In this paper, experiments and finite element analysis of the primary plus secondary local PWHT (PS-PWHT) are carried out on the cylinder girth weld of the atmospheric tower. The evolution law of stress, strain, and deformation during the PS-PWHT is clarified, and the residual stress relief mechanisms of the PS-PWHT are also elucidated. It is found that during the heating stage of primary heating, in addition to the material softening at high temperatures releases parts of residual stress, the expansion deformation generated during the heating process plays a dominant role in the residual stress relief on the inner surface, and the influence of creep effect is weak. During the cooling stage of primary heating, the material's yield strength and elastic modulus increase as the temperature decreases. At the same time, the primary heating zone undergoes shrinkage deformation, and the unheated zone has a significant constraint effect on the heating zone. After heat treatment, the residual stress distribution shows the tension on the inner surface and compression on the outer surface. It has been proven that in local heat treatment, the constraint effect is the main reason for the difficulty in mitigating residual stress on the inner surface, and the creep effect has a negligible impact on the residual stress relief. During the secondary heating process, since the secondary heating temperature is lower than 300-400 degrees C and the primary heating is not heated, the creep effect does not occur. When the secondary heating is cooling, the primary and secondary heating zones shrink. Due to the higher temperature of the secondary heating, the shrinkage speed of the secondary heating is faster than that of the primary heating, resulting in the reverse bending moment in the primary heating zone. The PS-PWHT method utilizes the reverse bending moment generated by the temperature gradient between the secondary heating zones and weld zones to mitigate welding residual stress. Therefore, the residual stress relief induced by the secondary heating also mainly occurs during its cooling stage.

The development of the Ordovician carbonate karst reservoir in the Tahe Oilfield is intricately linked to paleogeomorphology and the evolution of faults. Clarifying the genetic relationship between faults and karst paleogeomorphology is crucial for understanding reservoir distribution as well as for exploration and development efforts. Using high-precision 3D seismic data for the T74 unconformity in the Tahe main area, this analysis includes detailed geomorphology characterization, fault interpretation through the extraction of seismic attributes, and a description of karst reservoirs based on impedance inversion data. The local geomorphological units, including valleys and dissolution peaks, exhibit a strong correlation with particular faults. The dynamics of thrust faults and NNE strike-slip faults within the study area influence the watershed and geomorphological zoning, directing the flow patterns and distribution of karst water systems. Minor faults and localized fault combinations exert a more significant influence on the formation of local landforms. In the karst period, local faults and fractures resulting from extension are likely to exhibit negative geomorphology under northwest compressive stress. This condition enhances the water conductivity of paleogeomorphology, facilitating karstification and the development of fracture and vug reservoirs. Precise fault interpretation and kinematic dynamic analysis are essential for investigating the genetic mechanisms of karst fractures and cave reservoirs, providing valuable insights for predicting advantageous karst reservoir spaces.

The Ordovician karst fracture-cave reservoir in Tahe oilfield has strong heterogeneity, and palaeogeomorphology, fault and fracture play important roles in the development of the complexity of the fracture-cave reservoir. Based on rich geological and geophysical data, the influence of faults on the karst reservoir development in carbonatite under different palaeogeomorphic conditions are analyzed through the interpretation of faults and the activity of internal faults in carbonate rocks in different periods, combined with palaeokarst environment and karst products. The results show that there are not only strike-slip faults but also an NNE-thrust fault in the sixth and seventh districts of Tahe Oilfield, which control the direction of long-axis anticline in the center of the study area. The anticline becomes an important watershed and most of the surface gullies develop along suitable faults from the top of the anticline to lower areas. According to the karst geomorphology, water system and fracture-cave distribution, landforms are divided into three types: hoodoo-upland, karst depression and karst basin. In the hoodoo-upland, the fracture networks around the faults are dissolved and small and medium-sized fractures develop, and the reservoirs have low filling degree and good performance. In the karst depression, the landforms are transformed by strong water erosion and karst dissolution. The underground rivers and the palaeogeomorphic gullies controlled by high-angle strike-slip faults are relatively straight, while the others controlled by low-angle faults are tortuous. Unfilled caves and intergranular pores in cave fillings are the main reservoir spaces. In karst basin, the Ordovician soluble limestone is covered by stucco deposits, which greatly weakens the karstification. The fractures and caves can develop only along the faults and fractures at a very deep depth. The spatial structure, connectivity, porosity and permeability are complicated. The main reservoir types are fractures, fracture-cave and isolated caves. The filling types are fault karst breccia, giant crystal chemical filling or no filling. Therefore, faults affect the development of reservoir types and fillings under different geomorphology and karst water conditions, which has important guiding significance for the accurate exploration and development of carbonate fracture-cave reservoirs.

Super 13Cr, as an economy stainless steel (SS) for oil country tubular goods, needs stable corrosion resistance in high-pressure and high-temperature (HPHT) downhole medium. Severe plastic deformation (SPD) are the surface modification technology to improve mechanical properties, fatigue behavior and corrosion resistance of metals, and shot peening (SP) has been the most widely used SPD process. However, there are quite limited studies about the microsutructure evolution, residual stress, and high-temperature corrosion behavior of SP-treated martensitic SS. In this study, super 13Cr martensitic SS was treated by SP with various air pressures and nozzle speeds. The surface characteristics and high-temperature corrosion behaviour in 3.17 mol/L K2HPO4 solution were investigated through finite element model analysis, characterization of residual stress and microstructure, as well as electrochemical and stress corrosion cracking (SCC) tests at 160 °C and 10 MPa. The results showed that SP-treated super 13Cr could generate high-level compressive residual stress and SPD microstucture, including nano-sized equiaxed grains, gradient lamellar structure and fragmented carbides. Increasing air pressure contributed to achieve uniform nanocrystalline, but tended to generate high dislocation density and surface defects. The improving effect of SP treatment at low air pressure of 0.15 MPa on passivation ability was limited, and high air pressure adversely impacted corrosion resistance. SP-treated specimens showed high SCC susceptibility, due to the introduction of more surface defects, high angle grain boundaries, and dislocations.

Understanding the relationship between faults and underground rivers is crucial for oil and gas exploration. The presence of faults in the Ordovician carbonate rocks plays a significant role in the formation of fracture-cave reservoirs in the Tahe Oilfield that located in Tarim Basin, Northwestern China. In this research, faults analysis and thorough characterization of karst caves and fractures have conducted utilizing the extensive drilling wells and detailed 3D seismic data available in the Tahe area. The results suggest that underground rivers are commonly not found in the higher regions of the paleo-morphology. Multilayer underground rivers are developed in the part of the karst depressions, which is closely related to the nasal structure (anticline on a monoclinic strata) influenced by thrust faults in the center of the study area. The formation and subsequent changes of underground rivers in various ancient watershed are heavily impacted by fault activities. The direction of the watershed and geomorphological zoning, as well as the flow direction of karst water and the water system, are influenced by the activities and tectonic patterns of larger-scale faults. The geometric morphology of the river network system is not strictly limited to larger-sized faults. The activities of small-scale faults, their intensity, the mode of movement and the state of their stress control the development of the local water drainage segments. The morphology of the underground river is influenced by the morphology, fault activities, and the control of the floating diving surface. These factors play a role in shaping and transforming the underground river after its formation. These findings contribute to the study of reservoir connectivity and oil and gas distribution patterns in multi-layered underground river caves.

This study endeavors to formulate a comprehensive methodology for establishing a Geological Knowledge Base (GKB) tailored to fracture-cavity reservoir outcrops within the North Tarim Basin. The acquisition of quantitative geological parameters was accomplished through diverse means such as outcrop observations, thin section studies, unmanned aerial vehicle scanning, and high-resolution cameras. Subsequently, a three-dimensional digital outcrop model was generated, and the parameters were standardized. An assessment of traditional geological knowledge was conducted to delineate the knowledge framework, content, and system of the GKB. The basic parameter knowledge was extracted using multiscale fine characterization techniques, including core statistics, field observations, and microscopic thin section analysis. Key mechanism knowledge was identified by integrating trace elements from filling, isotope geochemical tests, and water-rock simulation experiments. Significant representational knowledge was then extracted by employing various methods such as multiple linear regression, neural network technology, and discriminant classification. Subsequently, an analogy study was performed on the karst fracture-cavity system (KFCS) in both outcrop and underground reservoir settings. The results underscored several key findings: (1) Utilization of a diverse range of techniques, including outcrop observations, core statistics, unmanned aerial vehicle scanning, high-resolution cameras, thin section analysis, and electron scanning imaging, enabled the acquisition and standardization of data. This facilitated effective management and integration of geological parameter data from multiple sources and scales. (2) The GKB for fracture-cavity reservoir outcrops, encompassing basic parameter knowledge, key mechanism knowledge, and significant representational knowledge, provides robust data support and systematic geological insights for the intricate and in-depth examination of the genetic mechanisms of fracture-cavity reservoirs. (3) The developmental characteristics of fracture-cavities in karst outcrops offer effective, efficient, and accurate guidance for fracture-cavity research in underground karst reservoirs. The outlined construction method of the outcrop geological knowledge base is applicable to various fracture-cavity reservoirs in different layers and regions worldwide.

An integration of outcrop observations,as well as data from drilling,logging,and seismic surveys in an oilfield is applied to analyze the filling types and filling cycle assemblages of karst caves associated with paleokarst buried rivers;accordingly,the filling sequences and patterns of the paleokarst buried rivers,as well as the discussion on their petroleum geological implications.The results show that the Ordovician buried-river karst caves with a filling rate of 89.9%in the Tahe oilfield,are predominantly filled with sandy mudstones and collapse breccias.These karst caves host multiple combination cycles featuring coarse-grained lower parts and fine-grained upper parts,which can be classified into polycyclic sedimentary assemblages and polycyclic collapse-sedimentary assemblages for filling.The former is distributed in the karst slope's lower reaches of flat landform,where wells with lost circulation and stringers account for small and high proportions,respectively.In contrast,the latter is situated in the karst slope's upper reaches featuring landform of great drops,where wells with lost circulation are of high proportion together with multiple high-yielding wells.The following conclusions can be reached through analysis:(1)The tortuous spatial structure of buried rivers,combined with their strong runoff transport capacity,facilitate the filling of large amounts of karst detrital materials,resulting in an extremely high filling rate;(2)The seasonal fluctuations in the phreatic surface lead to the formation of cyclic and comparable fillings.This,coupled with water erosion and tectonic activities,gives rise to multi-phase collapses of karst caves.Consequently,polycyclic collapse-sedimentary filling assemblages are formed in the upper reaches,with unfilled spaces developed;(3)The relatively closed underground environment supersaturated with calcium carbonate,results in severe calcareous cementation of fillings,decreasing the intergranular porosity;(4)The unfilled spaces serve as the major targets with potential for oil and gas exploitation.

Based on core observation, thin section examination, fluid inclusions analysis, carbon and oxygen isotopic composition analysis, and other approaches, the structural and burial evolution histories were investigated, and the diagenetic evolution process and genetic/development models were systematically discussed of the Upper Paleozoic Permian clastic rock reservoirs in the Bohai Bay Basin, East China. The Bohai Bay Basin underwent three stages of burial and two stages of uplifting in the Upper Paleozoic. Consequently, three stages of acid dissolution generated by the thermal evolution of kerogen, and two stages of meteoric freshwater leaching occurred. Dissolution in deeply buried, nearly closed diagenetic system was associated with the precipitation of authigenic clay and quartz, leading to a limited increase in storage space. Different structural uplifting–subsidence processes of tectonic zones resulted in varying diagenetic–reservoir-forming processes of the Permian clastic reservoirs. Three genetic models of reservoirs are recognized. The Model I reservoirs with pores formed in shallow strata and buried in shallow to medium strata underwent two stages of exposure to long-term open environment and two stages of meteoric freshwater leaching to enhance pores near the surface, and were shallowly buried in the late stage, exhibiting the dominance of secondary pores and the best physical properties. The Model II reservoirs with pores formed in shallow strata and preserved due to modification after deep burial experienced an early exposure-open to late burial-closed environment, where pore types were modified due to dissolution, exhibiting the dominance of numerous secondary solution pores in feldspar and the physical properties inferior to Model I. The Model III reservoirs with pores formed after being regulated after multiple periods of burial and dissolution experienced a dissolution of acidic fluids of organic origin under a near-closed to closed environment, exhibiting the dominance of intercrystalline micropores in kaolinite and the poorest physical properties. The target reservoirs lied in the waterflood area in the geological period of meteoric freshwater leaching, and are now the Model II deep reservoirs in the slope zone–depression zone. They are determined as favorable options for subsequent exploration.

局部热处理是保证承压设备全寿命周期安全性的重要手段.文中以某二甲苯塔分段筒节为研究对象，提出了一种主副加热分布式热源局部热处理方法，在传统单加热基础上，距离焊缝一定位置施加副加热区，主加热用于改善焊缝微观组织、消除部分残余应力，副加热在焊缝产生反变形，抵消主加热产生的“收腰变形”，消除焊缝内表面残余应力.采用试验、数值模拟和理论分析，建立了主副加热局部热处理有限元模型，研究了副加热带温度、宽度、主副加热间距对应力消除效果的影响规律.结果表明，采用传统单加热热处理方法，降温阶段，焊缝受到拘束作用在内表面产生新的二次应力.主副加热分布式热源局部热处理利用副加热区的反变形，可以在焊缝内表面产生压应力.主副加热带宽度、间距和副加热温度是应力消除效果的关键因素，提出了主副加热局部热处理工程设计方法，为重大承压设备局部热处理提供依据.

The Carboniferous-Permian was an important period for the formation of coal mines and coaly source rocks across the world. Controlled by the paleoclimate, Cathaysia flora, and transitional sedimentary environment of the delta, the Early Permian Shanxi Formation in the Huanghua Depression formed several layers of coal and coaly source rocks that can be explored in the whole depression. However, the development regularity and distribution prediction of high-quality coaly source rocks are still not well understood. The coaly source rocks of the Shanxi Formation in the Huanghua Depression were taken as the research object. With the determination and analysis of organic carbon content, rock pyrolysis, and vitrinite reflectance, we found that the organic matter abundance (i.e., TOC which changed from 20.3 % to 80.0 %), hydrocarbon generation potential (i.e., S1 + S2 which varied from 7.82 mg/g to 208.81 mg/g), and kerogen types (mainly type II2) of the coal were better than carbonaceous mudstone and coaly shale. Maceral component identification indicated that coal and carbonaceous mudstone had more liptinite (i.e. cutinite and sporinite)and hydrogen-rich vitrinite, while coaly shale was mainly composed of hydrogen-poor vitrinite and a small amount of liptinite. The analysis of the ratios of major and trace elements, normal alkanes, and isoparaffin suggested that the paleo-water salinity of coal and carbonaceous mudstone deposition was more than that of part coaly shale. Revealed by the weak reduction of their depositional environment, the development of high-quality coal and carbonaceous mudstone was mostly controlled by the input of oil- and gas-prone organic matter. The formation of high-quality coaly shale was chiefly dominated by a strong reduction environment with an insignificant amount of organic matter input. The formation model of high-quality coaly source rocks was established. This model can be used to predict the distribution of coal mines and coaly source rocks in the Huanghua Depression and Bohai Bay Basin.

为了实现承压设备总装环缝局部热处理，基于中频感应加热技术，研究了超厚板在感应加热过程中的温度分布规律及温度均匀性。热处理过程中均温区的温度均匀性是保证局部热处理效果的关键。以马鞍形厚板为研究对象，进行感应加热试验，利用布置在不同深度的热电偶测量感应加热过程中沿壁厚方向的温度演化曲线。同样，将感应加热应用于加氢反应器筒体，测量感应加热过程中沿轴向方向的温度演化曲线。结果表明：马鞍形厚板在整个感应加热过程中沿壁厚方向最大温差在17℃以内，在保温阶段的最大温差为14.4℃；加氢反应器筒体焊接接头均温区在整个感应加热过程中最大温差在42℃以内，在保温阶段的最大温差为12℃。感应加热温度控制精度能够满足超厚板局部热处理均温性的要求，可在大型厚壁容器局部热处理中推广应用。

微生物降解是浅层原油常见的次生变化,为了简单快捷地确定原油遭受生物降解的程度,提出一种利用饱和烃降解率划分原油生物降解级别的方法.该方法利用生物降解原油的饱和烃色谱图会出现"UCM"峰的特点,在同一比例尺下读取"UCM"峰面积和残留饱和烃包络面积,计算饱和烃降解率,并依此将原油降解级别划分为10个等级.利用该方法对LDW坳陷32个原油样品饱和烃降解率进行计算,并对生物降解级别进行划分.结果表明:LDW坳陷原油生物降解级别分布在1～7级,且不同构造位置原油降解级别存在差异,同一构造不同深度原油的降解级别也不尽相同;总体上中南部(D36-1构造以南)原油降解级别较高,Z25-1构造及其以北原油降解级别较低,原油降解级别随油藏埋藏深度变浅而升高,反映浅埋原油易于降解的特征;该方法步骤简单,且具有分析周期短、成本低、精度高的优点,为定量划分原油生物降解级别提供了高效方法.

塔河油田上奥陶统覆盖区断裂发育特征显著,对碳酸盐岩岩溶缝洞储层的发育控制明显,分析断裂活动与岩溶缝洞发育之间的关系对储层预测具有重要意义.本文运用蚂蚁追踪数据体、地震拓频数据体、地震绕射波叠后偏移数据体及钻测井等资料,对塔河地区T705-S86区块岩溶斜坡上发育的断裂进行了精细解释,利用平剖面组合样式分析了不同时期断裂的运动学动力学特征,配合缝洞体预测结果明确了断裂活动特征对岩溶缝洞发育的影响,认为断裂活动通过影响古地貌和断裂对地表水的沟通来控制储集体发育厚度进而影响单井油气产量.研究结果表明:研究区构造样式复杂,既有走滑断裂样式也有逆冲断裂样式;岩溶期活动强烈并处于局部张性应力状态的花状构造次级断裂和断背斜顶部的次级断裂利于地表水的下渗,会对岩溶地貌进行改造,产生的局部负向地貌部位有利于岩溶作用沿断裂进行,发育优质储集体.相对于裂缝型储集体,溶洞型储集体厚度多超过120 m,单井累计产量超过5X104t,且产量与厚度具有明显正相关关系,其发育部位和储集体厚度对单井的产能具有较大的影响.溶洞分布集中、缝洞储层厚度较大、缝洞之间的连通性较好并且处于相对的构造高点容易发育优质岩溶缝洞储集体.

随着全球能源结构调整及能源利用效率的提高,石化、核电等承压设备日益朝着大型化方向发展,焊接作为一种传统连接工艺,依然是大型承压设备制造的关键技术。然而,焊接不可避免带来残余应力,是引发应力腐蚀、疲劳、断裂等失效的主要原因之一,对承压设备结构完整性及安全服役产生重要影响。因此,有效调控焊接残余应力是保障大型承压设备结构完整性的关键。而焊接残余应力作为一种"看不见、摸不着"的天生缺陷,其精准的计算方法和可靠的测试手段亦是实现其科学有效调控的基础。基于国内外研究成果以及笔者研究团队的研究工作,系统总结了近半个世纪以来在焊接残余应力计算、测试及调控等方面所取得的研究进展,分析工艺、材料与结构仿真三位一体的焊接残余应力集成计算方法研究现状,详细梳理各类焊接残余应力测试方法,总结其优缺点,而后对残余应力调控方法进行分类阐述,重点阐述了最近新出现的残余应力调控方法,并展望发展趋势。

The welding residual stresses (WRS) in a cracked head-cylinder joint of a large rectifying tower were studied by finite element method (FEM) and experimental study. The effects of welding layer sequence, cover welding direction and weld reinforcement have been fully studied. The results showed that the stress concentration and plastic strain accumulation caused by unreasonable welding process and structural discontinuity are the main reasons of cracking. Furthermore, the order of welding layers has a significant influence on the distribution of axial stress: the inside and outside alternating welding process is superior to non-alternating welding process. The direction of cover welding markedly influences the hoop stress: the location of maximum stress is related to the welding start-end position. Besides, the removal of weld reinforcement after welding helps to release subsurface tensile stress and solve the stress concentration problem.

Local post-weld heat treatment (PWHT) is often used for mitigating welding-induced residual stresses in pressure vessels and piping systems. As large and ultra-large pressure vessels are increasingly used in petrochemical and power generation industries, traditional local PWHT procedures stipulated in Codes and Standards become difficult to implement for some of the ultra-large vessels due to their very large diameter and overall length. In this paper, a new method referred to as primary-secondary heating based local PWHT technique (PS-PWHT) is proposed. Both finite element residual stress modeling and experimental residual stress measurements were performed for both validating the effectiveness of the proposed technique and elucidating the underling mechanisms. The results show that the PS-PWHT method can reduce welding-induced residual stresses in a significant manner, even leading to some level of compressive residual stresses at the vessel weld region.

Local post welding heat treatment (PWHT) is a feasible method to eliminate weld residual stress for ultra-large pressure vessels. This paper is focused on the discussion of weld residual stress and deformation for the typical ultra-large mechanical penetration inserted plate (MPIP) during the local PWHT. The reason why the MPIP subjected to local PWHT causes cracking is clarified. A rigid-flexible coordinated control method is proposed to prevent cracking during local PWHT for the ultra-large pressure vessels. The results show that the inconsistent deformation and greater stress concentration in weld toe are the main reason to result in cracking during PWHT. The axial stresses and radial deformation in the welded joints can be reduced by the rigid-flexible coordinated control method. The axial stress is changed to compressive stress, and the radial deformation is reduced by about 58%. And the inconsistent deformation in welded joints during the heat treatment can be obviously improved, which is of great significance to ensure the safe service for ultra-large pressure vessels.

The paleokarst zones developed in the Ordovician Yingshan Formation carbonates represent significant hydrocarbon reservoirs in the Tahe area, western China. In this type of reservoir, the identification of pay zones is problematic. The challenge is due to high uncertainty regarding spatial dimensions, sorting, lithological heterogeneity, and the texture of paleokarst fillings. Therefore, we focus on the physical characterization of these reservoirs using an integrated multidisciplinary approach applied to each filling type. Our methodology includes scanning electron microscopy (SEM) and micro-macroscopic sedimentological analyses, as well as petrophysical evaluations using the borehole image logs (FMI) and dipole sonic imager (DSI). The study specifically focused on three filling types: (i) clastics, (ii) breccia, and (iii) chemical deposits (i.e., chert and calcite cement). We generally recognized these fillings in well core samples recovered from the study area. Our results revealed that the lithofacies with the best features for oil recovery are related to fine-grained sandstones. This lithofacies is characterized by an average effective porosity and permeability range from 5 to 12% and from 5 to 50 mD, respectively. The unfilled crackle breccia and empty cavities also show an average effective porosity and permeability range from 4 to 9% and from 10 to 20 mD, respectively. Although the chert deposits interbedded with carbonates exhibit substantial fracture density, their detection using well logs remains a challenge because of the deposits’ thin thicknesses (around 10–15 cm in vertical scale). Moreover, we highlight how the textural immaturity and high calcite precipitation in the matrix significantly impact the reduction of storage capacity in the chaotic breccia. As a validation method, we compare rock typing results obtained from well logs and core sample data. The outputs show an excellent general correlation between the determined rock types. Finally, we propose a classification scheme for the paleokarst fillings exclusive to the Tahe area.

In the Paleogene Shahejie Formation of Liaodong Bay Depression, two sets of main source rocks are developed, namely the Es1 and the Es3 Formation. In order to determine the characteristics, main controlling factors and patterns of source rock development, firstly, we comprehensively use source rock geochemical and logging data to establish TOC logging prediction models for source rocks in two formations; secondly, we predict the TOC plane distribution of the two layers separately according to the prediction model; then, we use the tectonic subsidence history and sedimentary background data of the study area to analyze its relationship with the source rock development and determine the main controlling factors for the source rock development; finally, the source rock deposition models are established according to the main controlling factors of source rock development. The results show the source rock of the Es1 has high abundance of organic matter, the average TOC of the sample is as high as 2.41%, but the thickness of the source rock does not exceed 130 m; the abundance of source rocks in the Es3 is slightly worse than that of the Es1, the average TOC of the samples is 1.75%, the thickness of source rocks is generally larger, mainly 200-350 m; the rate of tectonic subsidence controls the thickness of the source rock, the amount of fracture extension controls the distribution shape of the source rock, and the degree of water stratification controls the degree of source rock enrichment; in the Es1 Formation, the source rock deposition model is the deposition model of the salinity layered water body in the saline lake basin; in the Es3 Formation, the source rock deposition model is the deposition model of deep water temperature stratification in the separated lake basin. To determine the main controlling factors and depositional patterns of source rock development provides a direction for subsequent exploration of favorable areas.

Abstract Local heat treatment is a widely used to control the welding residual stress for ultra-large pressure vessels due to the upsizing of pressure vessels such as the super-large diameter and overlength. Aiming to effectively reduce the harmful residual stress on the inner surface, a new method called the primary-auxiliary local post-welding heat treatment (PA-PWHT) is proposed in this paper and verified by experiment and finite element analysis. The mechanism for reducing the welding residual stress on the inner wall was also provided. The results show that the thermal deformation during the traditional local PWHT will lead to a secondary tensile stress on the inner surface of the welds, which make the residual stress distribution on the inner face deteriorates after local PWHT. The PA-PWHT method can produce small tensile stress and even compressive stress regardless of the stress distribution on the inner surface or the outer surface. For the typical closed welds studied in this paper, the axial and hoop residual stresses on the inner surface are reduced by 120% and 105%, respectively. It is verified that the proposed method is effective and feasible to implement, and able to suppress the risk of stress corrosion cracking (SCC) of pressure vessels from the perspective of residual stress.