【作者】 张玲玲；

【导师】 汪宏年；

【作者基本信息】 吉林大学 ， 理论物理， 2007， 硕士

【摘要】 双感应测井技术是测量地层电阻率的重要手段之一,该仪器通过同时测量两个探测深度不同的视电阻率,并与球型聚焦测井仪器组合在一起,广泛应用于油水层的划分以及储层的定量解释和评价等。然而,在进行薄储层评价和解释中,由于受仪器纵向分辨率的限制,围岩和邻层的相互作用对测量结果影响较大,如果直接根据测量结果进行储层的解释和评价,往往不能取得理想的应用效果。应用正反演理论建立双感应测井资料反演技术,消除或降低围岩和邻层对测量结果的影响,以便提取出更加可靠的地层电阻率、提高测井资料解释的符合率等,一直是石油测井中重要的研究课题。为进行双感应测井资料的反演处理,涉及到如下四个方面的主要内容:1)、综合分层理论与技术,以便从测井资料中划分出层界面和各个地层上的电阻率初值;2)、原始视电导率的提取,设法消除三点反褶积和趋肤效应校正对原始视电阻率的改变,提取出准确可靠的视电导率;3)、快速数值模拟,以便计算层状介质中双感应仪器的响应;4)、非线性反演理论,通过微分方程反演的理论研究建立了一套快速迭代算法,实现测井资料与数值模拟结果的最佳拟合,得到各个地层上的真实电阻率。本论文将重点介绍2)～4)中的主要研究内容,并通过理论和实际资料的处理对所有软件进行检验,特别是结合大庆油田的实际情况,对大庆油田五十多口实际双感应测井资料进行了独立的综合处理,处理解释与试油结论对比显示,符合率得到80%以上,极大提高了双感应资料的应用效果和应用潜力,取得了非常满意的应用效果。更多还原

【Abstract】 Dual induction logging tool (DIT) has been used in oil industry as one important logging means for several decades. The tool consists of several transmitter and receiver coils with different spacing, measures two apparent resistivities with different investigation depth simultaneously. Using the measurement, we can recognize the invasion characteristics of formation and find positions of oil and gas bed. However, the measurements become to impossibly reflect the real invasion of natural formation and the true value of formation resistivity in thin bed because of influence of shoulder beds and invasion zone invasion depth in thin reservoir or deeper invasion formation, so it will causes more difficultly to process and explain logging datum. How to deal with dual induction logging datum, eliminate the effect of shoulder bed and invasion zone on measurement result, and recover true invasion character and formation resistivity, by modern numerical process and inversion method, is an important research task in geophysical logging.Putaohua formation in eastern of Daqing is a key exploring part for a long time, where the geological conditions are complicated, transverse connectivity of reservoirs is somewhat bad, and the distribution of oil and water are irregular. Due to the thin reservoir, the excessive mud and deep invasion, the logging data is often far from the true values of formation so it leads to the evaluation of oil and water more difficult. Presently, the second process and interpretation of well logging in Daqing oil field is executed so that we can find new oil beds. Prof. Wang Hongnian, my supervisor finished the project titled as identification of oil and water layer through inversion of DIT supported by Daqing logging company. In the project, a fast inversion of software for DIT has been developed to solve the previous problems, and greatly improve evaluation of well logging data.For finishing my candidate thesis, I attended the project and finished some of the research. In this paper, I systematically summarize the main work and achievement in the project, including the fast forward algorithm, the picking out raw apparent resistivity, and new iterative inversion algorithm. The main contents are following as:In Chapter 1, I summarize and point out the present status, signification of the inversion of DIT, the main contents in this paper.In Chapter 2, we study fast forward algorithm of DIT by the mode matching method (NMM), and investigate the response character in several different environments. Simulation results indicate the resolution of DIT is usually very low in the high resistance, its apparent resistivities are still largely different from the true value of formation even in bed thicker than 8.m. Furthermore, the influence of change in mud resistivity on the response is small. In addition, the invasion zone affects the response. In the case of shallow invasion (invasion radius less than 0.7 m), the effect of the change in invasion radius on middle induction logging response is larger than that of deep induction response. However, when invasion zone becomes deeper, e.g. larger than 1m, the effects of change in invasion radius on responses of both deep and middle induction loggings are almost same.In Chapter 3, I give an approach to eliminate the skin effect correction and three-point deconvolution entirely. Apparent resistivities of DIT have been processed by skin effect correction and shoulder bed correction so the raw apparent resistivities must be recovered before inversion. An iterative method is advanced to eliminate skin effect. Compared with previous method, the new method can greatly enhance the precision of algorithm of elimination of skin effect. The numerical tests show that after 5 iterations, correction of skin effect can be completely removed. After removing of the skin effect, the inverse filter of three-point deconvolution is accurately obtained by Z-transformation theory, so that we can entirely eliminate the influence of three-point deconvolution on the deep induction logging through the 7 or 9 points of inverse numerical filter.In Chapter 4, it is first given that the relation of spatial distribution of formation conductivity to the model vector consisting of the virgin formation resistivity, flushed zone resistivity, invasion radius and horizontal boundary depth of each bed. And through differential formula, the equation of perturbation in formation conductivity with the change in model vector is derived. In addition, the fast algorithm of Fréchet derivative matrix of DIT is established on base of Born approximation and the semi-analytic expression of electromagnetic (EM) field. Then, normalization is introduced to transform the model vector and logging data into dimensionless variables. Model parameters are iteratively updated to realize best fit of field logging data with synthetic logs through singular value decomposition (SVD).Theoretically, the inversion algorithm can simultaneously reconstruct all model parameters. However, due to two logs being available only during inversion, an approximative algorithm is used to reconstruct virgin resistivity for improvement of stability of inversion results. First, resistivity in a investigation depth can be gotten through the inversion of the medium induction log (IM) only, then fixing the interface positions. Then, deep induction log (ID) is only used to reconstruct other different bed resistivities. Since IM and ID have different investigation depth, the inversion results from ID will be closer to virgin. So we can know the invasion character (high invasion or low invasion) around borehole by their relative sizes,and help to identify oil or water formation. Besides, because of ID with deep exploring depth, errors of inversion resistivity of ID from formation virgin resistivity are largely less than that of apparent resistivity of ID in either deep or shallow invasion bed, so the better estimation of formation virgin resistivity is also obtained.更多还原