Challenges of heavy oils call for innovative downhole pumps

With recoverable reserves of heavy crude approximately twice as prevalent as those of light crude, it is no surprise that exploration and production companies continually seek to optimize production operations for this resource. There is a keen interest in finding innovative solutions to the unique challenges that heavy oil and oil sands present, especially in markets such as Canada where these properties are abundant.

One unique challenge of handling this type of production is the commonly associated high temperatures. Addressing this challenge head-on is a specially engineered line of Moyno downhole pumps offered through the National Oilwell Varco Mono division (NOV Mono). Specifically designated Moyno HTD pumps provide unique solutions to high temperature applications which previously have prevented utilization of downhole progressing cavity (PC) Pumps.

Within this line of high temperature pump technology are two new developments which further expand application capabilities: mechanical lock stators and metal-to-metal pumps.

Mechanical lock stators
Although most PC Pumps have not been capable of handling high-temperature applications, the Moyno HTD elastomers have proven capable of temperatures up to 175 degrees Celsius (350 degrees Fahrenheit). Yet, the challenge still remained when dealing with temperatures above this range where the bonding agent would start to break down. Now, the new designed mechanical lock stator is the solution to applications above 175 degrees Celsius. With this technology, the bonding agent is effectively taken out of the equation and replaced by an elastomer molded into a mechanical cage affixed inside the stator tube. In other words, the elastomer is mechanically secured to the stator tube without using a bonding agent. Thus, when the temperature gets hot there is no glue to separate and cause de-bonding.

With this new capability the door to more applications opens up to the 175 degree Celsius heat range in wedge wells, perimeter wells, and wells aging in their steam lifecycle. As a result, the run times for many wells are extended much longer before having to be steamed again and many of the wedge wells do not get as hot as ones in the core of their steaming. Given its compatibility with steam injection, the stator does not have to be removed during injection. Currently, there have been more than 100 installs of the Moyno mechanical lock stators, with operators experiencing considerable success in extending run lives.

With variable lifts available, the Moyno pump line offers four mechanically secured models HTD350TM from which to choose. These are: 17 m3/d@ 100 rpm, 44 m3/d@ 100 rpm, 75 m3/d@ 100 rpm and 150 m3/d @ 100 rpm.

Metal-to-metal pumps
Metal-to-metal takes high temperature to a completely new level. By working in the 350 degrees C (660 degrees F) range, a much wider range of applications opens up. Specifically, in metal-to-metal technology, the Moyno pumps are differentiated with the one-piece stator technology which is currently offered in three different sizes handling production levels up to 600 m3/day.

From a design perspective, the metal-to-metal is very robust, primarily due to being constructed in one solid piece with a heavy durable stator. This contrasts with similar products constructed of multiple small pieces and fused together rather than manufactured from a solid length of steel. Typically that translates into the capability of handling considerably more environmental occurrences downhole.

Another unique aspect is the rotor swap. Using proprietary technology the stator is manufactured precisely the same every time by cutting the stator instead of forming it.

So, when operators see an efficiency drop indicating the rotor is wearing out, they can do a rotor swap because of the precisely replicated rotors. With the metal-to-metal technology, the rotor is designed to fail before the stator and it is far less expensive to replace. With the unique rotor swap capability, operators are saved from having to utilize a costly service rig.

Ordinarily, to change a stator the entire tubing string must be pulled and rotor changes require pulling the rod string. By bringing a flush-by truck on-site instead of a service rig, a rotor swap can be completed in half a day and the well is up and running again.

Additionally, the metal-to-metal technology is ideal for steam-assisted gravity drainage (SAGD) and cyclic steam stimulation (CSS) applications.

With these different technologies, the purpose is primarily loosening the oil when a well pair is drilled; steam is injected into one of the two wells and the oil is then freed to be pumped or lifted to surface. Essentially, the steam gets the oil out of the sand and allows the well to produce.

Another application for the metal-to-metal PCP is when injecting chemicals or gases such as butane or propane are being injected. Using this technology, operators do not have to be concerned about the elastomers getting damaged by the gases since there are none.

Metal-to-metal PCPs are available in three models: 12-M-80, featuring 80 m3d @ 100 rpm (1,200 m of lift), 12-M-110 featuring 100 m3d @ 100 rpm (1,200 m of lift) and 7-M-206 featuring 206 m3d @ 100 rpm (700 m of lift).

Better economics & performance
With these new technologies, operators can consider the economics of using PC Pumps in more widely varied applications than before. Moyno high-temperature downhole pumps feature the mechanical lock stators (mechanically secured elastomers) in two models, HTD300 and HTD 350. The metal-to-metal rotor/stator technology is featured in the HTD660 model. Each model number refers to the downhole temperature (in degrees Fahrenheit) these pumps can handle. In addition to handling 300-degree downhole temperatures the HTD300 works ideally in water, oils and aromatic environments as well as providing high resistance to gas permeation.
It also minimizes stator swell and property loss. The other downhole pump with a mechanical lock stator, the HTD350 handles a slightly higher temperature and the stator does not have to be removed during steam injection. In the metal-to-metal model, the HTD660 works extremely well in CSS and SAGD applications. Its low vibration is comparable to conventional PC Pumps and its low tolerances deliver exceptional performance.
NOV Mono provides artificial lift equipment and solutions to the Canadian and US markets to meet their specific applications needs. The company offers a combination of innovative technology, products, and full-fledged technical expertise and field support to deliver a complete solution package.