Overall Prediction Of Fracture Growing Of Xujiahe Formation In DY Region Chuanxi Depression

It is believed that Chuanxi region experienced extremely complex regional geology and structural evolution. The oil and gas reservoirs are reconstructed repeatedly and become extremely abnormal and extra tight and low-porosity reservoirs. XuIII and XuII zones of Xujiahe formation in DY region are generally tight. With this limit, the formation cannot get good deliverability in spite of its good conditions of structure, mother rock and cap rock. So it is necessary to reconstruct the formation by fracture system. As for tight sand reservoir, the function of fracture network is not only supplying reservoir pore space but also supplying migration pathway for oil and gas. Therefore, fracture prediction is of great significance in identifying tight sand reservoirs. Meanwhile, identification of rich region under control of fracture is of great significance for drilling success ratio.Based on former research achievements, aiming at XuIII zone in Xujiahe formation of DY region, this paper launched comprehensive evaluation of near well-bore fracture development, seismic fracture prediction and comprehensive evaluation of rich region under fracture control. The master line is fracture evaluation, combined with geology, logging and seismic. It concludes that the different fracture orientations of the drilled wells prove to some extent that this region is influenced by multiple phase tectonic movement. The analysis of the relationship between fracture and deliverability shows that the fractures of Xu III zone and Xu II upper sun-zone that contribute most to deliverability are high angle (>60°) fractures and net like fractures. Besides, the most proper inversion method for current exploration situation of DY region is probability density function random seismic inversion method based on statistics. Based on overall evaluation of drilling fractures, several seismic fracture prediction methods are adopted to compare results of different seismic fracture prediction methods and results of logging fracture evaluation methods. It is concluded that it is best to use seismic information with structure geometry properties (curvature, dip angle, etc.) to comprehensively predict fracture development in DY region, whose result coincides well with logging fracture evaluation result. This paper applies clustering analysis and neural network gas bearing detection on DY region for the first time and its predicted result coincides well with current test result. The profile result of clustering analysis coincides well with"dim spot"pattern of"weak crest->weak valley complex wave shadow area", which shows that the"dim spot"characteristics is the basic pattern of seismic fracture and gas bearing prediction of the tight reservoir of Xujiahe formation in DY region.The form of fracture is influenced by many factors. Its physical property is complex. Fracture makes reservoirs strong heterogeneous. So the study on distribution regularity of fracture orientation and intensity (density) requires combination of multiple disciplines. Based on former research achievements, this paper comprehensively studies on fracture development in DY region by geology, logging and seismic methods, and the overall result evaluation graph of rich region is obtained, and support technologies of fracture development prediction for gas reservoirs of X III and Xu II zones are developed, which is technical support for exploration and exploitation of gas reservoirs of Xujiahe formation in DYregion.