Over time the internal pressure of oil wells drops and various methods and systems are incorporated to invigorate flow. When reservoir drive does not provide enough pressure to lift fluids to the surface, artificial lift equipment is installed to help lift the fluids. Artificial lift is used on oil wells to enhance oil recovery rates. Techniques such as “gas lift,” where expanding gas helps to lift fluids in a well’s tubing, lower the density of fluid to decrease the bottom hole flow pressure. These artificial lift pumping systems pose many challenges, particularly in sealing.
This is one of the reasons why leading oil and gas field service companies are continually evaluating advanced sealing technology; especially due to ever evolving operating conditions, such as elevated pressures, extreme temperatures, increased friction and smaller spaces inside the wellbore for upstream pumping. The conditions within these environments are harsh and very caustic and specifying suitable materials and seal designs capable of withstanding these factors poses real challenges.
Lowering downtime to keep costs down
Downtime for planned or unplanned maintenance on an artificial lift pump system can be a significant cost for operators. The key to decreasing downtime and extending seal material life is to understand how materials react over time when exposed to severe operating conditions. It is important to match seals to the arduous and difficult environments faced. This extends system life, optimizes production efficiency and ultimately reduces operator costs. In addition, selecting a seal supplier with a broad range of compliant materials has benefits in both vendor reduction and processing performance.
Sour gas or Hydrogen Sulfide (H2S) compatibility is often a sealing requirement for successful artificial lift systems. High levels of H2S may cause severe degradation of polymers typically used in oilfield applications, especially elastomer grades such as Hydrogenated Nitrile Butadiene Rubber (HNBR) and Fluoroelastomer (FKM). The material selection for such conditions is important to ensure the system’s high mechanical integrity and also to minimize potential seal failure and damaging leakage.
Materials are vigorously tested before implementation to ensure they meet required standards such as NORSOK M710, ISO 23936-2 and API; the minimum now demanded by the Industry. Controls such as these ensure safety and the governing bodies that help to set standards have made a positive impact. In addition, standards provide customers with an unbiased, accurate way to assess performance.
To meet standards, seal materials are batch tested and the parts themselves can undergo months or even years of testing to ensure they are able to withstand changing environments and conditions. This process sometimes needs to be done rapidly however. For instance, Trelleborg Sealing Solutions was able to deliver a seal developed in a compound to specifically address the impact of sour gas in just three weeks and saved a key project from delay.
Pressure-containing components are vulnerable to sulfide stress cracking (SSC) when exposed to sour environments and can lead to various modes of material failure depending on additional environmental conditions. Material damage can occur in a relatively short timeframe and can lead to catastrophic failure of equipment.
In such scenarios, companies should be aware of this potential occurrence and request specific testing of potential solutions; this may take years before actual implementation. Choosing a supplier with this level of technical support combined with sealing solutions meeting industry standards ensures a customer receives a very effective and reliable product.
Establish a supplier relationship
Long term relationships are valuable as in many applications operating parameters of systems change, such as, pressure and/or temperature levels. This should be monitored to ensure the sealing solutions will still operate effectively within amended operational constraints.
In conclusion, selecting the correct material to construct sealing solutions for artificial lift systems and matching them to the environment in the wellbore will help ensure a long production life in wells. It’s vital to choose a solution that meets industry standards with compounds and seal designs that have been proven with extensive testing, solid engineering expertise and offered with local technical support globally.