Experimental Study On Acoustic Characteristics Of Fractured And Holes Carbonate Reservoirs

In today's world,as the degree of oil and gas exploration continues to deepen,and the degree of exploitation of conventional reservoirs is increasing,many conventional oil reservoir have entered the stage of high water cut,the complex reservoirs of carbonate are rich in oil and gas resources,therefore,the focus of oil and gas development has turned to complex reservoirs.Because fractures and karst caves are the main reservoir spaces of carbonate rocks,so the study of fracture-cavity carbonate reservoirs is particularly important.On the other hand,fracture-cavity carbonate reservoirs have complex geological conditions,low porosity and permeability,and significant lateral heterogeneity.Therefore,exploration and development of fracture-cavity carbonate reservoirs are difficult.The acoustic experiments on the fracture-cavity carbonate reservoirs and to study the variation regularity of the elastic parameters of fracture-cavity carbonate reservoirs can provide the knowledge base and necessary data for the forward and inverse geophysical data,and also make the accuracy of reservoir prediction is greatly improved.This paper relies on the Earth Exploration and Information Technology Logging Laboratory of China University of Geosciences(Beijing)and the “Testing Rock Physics Experiment of Small-scale Cracked Caves Collectives” project.In the field,rock samples were collected and more than 80 pieces of standard cylindrical cores were made.Through simulation of rock acoustics experiments under the conditions of the formation,20 representative fracture-core carbonate cores were selected for analysis.A rock physics template for fracture-cavity carbonate rock was established,and the effects of porosity,pore aspect ratio,and shale content on rock elastic parameters were studied.The acoustic velocities predicted by petrophysical models were compared with laboratory measurements to verify the feasibility of using rock physics models to predict sound velocity.Through the analysis of laboratory measured fracture-cavity carbonate rock properties parameters and acoustic velocity,it can be concluded that for fracture-cavity carbonates,fractured reservoirs and dissolved pore reservoirs are discussed separately.Can better reflect the changes in the speed of sound waves.Rock physics simulation results show that the acoustic velocity increases rapidly when the pore aspect ratio increases from 0 to 0.1.When the pore aspect ratio continues to increase,the acoustic velocity slowly increases and gradually tends to remain unchanged.The 100% saturated acoustic wave velocity predicted by the fracture-cavity rock physics model is roughly in agreement with experimental measurements.The average error is about 5%.Therefore,the measurement of sound waves in the laboratory is consistent with the calculation of acoustic velocities through fracture-cavity rock physics models.