Method for simulating karst caves in different filling states and physical simulation test system

Abstract

The invention provides a method for simulating karst caves in different filling states. The method comprises the steps of employing a controlled compression-resistant material to make a karst cave simulation body according to the shape of a target karst cave, then making a model body wrapping the karst cave simulation body, and simulating the target karst cave through a cavity formed in the model body by the karst cave simulation body. The karst cave simulation body can maintain the structural form under specific conditions and has certain pressure bearing capacity, so that the karst cave simulation body can be modeled, and the shape of the karst cave simulation body is kept consistent with that of the target karst cave. The controlled compression-resistant material is controlled to be liquefied in the model body, the controlled compression-resistant material is taken out of the model body, and a cavity in the model body is formed for simulating the karst cave. According to the method for simulating the karst caves in the different filling states, the invention further provides a physical simulation test system for simulating the karst caves in the different filling states. The model manufactured through the method is very close to the actual karst cave stress state, and reliable data can be provided for karst cave research.

Description

technical field [0001] The invention relates to the technical field of geomechanical model tests, and more specifically, to a method for simulating caves in different filling states and a physical simulation test system for simulating caves in different filling states. Background technique [0002] The Ordovician fractured-cavity carbonate reservoirs in Tahe Oilfield are complex and special, and the reservoirs are deeply buried. Different types of large-scale karst caves are the main storage spaces, and these karst caves have different shapes and filling characteristics. After burial, the gravity of the overlying strata received by each cave body is different, the degree of hydraulic reformation is different, and the degree of cementation after collapse is different, forming a complex reservoir type of the collapse-filled reservoir. Therefore, it is urgent to study the impact of cave collapse on oil well production. . [0003] However, in the face of deep karst caves, tradi...

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Problems solved by technology

[0005] One is to pour raw materials into the mold and finally flatten the surface to simulate the horizontal section of the cavity. This mold can only be used for the study of plane strain problems and cannot be used for cavity formation of buried caverns;

[0006] One is to use the mortise and tenon structure to build the combined wooden formwork into a corresponding hole shape, and then pull out the wooden forms one by one to form a cavity. This method is costly, and the hole shape is not easy to control, and the limitation is relatively large;

[0007] One is the model test method of placing the filling medium at the bottom of the high-pressure vessel to simulate the filling state. This method simply considers the filling medium and ignores the influence of surrounding rocks around the cave, which is inconsistent with the actual stress state of the cave;

[0008] One is to form a simple karst cave and crack system by combining plexiglass plates, and use the formed karst cave and crack system to conduct tests. Water injection is carried out at the bottom of the cave, and oil is produced from the upper part. This method can only simulate the phenomenon of simple water flooding, and cannot withstand pressure, and cannot adapt to the needs of different filling states;

[0009] One is to make a model, and then use a water pump to pump out the prefabricated soluble salt in the model to form a cavity to simulate an unfilled cave. This method is only suitable for unfilled cavities, and the vertical pipeline formed by pumping out soluble salt cannot be eliminated. It is equivalent to artificially creating through-cracks, which has a great influence on the test results;

[0010] One is to prepare a model, set a prefabricated silica gel bag in the model, and use the silica gel bag to simulate the change of the internal pressure of the water cave. In this method, the cave can only be simulated when it is fully filled with water. Caves and caves filled with solid media cannot be simulated

[0011] Through the analysis of the above status quo, the existing problems in the existing technology are mainly: the existing filling caverns simply consider the filling medium and ignore the influence of the surrounding rocks around the cave, which is inconsistent with the actual stress state of the cave; The cavitation technology of reservoir caves can only be used for the study of plane strain problems and cannot be used for the cavitation of buried caverns; the existing filled reservoir caves can only simulate simple water flooding, and cannot withstand pressure and cannot adapt to different conditions. The requirement of filling state; the existing technology of filling reservoir caves artificially creates through-cracks, which has a great influence on the test results, and the method used can only meet a single requirement, and cannot simulate complex filling conditions

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