# Research on Key Technologies of 260 \({}^{\circ}\)C/210 MPa Ultra-Deep Logging Equipment
## 3 Research on Key Technologies of Ultra-High-Temperature and High-Pressure Logging
### 260 \({}^{\circ}\)C/210 MPa Ultra-High Temperature and Pressure Logging Sensors
#### 3.1.2 Lateral Electrode System  
The electrode system is the sensor of the array lateral logging tool, as shown in Figure 4. As a core component, its high-temperature and high-pressure performance directly determines the instrument's application range and logging effectiveness. According to the instrument's structure and the 260 \({}^{\circ}\)C/210 MPa temperature and pressure requirements, the electrode system is composed of a mandrel, metal electrode rings, PEEK insulating sleeves, pressure-sealing joints, and pressure balance components. The metallic parts are made of TC18 material, with an outer diameter of 92 mm and an inner diameter of 60 mm. The pressure bearing and sealing of electrode systems in high-temperature environments are critical factors affecting their performance and are currently the focus of technical research. 1. Pressure Bearing Issues and Solutions: based on the overall layout and structural characteristics of the electrode system, the following structures have been designed to address pressure bearing issues: 1. A Stress Spring Assembly is designed between the upper and lower parts of the A1U electrode to add a pre-tightening force to the integrated structure of the electrode ring and insulating sleeve, making the connection surface tighter and reducing the risk of looseness and failure. 2. A piston balancing structure is designed in the connection structure between the electrode, insulating sleeve, and metal mandrel to enhance the ability of the electrode and insulating sleeve structures to adapt to external environments. As shown in Figure 5, a pressure balance subassembly is designed between the A1L Lower Electrode Ring and the A1L Upper Electrode Ring. The balance piston separates the inner and outer chambers, with the outer chamber connected to the formation through a Mud Channel, and the inner chamber filled with high-temperature-resistant silicone oil. The balance piston can move left and right under the action of the silicone oil in the inner chamber and the formation fluid in the outer chamber, achieving pressure balance between the inside and outside of the instrument. A Balance Spring is designed in the outer chamber to cushion and limit the movement of the piston. When the pressure inside the instrument  
Figure 4: Array lateral electrode system. Figure 3: Acoustic performance testing of acoustic metrology station. is greater than the external pressure, the balance piston will slowly compress the Balance Spring and move outward. When the sealing position of the piston exceeds the Drain Port, the Drain Port connects with the silicone oil in the inner chamber, allowing oil to escape and release pressure, thereby protecting the instrument. A Pre-Tensioning Spring applies a small initial pre-pressure to the silicone oil in the inner chamber, making the silicone oil distribution in the inner chamber more uniform and filling it more fully, thereby improving the overall balancing effect of the instrument and the sensitivity of pressure transmission. (2) Sealing Issues and Solutions: Sealing is the core technology of ultra-high temperature and high-pressure lateral instruments. The sealing effect determines the insulation performance between electrodes and is crucial for the instrument's ability to measure effectively. To enhance the sealing performance, the following measures were taken:  
1. In terms of material selection, perfluoroether rubber material with a temperature resistance of 300 \({}^{\circ}\)C was chosen as the sealing component to ensure excellent sealing performance even at extreme temperatures. 2. In the overall structural design, as shown in Figure 6, the metal electrode rings and insulating sleeves were sequentially mounted on the insulating mandrel to form a sealed space filled with high-temperature silicone oil.