Informatics Publishing Limited

Chen Feiran ¹, Xing Xiang ², Zhang Zhiyao ¹, Zhou Xiaoxiao ³, Tan Cheng ³

Affiliations
1 PetroChina Research Institute of Petroleum Exploration and Development, Beijing-100083, CN
2 Enshi Development and Reform Commission, Enshi-445000, CN
3 School of Earth Science, China University of Petroleum, Beijing-102249, CN

Abstract

According to previous research, Cambrian Yuertus source rocks is considered to be an important source rocks in the Tarim Basin, which was affected by upwelling and deposited on the ramp platform facies. But the latest analysis of field reconnaissance and experimental results showed that Yuertus source rocks should be divided into two sections. Chert and mudstone are the main component of the lower section source rocks, Chert formation is influenced by the bottom of the hydrothermal which have been confirmed by trace element analysis, we believed that the source rocks formed in the restricted platform facies, and affected by the bottom hydrothermal; organic carbon content is relatively high, and average more than 5% in this section; kerogen carbon isotope ratios are mainly distributed in the -37‰∼-34‰.The main lithology of the upper source rock section was the shale interbedded with limestone, the sedimentary environment of the upper source rocks section is the slope basin facies, and controlled by the upwelling; total organic carbon content is relatively low, with an average of about 1% in this section; and kerogen carbon isotope ratios are mainly distributed in the-36‰∼-33‰, relative to the lower source rocks is more enriched ¹³C. Thus, the two sets of source rocks sedimentary environment and formation mechanism is completely different, we believe that the deposition process of Yuertus is complicated, so we should give full consideration about the main factors of the development of two sets of source rocks when predicting the distribution of Yuertus Formation source rocks.

Keywords

Tarim Basin, Yuertus Formation, Source Rocks, Controlling Factors.

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Xiong Jinhong ¹, Xing Xiang ², Chen Cen ³, Zhang Yueqiao ⁴

Affiliations
1 Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing-100081, CN
2 Development and Reform Commission, Enshi Tujia and Miao Autonomous Prefecture, Hubei 401331, CN
3 Chongqing University of Science & Technology, Chongqing-401331, CN
4 School of Earth Sciences and Engineering, Nanjing University, Nanjing-210023, CN

Abstract

Diagenesis and pore evolution characteristics of Feixianguan Formation in Dawan gas reservoir were fully studied based on the microscopic-analysis on casting thin sections, scanning electricity mirror and core analyzing materials. The results showed that the mainly diagenesis types of carbonate reservoir in Feixianguan Formation are as follows: dolomitization, compaction, cementation, filling, dissolution, recrystallization diagenesis, etc. According to comprehensive analysis of diagenetic features, reservoir rocks are mainly formed in sedimentary facies belt of Oolitic beach facies at platform margin, which has a strong wave action with following characteristics: Oolitic grain-refining dolomite and sand cutting grain-refining dolomite are the mainly rock types, with large particles diameter, high level of dolomitization and well-medium sorted, but strong diagenesis. In submarine and syngenetic stages, porosity drop rapidly because of compaction and the calcite cementation. During this stage, the primary pores reduce greatly, although mixed water dolomitization and meteoric fresh water dissolution can form secondary pores; in shallow burial stage, the pores are drastically reduced under the compaction and cementation; the later period of dissolution can form secondary dissolution pore, thus there are enormous contributions to the increase of porosity.

Keywords

Dawan Area, Feixianguan Formation, Diagenesis, Pore Evolution.

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