193 / 2022-02-28 19:02:07

Study on the distribution model of quality difference in the tight sandstone reservoir of sublacustrine fan from the Chang 6 interval of the Yanchang Formation in the Heshui Area, Ordos Basin, China

sublacustrine fan,tight sandstone,reservoir quality classification,reservoir quality distribution,Triassic Yanchang Formation,Heshui area,Ordos Basin

With strong heterogeneity and complex distribution of reservoir quality, the tight reservoir of sublacustrine fan is currently a hot topic in continental lacustrine basin research and an important target for tight oil and gas exploration and development. This paper takes the tight sandstone reservoir of sublacustrine fan in the Yanchang Formation in the Heshui area of the Ordos Basin as the research object. The sedimentary architecture of single sandbody and the diagenetic evolution mechanism in the study area have been investigated in previous studies. By integrating well logging and various test data of core samples, the spatial distribution model of matrix reservoir quality under the control of sedimentation and diagenesis was studied. The results show that the matrix reservoir quality of Chang 6 tight sandstone in the Heshui area can be classified into types I, II and III in order from good to poor. From the middle to the edge of channel branch and lobe as well as from the near provenance area to the far provenance area, reservoir quality is reduced due to the decrease of dissolution and the enhancement of compaction and cementation. There is a correlation between the thickness of different types of matrix reservoirs and the sandbody thickness of small layers. When the sandbody thickness of the small layer is greater than 10m, the thickness of the type II reservoir has a more obvious increasing trend with the increase of the sandbody thickness of the small layer than that of the type I reservoir. When the sandbody thickness of the small layer is less than 10m, the type III reservoir is obviously developed. The combination of the wide band-like type I reservoir and the sheet-like type II reservoir within sigle sandbody is developed in the small layer with sheet-like sandbodies, corresponding to the best reservoir quality. The research results are of great significance for guiding the exploration and development of tight oil and gas in the sublacustrine fan.