The Research Of The Fine Depiction And Differences On The Reefs Microfacies Of Changxing Formation In Northeast Of Sichuan

Guided by the theories of sedimentology, petrology, petroleum geology andpaleontology geological basic subjects, the paper took the reefs of ChangxingFormation in northeast of Sichuan as the research object. A research was made on thesedimentary microfacies and differences of the reefs in this paper, and thecorresponding evolutionary model of reefs was builed. Furthermore, the distributionand the regularity of development of the reefs also had been forecasted. All of thesecould provide important basic geological datas of oil and gas exploration for the reefsof Changxing Formation in northeast of Sichuan.According to the investigation on the field section outcrop and the observation ofdrilling cores in the northeast of Sichuan, this paper studied the identificationcharacteristics of facies marks,such as the colors of rocks, the types of rocks,sedimentary structure, paleontology. And two types of reefs mainly were developed inChangxing Formation of Upper Permian in northeast of Sichuan basin, including ofplatform margin reefs and intra-platform reefs. Based on the sedimentary microfaciesanalysis of single well and even wells, the reefs of Changxing Formation werediscussed in detail about the space distribution and evolution characteristics.Furthermore, the different sedimentary characteristics and topography of ancientgeography were deeply analyzed.The comprehensive research on the section outcrop, drilling cores, commonslices and cast slices in the northeast of Sichuan was carried out, and it was turned outthat the lithologies of Changxing reefs mainly were skeleton reef limestone, bondreef limestone, barrier sedimentary rocks and bioclastic limestone. The reefs ofChangxing formatrion in the northeast of Sichuan basin include the platform marginreefs on both sides of Kaijiang-Liangping trough, platform margin reefs on west sideof Hubei-Chengkou trough and intra-platform reefs. The differences were analyzedafter a fine description to the microfacies of reefs. And the following is the difference：(1) the differences of development times;(2) the differences of distribution anddevelopmental scale;(3) the differences of development styles;(4) the differences ofdolomitization strength. According to the different sedimentary microfacies, a preliminary study wascarried out to study the causes of differences, the development of reefs werecontrolled both by the tectonic environments and by the sedimentation, and theshallow sea where developed fracture and rase uplift was good for the development ofreefs.