The Characteristics of Fractures and Its Controlling on the Deep Basin Gas in the Yinan 2 Reservoirs of Kuqa Depression, China
Wang, Wei P.; Chen, Xiao; Pang, Qi X.; Guo, Chun Y.; Guo, Gang
Temporal coupling between the formation of tectonic fractures and deep basin gas reservoir is a significant element, while considering the influence tectonic fractures exerted on the deep basin gas reservoir. According to the observation of core and thin-section, shear fractures and tension fractures can be found in the Yinan 2 deep basin gas reservoir, kuqa depression of China. Shear fractures were formed by tectonic compression and faults-deriving, while tension fractures were produced by tensile stress generated by extensional tectonic stress field transformed from compression stress field due to fluid overpressure and by folding deformation at anticline axis. Combining tectonic evolution history and the formation mechanism of tectonic fractures, this paper holds that the formation period of tectonic fractures was later compared with that of Yinan 2 deep basin gas reservoir. As a result, the impacts of fractures developing in the tight sand reservoir on the Yinan 2 deep basin gas reservoir are as follow: 1) fractures can act as the main migration pathway for nature gas in the later period. 2) fractures within the tight sand reservoir improve the capability of storage and permeability, forming the "sweet spots" in the deep basin gas reservoir and "acid dew" during the shrinking of the deep basin gas reservoir as well. 3) fractures developing in the gas-water transition zone can change the critical condition of deep basin gas reservoir, resulting in the shrinking of reservoir, and even being destroyed. We can confirm these conclusion by the evidence that fractures in well Yinan 2 being located in the low position of structure are saturated with gas. However, fractures in the well Yinan 4 and Yishen 4 that are situated in the upper position of structure are full of water with little remaining gas.
AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013