Abstract
The sucker rod is an extremely important equipment in oil exploitation, but with the deepening and harsh environment of the petroleum well, higher requirements are put forward for the strength and corrosion resistance of the sucker rod. The most commonly used steel for H grade sucker rods is 4330 steel. However, it has characteristics such as high cost and relatively low sulfide stress cracking resistance. Thus, a novel sucker rod steel with a composition of 0.2 wt.% Cu and 1.2 wt.% Ni was designed. Normalizing + tempering (NT) and quenching + tempering (QT) heat treatment were optimized to render the mechanical properties of the novel sucker rod steel to reach the H grade. Additionally, effects of heat treatment on the microstructural evolution and mechanical properties of the novel sucker rod steel were investigated by optical microscope, scanning electron microscope and mechanical property tests. The results showed that the microstructure is tempered sorbite and the mechanical properties reach H grade after NT and QT. Specifically, the tensile strength, yield strength, elongation and impact toughness of NT/QT samples reached 1010.58/1124.37 MPa, 875.93/1042.63 MPa, 15.66/11.59% and ~77.48/~111.69 J/cm2, respectively. Furthermore, the finer and more dispersed carbides were observed in the QT sample, which means that the QT sample had better strength and toughness.
Highlights
Rod-and-pump oil recovery is the most traditional and widely used method of oil and gas development globally [1], and the proportion of oil produced by sucker rod pumping technology in China is as high as 75% [2]
The heat treatment processes were designed to make the novel steel meet the requirements of H grade according to granular bainite (GB)/T 26075-2010 standard [3], and the specific parameters are shown in Table 2 (Muffle furnace, Changsha, China)
The microstructure of the as-normalized sample consisted of granular bainite (GB) and a small amount of martensite with a volume fraction of about 5% (Figure 1a) with grain size ~25.61 μm by Nano Measure software (Shanghai, China, a software to measure length according to the scale; the grain size is the average grain diameter)
Summary
Rod-and-pump oil recovery is the most traditional and widely used method of oil and gas development globally [1], and the proportion of oil produced by sucker rod pumping technology in China is as high as 75% [2]. With the gradual increase in the number of deep and ultradeep wells in petroleum wells, higher requirements arise for the strength of sucker rod steel. Sucker rod steel is mainly divided into grades C, K, D, and H [3]. The H grade sucker rod steel is widely used in deep and ultradeep wells with a tensile strength range of 965–1195 MPa. with the improvement of oil recovery technologies such as wastewater reinjection [4], the environment in which the sucker rod is used has gradually deteriorated, and the corrosiveness (H2S, CO2, etc.) in the well fluid has aggravated the corrosion and failure occurrence of the sucker rod steel [5]. The production of oilfields must develop H grade high strength sucker rod steel with excellent performance
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