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疏松砂岩常规稠油油藏适度出砂提高产能基础研究
【作者】 何冠军;
【导师】 杜志敏;
【作者基本信息】 西南石油学院 , 油气田开发工程, 2005, 博士
【摘要】 油井出砂会造成井壁失稳、套管损坏、地层破坏、井下及地面设备的损害、管线的磨蚀及堵塞、油层被砂埋、修井作业及对采出砂的处理等问题,影响开发效果,增加开采成本,防砂一直是开采的关注点;而疏松砂岩稠油油藏中进行适度出砂生产,却能够大幅度提高油井的产能及一次采油的采收率,创造较好的经济效益和社会效益。本文针对油井出砂与防砂这一矛盾体,分析了油井出砂机理及其影响因素、出砂提高产能的机理、适度出砂适用条件,建立了油层开始出砂预测模型、出砂量与产量定量预测模型,奠定了适度出砂研究的理论基础。根据疏松砂岩稠油油藏的地质特征和开发特点,分析出砂生产的利弊,提出在疏松砂岩常规稠油油藏中进行适度出砂开采的观点,即在生产过程中根据需要对出砂量或其它出砂参数加以控制,进行携砂生产,达到既提高油井产能,又减少防砂费用的目的。 本文研究旨在充分发挥油井适度出砂生产的优点,把握适度出砂生产的特点和提高产能的机理;对开始出砂的临界条件、出砂量以及出砂量与产能两者之间的关系进行定量预测。 在研究过程中发现,本论文之前进行的出砂临界条件、出砂量预测等方面研究大多是采用Terzaghi有效应力理论,而且所得到的预测结果与实际情况有较大偏差,本文将双重有效应力应用于出砂临界条件预测和出砂量预测两个方面,取得了较好的结果,并解释了以前预测结果出现较大偏差的原因。 本文取得的主要成果: 在全面分析疏松砂岩稠油油藏生产过程中出砂与防砂生产特点的基础上,根据两者的优缺点,提出在疏松砂岩常规稠油油藏的开发过程中,进行适度出砂开发的方法; 详尽研究了疏松砂岩稠油油藏生产过程中出砂机理及出砂影响因素,出砂生产的特点,出砂提高油井产能的机理,适度出砂适用条件等; 对多孔介质有效应力进行系统分析和推证,证明双重有效应力的合理性,并推导了储层物性参数的动态模型。 将双重有效应力理论用于地层开始出砂临界条件的预测,并推导了地应力各向同性及各向异性条件下裸眼(或射孔孔道)发生剪切(或拉伸)破坏、射孔端部发生剪切(或拉伸)破坏时的预测模型; 应用双重有效应力理论推导了出砂量及出砂量与产能两者之间定量关系的解析模型,可用于出砂量及其适度出砂对产能影响的预测; 将双重有效应力原理应用到流固耦合理论中,对非混溶饱和两相渗流
【Abstract】 Sand production becomes a growing concern to more and more petroleum engineers. On the one hand, it will bring a lot of production troubles, such as the erosion of pipelines, plugging, oil zone buried by produced sand, and dealing with the produced sand, which costs billions of dollars each year. On the other hand, producing with limited sand in unconsolidated sand reservoir will enhance the oil rate and lower the costs of sand proof. Based on the detailed analysis of sand production while producing, a new method-producing with controlled sand in unconsolidated sand reservoir was presented, say, according to the facts of reservoir and the target, we can produce with limited sand by controlling the sand rate and other producing parameters.In order to maximize the profits of producing with limited sand, the following items are the concerns. It is necessary to study the characteristics, the mechanism of improving production rate about sand production. The onset of sand production, the sand rate and the relationship between production rate and sand rate should be predicted and they are the basis for decision making of producing with controlled sand.During the research, the past methods used to predict the onset of sand production, the prediction of sand rate and the quantitative relationship between the sand rate and production rate was discovered some wrong. It results from the theory of Terzaghi effective stress the past researchers used. By using the double effective stress, the difference between the prediction data and real data is minimized and it explained the reasons of the difference between them.Based on the above study, the following conclusions were achieved:Through comparing the methods of sand proof and cold production with sand, a new method—producing with limited sand was formed and presented here. This method is suitable to heavy oil reservoirs in unconsolidated rock and will benefit from the both methods of sand proof and cold production.In order to make the method of producing with limited sand more acceptable and practicable, this paper analyzed the mechanisms sand production, the characteristics of producing with sand and the factors which plays a role in sand production, and the aspects that enhance the production rate while producing with sand in detail.This paper proposed to predict the onset of sand production by using double effective stress and we demonstrate the structural effective stress is more suitable forpredicting the onset of sand production, and derived the formulae that used to predict the onset of sand production due to shear failure of wellbore(perforation tunnel), perforation tip.The analytical model used to predict quantitatively the effect of sand production on the production rate was derived, and it can be used to make the decision of producing with limited sand.The past coupled model used in reservoir engineering was modified by applying the primary effective stress and the finite element formulae of this model were achieved. Based on this coupled model, the immiscible sand and liquid flowing model used to predict quantitatively the rate of sand and oil was derived and built The results calculated from the modified model were demonstrated more reasonable.This paper analyzed in detail the characteristics of producing with sand, the factors which affect sand production and the mechanism of production rate enhancement due to sand production. Based on the above-mentioned research, a new method which allows limited sand production is presented. The basic research on putting the method of producing with limited sand into practice was carried out, such as the prediction of the onset of sand production, the quantitative relationship of the sand rate and production rate. The conclusions achieved in this paper are the basis for making the method of producing with limited sand in unconsolidated sand rock reservoirs, and more research should be furthered such as the reasonable limit of sand rate, when and how to begin sand proof, how to determine the parameters and the related research about producing with limited sand.
【Key words】 unconsolidated sand reservoir; heavy oil; producing with limited sand; double effective stress; coupled model; sand production prediction;