The Structure And Distribution Of Cambrian-Ordovician Carbonate Platform Margin In Tarim Basin

Cambrian-Ordovician carbonate reservoir of Tarim Basin has drawn more and more attention in recent years, and reef-shoal facies reservoir in platform margin is one of the most important types of exploration area. Under the guidance of geological theories such as sedimentary, sequence stratigraphy etc, this paper applies basic data including outcrops, well drilling and logging information, seismic data to recognize the platform margin facies and to determine their distribution areas of every single formation in Cambrian-Ordovician, and makes clear the structure patterns of platform margin of different regions in different time, as well as their migration and evolution characteristics.First, sequence stratigraphic framework of Cambrian-Ordovician is established based on drilling, seismic data and Xiaoerbulake and Dawangou outcrop located in North Tarim Basin, and Cambrian-Ordovician can be divided into 4 super sequence groups and 13 super sequences.9 seismic horizons were interpreted across the entire Tarim Basin, and the thickness contour maps of every group were mapped. Then the development characteristics and distribution of the sequences were made clear.Identification marks of platform margin-slope facies were summarized: Low-middle amplitude, discontinuous seismic texture with high amplitude chaos seismic texture and mound-like oblique or "S"-shaped progradational configuration represents platform margin sedimentation, while high amplitude, continuous texture with little low amplitude and chaos texture, and oblique, convergent or wedge shaped configuration represents platform margin slope facies. At last, confirm those recognized facies with drilling lithology. Reef-building organisms are well developed in reefs and shoals at platform margins, and the lithology is the reflection of high energy sedimentation such as algae bonded dolomite, algal laminated dolomite, sparry oolitic dolomite, sparry oolitic dolarenite.According to the change of strata thickness, seismic reflection features and drilling control, this paper analyzed the distribution of each period of platform margin-slope facies, and makes clear the structure patterns of platform margin of different regions in different time, as well as their migration and evolution characteristics.