单井化学示踪剂法测残余油饱和度数值模拟研究

【作者】 胡书勇；

【导师】 张烈辉；

【作者基本信息】 西南石油学院 ， 油气田开发工程， 2003， 硕士

【摘要】 经过第一次和第二次采油后，还有大量的石油滞留地下深处不能被有效采出。而每年新发现的石油地质储量在不断减少，勘探开发的难度越来越大，这就要求必须采用先进的方法和技术将残余在地下的原油采出，也就有了确定S_OR的需要。在进行三次采油的潜力评价中，S_OR是一个至关重要的参数。测残余油饱和度的方法较多，但各有优缺点。单井化学示踪剂是其中一种较为有潜力的方法，它始于60年代后期，由Cooke首先提出，它利用地层的色谱效应，用示踪剂法测残余油饱和度。Deans于1967年用此法在室内成功地测定了模型内的残余油饱和度，1968年应用于现场获得成功。该法首次现场测试获得成功以来已广泛应用。单井示踪法成本低，测定简便，测定体积大并且可调，应用范围广，灵敏准确，是测定残余油饱和度的理想方法。 单井化学示踪剂法测残余油饱和度就是向油层中注进一种酯类作为原生示踪剂，然后关井，让其在油层中遇水发生水解，生成次生示踪剂醇类，最后进行回采。对回采的示踪剂基于色谱效应进行分析，绘制“示踪剂浓度累计采出液体积“的回采曲线，由于这两种示踪剂在油水中的分配系数不同，它们以不同的速度被回采出来，因而两种示踪剂峰值到达地面的时间不同，产生了一个时间差。这种时间差与残余油饱和度有直接数学关系，残余油饱和度越大时间差越大，据此关系编制数值模拟程序，模拟回采曲线，通过反复模拟来确定残余油饱和度值，这种方法的精确度为孔隙体积的±2％—±3％。 该技术的关键是解释工作，其测试成功与否，最关键的还是在于对现场中采集到的数据进行拟合来确定残余油饱和度。对测试数据的解释包括直接求解和用计算模拟程序来模拟。在直接求解方面，国内外目前还没有出现解释精度较高的常规解释模型。而对于应用数值模拟方法来处理现场测试数据方面，则发展了三种数值模型，即“理想”的单层模型、多层模型、漂移模型。随着油藏模拟器模型复杂程度的增加，为获得现场数据的满意的拟合，需要试算的步数也会迅速的增多。这样常规拟合程序就会变得相当笨重，其计算费用可能会大大增加。于是人们不断改进示踪剂测试的数值模拟算法。 同时，在解释技术上，单井化学示踪测试的常规解释模型忽略了扩散的影响，是通过分析的方式来求解的，其解释精度受到很大影响 对于存在流体漂移现象的测试，这种情况更为严重。 本文针对上面提到的问题，先简要回顾单井化学示踪测试I们…史和现状，在对其数学理论和方法、原理进行阐述的基础上，对其测试全过程（从室内＿测试到现场测试〕和常规解释模型作了描述；最后着重研究了u数值模拟解释模型。重点对单井示踪测试的数值模拟理论、方法及解释工仆进行了研究，特别是对存在流体“漂移”现象的二维模拟作了深入研究。作”～全文的研究成果，编写了研制了用于解释残余油饱和度的一维、二维多以t值模拟程序和存在“漂移”现象的二维数值模拟程序。 所取得的主要研究成果： O）建立了单井化学示踪刑法测残残余油饱和度技术的数，f模型，即单层模型、多层模型和流体“漂移”模型，并研制了在理想情况l、的常规解释模型； C 研制了用于解释残余3由饱和度的一维、二维多层数值N拟程序： ”o)研制了存在“流体漂移”时的数值模拟程序。本程序、；；合化学示踪3卯〕特证速度，建立了无条件稳定、收敛的有限差分格式，并血过把二维模W价为 创ZZ模型，提高了数值模拟求得的代余汕饱和度的精地，减少了计算 1k十卜更多还原

【Abstract】 a mass of oil that be reserved after primary and secondary recoverying can not be availability recovered. Exploitation is becoming more and more difficult while the newly discoverable petroleum oil is less and less. New fields were not being discovered fast enough to replace the old one as they were depleted. It became clear that the oil remaining in our developed reservoirs could be considered a valuable primary resource. The need for determining residual oil saturation (Son) has existed. SOR is a critical parameter in the evaluation of the potential for the third recovery. There are a number of recognized methods for estimating remaining oil content of reservoirs and these methods have inherent advantages and limitations. One method which was thought to be further development was the single-well chemical tracer procedure. The method is developed by Deans in later 1960’s. The chromatographic effect was first proposed as a way to measure SOR. The first laboratory experiments using a chemical reaction to produce a tracer in-situ in a sand pack containing a refined oil at residual saturation has succeeded. And the was applied in fields in 1968. The technology is proprietary to Exxen produotion Research Company in 1971.lt was applied widely since advantages of the single-well method are the ability to detect the larger amount of reservoir volume and to control the depth that is sampled as compared to other methods.In the single-well chemical tracer (SOR) method for measuring residual oil saturation, injecting Ethyl acetate dissolved in brine as the primary tracer into target well, and shutting in. The primary tracer hydrolyzed into product tracer during shutting in. Then producing back the brine and tracers, the primary tracer and the product tracer have different distribution ratios between oil and brine, they would separate during the flow back. When the flow was reversed, the ethyl alcohol was produced first; followed by the unreacted ethyl acetate. The separation between the two concentration peaks was used to calculate a value for SOR because the relative amount of separation could be related quantitatively to SOR. This is equivalent to the separation obtained in an analyticalchromatographic column used to analyze mixtures. The results are used to protract the plots of tracer concentrations vs. volume of fluid produced. Getting the SOR is by matching the plots. The method’s precision is 2% ?%PV.The interpretation is critical in this method. The success of the method depends on matching the plots of tracer concentrations vs. volume of fluid produced obtained from field to measuring SOR. Interpretation methods of the field data include analytic interpretation and numerical simulation interpretation. There is no analytic interpretation model to get a reliable precise at present. In numerical simulation interpretation, there had been developing three numerical simulation models to interpret the field data. The models are "ideal" one-layer model multi-layer model fluid drift model It requires more trial calculation to obtained matching the field data very well with the increasing complexity of the reservoir simulation model. As a result, the general simulation procedure becomes very unwieldy and the calculation workload will increase. So the researchers have been improving the numerical simulation arithmetic applied in the single-well chemical tracer test.The precision of the analytic model applied in the single-well chemical tracer test was affected because its ignoring the diffusibility in interpreting with analytic method. The affection is very severity in the case of "fluid drift" test.The paper reviewed the background history and actuality of the single-well chemical tracer (SOR) method for measuring residual oil saturation at first. Then describe its whole process(from library experiment to field testing) and general interpretation model after expatiating its mathematics theory method principle. Finally researched its numerical simulation model, this paper emphases on the research in th更多还原