DIAGENETIC CONTROLS ON THE RESERVOIR QUALITY OF TIGHT OIL-BEARING SANDSTONES IN THE UPPER TRIASSIC YANCHANG FORMATION, ORDOS BASIN, NORTH-CENTRAL CHINA
DIAGENETIC CONTROLS ON THE RESERVOIR QUALITY OF TIGHT OIL-BEARING SANDSTONES IN THE UPPER TRIASSIC YANCHANG FORMATION, ORDOS BASIN, NORTH-CENTRAL CHINA
复制标题
鄂尔多斯盆地上三叠统延长组致密油砂岩储层质量的成岩控制
DOI：
10.1111/jpg.12759
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发表时间：
2020
影响因子：
1.8
通讯作者：
Zhang Jinliang
中科院分区：
文献类型：
--
作者：
Zhang Penghui;Lee Yong Il;Zhang Jinliang
Tight oil‐bearing sandstones in the Chang 4+5, 6 and 7 Members of the Upper Triassic Yanchang Formation in the Ordos Basin, north‐central China, in general consist of fine‐grained, moderately‐ to poorly‐sorted lithic arkoses (average Q53F30R17) deposited in a fluvial‐dominated lacustrine‐deltaic environment. Diagenetic modifications to the sandstones include compaction and cementation by calcite, dolomite, ankerite, quartz, chlorite, kaolinite and illite, as well as partial dissolution of feldspars and minor rock fragments. Porosity ranges up to ~7% of the rock volume and was reduced more by cementation than by compaction. Fractures (tectonic macrofractures and diagenetic microfractures) provide important oil migration pathways and enhance the sandstones' storage potential. The pore network is heterogeneous due to processes related to deposition and diagenesis, and there are considerable spatial variations in porosity and pore connectivity. The pore system includes both macropores and micropores, and pore network variations depend on the type and distribution of authigenic cements.An analysis of the diagenetic and porosity characteristics of core samples of the Yanchang Formation sandstones from wells in the Youfangzhuang oilfield resulted in the recognition of six petrofacies (A‐F) whose characteristics allow reservoir quality to be predicted. Fluid performance analysis for selected sandstone samples using nuclear magnetic resonance combined with helium porosity and air permeability shows that high permeability and large pore throats together result in high movable fluid saturation potential, and that effective pore spaces and throats are beneficial for hydrocarbon storage and flow. Relatively higher porosity and permeability tend to occur in petrofacies B sandstones containing abundant pore‐lining chlorite with lesser kaolinite and minor carbonate cements, and in petrofacies C sandstones with abundant pore‐filling kaolinite cement but little chlorite and carbonate cements. These petrofacies represent the best reservoir‐quality intervals.A reservoir quality prediction model is proposed combined with the petrofacies classification framework. This model will assist future development of tight sandstone reservoirs both in the Upper Triassic Yanchang Formation in the Ordos Basin and elsewhere.
