【作者】 张峰；

【导师】 陈建平； 岩楯敞広； 铃木浩一；

【作者基本信息】 中国地质大学 ， 岩土工程， 2010， 博士

【摘要】 研究流动电位产生的原理可知,当高压水流注入地下时,地层水压力进行重新分配,将会同时伴随产生流动电位。我国二次采油一般都采用注水(气)的方式,有的油田甚至一次开采时就直接采用注水开采,在油田的三次开发中也广泛采用了聚合物驱油等向油层注液开采的方式。如果能利用注液产生的流动电位来推测储层流体的即时状态,则有望提高采油效率和节约综合采油费用。结合论文研究目的,首先介绍了流动电位现象研究的历史,探讨了流动电位产生的基本原理以及目前在国内外进行实际应用的现状。从文献可以看出,目前对流动电位法的研究主要考虑的对象大多是各种膜的动电现象,对于地下流体在流动过程中的流动电位现象虽然早有发现,但是尚处在定性研究阶段,在监测流体流态应用方面基本没有专门的讨论。论文对我国油田开发不同时期的开采方法进行了研究总结。通过研究我国三代油田开发方法的主要技术及其各自的驱油原理,提出二代的注水和注气驱油,以及三代的聚合物驱油、碱水驱油、微生物驱油、热水驱油等方法实质上都是属于将各种注入液(流体)在压力作用下从油层(固体)中通过的流体流动方式采油。结合流动电位产生的基本原理提出了只要是采用了将流体注入油层驱替石油的方式,都可能产生流动电位,也就都有可能使用流动电位法来进行流体流态的监测。研究我国油藏的基本特点后可知,油藏储层可以划分为裂缝控制、断层控制、非渗透性层控制、层理构造控制、渗透率韵律性控制、孔隙结构控制的六种非均质储层类型。研究当前我国推测油藏状态的主要方法后可知,目前各油田由于储层的非均质性、岩性的复杂性以及注入水的变化和水淹状况差别较大,给我国常用的测井技术带来严重困扰。但是这些大量分布的非均质储油层,注液时很容易产生流动电位,给流动电位法的应用提供了物理条件。论文讨论了油藏开发过程中的流动电位现象产生的基础理论。注水采油时,在断层裂隙、非均质性储层以及高压注水等因素的控制下,注入流体在不同层段间推进不均衡,油藏内部原来静态的压力系统变成了动态压力系统,这些现象均可以产生流动电位。讨论了影响地层中流体流动电位的三个主要因素：储层地质结构、压力异常、地层水矿化度。提出对流动电位法的定量研究是今后流动电位法实际应用前必须经过的环节。论文对流动电位定量研究实验测试系统相关的影响因素进行了讨论。为较好的拟合实验条件和实际地层条件,本文简要研究了我国实际油田的主体岩性、地层水矿化度、注入液矿化度等状况,确定了室内实验的岩心采用我国油藏的主体岩性砂岩,饱和岩心溶液和注入液矿化度采用蒸馏水和20-32500mg/L的盐水溶液及稀油,结合将来流动电位法应用的实际背景条件和室内实验的目的以及相关影响因素,设计了与油藏开发条件匹配的室内岩石流动电位基础实验测试系统,推出了实验系统平台,介绍了实验测试设备的组成部分。利用实验平台对选定的岩心进行了多种工况的流动电位室内测试实验。论文首先进行了变注入压条件下的流动电位测试实验。简要介绍了实验的基本步骤,详细给出了岩心前处理的过程。由于所有的实验均在日本进行,对Berea砂岩(来自美国某油田)进行实验的工况是分别采用稀油和浓度为20、200、2000、20000mg/L的盐水溶液饱和岩心,第一步采用和饱和岩样浓度一样的盐水注入岩心进行测试实验,第二步采用蒸馏水注入岩心实验。注入压设定为0、200、400、600、800、1000kpa阶段上升,围压采用实际地层压力20MPa。对实验结果进行了计算分析,算出了不同矿化度条件下Berea砂岩的流动电位系数。论文对日本某油气田的Tako砂岩也进行了流动电位测试实验,实验工况是分别采用蒸馏水、稀油和矿化度为200、2000mg/L的盐水溶液饱和岩心,每个阶段实验采用和饱和岩样浓度一样的盐水注入岩心。注入压设定为0、300、550、800、1050kpa进行压力分段上升实验,围压采用实际地层压力20MPa。对Tako砂岩的实验结果也进行了计算分析,算出了不同矿化度条件下Tako砂岩的流动电位系数。论文对Berea砂岩和Tako砂岩的实验结果进行了计算对比,并对两种岩心进行了切片显微镜对比。从变注入压条件下的室内流动电位测试实验的结果可以看出：①随注入压的阶段增大,流动电位呈阶段性增大,两者具有良好的相关性。②当注入压力变为0的时候,流动电位也同时变为0。③随着注入岩心溶液的电阻率降低(矿化度增大),流动电位变化幅度也降低。④使用同饱和岩心一样矿化度的注入溶液与使用蒸馏水注入相比,流动电位差别不大。⑤用油饱和岩心的实验中,各个阶段流动电位的平均值和压力变化的相关性也很明显。⑥用油饱和岩心的实验中,用蒸馏水注入比用油注入有更大的流动电位产生。通过对比研究认为,在中砂岩和粗砂岩中,流体注入时产生的流动电位现象都较明显。限于论文中所有的实验都在日本进行,未能采用我国实际油田砂岩岩心进行实验。今后如果可以对我国不同油藏区域,不同孔隙率的砂岩进行大量的实验统计,对于某一固定油藏区域,即可以利用采集到的流动电位数据和室内实验计算的流动电位系数关系,较快的推算出某一特定区域的压力分布情况,可以有效指导地面采注工作。论文还进行了定注入压条件下的流动电位测试实验。岩心采用美国的Berea砂岩,饱和岩心的溶液使用稀油和1000mg/L(近似淡水)、6000mg/L(中等矿化水)、32500mg/L(高矿化度)三种矿化度的NaCl溶液,岩心注入液全部采用蒸馏水,每次测试实验使用的注入压是不同的定值,分别进行数小时的蒸馏水注入实验。观测在定注入压条件下,从注入流体开始到岩心内部孔隙水被全部置换的过程中,电阻率和流动电位变化的情况。通过对复杂工况组合条件下大量的实验结果进行解析处理,计算出了注水停止前后的流动电位,并算出了流动电位耦合系数Cc。分析定注入压实验结果,可知：①在蒸馏水注入置换岩心孔隙水的过程中,电阻率增大,在一定的注入压力条件下,流动电位逐渐变大。②当岩心中的孔隙水被注入的蒸馏水全部置换完毕,电阻率停止变化时,仍然有一定的流动电位发生,注入压变为零时,流动电位迅速降低到0。综合室内实验结果,论文对流体流动电位发生的机理进行了推测：①向岩心注入溶液开始时(实验开始的几分钟),向岩心内渗透很小的流量时,岩心的电阻率几乎不变,却渐渐产生了和注入压力有一定比例关系的流动电位。当注入压变为一个定值时,对应发生的流动电位也是一个定值。②继续注入溶液,随着流量的增大,岩心内的孔隙水慢慢被注入溶液(蒸馏水)置换,电阻率也随着逐渐增大。受溶液电阻率增大的影响,流动电位也慢慢变大。③当岩心内部的孔隙水被注入溶液置换完毕后,电阻率的变化也随即停止,同时产生了和注入压有一定比例关系的流动电位。当注入压力成为一个定值时,流动电位也变为一个定值。为探讨野外作业中流动电位法使用的可行性,在日本某野外区域进行了小规模地层条件下流动电位注水实验,探讨野外作业中流动电位法使用的可行性。野外地下注水流动电位测试实验注水孔深度为21.6m,注入水压为0.23MPa,注入流量为1441/分,共注水16分钟,注入水为淡水,实验采集到了1.5mV的流动电位。从野外流动电位测试实验结果可以看出：①注水开始时,注水孔周围产生明显的流动电位,随着离注水孔距离的加大,流动电位变小；②在注水开始时流动电位最大,随着时间的延长流动电位逐渐衰减；③注水结束后,仍然可以看到流动电位,这是由于地表的注水虽然已经结束,但是水流在水头的压力下,仍然在进行地下水平衡状态的调整,仍然在流动。室内外流动电位测试实验,研究了注入压力与注入溶液矿化度和流动电位产生的相互关系。计算出了相关岩石不同矿化度下的流动电位系数,为野外实际石油开发的高精度化、高效率化的实现奠定了一定的量化评价基础。研究大量室内实验的结果和小规模野外注水实验的结果,可以认为地层中流体流动电位的变化是地下流体进行压力分配的直接表现,在地面采集地下流体流动电位变化的数据,结合实验分析和数据的解析处理可以了解流动电位变化的规律。科学利用地下流体由于压力变化产生流动电位这一现象,就可以对地下流体的流动状态进行有效的监测。流动电位法为我国的油藏测井技术提供了一种新的思路,在监测地下流体流态方面应用前景广泛。更多还原

【Abstract】 According to literature view, water pressure inside stratum tends to reallocate with appearance of streaming potential when inject high pressure water. High-pressure water injection is widely used in secondary oil recovery, sometimes even in first oil exploitation, while high pressure polymer injection is used in third oil recovery. So if the real-time status of reservoir fluid can be monitored and calculated by the streaming potential of injection fluid, it could improve the exploitation efficiency and save exploitation cost.This thesis, firstly, introduces the research history of streaming potential, and then discusses the basic principle and application situation of streaming potential in the world. According to literature view, current researches are focus on electro-kinetic phenomena of different fluid envelope, while the streaming process of potential is still on qualitative status without technical application study on streaming potential monitor.This thesis summary the used approaches and responding principle on oil exploration at different times over three epochs, and then found that water and gas injection approach used in second generation and polymer, alkali water, microorganism, hot water and so on, injection approach used in third generation apply the same principle that the pressure caused by fluid injection accelerate the rate of fluid flow. Combing the basic principle mentioned above and literature view, thesis points out that any fluid injection to oil layer will lead to streaming potential, which means potential monitors could be used to track the streaming behavior.Oil reservoirs were divided into six groups in China, crack-controlled, fault-controlled, impervious-controlled, bedding structures controlled, Permeability rhythmic controlled, pore structure controlled. However, due to no uniformity, complexity, injection variation and water out behavior, there are lots of technical problems with oil explorations in China. Injection in reservoir heterogeneity tends to generate streaming potential, which is suit for application of streaming potential monitor approach. Inhomogeneous of fluid streaming in different layers and transition from static pressure to kinetic pressure usually lead to streaming potential, during oil exploration by water injection. Three primary factors are discussed in this thesis, which are geologic framework of oil reservoir, unusual pressures, reservoir water salinity separately. What’s more, quantitative research on streaming potential monitor lays groundwork for future application.Factors relative to testing system of streaming potential monitor were discussed firstly. In order to match the testing condition to real oil layer status, this thesis lists the major litho characters, reservoir water salinity, injected fluid salinity to make sure sandstone as testing sample, distilled water and 20-32500mg/L as SPG. What’s more, streaming potential testing system for oil exploration was designed in term with application background, testing aim and corresponding factors, which includes of testing bed and testing equipment.Firstly, Streaming potential testing was carried out with different injection pressure. This thesis introduces the testing procedure and then gives the detailed process of core sample handling. Berea sandstone, as testing sample, is from certain oil field of USA, and testing conditions were saturated salt with 20,200,2000,20000mg/L concentration. While, injection pressure was 0, 200,400,600,800, 1000kpa separately with constant ambient pressure 20MPa. Streaming potential coefficient of Berea sandstone with different mineralization will be available based on testing result analysis.Then, Tako sandstone from a oil field in Japan was testing in this research with testing condition oil, distilled water,200,2000mg/L saturated salt concentration,0,300,550,800, 1050Kpa increasing injection pressure and 20MPa ambient pressure. The final streaming potential coefficient was developed according to analysis on testing result. Next, this thesis compares the testing result between Berea sandstone and Tako sandstone.The results of in-door streaming potential testing with different injection pressure show the following characters:1. The increasing trend of streaming potential shows a closed relativity to increasing injection pressure.2. When injection pressure declines to 0, the streaming potential goes down to 0.3. The variation rate declines with electrical resistivity decreasing of core sample.4. Streaming potential shows litter change between the fluid injection and distilled water for same saturated core sample.5. The average value of streaming potential shows obvious relativity to pressure variation in the core sample with saturated oil.6. Distilled water injection generates lager streaming potential than oil in the core sample with saturated oil.In term with comparative analysis between medium-sandstone and grit sandstone, it believe that they present similar distinct streaming potential during fluid injection. However, all of these tastings were carried out in Japan and none one core sample is from China, so the next researches could be carried out in China with sandstone samples from different oil fields in order to collect relative statistical data, which help engineer and designer calculate the pressure distribution by streaming potential monitor.What’s more, constant injection pressure testing is also carried out with thin oil,1000,6000, 32500mg/L as core-saturation fluid, distilled water as injection fluid. What’s more, the injection pressure was different during several hours’ injection process. This testing recorded all of the variation data both of electric resistivity and streaming potential from intact status to thorough going replacement of pore water inside core sample.The streaming potential value and coupling coefficient after stopping injection can be calculated by means of analytic data process on abundant of testing result with different test condition. The following shows the analysis result:1. The electrical resistivity increases during the pore water replacement process and the streaming potential shows the same trend under one injection pressure.2. After the pore water have been completely replaced by distilled water, the variation of electrical resistivity stopped immediately. However, the streaming potential still kept changing.Based on in-door testing results, thesis evaluates the generation mechanism of streaming potential as following:1. Electrical resistivity shows little change due to lesser permeability during the testing beginning. However, with the increasing injection pressure, the streaming potential rises obviously. When the sample is getting to be saturated, the injection pressure is up to maximum and streaming potential tends to be a constant.2. With the increasing injection volume, pore water inside sample was replaced step by step, which leads to variation of electrical resistivity. What’s more, streaming potential is also increasing due to electrical resistivity.3. After the pore water inside sample has been completely replaced by injection fluid, the electrical resistivity of sample stops changing while generates a streaming potential relative to injection pressures.With the objective to validate application of streaming potential methods, out-door water injection testing was carried out in certain suburb in Japan. The depth of testing hole is 21.6m, with 0.23MPa injection pressure. Freshwater injection process lasted 16 minutes with 1441/min throughput. In this testing, streaming potential showed 1.5mv.Followings are conclusions of out-door testing:1. At the beginning of water injection, the injection area shows obvious streaming potential, and then the streaming potential declines with the increasing injection distance.2. Streaming potential is up to peak at the beginning water injection and then declines.3. Streaming potential is still existed after water injection process. It is believed the reason is that the balance procedure of underground water hasn’t stopped due to the pressure head after water injection.The relationship between injection pressure, salinity of injection fluid and streaming potential was analyzed in both of in-door and out-door testing. The streaming potential coefficients with different salinity can be calculated, which lays the ground work for high precision and efficiency of oil exploration.It is proved that the variation of streaming potential of fluid inside stratum directly results from the variation of fluid pressure distribution according to masses of in-door testing results and some of out-door testing results. This relationship can be developed by data collection, data analysis and evaluation. Furthermore, the relationship between pressure and streaming potential assists us to monitor the moving condition of underground fluid. The streaming potential monitor method presents a new idea for oil exploitation technique with bright future prospects.更多还原