Abstract:

Well trajectory has important impact on the drilling encounter ration of fractures. In order to study the influence of wellbore inclination angle on the statistics of fracture characteristic parameters, over 100 wells with FMI data are grouped into wells with small inclination angle (including vertical wells) and wells with large inclination angle (including horizontal wells). The author  carried out the statistics of average fracture dip and fracture intensity by using FMI data of the two grouped wells respectively, and compared the results with the statistics derived from all ungrouped wells. It shows that the average fracture dip and fracture intensity are both smaller than the statistic results from the wells with large inclination angle and ungrouped wells. So, the drilling encounter ration of fractures for wells with small inclination angle is obviously smaller than the one for wells with large inclination angle. This conclusion is of significance in three aspects, first, for the G-H layer of the fractured carbonate reservoir described, wells with large inclination angle should be drilled in order to  further evaluate the oil exploration potential. Secondly, only the drilling and well data from the wells which are nearly perpendicular to the fracture surface should be used if we want to get accurately statistics of fracture inclination angle and a more objective evaluation of fracture density. In addition, for the exploration and development of the same high angle fractured reservoirs, it strongly suggests that slant wells with large inclination angle should be used.

Key words: wellbore inclination angle, fracture dip, fracture intensity, fractured reservoirs, carbonatite rocks, oil reservoir