GSA Annual Meeting in Phoenix, Arizona, USA - 2019

Paper No. 151-6
Presentation Time: 2:50 PM


HAN, Yang, Northwest University, State Key Laboratory for Continental Dynamics, Xi’an, 710069, China and SUN, Wei, Department of Geology, Northwest University, No. 229, North Taibai Road, Xi'an, 710069, China

The Triassic Yanchang Formation in the Ordos Basin is currently a hotspot of Changqing Oilfield and one of the major oil production sites. The Banqiao-Heshui area in the southwestern part of the Ordos Basin has become a key area for oil and gas exploration and development in recent years. In Banqiao-Heshui area, the Chang 6 layer is the main oil layer group. Although some wells have a good display on oil and gas production, the overall production does not make a breakthrough. The preliminary analysis of reservoir physical properties was carried out by using experimental thin sections, scanning electron microscopy, X-ray diffraction and well logging in the Chang 6 layer of study area. The affection of sedimentation and diagenesis on reservoir physical properties were also analyzed. The results show that the clastic composition of sandstone in Chang 6 layer in study area is dominated by feldspar and quartz. The Chang 6 layer of study area mainly develops semi-deep lake-deep lake sediments, including two microfacies which is the gravity flow composite channel and the water channel. The high content of debris interstitials is one of the important reasons for the poor physical properties of the Chang 6 layer in this area. The low maturity of the reservoir structure is responsible for the sedimentation of the reservoir 6 with low permeability in the study area. The Chang 6 layer belongs to the typical ultra-low permeability reservoir, and the diagenetic transformation is strong. The diagenetic changes have a great influence on the physical properties of the sandstone.