油田水力压裂裂缝监测的井地电阻率法研究与应用

发布时间：2018-09-11 11:25

【摘要】：油田水力压裂裂缝方位的准确监测可以有效的评价压裂效果，并为下一步压裂参数的设计提供依据。除此，可以推断出剩余油的分布。井地电阻率法是目前比较成熟、应用比较广泛的监测水力压裂裂缝方位的方法之一。井地电阻率法是一种将电测井法和地表直流电法相结合的综合地球物理勘探方法。基本原理是将供电电源置于井中，供电过程中测量由地层电阻率变化引起的地表各个观测电极的电位或者电位梯度的变化，来反映地下介质的电阻率特征。由于其具有成本低、操作简单、实施方便、场源实现容易、不破坏井况和不影响生产等有别于其他地球物理勘探方法的优势，所以本文对基于井地电阻率法的油田水力压裂裂缝监测展开了研究。首先，三维井地电阻率法数值模拟正演计算是井地电阻率法在油田裂缝监测中应用的理论基础。本文根据地下任意线电流源产生的电位公式和有限差分法等理论进行了正演研究，通过建立不同的地电模型（异常体埋深不同模型，异常体长度不同模型，储层电阻率不同模型，存在地表漏电流模型，观测点布置不均匀模型），对比了电位法和电位梯度法观测方式下的地表观测结果及其探测深度。分析了储层电阻率不同、地表漏电流的存在和复杂地形对观测结果的影响。其次，，消除噪声是野外实验数据处理中的一个重要环节。本文分析了野外实验的采集数据，主要包括漂移干扰、工频干扰和随机干扰等，并分别采用最小二乘多项式拟合法、巴特沃斯低通滤波（中值滤波）和数字式平均技术消除，提高信噪比。除此，提出采用BP神经网络校正由地形（观测点布置不均匀）引起的畸变场响应。最后，将编码信号引入到井地电阻率法裂缝监测中，编码信号作为供电电流源，利用相关法消除干扰，提高了信噪比，加大了探测深度。本文介绍了编码信号的产生、自相关特性和相关检测原理，分析了编码信号相关检测法消除干扰的原因及参数选择原则。在吉林省科技发展计划重大项目“井地网络化油水界面电阻率成像仪的研制”的支持下，研制了具有自主知识产权的井地网络化油水界面电阻率成像仪，利用该套仪器在大庆、辽河、吉林等油田进行了60多口井次的野外实验，并取得了良好的效果。本文以大庆十厂朝阳沟的一口压裂井为例，说明了野外实验概况。
[Abstract]:The accurate monitoring of hydraulic fracturing fracture azimuth in oil field can effectively evaluate the fracturing effect and provide the basis for the design of fracturing parameters in the next step. In addition, the distribution of the remaining oil can be inferred. Well-ground resistivity method is one of the more mature and widely used methods to monitor the orientation of hydraulic fracturing fractures. Well-ground resistivity method is a comprehensive geophysical exploration method which combines electric logging method with surface direct current method. The basic principle is to put the power supply in the well and measure the change of the electric potential or the potential gradient of the observed electrode caused by the change of the formation resistivity in the process of power supply to reflect the resistivity characteristics of the underground medium. Because of its advantages of low cost, simple operation, convenient implementation, easy realization of field source, no damage to well condition and no influence on production, it is different from other geophysical exploration methods. In this paper, hydraulic fracturing fracture monitoring based on well-ground resistivity method is studied. Firstly, the forward modeling of 3-D well ground resistivity method is the theoretical basis of application of well ground resistivity method in oil field fracture monitoring. In this paper, the forward modeling is carried out according to the potential formula and the finite difference method of the current source of any underground line. Different geoelectric models (different models of abnormal body buried depth, different length of anomalous body) are established in this paper. Different models of reservoir resistivity exist surface leakage current model and non-uniform model of observation points. The surface observation results and their detection depth are compared between the potential method and the potential gradient method. The effects of surface leakage current and complex topography on the observation results are analyzed. Secondly, noise elimination is an important part of data processing in field experiments. In this paper, the collected data of field experiments are analyzed, including drift interference, power frequency interference and random interference. The least square polynomial fitting method, Butterworth low-pass filter (median filter) and digital average technique are used to eliminate the data, respectively. Improve the signal-to-noise ratio. In addition, the BP neural network is used to correct the distortion field response caused by the topography (uneven distribution of observation points). Finally, the coded signal is introduced into the well ground resistivity fracture monitoring, the coded signal is used as the power supply current source, the correlation method is used to eliminate the interference, the signal-to-noise ratio (SNR) is improved, and the detection depth is increased. In this paper, the generation, autocorrelation characteristics and correlation detection principle of coded signal are introduced, and the reason of eliminating interference and the principle of parameter selection by correlation detection of coded signal are analyzed. Supported by the important project of Jilin province science and technology development plan, "the development of oil-water interface resistivity imager with well-to-ground network", a oil-water interface resistivity imager with independent intellectual property rights has been developed and used in Daqing. Field experiments of more than 60 wells have been carried out in Liaohe, Jilin and other oilfields, and good results have been obtained. Taking a fracturing well in Chaoyang ditch of Daqing No. 10 Factory as an example, the general situation of field experiments is explained.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：P631.811

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