充气钻井井筒流动稳定性研究.pdf

[ 收稿日期] 2009 11 08 [ 基金项目] 国家 863 计划项目 2006AA06A109 4 。 [ 作者简介] 夏宏南 1962 , 男, 1982 年江汉石油学院毕业, 博士, 教授, 中国石油学会会员, 硕士研究生导师,现主要从事钻 头、钻井工艺和钻井仪器等方面的研究开发工作。 充气钻井井筒流动稳定性研究 夏宏南 长江大学石油工程学院, 湖北 荆州 434023 韩先柱 新疆油田分公司井下作业公司钻井项目部, 新疆 克拉玛依 834000 朱忠喜 长江大学石油工程学院, 湖北 荆州 434023 [ 摘要] 以气液两相流理论为基础, 分析了充气钻井的井筒压力分布问题。针对井筒压力分布对井眼尺寸 的敏感性, 给出了注气量计算方法。对井底压力和注气压力随井眼尺寸变化的情况进行了分析, 给出了 注气量与井筒压力分布的关系, 并对其变化情况进行了解释。在满足携岩的前提下, 大井眼所需的注气 量与小井眼之间存在差别, 同时指出了采用复合式井眼进行充气钻井的优势。所得结论对指导和实施欠 平衡钻井作业和研究具有一定的理论参考价值。 [ 关键词] 充气钻井; 注气量; 井底压力; 复合井眼 [ 中图分类号] TE242 6[文献标识码] A [ 文章编号] 10009752 2009 06 0123 04 充气钻井时使气体以气泡状态均匀分散于钻井液中,从而降低环空当量密度,这样可以减少井底压 差、发现和保护储层, 同时还可以安全钻过严重水敏性地层及漏失严重的地层, 避免大量钻井液漏失, 降低了钻井成本。充气钻井在以往难钻地层得到了很好的应用, 其优越性也得到了充分的体现。 由于充气钻井最简单最常用的注气方式就是钻杆内注气,而钻杆内注气时全井筒内含有可压缩气 体,流动状态复杂,钻杆内呈现气液两相流动状态,环空内呈现气液固三相流动,使得环空压力分布复 杂化, 这将直接影响井底压力稳定性,所以必须保持充气钻井过程中井筒流动处于稳定状态, 从而确保 井底压力和携岩效率稳定。因此,对充气钻井井筒流动稳定性研究将有助于充气钻井工程设计和现场施 工。井筒流动稳定的标准就是流量在一定范围内变化时井筒内的流动状态不会发生突变, 也就是流动状 态对影响参数不敏感。在充气钻井工程设计中对注气量的设计是至关重要的,因为在钻井液排量一定的 条件下,维持井筒流动稳定的条件主要集中在井眼尺寸和注气量。下面就结合流体力学的基本理论,分 析充气钻井井筒流动稳定状态, 即分析井底压力和井眼尺寸与注气量之间的关系。 1 井筒流动模型及井底压力计算方程 充气钻井中常见的注气方式是钻杆内注气,因此在研究井筒流动时,就以此为基础来进行。充气钻 井井筒流动模型如图 1所示。由于充气钻井时,井筒内不但有钻井液而且还有注入井筒内的可压缩性气 体,而井筒轴向上不同深度处的压力和温度都将不同, 注入的气体受气体状态方程的影响会发生相应的 变化, 因此充气钻井的井筒内为多相流动状态,流体 尤其是气体 物性参数随井深而变化。 整个井筒内流动问题的计算过程为 在已知循环系统出口处的压力和温度条件下,逆着流动方向从 井口沿环空向下推导计算流动方程, 然后到达钻头喷嘴, 再到钻柱内向上直到地面。 在环空内任一截面 如图 1 所示 处的压力为 P, 温度为 T , 该位置的深度为 h。 则该截面的压力梯度为 dP g 1 f v 2 2g dh- dp dh 1 式中, P 为计算截面压力, MPa; 为计算截面混合物密度, kg/ m3; g 为重力加速度, m 2/ s; f 流动摩阻系数, 123 石油天然气学报 江汉石油学院学报 2009年 12 月 第 31 卷 第 6 期 Journal of Oil and Gas Technology J JPIDec 2009 Vol 31 No 6 图 1 充气钻井井筒流动模型 无因次; v 为计算截面混合物流速, m/ s; h 为计算截面深度, m; dh、 dp为井眼内径和钻柱外径, m。 通常都是以地面大气压和温度为参照, 结合气体状态 方程将地面气体体积流量 QgG换算成计算截面处对应压力 P 和温度T 下的真实气体体积流量 QgPT QgPT PGT PTGQ gG2 式中, PG为地面条件下的压力, MPa; TG为温度, K; QgG为 气体体积流量, m3/ s; T 为温度, K; QgPT为气体体积流量, m3/ s。 应用式2 可得环空内混合物的体积流量 QPT计算公 式为 QPT QginPT QgFPT QlF Qm Qr PGT PTG QginG QgFG QlF Qm Qr 3 式中, QPT为环空内混合物的体积流量, m 3/ s; QginPT 为折算到计算截面处的注气量, m3/ s; QgFPT为地层产 出气体折算到计算截面处的体积流量, m3/ s; QlF为地层产液量, m3/ s; Qm为钻井液流量, m3/ s; QginG为折 算到地面条件下的注气量, m 3 / s; QgFG为地层产出气体折算到地面条件下的体积流量, m 3 / s; Qr为岩屑体 积流量, m 3/ s。 环空内计算截面处混合物流速计算公式为 v QPT 4 d2h- d2p 4 环空内计算截面处混合物密度为 M QPT 5 式中, M 为混合物质量流量, kg/ s。 将式3 5 代入式1 后, 积分, 整理可得 PbH Pat dP M PGT PTGQginG QgFG QlF Qm Qr g 1 f 2gdh- dp PGT PTG QginG QgFG QlF Qm Qr 4 d2h- d2p 2 H 0 dh 6 式中, PbH为井底压力, MPa; Pat为地面大气压, MPa; H 为积分井段深度, m。 从式6 可知, 注气量与井眼尺寸井眼直径、 钻柱外径和井深 和压力之间是相互制约的, 通常采用 数值迭代的计算方法对式6 求解。 从井口逐渐向井底计算过程中, 井深 h 逐渐增加, 井眼尺寸也在变化。 这样逐步进行求解, 可以得到注气量和井眼尺寸和井底压力之间的影响关系。 2 井底压力与注气量的关系 在井眼尺寸和钻井液流量一定的情况下, 井底压力与注气量的关系如图 2 所示。压力变化区间可以 分为两个部分静压控制区和摩阻控制区。在静压控制区内, 静液柱压力是影响井底压力的主导因素, 注气量的变化对井底压力的影响非常敏感;而在摩阻控制区内, 摩擦阻力产生的压降对井底压力的作用 占主导地位, 注气量的增加对井底压力的影响不显著, 是相对稳定的区域。因此可将两个控制区从拐点 处划分开, 把井底压力受注气量的影响关系表示为 124石油天然气学报江汉石油学院学报2009 年 12 月 PbH PbH1Q PbHc, 0 Q PbHc, Qopt Q 7 式中, PbHc为临界井底压力, MPa; Qopt为最优注气量, m3/ s; PbH1、 PbH2分别为静压控制区和摩阻控制区受 流量影响的井底压力, MPa。 图 2 井底压力与注气量关系曲线 在进行充气钻井工程设计时, 一般要求尽量将注 气量控制在摩阻控制区内, 这样井底压力受注气量的 影响不显著, 有利于维持井底压力稳定。但是由于摩 阻控制区内要求的注气量较大,因此为了既能满足充 气钻井时井筒流动状态能在摩阻控制区内工作,又能 避免注入的气量不出现太大浪费, 在充气钻井工程设 计时, 注气量通常选择在临界点处对应的气体流量为 最优注气量。加之,充气钻井属于欠平衡钻井的一个 分支, 在实施充气钻井过程中, 若有地层流体产出, 尤其是气体产出, 那么井筒内的气体增多会使得流动 处于摩阻控制区, 而不会导致过大的井底压力波动。 但是若地层产出的是水或油, 那么在施工允许的条件 下还是要尽量增大注气量。 从上面的分析可知,在井眼尺寸和钻井液流量一定的条件下,为了维持井筒内流动状态稳定, 就对 应一个临界注气量值。由于充气钻井中钻井液的流量设置主要目标是满足最小携岩能力, 注入气体的主 要目的是降低钻井液环空当量密度, 因此当井眼尺寸发生变化时,钻井液流量和注气量临界值必然要发 生相应改变, 才能保证在井底压力达到设计要求的同时,实现井筒内流动状态稳定。 3 井眼尺寸与注气量之间的关系 充气钻井时既要实现携岩要求, 又要实现所需要达到的稳定井底压力值。那么在设计充气钻井井身 结构时,还要考虑最经济合理的注气参数和钻井液流量。因此在地层和现场施工能够满足的条件下,优 化设计井身结构, 使充气钻井的井筒流动状态达到最佳状态的同时, 实现最经济的工程效益。下面以实 例计算进行相应的讨论,分析井眼尺寸对注气量的影响。 3 1 环空过流面积对注气量的影响 在井深为 1700m,井眼尺寸分别为3112mm 和 152 4mm 的井身结构条件下,对注气量与井底 压力之间的关系进行了计算,结果如图 3 和图 4 所示。 从图 3 和图 4可以看出,当井眼尺寸处于大井眼时,只要注气量足够大,可获得较低的井底压力, 环空压力分布受摩阻控制的影响程度比较小,主要是处于静压控制区。而小井眼很容易进入摩阻控制 区,井底压力对注气量比较敏感。 3 2 复合井眼对注气量的影响 结合上面的井身结构特点,用315 3mm 套管与 152 4mm 井眼进行复合形成复合井眼。在其他 参数相同条件下, 计算井底压力和环空当量密度的分布与注气量关系, 结果见图 5 和图 6。 从图 4 和图 5上分析可知, 与大井眼相比,在同样的注气量条件下采用复合井眼时环空摩阻较小, 可以获得较低的井底压力和注气压力。也就是采用复合井眼更容易在较小注气量条件下实现降低井底压 力的目的。从图 6中分析可知, 采用复合井眼时, 充气钻井液的环空当量密度有较大地降低。这主要是 由于在复合段上部环空截面增大,减缓了环空中充气钻井液的上返速度。同时, 也抑制了摩阻压降的强 势增长,使得环空段受摩阻控制的情况减弱, 静压控制作用增强。 125第 31 卷第 6 期夏宏南等 充气钻井井筒流动稳定性研究 4 结 论 1 充气钻井时, 井底压力所处的控制区域的稳定性不同,大井眼更容易进入静压控制区,井底压 力对注气量大小不敏感,小井眼易进入摩阻控制区,井底压力对注气量大小非常敏感。 2 复合式或横向井眼尺寸变化台阶较大时,更有利于在较小注气量条件下控制充气钻井的井筒流 动状态稳定, 提高携岩效率和维持井底压力稳定。 [ 参考文献] [ 1] William C L, Boyun Guo, Frank A S Air and gas drilling manual [ M] New York The McGrawHill Companies, 2001 [ 2] Supon S B, Adewumi M A An experimental study of the annulus pressure drop in a simulated air drilling operation [ J] SPE 19334, 1989 [ 3] 刘刚, 朱忠喜, 张迎进, 等 空气钻井中的压力及注气量问题研究 [ J] 钻井工艺, 2005, 28 2 4 6 [ 4] 马光长, 李向碧, 杨勋建 充气流体钻井技术在矿 2 井的应用 [ J] 钻井工艺, 2004, 27 1 4 5 [ 5] 周英操, 王广新, 赵德云, 等 充气钻井技术在大庆油田的应用 [ J] 探矿工程 岩土钻掘工程 , 2006, 40 9 51 54 [编辑] 萧 雨 126石油天然气学报江汉石油学院学报2009 年 12 月 Abstract The tight clastic reservoirs of the Eogene ation, w hich had the character of lowporosity and low perme ability, were greatly grown in Kuche Region, Tarim Basin On the basis of experimental data, for the needs of fine res ervoir uation, the main geological factors of m exponent and nexponent the exponents of Archie ula were ana lyzed qualitatively, including the geological factors of porosity, average grain size, calcite cement, gypsum cement By geological statistics, the qualitative correlation between m, nand major influential factors are determined T he values of m and nare continuously calculated by using logging data, and oil and gas saturation is consequently calculated Applica tion show s that this is used for improving the adaptability of Archie ula and precision of saturation ua tion Key words m exponent; n exponent; hydrocarbon saturation; lowporosity and lowpermeability reservoir; Kuqa Region; Tarim Basin 104 A of Project Mapping for Correcting Mud Invasion and Calculating Apparent ationwater Resistivity and Water Saturation LIU Ruilin College of Geop hysics and Oil Resources, Yangtze University , J ingzhou 434023, H ubei, China FAN Zhengjun, LIU Jianhua Research Institute of Petroleum Exp loration and Develop ment, N orthwest Branch, SIN OPEC, Urumuqi 830011, Xinjiang, China Abstract In carbonate and vug reservoirs, it w as difficult to identify fluid property w ith the parameters of w ater satura tion and apparent ationw ater resistivity A w as presented to calculate mixed fluid resistivity based on the component of porosities calculating by triple model and project mapping for removing mud invasion effects The is verified by using w ell logging data of Ordovician carbonate in northern Tarim Basin Key words carbonate reservoir; fracture and vug; triple porosity model; project mapping; saturation 108 Logging uation Technique for Compact Clastic Rocks in West Sichuan CHEN Bixiao , XU Binggao Welllogging Branch of Southwest Petroleum Engineering Ltd Co , SIN OPEC, Chengdu 610100, Sichuan, China AbstractNatural gas reservoirs were distributed in compact clastic rocks of shallow , median and deeper layers in West Sichuan For the hallow median and near conventional reservoirs, the conventional logging data w ere used for ua tion, the techniques for reservoir uation were established for multiparameter appraisal, apparent ationw ater resistivity, and based on neutron dig ffect For the compacthypercompact deeper reservoirs in Xujiahe Are a, the techniques of fracture recognition, fracture effective uation and reservoir uation w ere also built on the ba sis of ation micro imaging logging, nuclear magnetic logging, and dipole acoustic logging The key of reservoir e valuation is the fracture recognition and the uation of fracture effectiveness The nuclear magnetic logging is an ef fective of identifying fluid types According to application analysis, it is considered that special well logging is not necessary for uating the hallowmedian reservoirs, but it is necessary to uate the deeper reservoirs T he shortage of technique for uation of the reservoirs and research direction are pointed out For the hallowmedian res ervoirs in different areas and horizons the uating s should be mainly researched And for the deeper reser voirs, the research on the uation of reservoirs should be emphasized by using nuclear magnetic logging Key words west Sichuan; compact clastic rock; logging uation; fracture recognition; fluid identification 115 Lithologic Identification Based on Fuzzy Support Vector Machines ZHANG Xiang K ey Laboratory of Ex p loration T echnologies f or Oil and Gas Resources Yangtze University , Ministry of Edu cation, Jingzhou 434023, H ubei, China XIAO Xiaoling College of Comp uter Science and Technology , Yangtze University , J ingzhou 434023, H ubei, China YAN Liangjun, HU Wenbao Key Laboratory of Ex p loration T echnologies f or Oil and Gas ResourcesYangtze University , Ministry of Education, J ingzhou 434023, H ubei, China Abstract Aiming at the fuzzy characters existed in the complex lithologic classification, a kind of lithologic identifica tion based on fuzzy support vector machine was proposed The consideration of the fuzziness of reservoir lithol ogic classification and the same lithology w ere corresponding to great value scope, fuzzy memberships of samples in dif ferent lithologies w ere introduced in traditional support vector machine T he corresponding fuzzy memberships of differ ent samples are given according to the important degrees of the samples in classification that different samples can make different contributions to the optimal decision surface in fuzzy support vector machine Experimental results show that the lithology identification based on fuzzy support vector machine has high adaptability and identification accura cy Key words lithologic identification; support vector machine; fuzziness; membership 119 Research on Interpretation of Condensate GasReservoir Production Profile Based on Phase Dia gram GUO Haimin, FAN ChuanK ey Laboratory of Ex p loration T echnologies f or Oil and Gas Resources Yangtze University , Min istry of Education, College of Geophysics and Oil Resources, J ingzhou 434023, H ubei, China TIAN Zuhong , WANG Jieyi Well Logging Comp any , Western Drilling Engineering Corp oration of CN PC, Karamay 834000, Xinjiang, China AbstractOver the last decade, many oilfields in China have found a number of condensate gas reservoirs And now , Chinese majority condensate gas resources have entered into a stage of development and utilization In the process of condensate gas increase along the wellbore, w ith the reduction of temperature and pressure, condensate gas w as changed into condensate oil The change of phase makes it difficult to calculate each perforating zone s output oil and gas pre cisely, and this change also makes it im possible to monitor the production of oil well To solve the problem stated, a new on the interpretation of condensate oil production profile is proposed It provides a new idea on condensate oil production profile interpretation Key words condensate oil; production profile interpretation; phase diagram; twophase flow ; new 123 Study On Wellbore Flow Stability during Aerated Drilling XIA Hongnan College of Petroleum Engineering, Yangtze University , J ingzhou 434023, H ubei, China HAN Xianzhu Xinjiang Oilf ield , CNPC, Karamay 834000, Xinjiang, China ZHU hongxi College of Petroleum Engineering, Yangtze University , J ingzhou 434023, H ubei, China Abstract Based on the theory of gas liquid tw o phase flow , the w ellbore pressure distribution problems w ere analyzed in the aerated drilling In allusion to the sensitivity of w ellbore pressure distribution on w ellbore size, a w as pro vided for gas injection rate calculation The relationship w as discussed and explained betw een the bottomhole pressure and injection gas pressure and the variable size of borehole T he rate of gas injection is different betw een large borehole and slim hole to meet the premise of rock carrying, at the same time, the advantages of using composite wells for aera ted drilling are pointed out The result provides a theoretical reference for studying the unbalanced well drillings Key words aerated drilling; gas injection rate; bottomhole pressure; composite borehole 127 Study on Characteristics of Permeability of Coalbed Gas WANG Weiying , WANG Yarong College of Petroleum Engineering , Yangtze University , Jingzhou 434023, H ubei, China ZOU Laifang Research Institute of Drilling Technology , CN PC, Beij ing 100000, China SHI Huining Institute of Oil Production of T echnology , H uabei Oilf ield Comp any , PetroChina, Renqiu 062552, H ebei, China Abstract The law of the gas seepage in coalbed reservoirs w as studied The effect of gas slippage and effective stress on coal permeability was investigated by using core flow experimental apparatus The characteristics of coalbed porosity was theoretically studiedThe results show that due to the characteristics of special double porosity media of coal rocks, the effect of effective stress on permeability is serious Permeability of coal rocks reduces w ith the increase of to tal effective stress When pressure is released, the permeability can only restored to a certain extent, and result in per meability loss Key words coalbed methane; effective stress; permeability; slippage effect 129 A Numerical Well Testing Model for A Fractured and Vuggy Reservoirs Containing Big Fractures and Vugs WANG Xinhai Key Laboratory of Exp loration T echnologies f or Oil and Gas ResourcesYangtze University , Ministry of Edu cation, J ingzhou 434023, H ubei, China; Key Laboratory f or Petroleum Engineering of the Ministry of Education, China University of Petroleum, Beijing 102249, China ZHANG Dongli, LI Jianglong ResearchInstitute of Petroleum Exp loration large size; fracture; vug; numerical well testing 136 Optimization of Well Pattern Using Horizontal Well for the Development of Low Permeability Reser voirs LIU Dehua , LIU Zhisen, LI Jiuhua College of Petroleum Engineering, Yangtze University , Jingzhou 434023, H ubei, Chi na Abstract Using horizontal w ell to develop reservoir was one of the important means for enhancing control extent of re serves and improving the effect of oilfield development It w as w idely used in the oilfields of China According to the reservoir adaptive conditions