Отправлено: 12.05.17 06:42. Заголовок: Two effective methods for calculating water saturations in shale gas reservoirs

Two effective methods for calculating water saturations in
shale gas reservoirs

Jingling Xu1,2,3*, Lei Xu1,2,3 and Yuxing Qin4
Right Running Head: Calculating methods of water saturations
1
School of Geophysics and Information Technology, China University of Geosciences
(Beijing), Beijing 100083, China. E-mail:jlxu@cugb.edu.cn.
2Key Laboratory of Geo-detection (China University of Geosciences, Beijing), Ministry
of Education, Beijing 100083, China. E-mail:jlxu@cugb.edu.cn.
3
State Key Laboratory of Geological Processes and Mineral Resources, China
University of Geosciences, Beijing 100083, China. E-mail:jlxu@cugb.edu.cn.
4Wireline Logging Company, BHDC, Tianjin, China. E-mail: qinyux@petrochina.cn.

Abstract:
Water saturation is one of the most important parameters in petroleum
exploration and development. However, its calculation has been limited by the
insufficient logging data required by a new technique that further influences the
calculation of the free gas content.. The accuracy of water saturation estimates is also a
critical issue because it controls whether we can obtain an accurate gas saturation
estimate.
Organic matter plays an important role in shale gas reservoirs, and the total
organic carbon (TOC) indirectly controls the gas content and gas saturation. Hence,
water saturation is influenced by inorganic components and organic components. After
analyzing the relationship between TOC, core water saturation and conventional gas
saturation, considering the influence of TOC on gas saturation in organic-rich shale
reservoirs, two new methods are proposed to improve the accuracy of water saturation
estimates: the revised water saturation-TOC method and the water saturation separation
method, in which Archie water saturation, modified total shale water saturation, and
TOC are integrated.
According to the case studies of Longmaxi-Wufeng shale,
southeastern Sichuan basin, China, the water saturation results from these two methods
in shale reservoirs with different lithology are consistent with those from core analysis.
It is concluded that these two methods can be evaluated quickly and effectively evaluate
the water saturation of shale reservoirs.

Keywords: Shale gas reservoirs, Revised water saturation-TOC method, Water
saturation separation method, Conventional water saturation