Research On The Sequence Stratigraphy And Reservoir Physical Property Of Clastic Stone Of Paleozoic And Triassic In Akekule Uplift

The Akekule Uplift has great hydrocarbon resource potential. As the first big marine oilfield that found in China, there have lots of exploration result. But these results are mainly about marine carbonate layers, and few are on clastic stone.In this these paper, taken the clastic layers on Paleozoic and Triassic as the object, combined with the analysis result of core, logging, seismic data, flake, isotopic data and SEM, the geological framework has been summarized. And it has been studied in detail of the sequence stratigraphic frameworks, sedimentary facies, paleo-geography, diagenesis and reservoir characteristics. Based on this research, the favorable exploration areas have been evaluated of Paleozoic and Triassic.With the analysis of drilling, logging and seismic study, there are 23 3^rd -level sequence stratigraphy have been identified. Among them, there are 5 in Upper Ordovician, 6 in Silurian, 1 in Donghe Sandstone, 5 in Carboniferous and 6 in Triassic.As the mainly reservoir layer in the Akekule, Donghe Sandstone is the sedimentary result of a whole cycle of sea-level. Within it, the Transgressive System Tract (TST) and Highstand System Tract (HST) can be identified clearly, and these two system tracts can be correlated in area, but the Lowstand System Tract, which is characterized with fluvial deposition, is not developed well. The depositional environment of TST is shore controlled by tides, and that of the HST is shore controlled by wave.By the research of the original basin of Akekule Uplift, the Triassic depositional background is about the flat part above the fold of slope. The sedimentation is influenced very much by the fluctuation of lacustrine level. And the main sequence boundaries are the type I that characterized with rejuvenation of rivers. The LST developed well characterized by coarse fluvial sedimentation, and the TST characterized with lacustrine mudstone. Because of no deposition or erosion, the HST developed not so well.With the reservoir research and combined with the sequence stratigraphic frameworks, the spreading of reservoirs are controlled by sequence stratigraphy. In the sequences of Donghe Sandstone and Carboniferous, the reservoir stones are mainly within the HSTs, while in that of the Triassic, reservoir stones are mainly within the LSTs.Through careful observation of flakes, SEM and CLM, the mainly diagenesis in the research area are compaction (pressolution), cementation, metasomatism and filling of authigene and corrosion. By research of the characteristics and stages of diagenesis, the Donghe Sandstone and carboniferous are mainly in the A stage and B stage of late diagenesis. While the Carboniferous is mainly in A stage of late diagenesis, and, in some holes that are deeper than 4500m, it is in B stage of late diagenesis.The holes of clastic stone in Akekule Uplift are mainly induced porosity. And the hole types are inter-particle porosity, intra-granular porosity, followed by mould porosity, primary inter-particle porosity, remained inter-particle porosity. While the inter-crystal micro-pore, dissolution pore of fillings are seldom.Based on the analysis result of physical property, mercury penetration and seismic inversion, the reservoirs of Triassic are the best, mainly about level I or level II, followed by that of the Carboniferous about level II to level III. That of the Donghe Sandstone is the worst, mainly about level IV to level V. The main reasons that influence the physical property of reservoir are mainly sedimentary environment and diagenesis.