Study on dynamic sealing performance of combined sealing structure of telescopic type of downhole robot by using HTHP coupling method

Abstract

The sealing performance will directly affect the operation of downhole robot under HTHP condition. Traditional analysis methods of sealing performance are that the temperature and pressure is loaded respectively. This can not really evaluate the sealing performance. Besides, the simulation process is: Step 1: pre-compress O-ring to produce contact force. According to the contact pressure, select the compression ratio to calculate the displacement of the slip ring. Step 2: load fluid pressure on the O-ring. This simulation method is to directly load pressure on the undeformed O-ring. However, the O-ring will deform after pre-compression. Therefore, this simulation method is not accurate. In order to make the simulation data more accurate, calculate the data of shape, stress, and strain of O-ring caused by pre-compression caused by assembly. Then, import the deformation body containing the real data of shape, stress, and strain into a new model. On the basis, establish the numerical simulation model of piston, piston guide rod, O-ring, and FTS-ring with HTHP loads is. Finally, calculate and analyze. When the compression ratio of the O-ring is about 14%, the sealing performance is good. What’s more, the distribution of contact stress and Von Mises of the O-ring at 8.3 mm/s of motion speed are analyzed. The results show that the foot shaped combined sealing structure can keep a good dynamic sealing performance under HTHP condition. This paper provides a theoretical basis for the analysis of the dynamic sealing performance by using HTHP coupling method. In the analysis of sealing performance: the hydraulic pressure is loaded to the real model with the real shape, stress, and strain produced by the O-ring assembly. This can more accurately evaluate the sealing performance under HTHP condition. It also provides a reference for the dynamic sealing structure design of downhole tools.

Structure design and sealing performance analysis of the sealing mechanism of the drilling tractor

“…The application of drilling tractor is mainly to drag coiled tubing and downhole tools to achieve long/ultra‐long horizontal wells crossing distances, so that deep/ultra‐deep oil and gas can be developed smoothly and make up for the lack of medium and shallow oil and gas resources. However, the downhole working conditions of deep/ultra‐deep oil and gas wells are very harsh, and the drilling tractor always has to withstand a high temperature of 150°C and a high pressure difference of 20 MPa 4 …”

“…However, the downhole working conditions of deep/ ultra-deep oil and gas wells are very harsh, and the drilling tractor always has to withstand a high temperature of 150 C and a high pressure difference of 20 MPa. 4 At present, Liu et al 10 and He et al 11 have developed a telescopic drilling tractor, the structural design of which is mainly composed of two dragging cylinders, two gripping cylinders and a control system, the schematic diagram is shown in Figure 1.…”

“…So far, the drilling tractor can perform simple operations in the well, such as transportation logging tools, milling bridge plugs, and so forth, but there is no report on using the drilling tractor for drilling operations in long/ultra long horizontal wells. Through analysis, it is found that in long horizontal wells/ultra long horizontal wells, the drilling tractor needs to withstand the high‐temperature and high‐pressure downhole working environment, and the high‐temperature and high‐pressure resistance of the sealing structure is one of the main reasons restricting the application of the drilling tractor 4 …”

“…Through analysis, it is found that in long horizontal wells/ultra long horizontal wells, the drilling tractor needs to withstand the hightemperature and high-pressure downhole working environment, and the high-temperature and highpressure resistance of the sealing structure is one of the main reasons restricting the application of the drilling tractor. 4 As the sealing system of the drilling tractor needs to balance the internal and external pressure differences, the external part of the hydraulic system is mainly mud, and the internal part is hydraulic oil. The internal operation of the drilling tractor requires reciprocating sliding seals.…”

Rigid-hyperelastic Coupling Dynamic Model and Dynamic Characteristics of Spring type of Traction Robot

“…The traction robot has two support cylinders, and the O-ring is a seal inside the support cylinder. Therefore, it is necessary to calculate the size of the friction resistance generated by the O-ring [20] in the support cylinder. Xu [21], Xiao [22], and Zuo and Zhang [23] studied the friction force generated by the O-ring in the hydraulic cylinder.…”