Risk analysis of extended reach wells in the Liuhua Oilfield,South China Sea,based on comprehensive fuzzy evaluation method

Drilling engineering has great uncertainty and it always involves huge investment and high risk. Risk analysis of extended reach drilling （ERD） is very important to prevent complex failures and to improve drilling efficiency. Nowadays there are few reports on how to analyze quantitatively the drilling risk for extended reach wells （ERWs）. Based on the fuzzy set theory, a comprehensive fuzzy evaluation model for analyzing risks of ERD is proposed in this paper. Well B6ERW07 is a planned 8,000-meter ERW with a high ratio of horizontal displacement （HD） to vertical depth （VD） in the Liuhua Oilfield, the South China Sea, China. On the basis of the evaluation model developed in this study, the risk for drilling Well B6ERW07 was evaluated before drilling. The evaluation result shows that the success rate of drilling this well is predicted to be 51.9%, providing important rational and scientific information for the decisionmakers.

Limit analysis of extended reach drilling in South China Sea

Extended reach wells （ERWs）, especially horizontal extended reach well with a high HD （horizontal displacement） to TVD （true vertical depth） ratio, represent a frontier technology and challenge the drilling limitations. Oil and gas reservoir in beaches or lakes and offshore can be effectively exploited by using extended reach drilling （ERD） technology. This paper focuses on the difficult technological problems encountered during exploiting the Liuhua 11-1 oil field in the South China Sea, China. Emphasis is on investigating the key subjects including prediction and control of open hole limit extension in offshore ERD, prediction of casing wear and its prevention and torque reduction, φ244.5mm casing running with floating collars to control drag force, and steerable drilling modes. The basic concept of limit extension in ERD is presented and the prediction method for open hole limit extension is given in this paper. A set of advanced drilling mechanics and control technology has been established and its practical results are verified by field cases. All those efforts may be significant for further investigating and practicing ERD limit theory and control technology in the future.

A numerical method for determining the stuck point in extended reach drilling

A stuck drill string results in a major non-productive cost in extended reach drilling engineering. The first step is to determine the depth at which the sticking has occurred. Methods of measurement have been proved useful for determining the stuck points, but these operations take considerable time. As a result of the limitation with the current operational practices, calculation methods are still preferred to estimate the stuck point depth. Current analytical methods do not consider friction and are only valid for vertical rather than extended reach wells. The numerical method is established to take full account of down hole friction, tool joint, upset end of drill pipe, combination drill strings and tubular materials so that it is valid to determine the stuck point in extended reach wells. The pull test, torsion test and combined test of rotation and pulling can be used to determine the stuck point. The results show that down hole friction, tool joint, upset end of drill pipe, tubular sizes and materials have significant effects on the pull length and/or the twist angle of the stuck drill string.

Prediction of casing wear in extended-reach drilling

Intermediate casings in the build sections are subject to severe wear in extended-reach drilling. This paper presents a new method for predicting the depth of a wear groove on the intermediate casing. According to energy principle and dynamic accumulation of casing wear by tool joints, a model is established to calculate the wear area on the inner wall of the casing. The relationship functions between the wear groove depth and area are obtained based on the geometry relationship between the drillstring and the wear section and the assumption that the casing wear groove is crescent-shaped. The change of casing wear groove depth versus drilling footage under different-sized drillstrings is also discussed. A mechanical model is proposed for predicting casing wear location, which is based on the well trajectory and drillstring movement. The casing wear groove depth of a planned well is predicted with inversion of the casing wear factor from the drilled well and necessarily revised to improve the prediction accuracy for differences between the drilled well and the planned well. The method for predicting casing wear in extended-reach drilling is verified through actual case study. The effect of drillstring size on casing wear should be taken into account in casing wear prediction.

Annual Output of Five Horizontal Wells Reaches One Million Tons

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防漏堵漏低密度水泥浆技术

跃进3-3XC井完钻井深达9432 m,水平钻进距离超过3400 m,刷新了亚洲最深和超深水平大位移井的纪录。该井地质结构复杂,施工难度大,对水泥浆性能要求高,除了高温、高压外,地层承压能力低,极易发生漏失。针对此类问题,通过研发新型功能性材料,构建了C-Lo PSD(1.30 g/cm^(3))、C-Lite STONE(1.60 g/cm^(3))与C-Hi PSD(1.40 g/cm^(3))三套低密度水泥浆体系,涵盖了中低温、高温等应用条件,并在跃进3-3XC井中成功应用,水泥浆性能满足固井需求。与之前用水泥浆体系相比,混浆效率、流变性、悬浮稳定性、水泥石抗压强度等明显提升。其中,C-Lite STONE(T_(BHC)=75℃/T_(TOC)=30℃)与C-Hi PSD(T_(BHC)=145℃/T_(TOC)=105℃)水泥浆体系在温差分别为45℃和40℃下,顶部48 h抗压强度达到8.1 MPa和14.3 MPa。跃进3-3XC井在施工期间多次遭遇漏失,通过使用自研的新型堵漏材料C-B62和C-B66,成功封堵裂缝,保证了固井施工的顺利进行。

硫化脂肪酸酯的合成及其在高温高压钻井液中的应用

大位移井高温储层水基钻井液在高负荷、高盐度、高温条件下,液体润滑剂的润滑性能不足,导致憋钻具、卡钻和钻具磨损等问题,实验室合成了一种硫化脂肪酸酯,将其与润滑剂复配后得到复合硫剂(QT311),添加至HTFlow高温高压水基钻井液中,能够提升钻井液的润滑性能。通过四球试验机测试可知,添加1%QT311后,其COF能够下降64%,磨斑直径降低43%,润滑性能优于几款常用市售钻井液用润滑剂。通过电镜分析摩擦副表面,发现硫剂在摩擦过程中发生摩擦化学反应生成硫-铁极压膜,从而提升钻井液的减摩性能,且该剂在HTFlow钻井液体系中表现出优异的配伍性、抗水解性能、抗盐及抗温性能。试验结果为钻井液用润滑剂的进一步研究提供参考。

聚胺复合盐润滑防塌钻井液在樊斜166大位移井的应用

樊斜166井位于济阳拗陷东营凹陷博兴洼陷高青断层下降盘樊斜166块,为中国石化胜利石油工程有限公司油气勘探管理中心重点评价井。区块地层岩性复杂,该井设计井深5664.07 m,井底井斜近60°,水平位移近3000 m,井底温度近190℃,钻井施工中钻井液维护井壁稳定、井眼净化及润滑防卡技术难度大。为此,针对该区块地层岩性特点及施工技术难点,制订了樊斜166井钻井液技术对策,并通过钻井液处理剂优选,构建了聚胺复合盐润滑防塌钻井液体系,进行了评价实验与现场应用,均获良好结果。评价实验结果表明,该钻井液体系不仅抑制性能好、封堵能力强,而且具有良好的润滑性和抗温性,在190℃仍保持良好的流变性。现场应用结果表明:①在相应的钻井液现场维护处理工艺辅助下,聚胺复合盐润滑防塌钻井液实现了优快钻井;全井钻井时效高,实钻周期仅54.5 d,比设计钻井周期提前了39.4%;平均机械钻速12.89 m/h,创区块同类型井机械钻速新纪录。②聚胺复合盐润滑防塌钻井液体系解决了该区块大位移井钻井过程中易出现的井壁失稳、井眼净化及润滑防卡的难题;钻进过程中井壁稳定,三开井段井径平均扩大率仅为3.16%;井眼净化良好,钻井液高温下悬浮携带能力强;润滑防卡性好,定向过程中摩阻和扭矩低,起下钻畅通无阻,完井作业顺利。该钻井液体系的成功应用,为区块的后续钻探开发提供了技术支撑,对其他区块相似大位移井的钻井液构建亦有参考意义。

对FETKOVICH(费特科维奇)典型曲线的质疑与评论

FETKOVICH(费特科维奇,以下简称为费氏)于1971年和1980年,分别提出的有限水域水侵量方程和定压典型曲线,受到国内外专家的重视和引用。由于费氏典型曲线可以通过实际数据的拟合,确定井的驱动半径和驱动面积,因此,受到业内专家的青睐。通过推导表明,费氏有限水域水侵量方程,是一个指数递减方程。费氏将该方程直接应用于定容封闭边界油井的产量递减分析,并基于初始递减率的关系式,得到了费氏典型曲线的无因次时间。费氏利用无因次压力的倒数作为无因次产量,得到了典型曲线的无因次产量。然而,由于费氏典型曲线的无因次时间和无因次产量之间没有直接的函数关系,无法建立费氏的无因次典型曲线,因此,对费氏的有限水域水侵量方程和典型曲线的无因次时间和无因次产量进行了推导,并对存在的问题提出了质疑和评论。

基于对数型障碍Lyapunov函数的俯仰驾驶仪设计

相控阵雷达制导拦截弹在拦截高速大机动目标时,弹体气动参数剧烈非线性变化影响控制系统对大攻角的响应效果,应设计考虑攻角指令跟踪误差约束的鲁棒自动驾驶仪控制律。基于双幂次趋近律和对数型障碍李雅普诺夫函数设计了鲁棒非线性自动驾驶仪控制律,可将攻角指令的跟踪误差快速收敛于约束范围内。通过降阶扩张状态观测器对系统中存在的气动参数不确定性和系统外部扰动进行在线估计和补偿。稳定性分析和数值仿真表明,攻角可在1 s内达到稳态且攻角响应的稳态误差<10-4°,所提出的自动驾驶仪控制律具有较强的鲁棒性,能够准确稳定地跟踪攻角指令,控制导弹产生所需过载进而精准拦截目标。

径向井辅助前置液酸压裂缝扩展数值模拟

基于扩展有限元及双尺度连续模型理论建立径向井辅助前置液酸压裂缝扩展模型,引入偏离系数作为量化评价指标,分析各因素对裂缝形态的影响,并利用灰色关联分析方法明确主控因素。结果表明:径向井对前置液酸压裂缝扩展具有显著引导作用,裂缝优先沿径向井方向起裂并扩展一定距离,而后逐渐偏向最大水平主应力方向;径向井方位角、水平地应力差和地层弹性模量越小,径向井长度越长,偏离系数越小,径向井引导效果越好,其中水平地应力差为主控因素;当径向井方位角为15°时,前置液酸压裂缝沿着径向井方向扩展14.32 m后偏向最大水平主应力方向,径向井的引导效果最好,偏离系数为0.005。

Numerical simulation of cementing displacement interface stability of extended reach wells

The well cementing is important during the extended reach well drilling and the completion, whereas the displacement efficiency and the interface stability are important to guarantee the success of the cementing. In this paper, the interface stability of the cement slurry is simulated using the computational fluid dynamics software. The calculation results indicate that during the displacement, the length of the displacement interface increases with the increase of the deviation angle. The larger the eccentricity, the more significant the velocity difference, along with a longer displacement interface length, a less stable interface, and a lower displacement efficiency. Therefore, to guarantee the cementing quality and maintain a high displacement efficiency, the eccentricity should be controlled within 0.5. Application of a casing centralizer will dramatically improve the interface stability, decrease the dilution zone length of the interface and thus, is beneficial to the slurry cementing and displacement. The simulations are verified with an average absolute deviation less than 3.76% and the 45？ helix angle of the rigid centralizer is recommended. Combining the data of an extended reach well on-site, methods are proposed for improving the displacement efficiency and the interface stability during the well cementing and displacement with complex boreholes. These numerical methods can be used to provide some theoretical guidance for designing the cementing of an extended reach well.

海洋石油工程发展的思考

俄乌冲突等地缘政治影响叠加全球通胀,油气能源价格持续高位震荡,面对日益紧张的能源供需关系,亟需从战略视角出发,关注海洋油气增储增产,中国石化滩浅海领域初具一定规模和实力,但中深海工程技术与装备尚有差距。该文从钻完井、海洋工程、新能源等几个方面深入分析了国内外海洋石油工程行业发展现状以及中国石化中深水自营区块勘探开发的需求,并结合未来海上新能源发展,提出了中国石化海洋石油工程下一步发展的方向和路径。为培育具有中国石化特色的海洋石油工程技术体系,做精做强海洋石油工程提供参考。

基于滑模自抗扰的储能变流器控制策略

为了提高储能变流器(PCS)的动态性能,设计基于降阶级联扩张状态观测器(ESO)和互补滑模控制(CSMC)的改进自抗扰控制(ADRC)策略,将改进ADRC策略应用于PCS的双向DC/AC变流器电压外环.改进ESO为降阶级联ESO以提高状态变量和系统总扰动的估计速度,增加扰动估计能力;更改PD控制为CSMC以设计状态误差反馈律,提升PCS的系统鲁棒性;设计改进指数趋近律以抑制抖振现象.为了证明改进ADRC策略相较于PI控制和传统ADRC的优越性,建立仿真模型并搭建相关实验平台.仿真与实验结果表明,改进ADRC策略减小了PCS暂态时直流母线电压波动,提高了PCS交流侧功率响应速度,改善了交流侧的输出电能质量.

面向永磁同步电机负载转矩观测的自抗扰改进滑模控制

针对传统永磁同步电机滑模控制中存在的滑模抖振大及响应速度慢的问题,设计了一种新型趋近律,在传统指数趋近律的基础上加入可变比例系数并引入系统状态变量和滑模面的幂次项,减小抖振的同时提高了趋近速率。随后,为了避免引入转速误差的微分项,减小系统高频抖振,采用积分滑模面,设计了永磁同步电机改进滑模速度控制器。针对控制策略中负载扰动波动会导致系统控制精度降低、抖振增大的问题,设计了一种基于新型饱和函数的扩张状态观测器估计负载扰动,并将扰动估计值前馈至改进滑模控制器中,进一步提高了系统的抗扰性能。数值仿真结果表明:所提出的控制策略可显著提高电机动态性能和抗扰性。在电机受负载转矩波动影响时,比PI控制电机超调量减小约23.1%,响应速度提高62.5%,比传统滑模控制电机超调量减小约15.3%,响应速度提高50%。新型滑模趋近律还可以有效降低滑模抖振,与传统滑模控制器相比,采用改进滑模控制器电机抖振降低约50%。

海上CO_(2)回注大位移井工程关键技术研究

CO_(2)回注实现碳捕获和储存是海上油气领域践行“双碳”目标的有效途径之一。针对我国海上CO_(2)回注首口大位移井存在的埋藏浅导致承压能力低、井壁稳定性差、浅地层高造斜率所致的定向钻井轨迹控制难、高浓度高压力超临界CO_(2)对井筒的完整性要求高等技术问题,基于南海东部前期大位移井设计和作业经验,通过理论分析、工程设计和技术攻关,形成了钻井液体系“复合固壁”、浅层大位移井ECD精控、浅地层高造斜率井段定向控制等技术,并构建了多套耐CO_(2)腐蚀的固井水泥浆体系。技术研究成果成功应用于E-X井工程,该井完钻井深3709 m、水平位移3212.96 m、垂深894.31 m,井壁稳定性和井筒完整性良好,满足了CO_(2)回注相关技术要求。研究成果积累了海上CO_(2)回注大位移井工程技术经验,填补了国内海上CCS技术及其应用的空白。

南海东部浅层大位移井聚合物钻井液优化研究与应用

南海东部恩平油田浅层大位移井钻遇层位浅,地层胶结疏松,泥岩含量高,钻井过程中存在钻井液增稠、井壁失稳、循环当量密度升高诱发井漏、摩阻扭矩大等问题。优选了低分子量酰胺基聚合物PF-BIOCAP、胺基聚合物PF-UHIB和硼酸酯复合植物油PF-EXLUBE以改善聚合物钻井液包被抑制性、造浆抑制性和润滑性。评价结果表明,优化后钻井液泥岩滚动回收率达到96%,经(w)15%泥岩钻屑污染后表观黏度上升率明显下降,摩擦系数和泥饼黏滞系数均低于0.1,表现出优异的抑制性和润滑性,且流变性能满足井眼清洁要求。该聚合物钻井液体系在恩平油田浅层大位移井中取得了良好的应用效果,解决了泥岩井壁失稳、泥岩岩屑造浆和高摩阻扭矩等技术难题,对海上浅层大位移井的推广应用具有指导意义。

非均质致密储层水平井分段压裂裂缝扩展模拟

针对非均质致密储层水平井分段压裂时裂缝的扩展延伸导致不同压裂缝簇产量差异大的问题,在考虑压裂液排量、黏度和地应力特征的情况下,开展非均质致密储层真三轴水力压裂实验和数值模拟研究,分析非均质岩石水平井分段压裂多裂缝扩展规律。结果表明:非均质性强的致密储层在水平井分段压裂时会产生不均一的裂缝形态,低两向水平应力差会强化储层非均质对裂缝形态差异性的影响,压裂液黏度对非均质储层改造时裂缝的形态影响相对较小,高弹性模量区域裂缝扩展相对更充分;数值模拟则证实储层非均质性会增加应力干扰的影响程度,通过改变弹性模量、压裂液排量等压裂参数均可以实现裂缝扩展的起裂扩展调控,因此对于非均质性较强的储层而言,有必要通过限流法或者暂堵等其他工艺手段进行水平井分段压裂施工,其中限流法可以保证不同位置的裂缝可以均衡进液,实现段内裂缝的同步和充分扩展,暂堵压裂则可以实现储层的充分打碎。研究成果有助于指导不同改造思路下的水平井压裂工艺优选。

大位移井岩屑床厚度预测模型与现场应用:以CH1-1-XX井钻井为例

大位移井钻井过程中,岩屑极易在斜井段及水平段环空底部积聚成床,导致憋泵、卡钻等事故,严重影响钻井施工安全和钻井时效。现有的岩屑运移及岩屑床清除模型均针对标准圆球状岩屑,与实钻中返出的岩屑形状差异较大,导致模型应用范围受限,无法提供更准确的现场指导。为探究大位移井非标准圆球状岩屑运移规律,通过可视化岩屑运移实验与计算流体动力学(computational fluid dynamics,CFD)数值模拟结合的方法,建立了一套大位移井岩屑床厚度预测经验模型,并在CH1-1-XX井开展了现场应用,对不同开次下的钻进参数进行了优化,取得了良好效果。结果表明:利用模型预测岩屑床厚度并进行钻进工艺参数优化后,一开与二开钻井时最高岩屑床厚度分别为40.6 mm和33.9 mm,均低于同井深处的岩屑床厚度安全线,表明井眼清洁程度高,无憋卡风险。建立的岩屑床厚度预测经验模型对提高大位移井井眼净化效率,保障大位移井安全高效钻进具有重要意义。

基于自抗扰滑模控制的开关磁阻电机转矩分配控制策略

针对开关磁阻电机运行时存在的转矩波动大与外部干扰下电机运行不稳定等问题,该文提出了一种基于自抗扰滑模控制的开关磁阻电机转矩分配控制策略。由于传统滑模控制中趋近律采用的符号函数引起系统振荡频率高,造成被控对象抖振大,该文采用新型滑模趋近律,用平滑函数代替符号函数,并引入状态变量,同时提升了响应速度并降低抖振;此外,为了解决开关磁阻电机外部干扰对电机运行带来的稳定性问题,该文设计了一种自抗扰扩张状态观测器,这种观测器可以实现对负载扰动的实时观测,将观测值作为滑模速度控制器的前馈补偿,减小电机固有参数不确定对控制系统的影响。最后,通过仿真和实验验证了所提出的方案能够有效地改进控制系统在不同工况下的动态性能。