ABSTUCT Many normal and a few reversed characteristic directions of magnetization have been obtained by predominantly thermal demagnetization from ten sites of the Late Permian Emeishan Basalts collected near Kunming, Yumran Province. The normal ma~etization directions pass a fold test at the 99% confidence level and yield d~ination/~clina~on = 26"/ -12", k = 46, qg = 6" and a paleopole at 50"N, 241"E. However, the reversed-polarity directions, with d~lination/inc~ation at 244"/+ 3" are not antipodal to the normal ones, which is also noted in other studies of the Emeishan Basalts of the Yangtze Paraplatform of the South China Block. Speculations about the cause of this lack of antipodaiity center on: (1) local relative rotations, (2) incomplete demagnetization, (3) unusually large non-dipole fields, secular variation or asymmetric reversals in the Late Permian, (4) errors in sample orientation, or (5) later remagnetization represented by one or the other polarity group. The first two causes are ruled out by our obsetvations, and the third cannot be tested with data from China alone but is unlikely because it has not been observed elsewhere. Errors in sample o~en~~n may be present in those studies that used a magnetic compass, because sample intensities of magnetization are on tire high side. However, for the normal-polarity directions, a solar compass has been used in some of the studies and ail normal-polarity directions observed in the area are in agreement. Thus, sample orientation errors can be invoked only for the reversed-polarity directions. In order to test cause (5), we have examined the magnetic carriers in eight samples with scanning electron microscopy. Titanium-poor to titanium-rich magnetite, commonly cruciform in crystal habit, indicates primary igneous crystallization in two samples that have NE and WSW declinations. In contrast, six no~~-~Iari~ samples with NNE declinations show pervrsive replacement of original titanom~etite by titanic-me magnetite and sphene, indicating a high degree of alteration. We ascribe this alteration to late hydrothermal circulation and argue that it has caused remagnetization in post-Permian times. This study suggests, therefore, that the NE-SW directions are more likely to be representative of the Late Permian paleomagnetic field than the NNE directions.

Jimusaer tight oil reservoir is characterized by complex lithology, low permeability and high total organic carbon (TOC) content. These features make conventional logging responses very complicated and bring big troubles to reservoir identification. Horizontal well drilling is extremely difficult due to high heterogeneity and uncertain faulting. To maximize oil production with low cost, an integrated solution is provided. First, accurate reservoir characteristics of the pilot well was got using an unconventional evaluation approach by combining capture spectroscopy log, micro-resistivity imager log, nuclear magnetic resonance log, et al. Second, structure analysis for sidetracking well and well correlation between the sidetracking well and the pilot well were done to guide the horizontal section drilling. Third, reservoir quality and completion quality were evaluated for horizontal well, and a 3D structural model was built to optimize the stimulation design by combining reservoir quality, completion quality and natural fractures.

Fracture effectiveness, extension and connectivity from borehole surface into deep formation are the key factors to control producibility of volcanic formations. A systematic and integrated fracture delineation approach was set up which integrated available measurements with multi-scale depth of investigation to cover borehole surface, near wellbore and deep formation. High resolution micro-resistivity image was used to identify fractures on the borehole surface; shear anisotropy enhanced by dispersion analysis was used to evaluate fractures away from the borehole; Borehole acoustic reflection survey technique was applied in vertical wells to assess probable fracture networks deep into formation up to maximal 10 meters. This multi-scale approach had been implemented in multiple wells drilled in volcanic formations in Junggar basin, which helped a lot on fracture evaluation and productivity estimation.