| The Ordovician reef-beach complex on10th structure of Tazhong low uplift is a significant carbonate reservoir exploration point for its deep potential of oil and gas resources. While low achievements in sedimentary microfacies distribution research becomes a bottleneck. This dissertation, following the guidance of stratigraphy, Carbonate petrology, sedimentology, with the usage of Geology and physical geography researching methods, based on a research of stratigraphic division and stratigraphic distribution model of Lianglitage formation on the Ordovician reef-beach complex on10th structure, though the facies marks of core, slice, logging, recognizes different type of sedimentary microfacies model. With the analysis of sedimentary facies vertical development characteristics and stratigraphic correlation diagram, lead to a research of sedimentary facies lateral distributing character. Different types of seismic facies are recognized through well-log and seismic data. Sedimentary facies evolution model is established with the achievements of sedimentary facies and seismic facies. With all the goals and achievemts, subsection forecasting of horizontal distribution of sedimentary facies are made, as well as the reef-beach complex favorable area.There are5sections and12single layers which are divided from bottom up in the research area, each of them are thick in the middle and thin in the both sides. There are7rock types in the10th structure of Tazhong. Including calcarenite, bioclastic limestone, algal limestone, grained micrite, micrite, cryptalgalaminite, framestone. Mostly rock types are calcarenite and bioclastic limestone, contents are45.7%and24.35%.FMI imaging logging into lamellar phase, massive, porphyritic phase, its contents are56.18%,19.64%and24.18%.Sedimentary facies in the study area is divided into beach, slope, bottom land, reefs, table and eight kinds of sedimentary microfacies, Including Oolitic beach, calcarenite beach, oncolite beach, reefs, lime mud mound, algal flat, lime mud flat. Mainly consist of calcarenite beach and lime mud mound. At the longitudinal performance of Sedimentary facies, period of the fifth section in Lianglitage formation is grain beach. Later period of the Fourth section in Lianglitage formation, sea level rise to the highest point, and the type of sedimentary face is grain beach. The second and third periods of section in Lianglitage formation are Combination of bottom land and slope in the vertical. The first periods of section in Lianglitage formation are combination of slope, lime mud mound, grain beach and bottom land in the vertical, at the top develop tier thick oncolites beach. NW-SE direction, scale of reef-beach complex is becoming bigger from west to east, and thickness of reef-beach complex is becoming larger, lime mud mound was mainly developed in second Lianglitage formation. NE-SW direction, sedimentary facies manifest as interphase concave-convex, Between high-energy beach is slope and bottom land which was low-energy depositional. According to the characters of seismic reflection geometry, dividing seismic facies of the Lianglitage formation into mound reflection-Weak to high amplitude facies; mound reflection-high amplitude-middle continuous facies. Mound reflection and middle to weak-amplitude sub-paralle reflection was mainly distributed in high-energy beach and lime mud flat, middle to high-amplitude sub-parallel reflection was represents the slope and bottom land. The reef flat of sedimentary microfacies plane in the10th structure of Tazhong is zonal distribution. Between the reef-beach complex there was mainly slope and bottom land. The first to third of Lianglitage formation are good position for inner beach to develop. Beach and reef might be the best point to do reservoir study and further exploration. This research enriches the geological research of open platform deposition in Tazhong, and provides some guidance to exploration of oil and gas. |
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