How to extend the service life of the downhole pump valve?

Downhole operating condition diagnosis based on dynamometer card is a key subject for sucker rod pumping in oil extraction engineering. In this technology, feature extraction and diagnostic model are two indispensable elements. To accurately and automatically diagnose the operating condition by computer, a novel diagnostic method for sucker rod pumping is proposed. The first novel idea is to extract seven geometric features, which are obtained from dynamometer card using barycentric decomposition algorithm and valve working position.

The second novel idea focuses on the use of continuous hidden Markov model (CHMM) to create classifiers for diagnosing the down-dole operating conditions and then clonal selection algorithm (CSA) is used to optimize the selection of initial parameters for CHMM. Finally, the proposed method is tested on an oil field dynamometer card set. Furthermore, this technique is compared with some other existing approaches. The simulation results demonstrate that the performance using the method proposed in this paper is satisfactory.

The pump valve is a key part that affects the pump efficiency and service life of the sucker rod pump. It is equipped with valve ball and valve seat. Once damage occurs, the whole pump will fail. In recent years, with the continuous advancement of oil production depth and the increasing complexity of well conditions, the number of pumps that have failed due to broken valve covers has increased. The main reason for analyzing the rupture of the valve cover is that it is frequently hit by the valve ball. Due to the limitation of the pump barrel diameter or the size of the oil well outside the valve cover, the built-in pump valve causes the thin wall of the valve cover. The installation position of the suction pump will have a certain slope. Due to poor stability of crude oil flow and other reasons, the valve ball is usually not straight up and down when it is opened and closed. Instead, the valve ball side opens first. This makes it easy to rotate the valve ball and hit the side wall of the valve cover. In operation, the valve cover always bears alternating load, and is frequently impacted by the valve ball. As the working time increases, the valve cover is elongated and struck and becomes thinner and thinner. Eventually caused the valve cover to suddenly break. Among the main reasons for the thin wall of the valve cover, low mechanical strength, alternating load and valve ball impact, frequent impact by the valve ball is the most important reason for the valve cover to break.

In order to solve these problems, extend the service life of the pump valve. Sanjack Group has developed a long-life pumping valve with high strength, impact resistance and wear resistance, which effectively solves the problem that the valve cover is broken by the frequent impact of the valve cover. The design can be divided into three options:

Option 1: This design consists of joints, valve cover, valve balls and valve seats. The structure diagram is as follows:

 

 

 

1-1Joint
1-2Soft Anti-collision sleeve
1-3Valve cover
1-4Valve ball
1-5Valve seat

 

The valve cover of the new oil pump valve is lined with a soft anti-collision sleeve resistant to wear and corrosion. There is an axial and radial gap between the anti-collision sleeve, the valve cover and the joint. The joint and the valve cover are connected by threads. The soft anti-collision sleeve is made of high molecular material, which has excellent physical properties such as elasticity, flexibility, abrasion resistance, and chemical resistance to H2S, CO2 and other acids and salts. It integrates anti-partial wear and anti-corrosion performance, and does not scale or wax. It can absorb the impact of the valve ball and protect the valve cover.

Option 2: This design of pump valve is composed of joint, valve cover, valve ball and valve seat. The structure diagram is as follows:

2-1Joint
2-2Gasket
2-3Hard anti-collision sleeve
2-4Valve Cover
2-5Valve Ball
2-6Valve Seat

 

The valve cover of the pump valve is provided with a hard anti-collision sleeve which is resistant to wear and corrosion. A gasket ring is installed between the hard anti-collision sleeve and the joint. The gasket ring prevents the axial movement of the hard anti-collision sleeve and ensures the seal between the joint and the valve cover. The joint and the valve cover are connected by threads. The hard anti-collision sleeve is made of wear-resistant and corrosion-resistant tungsten alloy, and its hardness is higher than the valve cover and lower than the valve ball. The hard anti-collision sleeve has a radial gap with the valve cover, which can effectively protect the valve cover from impact.

Option 3: This design of pump valve is composed of joint, valve cover, valve ball and valve seat. The structure diagram is as follows:

3-1Valve Cover
3-2Hard Welding Layer
3-3Valve Ball
3-4Valve Seat

 

The inner surface of the valve cover of the new pump valve is welded with a hard welding layer resistant to wear, corrosion and impact. The length of the hard welding layer is greater than the contact point between the valve ball and the valve cover from the valve ball to the top dead point of the valve cover.

The hard welding layer material is resistant to high temperature, thermal shock and scratch resistance, and is firmly combined with the valve cover.

The design structure of those three new options is reasonable and compact. All of them can solve the problem of valve cover breakage which can greatly improve the service life of the sucker rod pump.

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