Upper Carboniferous Sedimentary Facies Of Wucaiwan Depression In Junggar Basin

The topic of study of this thesis is Wucaiwan depression in Junggar Basin, the object of study is Upper Carboniferous.Through investigation by the outcrop, drill core data we can identify four type depositional system, five type sedimentary facies and eleven type sedimentary intrafacies.By Rock in contrast to well and seismic combination of well we can established facies identification. Through core observation and well logging data we can learn that in this area on the development of a large area of Carboniferous volcanic rocks, volcanic rocks are divided into two major categories :volcaniclastic rock and volcanic lava. We can be carried out on the volcanic facies classification, eruption phase can be divided into air fall subfacies, hot base surge facies and pyroclastic bearing lava flows, overflow phase is divided into upper facies, middle and lower sub-facies phase. Through the sample characteristics of sheet rock can be developed that Wucaiwan depression has two primary and secondary storage space type, primary storage space mainly intergranular pore, porosity, shrinkage joint, inter-particle gap, etc.; secondary storage space include corrosion aperture, construction joints, weathered joints and so on. The aperture constitute the main reservoirs of Carboniferous space provided for the oil and gas reservoir sites. According to the interpretation of seismic data, the results can be the type of seismic phase in three categories, respectively, mainly volcanic seismic facies, mainly sedimentary seismic facies and transition facies. Through the preparation of single well facies and well tie facies and seismic phase, and combined with previous research on this area of the Upper Carboniferous ,to establishment of the phase .On the phase we learn that volcanic rocks are mainly distributed in northwest and southeast of the study area, the central area of depression have a partial distribution of volcanic rocks, sunken in the center of the lake sediments. General distribution of sedimentary facies by the regional tectonic control of the ancient topography and other factors. Through the volcanic properties of the statistical and research data show that the depression area Wucaiwan porosity and permeability generally poor physical properties, porosity, permeability slightly better than the point, which reflects the properties of the volcanic region is generally low, the overall depression poor property, which the study area and composition of rock types have a great relationship. Wucaiwan Depression favorable reservoir facies is divided into three levels, the findings showed that: the volcanic reservoir is not well developed, the low reservoir development, mainlyâ…¡, Classâ…¢reservoir; reservoir development have close relationship with the distribution of volcanic facies, overflow with the upper reservoir facies development well, eruption air fall phase which far off the crater, hot base surge facies and pyroclastic bearing lava flows development of the middle reservoir, overflow phase and near the lower part of the crater facies and volcanogenic sedimentation facies with poor reservoir development. The study suggested the relatively favorable reservoir facies area is the north-west of Dinan bump and the southeast of Baijiahai bump.