By Rob Caouette
When evaluating a surface rod pumping system, two main objectives are assessed. First, can the pumping unit achieve the desired loads and speeds to maximize production of the well? Secondly, does the pumping unit fit the economics of the well, including initial cost, as well as long-term operating and maintenance costs? Over the years, there have been many attempts to improve on the conventional pumping unit, but so far, all have been unsuccessful. Hydraulic pumping units have been rolled out by 100’s of manufacturers over the years, and they continue to be plagued with high maintenance costs, significant downtime as well as short life, which increase the overall cost dramatically. Mechanical units such as long-stroke belt type units have high upfront costs, as well as significant maintenance costs.
Let’s briefly look at the history of the pumping units, and why the conventional crank balanced unit will never be displaced as the long-term go-to unit for rod pumping.
Since the beginning of the modern oil industry in Titusville, Pennsylvania, the industry has been using rod pump technology for Artificial Lift (ALS). On the first well in Titusville, a common water well pump was used, and there began the long journey to the most common form of ALS in the world. The work that a pumping unit must perform is very specific, it requires the ability to move up and down, up to 12 times a minute, without intervention and with minimal maintenance – that equates to over 6,000,000 strokes per year. To achieve this, you have to reduce to basics, with a minimum amount of moving parts.
The Lever – the most basic machine. When one wants to move something heavy, with the minimal amount of effort, one would find a long board, fit a rock under the fulcrum and use gravity (and a bit of effort) to move the load on the other end. This is much easier than building a mechanical device over the load, or a hydraulic cylinder over it, which is wrapped in a frame. Common sense would always send you back to the easiest and most rational solution.
In the early 1900’s, many designs of pumping units began to enter the market. As you can see below, this early pumpjack was used in Pennsylvania, circa 1914. Overall, this pumpjack was very similar to modern equipment used today, with gas prime mover (not shown), full double reduction geartrain, pitman and beam. These units had limited applicability, as loads became heavier due to increased volumes and deeper wells. Many of these original units continued to run for many years, due to their simplicity and robustness, and they became the template from which the conventional unit developed.
Photograph by Patrice Gilbert, Library of Congress Prints and Photographs Division, Washington, D.C.
In 1925, Walter Trout introduced a prototype to the market, with improvements that included counterweights to allow for larger loads, as well as a curved horse head that enabled longer strokes to maintain polished rod centralization. As pictured below, one can see there have been very little changes over the past century since this design had been introduced.
Over those years, the following has been established drivers for the continued utilization of pumpjacks for rod pumping applications:
Sketched by Walter Trout in 1925, a prototype of his counterbalanced pump jack was in an oilfield before the end of the year.
Design – Simple – as few moving parts as possible, and very heavily built.
Reliability – Proven as most reliable short and long term.
Efficiency – Simple design can accomplish much more with less energy than comparable other PJ designs.
Longevity – Properly maintained, can last 40+ years in operation (@ 6 SPM = 126,144,000 strokes)
Cost-effectiveness – Can be more expensive up front, but low maintenance costs compared to Hydraulic or mechanical units reduce long-term costs significantly.
Overall, the design of a conventional pumping unit has been proven over the past 100+ years, and it continues to be the industry standard in rod pumping. The install base is too large to argue that something better can do the job – in over 100 years of trying, no one has yet been able to improve on the conventional pumping unit.
Redhead knows pumpjacks. Please contact us at today and discuss how our product & services can assist you.
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Rob is the CEO of Redhead Lift and a true blue Albertan, born and raised in the Edmonton area and still lives in Calgary today. He started in the oil and gas industry 27 years ago and brings this wealth of experience to Redhead.