【作者】 秦国伟；

【导师】 蒲春生；

【作者基本信息】 中国石油大学 ， 油气田开发工程， 2010， 博士

【摘要】 世界稠油资源极为丰富,稠油资源的开发在石油工业当中占据了重要的地位,但大部分稠油资源分布在疏松砂岩中;稠油本身物性决定了以强化采油为主,目前只有蒸汽热采(蒸汽吞吐和蒸汽驱)用于工业性开采。在稠油热采过程中,稠油油藏的疏松砂岩储层特征和蒸汽本身性质及其冲刷,造成了开发中出砂、汽窜等现象,严重影响了开发效果;针对蒸汽热采中出砂、汽窜等问题,本文提出了具有温度自适应性的复合调驱技术,即在前置液成胶固化后的防砂/封堵基础上,结合温敏凝胶体系可逆温敏增稠特性。本文首先采用自由基水溶液聚合法合成了三元共聚物P(A-AM-B)和离子型四元共聚物P(A-AM-NaAA-B),利用IR等技术对三元/四元共聚物进行了表征,确定了其组成和结构,且此三元/四元共聚物具有可逆热增稠特性,即在低温下粘度小为聚驱、高温下粘度增大具有封堵作用。温敏行为研究结果表明,在浓度高于一定值(质量浓度为2.0%),温度高于低临界溶解温度LCST时,体系形成具有三维网络结构的凝胶体系,且粘度随温度增加而增大,外界离子的加入增强了体系的温敏效果,表明合成出的三元/四元共聚物具有较好的抗温抗盐能力;但P(A-AM-NaAA-B)增粘效果好于P(A-AM-B),而稀溶液体系不存在LCST。同时结合DSC、DLS、荧光光谱等技术,利用渗透压动力学模型从理论角度探讨了该凝胶的温敏机理。利用HAAKE流变仪研究了P(A-AM-NaAA-B)凝胶体系的动静态剪切性能,结果表明该凝胶体系具有剪切变稀性,属于假塑性流体。温度范围内损耗角从56.27°递减到31.04°,此时亚溶液从粘性流体转变为粘弹性流体,并利用改进橡胶理论模型分析了体系的力学强度。在蠕变研究基础上,结合实验结果推导出了该凝胶的动力学模型。通过室内岩心驱替实验评价了温敏凝胶体系的封堵性能及驱替效果,指出高温下封堵率高于50%,而低温下只有9.8%,说明此凝胶体系具有温度自适应性;温度为65℃时,室内物理模拟实验结果表明提高采收率最高值可达18%左右。同时建立了笼统注入下对非目地层的损害程度数学模型,并评价了低温下(30℃)该凝胶的伤害程度;利用动态注入多轮次蒸汽压力反映了该凝胶封堵性能,结果表明在多轮次后仍对蒸汽具有封堵性。考虑到稠油油层出砂及合成的四元共聚物用量大等问题,提出了利用水溶性酚醛树脂与无机硅化物在酸性下复配作为防砂/封堵的前置液。通过正交实验优选出了前置液的最佳配方,并考察了稳定性、抗盐性及耐酸碱性等,结果表明330℃下比较稳定,Ca2+>0.5%或pH>11下90h不能成胶固化,但能基本满足蒸汽热采要求;为了保证前置液固化后具有一定渗透性,在前置液中加入了增孔剂,加量>40%时渗透率高于1.17×10-3μm2。对添加增孔剂的前置液进行了岩心流动实验,表明前置液固化后具有较高的封堵率(>95%)和突破压力梯度(>9.3MPa/m),但选择性注入较差,渗透率极差在17.64时剖面改善率才为87.9%。同时利用前置液动静态防砂实验研究了其防砂效果,并从键能和纳米级颗粒间作用分析了其耐温性和防砂功能的机理。最后室内研究了前置液与温敏凝胶相结合的复合调驱技术,通过正交实验测试了不同注入方式下的调驱效果,并利用软件拟合了实验结果,结果表明复合体系具有较好的温度自适应性,并预测了调驱指标,分析了实验值与拟合值间的误差(最大为5.10%);根据地质情况利用拟合关系式可以确定前置液与温敏凝胶的用量,从微观上探讨了温敏凝胶的自适应性复合调驱机理。针对温敏凝胶对温度敏感性效应,建立了温度场对流体渗流运动影响下的多场耦合动力学模型,在理论分析基础上详细推导了蒸汽热采中汽窜体积,并分析了调堵参数优化原理,为现场施工提供理论依据。更多还原

【Abstract】 In the world, heavy oil resources are extremely rich; their exploitation plays an important role in petroleum industry. But most heavy oil resources are distributed in loose sandstones. The physical property itself decides that heavy-oil resources must be exploited by enhanced oil recovery technique; but at present, only the thermal recovery method (mainly refers to steam stimulation and steam flooding) has been used. In the thermal recovery process, loose sandstone reservoir characteristics, steam property and its washing cause sand production, steam fingering/channeling and so on, which influence the exploitation effect. Due to these problems, based on sand control /sealing of compound preflush solidification, combined with the reversible temperature-sensitive thickening characteristic of gel system, the self-adaptive compound profile-control and oil displacement technology is proposed in this paper.Firstly by using free radical aqueous solution polymerization, ternary copolymer P (A-AM-B) and ionic tetra-copolymer P(A-AM-NaAA-B) are synthesized; and then they are characterized to determine their composition and structure by IR technique and so on. And the ternary/tetra-copolymer have the unique performance of reversible thermal thickening which it can be as polymer flooding at low-temperature and sealing at high-temperature. Temperature sensitive performance study illustrates that, when concentration is above certain value ( mass concentration is 2.0%) and temperature is above low critical solution temperature-LCST, the gel system with 3D net structure is formed; viscosity increases with temperature; the addition of external ion strengthen temperature-sensitivity; these show that the ternary/tetra-copolymer have a good heat and salinity tolerance. But the tackifying effect of P (A-AM-NaAA-B) is better than that of P (A-AM-B); and LCST doesn’t exist in dilute solution. At the same time, combined with the technique of DSC, DLS and fluorescence spectrum, by using of osmotic pressure kinetic model, the gel temperature-sensitive mechanism is investigated theoretically.The dynamic and static shear performance of P (A-AM-NaAA-B) gel system is researched by HAAKE rheometer; and the result demonstrates that this gel system has shear-thinning property and it belongs to pseudoplastic fluid. When temperature is in the range of and loss angle decreases from 56.27°to 31.04°, the inferior changes from viscous fluid to viscoelastic fluid; and the mechanical strength is analyzed by improved rubber theoretical model. On the creep study basis, combined with the experiment result, the system’s kinetic model is derived. The sealing and oil displacement performance of the temperature-sensitive gel system is evaluated by indoor core flooding test which show that the blocking ratio is above 50% at high temperature and only 9.8% at low temperature; these show that the gel system is temperature self-adaptive. At the temperature of 65℃, the indoor physical simulation test show that the oil recovery can be increased by about 18%. At the same time, the mathematical model of damage degree for non-destination when generally injected, is set up; and the gel damage degree is evaluated at low temperature (30℃). Making use of that the dynamic injection multi-cycle steam pressure reflects the gel blocking property, the result illustrates it still has the blocking ability for the steam after multi-cycle.Considering the problems of heavy oil reservoir sand production and large consumption of synthesized tetra-copolymer, it is proposed that the water soluble phenolic resin and inorganic silicide are compounded at acid condition to work as the sand-control/sealing preflush. The optimum recipe of the preflush is selected by orthogonal test; and its stability, salt resistance and acid and alkali resistance are observed; the result shows that it is comparatively stable at 330℃and when Ca2+>0.5% or pH>11 it can’t be solidified after 90h but can meet the thermal recovery requirement. In order to guarantee that it has a certain permeability when preflush is solidified, pore-agent is added into preflush; when added more than 40%, the permeability is above 1.17×10-3μm 2. The core flooding test show that preflush with pore-agent after solidification has a high blocking ratio (>95%) and breakthrough pressure gradient (>9.3Mpa/m), but its selective injection is bad-when permeability range is 17.64, the profile improvement ratio is only 87.9%. The sand-control effect of the preflush is studied by dynamic and static tests; and its mechanism of temperature-resistance and sand-control is analyzed from the aspect of bond energy and interaction between nano-paticles.Finally, the compound profile-control and oil displacement technology of preflush and temperature-sensitive gel is studied by indoor experiments; the profile-control and oil displacement effects in different injection manners are measured by orthogonal tests. And a software is programmed to fit the experiment data; the result show the compound system has a good temperature self-adaptivity; and the profile-control flooding index is predicted; the error (5.10% as the maximum) between experimental value and fitted value is analyzed. The consumption amount of preflush and temperature-sensitive gel can be determined by the fitting relation according to the geological conditions; and the self-adaptive compound profile-control flooding mechanism of the temperature-sensitive gel is investigated microscopically. Due to the gel temperature-sensitivity, the multi-field coupling kinetic model is set up, considering the influence of temperature field for fluid seepage; the steam channeling volume is derived from the theoretical analysis; the principle of optimizing profile-control flooding parameters is analyzed; these provide theoretical basis for field treatment.更多还原