浅层稠油蒸汽吞吐井套管柱应变设计与安全适用性技术研究

发布时间：2018-01-06 10:04

本文关键词：浅层稠油蒸汽吞吐井套管柱应变设计与安全适用性技术研究　出处：《中国石油大学(华东)》2015年博士论文　论文类型：学位论文

【摘要】：在西部浅层稠油蒸汽吞吐热采井中,虽然逐步完善的套管柱强度设计理论使套损得到一定遏制,但随吞吐轮次的增加,套损最终发生,而且使西部油田套损率不断增加。此外,无热采工况下套管适用性技术,也是套损率增加的另一主因。因此,改善套管柱设计和选材水平,增强管柱安全适用性,避免套损,提高吞吐作业轮次,增加生产效益,对于这种低效稠油开发是至关重要的。本文采用材料试验评价、全尺寸工况模拟试验、理论分析与数值模拟计算等方法相结合,研究了热采井套管适用性技术、时域性变形规律、预应力固井技术的适用性以及套管应变设计方法等问题,给出了相应技术指标、适用性评价方法和应变设计理论方法,并形成中华人民共和国石油天然气行业标准,为稠油热采井套管柱设计和安全适用性提供了技术依据,并在现场8口蒸汽吞吐热采井中获得成功应用,证实本文即有理论先进性,又有工程实用性。具体研究工作和得到结论如下:(1)建立了高温下套管强度模型和套管蠕变本构模型,并给出高温下套管强度性能变化的推荐值和最低限蠕变速率变化曲线。热采套管管体和接箍必须采用高匹配设计,管体允许在均匀变形范围内塑性变形,接箍不允许塑性变形。管体在室温下的均匀延伸率,对80ksi钢级最低为8%,对90ksi钢级最低为7%。提出了热采套管需要综合考虑材料强度、形变能力来适应热采工况,明确API标准N80套管不适用于稠油热采。(2)考虑“地层-水泥环-套管”热力耦合模型进行数值计算,发现随蒸汽吞吐轮次的增加,套管柱所受应力基本不变,但套管柱的变形不断增加,说明热采井套管柱变形具有随时间同步递增的规律。与试验结果对比,进一步证实稠油热采井套管柱强度均在安全应力范围内,但管柱实际变形量却不断累积,直至超出允许的变形范围,发生套管损坏。这种时域性变形规律,正是稠油热采井套管套损大量发生的根本原因。因此,在稠油热采井套管柱设计中,仅考虑管柱强度满足要求是不够的,必须考虑套管柱高温蠕变带来的应变累积,即综合考虑应力强度和应变变形进行稠油热采井套管柱设计。(3)套管预应力模拟试验说明套管在长期高温下会出现应力松弛现象,即在稠油热采井中所施加的预应力,经过一定时间后会降低,且API标准N80套管比热采80H套管应力降低更小,最终预应力失效。施加预应力虽会使套管所受Mises应力和Mises应变都降低,对套管起到了一定的保护作用,但这种保护会随时间的延长而消失,最长35天后消失。这也正说明了稠油注蒸汽热采井套损多发生在注蒸汽2轮之后的原因。故建议在浅层稠油热采井中不采用提拉预应力固井技术。(4)结合油田作业工况,利用全尺寸实物加载试验设备,建立了稠油蒸汽热采井套管柱适用性评价技术,即首先通过上卸扣试验确定套管抗粘扣性能,后通过恒位移试验测定套管柱热应力,确定气密封试验的拉伸/压缩循环载荷,然后结合吞吐轮次进行10或更多周次的拉伸/压缩循环气密封试验,或考虑弯曲载荷的多周次拉伸/压缩循环气密封试验,确定套管柱密封完整性,最后进行拉伸至失效试验测定套管柱结构强度,确定套管接箍是否高匹配。并建议在稠油蒸汽热采定向井或水平井中,在直井段推荐选用偏梯形+内平设计螺纹套管,其余井段选用气密封螺纹套管,既保证套管柱的结构和密封完整性,又可降低套管成本。同时,基于试验数据拟合修正了ISO/TR10400标准中的KT计算公式,使其更适用于高钢级套管。(5)结合试验结果,利用弹塑性力学理论,建立了套管柱应变设计模型,并通过套管材料应变与结构应变对比给出了应变安全系数最小取值,明确应变设计的判据,最终形成套管柱应变设计方法。同时,明确提出了套管柱应变设计是在套管柱强度设计的基础上进行的,即套管柱设计应首先进行强度设计,强度设计合格后,再进行应变设计。应变设计方法在西部油田8口稠油热采井中获得成功应用。
[Abstract]:In the shallow heavy oil steam injection wells, the casing the casing strength design theory and gradually perfect to get some curb but with the increase of steam stimulation cycles, casing damage has finally happened, and make the casing damage rate was increased. In addition, no thermal recovery technology for casing under the condition of casing damage is the rate of increase of another reason. Therefore, to improve the design of casing string and material level, enhance the column safety applicability, avoid casing damage, improve work throughput rounds, increase production efficiency, is of vital importance to the development of heavy oil. This paper adopts the inefficient evaluation by material test, full-scale simulation test, the combination of theoretical analysis and numerical simulation study of technology for thermal recovery wells, deformation law of time domain, the problem of pre-stressed cementing technology and applicability of casing strain method, gives the corresponding technical indicators, The applicability of the evaluation method and design theory and method of strain, the formation of People's Republic of China oil and gas industry standards, mining applicability of casing string design and safety provides a technical basis for heavy oil heat, and in the field of 8 steam thermal recovery wells successfully applied, this paper has confirmed the advanced theory and practical engineering. The detailed research work and conclusions are as follows: (1) to establish the model of casing strength under high temperature and creep constitutive model of casing, and given the high temperature performance of casing strength changes the recommended value and the minimum creep rate curve. The tube and collar must be used for the matching design of thermal recovery casing tube allowed in uniform deformation within the range of plastic deformation, the coupling is not allowed plastic deformation. The tube at room temperature, the uniform elongation of 80ksi steel, the lowest level was 8%, the lowest level of 90ksi steel 7%. proposed comprehensive thermal recovery casing Considering the material strength and deformation ability to adapt to the thermal recovery conditions, clear the API standard N80 casing is not suitable for thermal recovery of heavy oil. (2) consider the "stratum cement casing" coupled thermo mechanical model for numerical calculation, it was found that with the increase of steam stimulation cycles, the casing stress is basically unchanged, but the deformation of casing string increase in the description of thermal recovery wells casing deformation with time synchronous increasing law. Compared with test results, further confirmed that the heavy oil thermal recovery wells casing strength in the safe range of stress, but Guan Zhu is the actual deformation accumulation and exceeds the allowable range of deformation, deformation of casing damages. Time domain this law, is the root causes of a large number of well casing damage in heavy oil thermal recovery. Therefore, the thermal recovery of heavy oil well casing string design, considering only the string strength meet the requirements is not enough, must consider the creep of casing The strain accumulation, namely considering the stress intensity and strain deformation of heavy oil thermal recovery well casing string design. (3) casing prestressed simulation test shows that the casing stress relaxation phenomenon will appear under the high temperature, which is applied in prestressed in heavy oil heat, after a certain time can be reduced, and the API the standard N80 80H casing heat stress reduced smaller, eventually prestressed prestressed failure. Although the cause of casing under Mises stress and Mises strain are reduced to a protective effect on the casing, but the protection will disappear with the extension of time, the longest 35 days after it disappeared. The causes of steam injection after 2 rounds of casing damage of heavy oil steam injection. The thermal recovery of heavy oil in shallow layers in the well cementing technology of prestressed pull not used. (4) combined with the working conditions of oil, the full-scale loading test Set up equipment, heavy oil thermal recovery well casing string applicability evaluation technology, firstly through the shackle test to determine the anti galling property of casing, through constant displacement test of casing thermal stress, tensile / compressive cyclic loading test of gas seal, and then combined with the throughput of 10 or more times a week round of stretching the compression cycle / gas seal test, or considering the bending load multi cycle tension / compression cycle gas seal test, to determine the integrity of the casing seal, finally to tensile failure test determination of structural strength of casing, the casing collar is high, OK. And suggestions in heavy oil thermal recovery wells or horizontal wells in the direction. Straight wells recommended buttress thread casing + design, other wells selects sealing thread casing, both to ensure the structure of casing string and seal integrity, but also can reduce the cost of casing. At the same time, based on the test The data fitting and correction in ISO/TR10400 standard KT formula, which is more suitable for high grade steel casing. (5) according to the experimental results, using elastic-plastic mechanics theory, a strain of casing string design model, and through the material and structure of casing strain strain contrast gives strain minimum safety coefficient value, clear strain criterion design, and ultimately the formation of casing strain method. At the same time, clearly put forward the design of casing strain is based on casing strength design, namely the design of casing string should be the first strength design, strength design is qualified, then strain wells design. Design method of strain in the western oilfield 8 heavy oil thermal recovery the success of the application.

【学位授予单位】：中国石油大学(华东)
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TE931.2

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