safety. However, the behavior of drilling temperature and pressure in the polar cold sea remains unclear. This study applies non-Newtonian fluid mechanics and thermodynamic principles, considering the effects of mechanical energy input, hydraulic energy, and rock fragmentation at the drill bit to develop a coupled mathematical model for the temperature and pressure of riserless drilling systems in the polar cold sea. Using state-space methodology and control theory, the temporal distribution patterns of the temperature and pressure were determined. Sensitivity analysis revealed that flow rate significantly affect system temperature, with an optimal value for cooling at the wellbore bottom. Beyond this value, the heat removed by the drilling fluid diminishes. In polar cold sea regions at depths exceeding 600 m, increasing the input temperature of the drilling fluid has minimal effect on maintaining the fluidity of the drilling fluid at the seabed. The influence of cold seawater on the pressure loss of the drilling fluid within the pipeline is minimal, with a pressure increase of 0.9% after stopping the pump for 1 h. In contrast, cold air significantly impacts the pressure loss, resulting in a 12.5% increase after stopping the pump for 1 h. Insulation can maintain the fluidity of the drilling fluid, reducing the opening pump pressure required for operations.

Salt formations are commonly encountered during oil and gas drilling. Due to the rheological properties of salt rocks, casing collapse accidents happen frequently. Under action of nonuniform geostress, casing failure has become an important influencing factor that restricts the exploration and development benefits of deep and ultra-deep wells. Casing stress in a period after well cementation in the salt formation of Brazilian deepwater fields was analyzed. Results show that the nonuniform geostress is instantaneously applied on the cement sheath when well cementation is completed in the salt formation and then transferred to the casing. Stress on the inner wall grows with an increase in the angle with the direction of the maximum horizontal principal stress and it reaches the maximum in the direction of the minimum horizontal principal stress. As the creep continues, stress on the inner wall of casings gradually enlarges and the circumferential stress in inner rings tends to be uniform, which means that creep of the formation weakens the nonuniformity of casing deformation. The collapse pressure on the outer wall of casings tends to increase at first and then decrease as the angle with the direction of maximum horizontal principal stress enlarges. Stress on the inner wall of casings in the salt formation reduces with the increasing thickness of casings selected, and the casing strength is improved as the wall thickness increases. The research results provide certain theoretical guidance for the strength check of casings in well cementation engineering in salt formations.

The sensitivity of gas and water phases to DAS acoustic frequency bands can be used to interpret the production profile of horizontal wells. DAS typically collects acoustic signals in the kilohertz range, presenting a key challenge in identifying the sensitive frequency bands of the gas and water phases in the production well for accurate interpretation. In this study, a gas–water two-phase flow–acoustic coupling model for a horizontal well is developed by integrating a gas–water separation flow model with a pipeline acoustic model. The model simulates the sound pressure level (SPL) and amplitude variations of acoustic waves under different flow patterns, spatial locations, and gas–water ratio schemes. The results demonstrate that within the same flow pattern, an increase in the gas–water ratio significantly elevates acoustic amplitude and SPL peaks within the 5–50 Hz frequency band. Analysis of oil field DAS data reveals that the amplitude response range for stages with a lower gas–water ratio falls within 5–10 Hz, whereas stages with a higher gas–water ratio exhibit an amplitude response range of 10–50 Hz.

Introduction: Salt formations are complex and pose significant risks during oil and gas drilling. Creep behavior in salt formations under geostress can jeopardize drilling safety.Methods: This study analyzes the shrinkage behavior of boreholes drilled through salt formations in West Africa’s Block B, with emphasis on the differential creep rates in two horizontal principal stress directions and the evolution of wellbore shape over time. The impact of drilling fluid density on shrinkage rates is also investigated.Results: After drilling through salt formations, the creep rates differ between the two horizontal principal stress directions. Shrinkage is faster in the direction of minimum horizontal principal stress and slower in the direction of maximum horizontal principal stress. Over time, shrinkage rates converge, resulting in a transition from elliptical to circular wellbore shape. Higher drilling fluid density leads to reduced shrinkage rates.Discussion: These findings contribute to the theoretical guidance for drilling fluid density selection in salt formations.

Steel riser is an important structure to transfer oil and gas in the offshore oil industry field. Due to the highpressure environments, corrosion and complex stress, risers are prone to cracks and other forms of damage, which seriously threaten the safety of risers. It is of prime importance to monitor and evaluate cracks in risers using SHM methods to keep the structural integrity of risers. In this paper, the double modes of torsional guided waves are proposed for locating and quantifying cracks in the riser using the electromagnetic acoustic transducer. The novel ring electromagnetic ultrasonic transducer is designed to excite the torsional guided wave and receive the crack reflected wave. The torsional mode and the bending mode of the crack reflected wave are decomposed for locating and quantifying cracks in steel riser. The torsional mode is used to locate the crack in axial direction and the bending mode is used to locate the crack in both axial direction and circumferential direction. Both two modes are used to quantitative detection of cracks. The bending mode signal can effectively separate the characteristic information of cracks and significantly improve the quantitative accuracy of crack. The experimental results show that the maximum error of the location of the crack is 2.02%. The maximum error of the crack length is 6.53 mm. The maximum error of the crack depth is 1.87 mm.

深水高温高压气井钻井过程中,井筒大温差、大压差效应会使钻井液性能发生较大改变,进而影响井筒流动参数和钻井施工安全,因此准确模拟井筒温压场对确保深水高温高压井安全钻进至关重要.根据深水钻井工艺和高温高压地层的特点,充分考虑了井筒温压场和钻井液性能相互影响,结合增压管线流体进入隔水管环空引起的传热和传质,建立了适用于深水高温高压气井钻井的井筒瞬态温度压力耦合计算模型,提出了相应的迭代求解算法,并通过实例计算,进行了参数敏感性分析.研究结果表明:本文模型计算值与现场实测数据基本吻合,验证了模型的正确性;隔水管增压管线排量会使环空温度显著降低,进而影响整个井筒温度,因此不可忽略增压排量的影响;钻井液性能受井筒温度和压力影响较明显,在计算过程中忽略温度,压力和钻井液性能之间的耦合作用会产生较大误差.本文研究成果可为深水高温高压气井钻井过程中井筒温压场预测及水力参数设计提供理论指导.

Artificial intelligence is widely used in the oil industry. During the process of oil production, the parameters of oil wells will change under different working conditions, which may lead to abnormal operation of oil wells. Once the abnormal operation occurs, the whole production of the oil field will be affected, so it is very important to identify the abnormal operation of the production wellbore flow. To address this problem, an end-to-end deep learning fusion (EDF) model is proposed in this paper, which combines the advantages of deep neural network (DNN), convolutional neural network (CNN), and long short-term memory (LSTM) models to identify abnormal wellbore flow conditions. The experimental results show that the EDF model has higher accuracy and area under curve (AUC) value for identifying the abnormal working conditions of wellbore flow, which can perform the task of identifying the abnormal working conditions well.

深水钻井井控面临地层压力窗口窄、海底低温、水合物防治、圈闭气处理及存在浅层水流、浅层气等诸多风险.在对业界深水井控技术充分调研的基础上,结合近年来南海西部自营深水井作业实践经验,总结出一套针对南海西部深水井地层破裂压力低、压井方式的选择、圈闭气处理、水合物预防及呼吸效应识别等深水井控问题的处理措施,为成功发现LS17-2、LS25-1及LS18-1气田保驾护航,开启了我国深水勘探开发的新篇章.

Offshore drilling activates have been significantly impacted by severe weather conditions as oil and gas development has moved into deep and ultra-deep water. Under the situation of imminent arrival of a typhoon, emergency retrieval of the whole drilling riser is time consuming and tedious. A novel specialized soft hang-off system to improve the adaptability of the drilling riser system under hang-off or transit operations is developed to solve the low-efficiency and time limitation for retrieval all drilling riser joints during extreme storm environment. The specialized soft hang-off system improves its bending capacity and reduce the risk of interference with diverter housing and moonpool and partially compensate the heave motion of drilling platform, to ensure the drilling riser keep lower tension and not compression during hang-off or transit mode. A numerical solution with mechanical model, boundary condition, results validation is conducted and transit operation window is obtained. Sea trial investigation on the novel specialized soft hang-off system during transit operation are conducted to evaluate the performance on global strength and dynamic load compensation effect. The research can be a significant basis and of valuable reference for deepwater engineering and the manufactured novel specialized soft hang-off system is an important emergency equipment.

Ahstract-The Rate of Penetration (ROP) implies the drilling efficiency, which is a key indicator in the offshore drilling engineering. Precise prediction and combinatorial optimization of ROP can improve drilling efficiency and reduce business costs. However, the low quality of geological and lithological information interferes ROP prediction and optimization. Hence, in this paper, we propose an End-to-end Long-short Term Memory (LSTM) Fusion model to predict ROP in the absence of geological and lithological data. We employ an LSTM structure to learn ROP range real-timely and an ANN block to capture interrelationship between vital parameters and ROP without geological and lithological information. Furthermore, a Simulated Anneal (SA) algorithm is applied to control three adjustable parameters for an optimal ROP. The experiments on offline datasets show superior performance compared to traditional machine learning methods. Moreover, we conduct experiments on a real drilling scenario, and the average ROP performance is increased by 28.3%

针对目前深水钻井防台时隔水管处理方式存在的作业窗口小、作业模式选择困难、易发生事故等问题,本文提出了将隔水管硬悬挂与软悬挂方案相结合的新方法,既能快速操作,又能缓冲隔水管运动.为了降低新方法中隔水管的加速度,提出并分析了 3种控制方案对加速度的补偿效果,结果表明加速度峰值控制方案具有制造安装简单、实施方便等优势.在此基础上针对加速度峰值控制方案中封闭高压系统散热难的问题,提出了采用差动液压缸实现半开式循环散热的方法.本文提出的隔水管加速度峰值控制悬挂方法及其配套的差动散热-主动控制节流装置,具有较好的动载荷补偿能力,可为我国深水钻井防台提供技术支持.

海上气井井下油套管泄漏无法及时诊断将会引发环空带压,是海上油气生产安全的重要问题.针对井下油套管泄漏诱发的声波在井筒环境条件下的传播机理、泄漏信号远程探测方法、漏点准确定位方法和多源信息融合的泄漏状态评估方法研究,研发了海上气井井下油套管泄漏检测系统.新研发的油套管泄漏检测系统在东海某平台进行了 2井次的井下油套管泄漏检测和堵漏工程实践,结果表明,该系统实现了在浅井段(160～180 m)10 m误差范围内对单漏点和双漏点的准确定位,可满足环空带压井治理的需要.本文研究结果可为井下油套管泄漏修补作业提供技术支持.

Abstract In deepwater drilling, accurate prediction of wellbore gas‐liquid two‐phase flow behavior is significant for gas kick detection and well‐control treatment. In this study, a new transient gas‐liquid two‐phase flow model was developed to simulate the wellbore gas‐liquid two‐phase flow during gas kick in deepwater dual‐gradient drilling based on downhole separation. This model accounts for the impact of a sudden change in density on gas‐liquid flow behavior. The transient model was solved using the finite‐difference method. The accuracy and stability of the model were verified using data measured from a full‐scale experimental well. Using this model, the differences in the apparent liquid velocity and the flow rate at the annular outlet during gas kick were compared between deepwater dual‐gradient drilling and conventional single‐gradient drilling. Additionally, the influences of numerous factors on variations in flow rate at the annular outlet were also studied. A new method of early gas kick detection was proposed for deepwater dual‐gradient drilling based on downhole separation.

This paper aims to investigate the wellbore thermal behavior in multi-gradient drilling (MGD). Based on the principle of energy conservation, a synthetic transient heat transfer model was established, in which the mass and heat transfer of lightweight glass microspheres (GMSs) were considered for the wellbore fluid region, and the dynamic variation in the moving boundary was considered for the drill bit and separator region. The synthetic model was solved using the combination of finite volume method and dynamic laying method. The accuracy and capability of the model were verified using field measurement data and previous typical models. The calculation results suggested that the annular temperature near the separator dropped suddenly due to the mass and heat transfer of GMSs. Additionally, the dynamic drilling of the drill bit would increase the bottomhole temperature continuously. Furthermore, a sensitivity analysis indicated that when the GMS concentration increased from 5% to 45%, the annulus temperature at the separator reduced by 9.15%; when the distance between the drill bit and separator increased from 1100 m to 3000 m, the bottomhole temperature increases by 3.99%; and the effect of the separator number on annulus temperature combined the dual role of separator position and GMS concentration. (C) 2019 Elsevier Ltd. All rights reserved.

Because of the insufficient inversion parameters of the single point measurement data interpretation model, the pressure change cannot be accurately revealed. To address the problem, a real-time pressure interpretation model based on downhole dual pressure measuring point data is proposed using the unscented Kalman filter method and the hydraulic model. According to the characteristics of the managed pressure drilling, the inversion parameters of the model are determined as the density correction factor and the friction correction factor. The dual measuring point is theoretically proved to be more comprehensive than single measuring point in the inversion parameters. The calculation results show that the calculated values of the dual measuring point pressure and the inversion parameters can be corrected in real time according to the newly acquired measured data. The dual measuring point pressure correction value is quite close to the measured value. The calculated value of the inversion parameter is slightly fluctuated in the vicinity of the true value. The inversion accuracy of the inversion parameters increases with the distance between the two measuring points. Combined with the calculation error allowed in the engineering, the reasonable dual measuring point distance is 30 m, which ensures high inversion accuracy while reducing the cost of using wired drill pipe. The study results can provide references and theoretical guidance for the development and field application of the downhole dual measuring point tool.

深水钻井过程中高温会对钻井液性能和井下及井口设备、工具的密封件等造成严重损坏,因此准确的钻井温度模拟及控制至关重要.结合深水钻井工艺和高温地层特点,充分考虑钻井系统输入能量和隔水管对井筒温度剖面的影响,建立了新的深水钻井井筒循环温度分析模型,重点分析了温度剖面的影响因素及海底防喷器处的温度变化规律,结果表明:本文建立的深水钻井井筒循环温度分析模型计算结果与现场实测数据吻合;钻井系统输入能量、隔水管增压泵排量对井筒温度剖面的影响不可忽略,在钻井设计和作业阶段可分别通过优化井眼轨迹、采用高比热钻井液和增加钻井液润滑性、减小钻井液入口温度等方法来降低井底温度.本文研究成果可为深水高温钻井井底温度预测和控制提供理论指导.