【作者】 戴江；

【导师】 李子丰；

【作者基本信息】 燕山大学 ， 机械设计及理论， 2008， 博士

【摘要】 压裂在油气资源的勘探开发上起着重要的作用。目前大庆油田外围探井多为低渗透油层(渗透率小于50×10-3μm2),具有单层厚度较小、层数较多的特点,通常一口井中含有二个或二个以上需要压裂的油层,现有的压裂工艺是:压完第一层后,上提管柱逐层对第二层、第三层进行压裂,然后起出压裂管柱,再下入测试求产管柱,这样不仅劳动强度大,施工周期长,测试压力资料不连续,而且上提管柱过程中,油管内喷出的压裂液污染地面,不利于地面环保,同时也会影响压裂液反排量的准确计量。为此,本文针对压裂施工中存在的这些难题,采用理论分析与现场试验相结合的方法,设计了一整套不动管柱两层压裂、排液求产、测井温一体化管柱。主要取得如下研究成果:(1)机械设计根据现场生产实际,结合机械设计原理研制出了一整套压裂、排液求产、测井温一体化管柱,并研究设计、加工试制了上封隔器、控制开关、下封隔器、密封接头、同心大通径压力计托筒等八种二十余件新型井下工具。使其实现了一趟管柱并且在不动管柱的情况下完成两层压裂、压后排液求产以及压后测井温等工艺,达到了缩短施工周期、降低储层的损害程度、减轻工人的劳动强度、实现绿色施工的目的。(2)理论研究及应用根据不同储层特点,优选了与油气层配伍的压裂液,添加剂及配方,确保油气田增产、增注的效果。应用岩石破碎力学原理,建立了射孔完井条件下岩石破裂压力理论模型,计算了大庆油田海拉尔、古龙等区块的地层破裂压力,确保在不动管柱两层压裂排液求产一体化施工中压开地层而又不致产生窜层,同时井下工具具有足够的承压能力,保证安全施工。为验证管柱设计的合理性,以压裂管柱为研究对象,充分考虑影响管柱屈曲行为的主要因素,建立了描述管柱屈曲行为的一般性方程。通过对该方程的分析,揭示了管柱几何尺寸、物理特性参数、载荷等因素对管柱在三维弯曲井眼中屈曲行为的影响规律。应用现代数学分析方法求解管柱屈曲方程,得到三个不同状态(正弦、螺旋弯曲及自锁)的解和临界屈曲载荷以及弯曲管柱与井壁接触的正压力,分析了弯曲管柱与井壁之间的库仑摩擦力对管柱在井下的屈曲行为及轴力分布的影响。在准确认识井下管柱屈曲行为的基础上,进行井下管柱载荷、应力和变形的分析与计算。在实际计算时,考虑了管柱上有封隔器等井下工具,为生产参数的合理选择提供了理论依据。从理论上研究了具有启动压力影响的低渗储层垂直裂缝油井的产能预测方法,计算时考虑了启动压力梯度对产能衰减规律的影响,绘制了油井在定流压下生产时产量随时间变化曲线和不同生产时间下的IPR曲线(不稳定IPR曲线),得出如下结论,一是表皮系数越大,裂缝井初期产量就越低,随生产时间增长,表皮效应的影响逐渐消失。二是启动压力梯度越大,储层流动所需的生产压差越大。启动压力梯度对压裂井的初期产能影响不大,在生产后期,启动压力越大产量下降越快。三是对于不同的生产时间,当启动压力梯度较小时,它对产量的影响也较小;但随着启动压力梯度的增大,其对产量的影响程度增强,产量下降幅度显著。实现了对低渗、特低渗透储集层压后产能的准确评价。(3)现场试验在大庆油田有限责任公司采油工程研究院分层开采实验室模拟井上进行了室内试验。通过地面打压,验证水力锚锚定可靠,封隔器座封到位,底部开关销钉剪切值准确。通过油套管正反打压,验证了封隔器的密封性以及封隔器的可反洗功能,达到了设计的目的,证明了方案设计的合理性。在大庆油田探井及开发评价井上,共进行了31口井的现场应用,工艺成功率100%。实现了一趟管柱并且在不动管柱的情况下完成两层压裂、压后排液求产以及压后测井温等工艺;减少了作业费用,减轻了作业人员的劳动强度,实现了安全环保施工,可在油田范围内(3000米以浅井)普遍推广。更多还原

【Abstract】 Fracturing plays an important role in the exploratory development of oil-gas resources. At the moment almost every outer well of Daqing oil field are low permeability layer(permeability is lower than 50×10-3μm2), they have the feature that the thickness of individual layer is too small, and the number of the oil layer is large, there are usually two or more layers need to be fractured in one well. Available fracture technology is: after the first layer is fractured picking up the string and fracturing the second and third layer, then pulling out the frac-string and tripping in the testing and requiring production string. Using this method not only the work strength is large、the cycle time is long and the data of pressure testing is not continuously,but also in the process of picking up string the fracture fluid that blow out of the tubing can pollute the surface, this do no good to the environment, meanwhile we can’t metering the flowback volume exactly. For this reason, according to the these difficulty, using the combinated method of theoretical analysis and field experiment, we designed a battery immovable string which can fracture 2 layers at the same time、cleaning up the well and requiring production and testing the well temperature. Following is the outcome of this resrarch.(1) Mechanics design Designing a suit of fracturing、cleaning up and requiring production、well temperature testing string using mechanics design low,furthermore designing and producing upper-packer、control switch、lower packer、pack off adapter、concentric large bore manometer barrel etc. more than 20 kinds of down hole equipment. Achieving technology that finishing two-layer fracturing、cleaning up and requiring production in one time but not move the string. It can decrease the work time、the damage of formation, alleviating the work strength,acnieving the aim of green working.(2) Theoretical analysis and application According to the unique feature of different formation optimizing the fracture fluid、addition agent and dispensation that have no affect on the oil-gas formation,ensured that the effectiveness of stimulation and increase production in the oil field is good. Using theory of rock breaking mechanics can obtain the theoretical model of the formation breakdown pressure. The formation breakdown pressure of Hailaer、Gulong and other block of Daqing oil field are calculated. Ensured that in the workover of immovable String two-layer Fracturing、Cleaning up and Requiring Production can fracture the formation and not cause communication between zones, at the same time down hole tools have enough overpressure resistant capability, so the work will be safe.Using the frac-string as our research target, adopting modern mechanics mrthod, considering the affect of string’s buckle behavior as the main factor, establishing a general equation to describe the string’s buckle behavior. Through the analysis of the equation, we know that the affection rule of string geometry、physical characteristics parameter and load etc. to the buckle behavior in the triaxial bended borehole. Using the method of modern mathematics analysis, we can compute string buckle equation, so we can obtain the result of three different condition(sine、coiling and bending、self-locking)、interface buckled load and contacting normal pressure on the wellbore,analysising the affection of coulomb friction to the buckle behavior of string and axis force distribution in the hole. On the basis of recognizing wellbore string buckling behavior exactly, we can calculate and analysis the well bore string load、stress and aberration. When calculate practically, we considered the down hole equipment, such as packer etc. All these can offer theoretical reference to the reasonable option of producing parameter.Doing research about fluids rate forecast of low permeability formation vertical fracture well considering the affection of kick off pressure, when calculating, we must consider the affection of kick off pressure to the deliverability die-away law, describing the production changing curve following time under constant pressure and IPR curve under different time. Larger of the skin factor, lower the production of well early days, following time, the affection of skin effect will vanish. And the kick off pressure is larger,the producing pressure difference will be larger too. Kick off pressure have small affection to the early days production of fractured well, but on the later stage,the larger of kick off pressure, the lower of production; But with the increasing of kick off pressure, it can affect the production greatly, production drawdown is very marked. Achieving the accurate evaluation of low permeability and extra low permeability formation’s deliverability.(3)Field experiment and application We carried on an experiment on the well simulator in the lab of layer mining evaluating petroleum engineering collage daqing oil field Ltd. The justifiability and sealing property of string system is verified;the setting and sealing property of upper and lower packer is verified; The reliability of down hole control switch and accuracy of pin shearing value is verified too. We also verified the reliability of fishing tool and the backwashing performance of upper packer using pressure increased experiment.On the exploration and development evaluation well of Daqing oilfield, this technology is applied on 31 wells, the success ratio is 100%.更多还原