## 2 DGLS Design  
The measuring principle of DGLS is to design a suitable instrument structure to separate the gas phase and liquid phase before the fluid flows through the flowmeter, which is the phase isolation method. The specific method is to install an exhaust valve under the collection umbrella, design a gas circuit and a liquid circuit, and collect the gas under the collection umbrella by using the gas anchor principle to separate the gas and liquid phases. The oil-water two-phase flowmeter is placed in the liquid channel to reduce the gas's influence on the flowmeter's output characteristics. Figure 1 shows a schematic diagram of the logging principle. Firstly, the logging tool is lowered into a specific position at the wellhead, and the collection umbrella is opened to fix the logging tool. Then, the fluid flows into the gas-liquid separator from the bottom to the top. Another function of the collection umbrella is to increase flow velocity. The open collection umbrella hinders the fluid's upward movement and forces it to converge under the umbrella and enter the instrument's interior through the inlet under the umbrella. According to the orifice outflow in hydrodynamics, the fluid flow rate will multiply, thus increasing the flow rate.  
Figure 2 is a profile diagram of the DGLS. The DGLS is composed of a collection umbrella, a gas-liquid separating valve, a central pipe, and a flowmeter for measuring oil-water two-phase. The gas-liquid separating valve separates the gas from the oil-gas-water mixture. The central pipe is used for secondary gas separation. The working principle of the DGLS is as follows: in the annular tubing-casing space, when using a collection umbrella, the oil-gas-water multiphase flow separates. This is due to density differences upon reaching the collection umbrella. Low-density gases first occupy the top of the umbrella to form an accumulation of caps. The crude oil amasses under caps, and water accumulates under reservoirs. As oil-gas-water is produced and accumulates, the gas volume expands downward. When the gas gathers to a certain point, the float control valve opens, and the gas enters through the intake port. It then discharges into the wellbore along the instrument's central pipe and outer wall. When the oil and water reach the top of the umbrella, the float valve closes, and the above process repeats to achieve the gas-liquid separation effect.  
The DGLS's specific structural parameters are shown in Figure 3. The gas-liquid separating valve is composed of the gas inlet, the float valve, and the liquid inlet. The float valve is connected to the springs and the floater. There are two pairs of springs, one pair is above the floater and the other is below. The floater is composed of stainless steel. The  
Figure 1: Schematic diagram of logging principle.  
springs are used to offset part of the floater's gravity. Under normal circumstances, the air inlet remains open. When the upper part of the device fills with gas, the floater remains in the original position, and the gas discharges. When the floater is immersed in the liquid, it rises due to buoyancy, and the gas passage closes. In the small-diameter production profile logging, the instrument structure is affected by the size of the pipe. The main structural parameters of the gas-liquid separating valve are shown in Figure 3.  
Figure 3: Gas–liquid separating valve schematic diagram.  
Figure 2: DGLS profile diagram.