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Extended lifetime through PE-Xa tubing inliner
In oil production tubing failures are still one of the main reasons for unexpected and const intensive workovers of subsurface sucker rod pumps and progressive cavity pumps. In many cases, the actual root cause of tubing failures is a synergistic effect of both, the rods wearing on the tubing wall (abrasion) coupled with the electrochemical attack (corrosion). Regular tubing replacements result in high costs and loss of productivity. The consequences on the economics especially of mature oil fields can be tremendous and even lead to the abandonment of wells.
In order to increase the lifetime of tubing and the average time between workovers, the Austrian oil company OMV initiated an R&D project which has been strongly supported by Borealis and AGRU. The outcome of this project is an innovative technical solution which was patented.
Cause of wear
Due to the increasing demand for oil it is still economic to produce oil out of mature fields having water cuts of 90% or even more. Formation water but also other corrosive components of crude oil are the main reasons for corrosion. In case of sucker rod pumps and progressive cavity pumps at the same time the rods are wearing on the tubing wall which causes abrasion. Especially the combined occurrence of corrosion and abrasion is critical and responsible for early tubing failures as shown in the picture.
Thermoplastic inliners made of high-grade polymers are the best choice for oilfield tubular protection. Especially to protect the tubing string against corrosion as well as abrasion from reciprocating and turning rods in oil production. To select the best thermoplastic material a novel test station was developed. This test station simulates the movement of rod couplings against the lined tubing string under real service conditions, thus it evaluates the combined effects of abrasion and corrosion. Although polyethylene (PE) achieved good results cross-linked polyethylene (PE-Xa) in combination with special surface treated rod couplings is to prefer due to the outstanding abrasion resistance and the much higher temperature resistance (up to 90 °C).
PE-Xa tubing inliners are mainly have been developed for the onshore oil production using sucker rod pumps (SRP) or progressive cavity pumps (PCP). Best improvements can be achieved in mature oil fields with a high water cut and well deviations where tubing failures caused by abrasion and corrosion occur in short intervals.
PE-Xa tubing inliners with their high advantages can also be used in water injection wells.
The Austrian oil companies OMV and RAG as well as the Romanian oil company OMV PETROM have installed tubing inliners in more than 750 oil wells so far. Statistics clearly show that the maintenance intervals can be extended significantly. As a result users are experiencing considerable economical and ecological advantages.
Advantages of PE-Xa tubing inliner
- Lifetime increase of sucker rod pumped and PCP wells
- Abrasion and corrosion resistance
- Extended workover intervals, thus reduced workover costs
- Reduced production costs
- Reduced energy consumption of pumps (approximately 15%)