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Research Of Microseismic Source Inversion Methods In Hydro-fracturing

Posted on:2014-07-01Degree:MasterType:Thesis
Country:ChinaCandidate:Q H MaoFull Text:PDF
GTID:2250330401480759Subject:Earth Exploration and Information Technology
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The hydro-fracturing microseismic monitoring is an important new technology, which was developed in the field of low-permeability reservoir fracturing, reservoir drive and water displacement front. The technology is that multistage three component seismometer are arranged in neighboring wells. Then the seismometers monitor and receive the microseismic waves (microseismic events), which is produced in the fracturing process of fracturing well’s target layer. By the inversion of these events positioning, we will evaluate the microseismic source location parameters to describe the geometry of the crack growth and spatial distribution in the hydraulic fracturing process,which can provide real-time the fracture’s length, height, width and azimuth in the hydraulic fracturing process. By using these information, we can optimize fracturing design and optimize well network or other oilfield development measures, and finally improve the recovery factor of oil and gas.First, This paper discusses the principle of microseismic monitoring of hydraulic fracturing.Then we introduce the microseismic mechanism and the characteristics of high frequency and weak energy in the generated microseismic. Next, we expound forward algorithm based on ray tracing model and its process in detail, The main steps are described as follows:Firstly, it is necessary to establish the initial formation velocity model; Secondly, we will calculate each layer interface equation; Thirdly, in the given excitation point coordinates, we can determine whether to reach the observation point by using shooting Method. Fourthly, we will make the synthetic record. Then, we will describe model method research, arrival picking method, principles of polarization analysis and microseismic data inversion algorithm. We will introduce more inversion method principle, such as ordinary analytical inversion principle, Geiger principle, advanced exhaustive grid search method principle, Newton’s principle, genetic algorithms and gradient descent method principle. The researching inversion method in this thesis is the advanced exhaustive grid search method constrained by polarization analysis. We expound inversion method ideas and inversion module interface by using QT Creator, Finally, we deal with actual microseismic monitoring data by using this inversion method. If so, we can verify the correctness, effectiveness and practicality of this method.In the instance of the application, we deal with actual microseismic monitoring data by using the advanced exhaustive grid search method constrained by polarization analysis.The result mainly reflects the spatial form of fractures, and we can draw the following conclusion:i).The processing and interpretation processes of microseismic monitoring data may roughly consist of establishing microseismic work area, data preprocessing, loading microseismic data and well data, establishing velocity model and its calibration, first arrival picking of microseismic events, microseismic events inversion, the three-dimensional display of the fractures and interpretation of the fractures. But the ultimate purpose of dealing with the microseismic monitoring data is the inversion positioning of microseismic events. In this way, we can describe induced fractures due to fracture the formation quantitatively.ii).The core of the processing and interpretation processes in the microseismic monitoring is microseismic events inversion, but some factors affect its accuracy, such as the accuracy of the velocity model, the accuracy of first arrival picking of microseismic events, inversion method, and so on. In the fracturing wells, Fluid immerse strata,which will affect the its velocity. Therefore, we should real-timely correct velocity model in the later study. Only in this way can we provide the more accurately velocity information for the inversion research.iii).Because the accuracy of some first arrival picking of microseismic events are not high, we adopt inversion algorithm in the microseismic inversion positioning, and this method should does multi-parameter constraints that controls trend of inversion focal point, This thesis discuss the advanced exhaustive grid search method constrained by polarization analysis. In the practical microseismic data, we use the the relatively first arrival moveout difference between picked shear wave and theoretical calculations to establish of the objective function, and we use the advanced exhaustive grid search method constrained by polarization analysis to locate the spatial position of hypocenter reliably. On the display of three-dimension, we can see the general morphology of fracture space in the fracturing process.iiii).The research generally have not sure solutions. Consequently, in this inversion, we adopt the constraint parameter of microseismic events polarization direction to accelerate inversion speed and improve accuracy. As a result, we should add more suitable priori information to constrain the inversion of microseismic events in the later study.
Keywords/Search Tags:hydro-fracturing microseismic, forward algorithm based on ray tracingmodel, polarization analysis, advanced exhaustive grid search method, microseismicsource inversion
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