Abstract
The accurate identification of the horizontal well marker bed is to guarantee the soft landing of the well trajectory. With the intelligent development of the petroleum industry, it is feasible to apply computers to identify the marker bed automatically. In case-based reasoning technology, the data of well logging while drilling (LWD) as characteristic parameters are compared with those of adjacent well. By taking the depth sequence of LWD data as time series and using Dynamic Time Warping (DTW) similarity measure algorithm, the similarity index of each drilling depth is calculated corresponding to the marker bed in the adjacent well. The total similarity curve is obtained by giving different weights of different feature parameters. Selecting natural gamma, deep resistivity, and shallow resistivity LWD curves as characteristic parameters, two horizontal wells in JL block of Junggar basin are analysed by this method. The result of similarity curve indicates the location of the marker bed and the total similarity value reaches 78%. The research shows that the method based on case-based reasoning can identify the marker bed of the horizontal well accurately and effectively, assist the geologist to carry out formation correlation of multiple wells at the same time, reduce the cost of human labour force, and improve work efficiency.
Highlights
In the entire process of geosteering, comprehensive interpretation of geological information based on logging-whiledrilling data plays a vital role
This method mainly depends on geologists to observe logging while drilling (LWD) curves and compare the microscopic characteristics of the curves artificially, so as to find out the location of the marker bed while drilling. is artificial method requires geologists with abundant experience and extensive knowledge to do a great deal of data calculation and analysis. e guidance software can improve the efficiency and accuracy of on-site analysis
The analysis of LWD data can reflect the formation of drill bit in real time. e identification process of marker bed is similar to that of case-based reasoning (CBR) [7, 8]
Summary
In the entire process of geosteering, comprehensive interpretation of geological information based on logging-whiledrilling data plays a vital role. E similarity between the data of the adjacent well marker bed and the case corresponding to each well depth point in the case library is calculated on the curve value and the morphology. Erefore, the similarity search algorithm based on time series can be used when calculating the similarity between cases in the recognition problem of the marker bed. In the intelligent recognition problem of the marker bed, the DTW algorithm with better applicability is introduced, which effectively solves the limitation of the Euclidean distance calculation method in terms of time axis expansion and curvature [13,14,15,16,17]. TS : total similarity L : Marker bed Figure 2: Schematic diagram of similarity calculation of drilling well LWD curve and adjacent well marker bed in marker bed recognition based on CBR.
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