Detailed Description And Distribution Predicting Of Ordovician Fractures In Block 4 Of Tahe Oilfield

Tahe Oilfield is a fractured-vuggy carbonate reservoir. The superposition of multi-phase tectonic movements made the fractures developed very complex, the cave with which constituted a complex fractured-vuggy reservoir of Tahe Oilfield. However, so far, the fracture system in Tahe Oilfield is still insufficient understanding, which severely affects the exploration and development of Tahe Oilfield. Based on the study of the fracture characteristics, the controlled factors, the simulation of the palaeostress field and so on in the work area, combined with the logging data, et al., the text completed the prediction of the fracture development and the study of the fracture combination and zoning, then analyzed the type of relationship between fractures and caves.Through observation of the cores and the thin sections of more than 20 wells, combined with FMI and other analytical data, the text studied the dip, length, direction, volume density and other system characteristics of fractures. From the filling case of fractures, the text analyzed its effectiveness and the controlling factors of the fractures, which mainly included: tectonism, lithology, pre-fracture, rock stratum structure and local structures. And the fractures had been divided by stage, four stages divided : pre-Caledonian, Caledonian, Hercynian early and Hercynian late– Himalayan. On the basis of above, the genetic mechanism of the fractures was explored.In view of that, the early Hercynian in the area is the most important period of tectonic movement fractures formed and is the major developmental stages of karsts, the text conducted the simulation of tectonic stress field during early Hercynian, and predicted the major fracture zones, which were compared with the exploration practice in the area.Through analysis of logs and FMI, this text summarized the characteristics of conventional logging and FMI that responsed to the fracture sections, and used the data of cores and logging to identify 6 integrated characteristic parameters that was closely associated with the fracture sections. Based on this, it was proposed to using Bayes discrimination to predict the fracture sections. Through testing a few wells with the imaging logging data, the results showed that the method was simple, efficient, and feasible in predicting the fracture sections. Through the comprehensive use of the methods above in the study area, the fracture zones of nine sections were divided, and the thickness distribution of Ordovician fractures was summarized.On the basis of the aforementioned study, the text analyzed the combined relationship between fractures and caves, and obtained five kinds of fracture-cave combination, which were isolated cave, fracture-cave, hole- fracture, cave-fracture, fracture-cave- fracture. Using 60m from the Ordovician top the cave layer as the standard, and based on the principle that the same combination of fracture-carve and the fracture sections were not self-separated, the nine sections divided into caves and fracture sections were taken to zone...