Research On The Physical Scale Modeling Of Sea-to-Borehole Electromagnetic Method In Frequency Domain

Marine electromagnetic exploration usually emits and receives electromagnetic signals in the seabed or sea water,but this method requires a large transceiver distance in the exploration of deep oil and gas reservoirs,and is greatly affected by air waves in shallow sea oil and gas exploration.Sea-to-borehole electromagnetic exploration technology is a new monitoring technology for offshore oil and gas reservoir development.In recent years,it has been gradually applied in the process of monitoring the production and development of offshore oil and gas reservoirs in China.This method sinks vertical bipolar sources into submarine oil and gas wells.Near the target body,positive and negative interactive square wave signals with different frequencies are emitted,and the electromagnetic field response signals of submarine oil and gas reservoirs are received in the seabed or sea water.The variation trend of oil and gas reservoirs is inferred in order to achieve the delineation of oil.The purpose of gas reservoir range and dynamic monitoring of the change of submarine oil and gas reservoir during development is that this method can also obtain higher resolution for deep-sea oil and gas reservoirs with small migration distance,and is also less affected by air wave in shallow sea environment.It is a kind of high precision and low cost monitoring technology for submarine oil and gas reservoir development,which has gradually attracted the attention of offshore oil and gas development in the world.The physical simulation reduces the electromagnetic exploration process of the field actual system to the indoor laboratory according to the similarity criterion,which is convenient,fast,effective and low cost to complete the electromagnetic exploration simulation of the 3D geological body in the field.And can make up for three dimensions.The large amount of numerical simulation is insufficient to provide support for actually sea-to-borehole electromagnetic exploration.Based on the physical simulation and numerical simulation of the frequency domain borehole-surface electromagnetic method,which is an item on the surface of the National Natural Science Foundation of China,this paper has carried out one dimensional numerical simulation of sea-to-borehole electromagnetic based on the previous research results.The collection,processing and map interpretation of experimental data are studied and completed.The results are as follows:1)Based on the previous research results,the electromagnetic responses of three kinds of one-dimensional models(changing reservoir resistivity model,changing seawater depth model,changing excitation position model of excitation source)are calculated by using the one-dimensional forward modeling of sea-to-borehole electromagnetic method.From the point of view of numerical simulation,this paper verifies the validity of the application of the sea-to-borehole electromagnetic method in marine oil and gas reservoir scoping and monitoring of oil and gas exploration and development,and analyzes the characteristics and advantages of the well sea electromagnetic exploration method.2)On the basis of the similarity criterion of electromagnetic physical simulation,combined with the actual construction parameters of ocean electromagnetic method and the existing experimental conditions in the laboratory,using different proportions of brine,river sand,cement,paraffin,graphite to make the experimental sample model.The resistivity was measured and calculated by SI-1260 impedance / phase analyzer,and then the seawater was simulated by salt water,the sediment layer was simulated by saturated river sediment,the high resistivity target was simulated by paraffin graphite plate,and the middle and high resistivity oil and gas reservoir was simulated by cement graphite plate.The iron plate simulates the low resistivity abnormal body,obtains the suitable model parameter ratio,and makes a variety of electrical abnormal body models.Finally,the physical simulation experiment system has successfully completed the data acquisition of various models of sea-to-borehole electromagnetic experiment.3)The response characteristics of electromagnetic anomalies caused by high resistivity reservoirs and low resistivity anomalies at sea floor are analyzed.The validity and reliability of the experimental data are verified by comparing the results of physical simulation experiment with that of one-dimensional numerical simulation experiment.On this basis,the experimental results of the three models are compared,the advantages and disadvantages of the sea-to-borehole electromagnetic method compared with the conventional ocean electromagnetic method are analyzed,and the feasibility of using the sea-to-borehole electromagnetic method to monitor the development of marine oil and gas is demonstrated It provides theoretical guidance for further study of sea-to-borehole electromagnetic method and field exploration.