Composite sacrificial anode on outer wall of bushing

Abstract

The invention relates to a composite sacrificial anode on an outer wall of a bushing, which is used for protecting the cathode on the outer wall of the bushing in an oil field. The composite sacrificial anode comprises an inner layer aluminum alloy anode material and an outer layer magnesium alloy anode material and is formed by compounding two different alloy materials, wherein the outer layer magnesium alloy anode material comprises the following ingredients by weight percent of: 0.8 to 1.5 percent of aluminum (Al), 0.1 to 0.3 percent of zinc (Zn), 0.1 to 0.3 percent of calcium (Ca), 0.01 to 0.05 percent of manganese (Mn) and magnesium supplementing to 100 percent. The inner layer aluminum alloy anode material comprises the following ingredients by weight percent of: 3 to 3.5 percent of Zn, 0.1 to 0.15 percent of indium (In), 0.03 to 0.08 percent of Stannum (Sn), 0.05 to 0.1 percent of silicon (Si), 0.02 to 0.05 percent of titanium (Ti) and aluminum supplementing to 100 percent. The composite sacrificial anode has effects that: the electrochemical performance is excellent, the drive potential is large, the current efficiency is high, the corrosion-resistant protective effect is good, the corrosion-resistant technique requirement that the service life of the bushing is more than 10 years under the condition of different well depths can be satisfied, the service life of the bushing can be effectively increased by two to three times, and the economic benefit is vast. The composite sacrificial anode is easy to install, the service life is long, and the cost is low.

Description

technical field [0001] The invention relates to the technical field of metal anticorrosion, in particular to sacrificial anode cathodic protection on the outer wall of oil field casing, which is a composite sacrificial anode on the outer wall of the casing, which solves the problem of casing damage caused by corrosion. Background technique [0002] During the exploitation of natural gas, the accompanying corrosive media such as hydrogen sulfide, carbon dioxide, and water will cause harm to oil casings, downhole tools, and cement sheaths. With the prolongation of the development time of oil and gas fields, casing corrosion damage is becoming more and more serious, which has caused immeasurable losses to production. For example, since an oilfield was put into development in 1998, the number of wells with casing damage has increased year by year. According to statistics: as of the end of June 2010, there were 86 wells and 106 well-times with casing damage in this oilfield. Th...

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Problems solved by technology

Through the potential detection and the verification of pulling out the well anti-corrosion casing, these three types of anode materials meet the protection potential of most wellbore casings, but there are still problems: 1. The alloy corrodes quickly, the current efficiency is low, and the service life is short; 2. The alloy dissolves The uniformity is not good, and there is local corrosion; 3, high temperature is easy to passivate, and the protection fails; 4, the price is high, and the manufacturing process is complicated; 5, it contains toxic elements, which is harmful to human health and the environment

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