Seismic exploration is sensitive to elastic parameters and has basically solved the problem of oil and gas reservoirs, but its accuracy in identifying oil, gas, and water is relatively low.Logging confirms that there are significant differences in the electrical characteristics of different fluids, but it is only " a narrow view".The formation conditions of oil and gas reservoirs are complex, the relationship between oil, gas, and water is extremely complicated, and the difficulty of prediction is high, which seriously restricts the efficient exploration and development of oil and gas.
Using the combined method of logging seismic electromagnetic method, seismic spatial structure is used as the framework, electromagnetic results are used as attribute filling, and logging is used for calibration. Set up measuring points along the distribution range of the reservoir, and perform inversion of reservoir electrical parameters with known spatial distribution by transmitting and receiving different high-order complex pseudo-random signals. Combined with identification templates, accurately predict reservoir oil, gas, and water.
Selection of favorable exploration areas: Evaluate the oil and gas potential of reservoirs, determine areas with better oil and gas potential, and guide well location deployment.
Remaining oil dynamic monitoring: Evaluate the distribution of remaining oil, guide development technology policies and potential tapping directions, and improve the effectiveness of oilfield development.
Monitoring of water drive front: Analyze the coverage range and advantageous injection direction of planar injection water, evaluate the water drive effect, guide the adjustment of water injection and oil production technology policies, evaluate the vertical water drive utilization degree of reservoirs, and guide the profile treatment of injection wells.
Oil and gas reservoir water invasion front detection: predict the distribution of gas and water in the reservoir and the water invasion front, guide the drainage measures and production system optimization of gas wells, and improve the recovery rate of gas reservoirs.
Monitoring of water blocking and profile control effect: evaluating the effectiveness of profile control and flooding technology, and assessing the effectiveness of water breakthrough channel plugging.
The principle of wide area electromagnetic method is to determine the reservoir properties at corresponding locations based on the differences in resistivity detected in different formations and regions.
Case 1: Sichuan Province Tight Sandstone Gas Reservoir Gas Water Identification Project (Buried Depth 2700M).
The project is located in the Zhongjiang Block of Sichuan Province, which is a tight sandstone gas reservoir with complex gas water relationships. Water is produced in high areas and gas is produced in low areas, making it difficult to predict gas content. By using high-precision wide area electromagnetic methods that are more sensitive to fluids, and integrating the advantages of seismic spatial distribution characterization and electromagnetic fluid detection methods, gas water identification is carried out. The project has 14 survey lines and 685 survey points distributed along the river channel, with a total length of 101.8km.
Gas has high resistance, and according to the comparison between the detection results and the actual production effect in the relatively high resistance area, the gas production rate is indeed significantly better than that in the low resistance area. According to feedback from Party A, the detection accuracy rate is 91.7%. The logging resistivity of the newly drilled well is basically consistent with the trend of resistivity changes measured by the wide area electromagnetic method. The implementation effect of the project has been highly recognized by the Party A unit.
Case 2: Sichuan Province Carbonate Oil and Gas Reservoir Gas Water Identification Project (Buried Depth 5000M).
With the continuous development, the formation water of the carbonate gas reservoir gradually invades the interior of the reservoir as a whole. Formation water was found in Well 102 in 2022, and the area of the pure gas zone decreased towards the interior of the gas reservoir. The range of the gas water transition zone continued to increase, seriously threatening the waterless gas production period of high-yield wells such as Well 009-4 and 009-X5 in the area.
To further implement the predicted resource quantity in the peripheral 48 well area of Moxi block, well 048-H1 has been deployed. Through project implementation, the distribution interface of water and gas and the direction of water immersion have been delineated for the well area, which is of great significance for guiding target optimization, subsequent development deployment, and resource potential evaluation.
Case 3: Dynamic Monitoring Project of Remaining Oil in Gulong Shale Oil in Heilongjiang Province.
Using the combined method of well electric shock, the three-dimensional spatial electrical changes of reservoirs at different time stages are characterized, and the reservoir characteristics and dynamic changes at different time stages are evaluated to guide development technology policies and improve the effectiveness of oil and gas field development.
The project is expected to undergo a total of five monitoring sessions, and the second monitoring session has already been conducted. Relevant results have not yet been formed.
