Restoration Of Karst Paleo - Geomorphology At The Top Of G01 Tectonic Light Shadows In Central Sichuan And Its Impact On Reservoirs

Through the previous research in GST structure in Sichuan Basin, combined with drilling data, core data, logging data, mud logging data, seismic data and test analysis, according to tructural geology, seismic stratigraphy, petroleum geology methods and principles, using a combination of research methods of geological methods and geophysical methods to study tectonic evolution, sedimentary characteristics, reservoir characteristics, Karst Palaeogeomorphology and its influence on reservoir of The GST structure of the Dengying Formation.According to the analysis of seismic data, The GST structure has undergone the TongWan tectonic movement, the Caledonian tectonic movement, the Hercynian tectonic movement and the late Yanshan-Yanshanian-Xishan tectonic movement four main key periods. In the study area, the Dengying Formation can be divided into four sections, the first, second and forth sections of Dengying Formation belong to limited platform, the third sections of Dengying Formation belong to mixed product shelf. The lithology is fine-grained dolomite with sedimentary characteristics of enriched algae. The types of reservoir space mainly include secondary corrosion pore, hole and fracture, most of the primary pores were destroyed, the types of reservoir include fractured-vuggy type reservoir and fractured-porous type reservoir. The average porosity is2.42%, and the average permeability is6.53mD, it is a type of low porosity and low permeability reservoir. The main control factors of reservoir are stratum structure, sedimentary face, tectonic movement, karst process and Karst Palaeogeomorphology.Using the backstripping method, according to the seismic data, by means of the GoCAD and2DMove software, the restoring of the Karst Palaeogeomorphology with not decompaction, decompaction and eliminating the infulence of fault are done at the top of Dengying Formation in the GST structure, and the3levels Karst landform units are divided in detail. Through comparison and analysis, the palaeogeomorphic map of decompaction and eliminating the infulence of fault is determined as the final result. From north to south, the study area can be divided into five geomorphic units in turn, namely Karst depression soluble depression, gentle slope, soluble ping, monadnock, solution groove. Then, according to the actual drilling and well logging, production data, combined with the theoretical knowledge, from the reservoir space, physical property and gas production, I study the effect of different geomorphic units on reservoir, and get that the Karst Palaeogeomorphology at the top of the Dengying Formation affects the reservoir performance of the fourth Dengying Formation, and the monadnock is the best oil and gas reservoir unit, followed by the gentle slope, soluble ping, solution groove and Karst depression. Finally, according to the single factor control of the Karst Palaeogeomorphology, the fourth Dengying Formation of the GST structure can be divided into four types of reservoirs, namely, Ⅰ, Ⅱ, Ⅲ, Ⅳ reservoir. The Ⅰ reservoir (monadnock), mainly distributed in the south of the study area; The Ⅱ reservoir (gentle slope), mainly distributed in the west and the northeast of the study area; The Ⅲ reservoir (soluble ping), mainly distributed in middle and south-east in the study area; The IV reservoir (solution groove, Karst depression), mainly distributed in the north of the study area and surrounding the southern monadnock.