Centrifugal pump technology plays critical role in many oil and gas applications.
Significant advancements have occurred in the technology used to identify oil deposits below the Earth’s surface, most notably in the vast shale plays in North Dakota, Pennsylvania, Montana and Texas. This technology combined with innovative new drilling and enhanced recovery procedures, such as hydraulic fracturing, have led many to comment that the U.S. is on the verge of a new golden era in oil and gas exploration and production.
In fact, the New York Post made that argument in July 2011, noting that the U.S. is the world’s No. 3 oil producer, at 7.5 million barrels per day (bpd), with the ability to add another 1.5 million bpd by 2015. This would mean that, by 2015, the U.S. would produce more than traditional oil producers—Iran, Kuwait and the United Arab Emirates—in terms of daily production. This increased U.S. production will be driven by the shale formations that could eventually yield more than 4 billion barrels of oil before they are played out.
Hydraulic fracturing and other advances in sophisticated systems for enhanced oil recovery (EOR)—such as chemical injection, gas injection or thermal recovery—have also made it economically viable for producers to return to sealed-off wells that were considered fully depleted or too expensive to produce further. Many of these wells may still hold up to 75 percent of their recoverable oil, some of which can be recovered using the new EOR techniques.
Natural gas is experiencing the same type of increase in production in the U.S., with the International Energy Agency (IEA) predicting in June 2011 that the world was entering a golden era for natural gas, as well. Under the IEA’s scenario, global natural gas demand from now until 2035 will grow 2 percent each year, compared to a growth of 1.2 percent in total energy demand during the same time period. At that rate, demand levels for natural gas would surpass those of coal by 2030 and approach the demand level of oil by 2035. Additionally, 40 percent of the increase in global natural gas production up to the year 2035 would come from unconventional production processes, such as the hydraulic fracturing of shale beds or exploiting deposits of coalbed methane gas. Much of that increased production will come in the form of natural gas that is found in North American shale beds.
Centrifugal pumps, engineered for operational flexibility, efficiency and durability, meet the pumping needs of many oil and gas applications.
With this recent 21st Century U.S. oil and gas boom is the increased need for oil producers to get their drilling and recovery operations online quickly. These multimillion-dollar systems require a wide range of unique equipment to run efficiently, safely and cost effectively, not only with regard to the recovery of oil and gas, but also in the ancillary operations during the production and transportation process. This Efficiency Matters examines how centrifugal pump technology can be used to maximize operations in two crucial areas of oil and gas production.
Produced Saltwater Handling Challenges
Oil and gas drilling and production would be simple if only oil and gas flowed to the surface when a well is drilled. That, however, is not the case as a number of byproducts reach the surface along with the desired oil and gas. One of the more voluminous byproducts is saltwater, which has been trapped for centuries with the oil and gas in the formation.
When the saltwater reaches the surface, it must be separated from the oil and gas. Once separated, the production company handles it in one of two ways:
- It is shipped away via truck.
- It is pumped via pipeline for disposal or re-injection into the formation.
These saltwater-handling and transfer processes can only be completed successfully if the production company has the proper pumping equipment. The salt-water transfer pumps move the saltwater from stock tanks into a pipeline, which eventually feeds an injection pump that injects the saltwater back into the formation. They may also pump the saltwater into trucks for shipment out of the area.
Oil & Gas Transfer Challenges
A second, crucial pump-related application in the oil and gas production and supply chain is Lease Asset Custody Transfer (LACT). A LACT unit automatically measures, samples and transfers oil from a lease location in the oilfield into a pipeline. It is a critical component in the ownership transfer of oil from the production site to trucks, pipelines and storage tanks of the terminal or end user. Think of it as a “cash register” between a company that is selling oil and a company that is buying the oil. Key to helping these LACT units operate efficiently and reliably is the pump that transfers the oil from the owner’s transport unit or storage vessel to the buyer’s.
LACT units can be stationary or mounted on skids for use in portable applications, and the same type centrifugal pump that is used in saltwater transfer is used in this application. However, normally iron or ductile iron is used unless hydrogen sulfide (H2S)—a colorless, poisonous, flammable gas with the characteristic odor of rotten eggs—is present. This portability pays dividends when an oilfield’s oil-gathering system is not close to its production operations. In that case, a transport tanker can go and receive a load of oil, perhaps 10,000 gallons. At that point a ticket is printed with the amount that is contained in the tanker. The transport will then drive to the buyer’s storage terminal where the oil will be offloaded through a skid-mounted LACT unit, which will track the amount of oil that is delivered. When the offloading is completed, the totals on the two tickets will be compared to confirm that 10,000 gallons of oil have been delivered to the buyer.
Not only are these applications crucial to keeping the oil and gas production and supply process moving efficiently, they also occur in difficult and harsh conditions. Most of the operations take place in isolated areas of the country that are at the mercy of the elements—including wind, rain and snow with extreme heat and cold. The oilfield landscape also does not allow for neat installations such as those found in a nice, clean indoor application. Therefore, the mounting of any pumping equipment is often not precise, which can lead to increased stress and opportunities for equipment breakdowns, putting an undesired halt to the production process.
Saltwater and LACT Solutions
Faced with the unique challenges of saltwater-handling and LACT-related operations as well as the need for robust equipment that can withstand extreme operating conditions, more oil and gas production companies are turning to centrifugal pumps to optimize their operations.
One type centrifugal pump, which was among the first to meet the centrifugal pump manufacturing criteria established by the American National Standards Institute (ANSI) in 1977, meets the pumping needs of varied oil and gas applications because they have been engineered for operational flexibility, efficiency and durability. They have two times the wear area between the case and impeller when compared to closed-impeller designs. This extra wear area optimizes the performance of the pump’s open impeller. The open-impeller design also minimizes concentrated wear by balancing the hydraulic axial thrust load and reducing the stuffing-box pressure. This maximizes pump performance, simplifies maintenance, extends pump life and reduces repair costs.
The pump’s casing can be constructed of a wide choice of materials. Some of these are ductile iron; CDM4Cu; alloy 20; and stainless steel, which can be used in harsh applications such as those in which produced saltwater has a high level of H2S. The pumps handling saltwater are often made with a solid stainless steel shaft, stainless steel impeller and mechanical seals with silicon carbide seal faces and API plan 11 seal flush. A heavy duty baseplate re-enforced for field service is also used.
This pump type is constructed through an investment and no-bake casting process that ensures smooth, precise and superior finishes and consistent, reliable performance. The pump manufacturing is overseen by metallurgists that strictly supervise all heat-treating operations so that maximum durability for all alloys is achieved.
These centrifugal pumps are available in a full range of sizes, as well as options and upgrades that can be tailored to meet virtually any liquid-handling flow rate, up to and including 4,000 gallons per minute (15,142 liters per minute). A variety of mechanical seal options, which give the pumps the ability to operate in temperatures up to 500 F (260 C), are also available with this type pump.
Other standard-setting features are self-tightening impellers that reduce leaks and failures and the ability to externally adjust the clearance so that peak efficiency is maintained, even after wear-area loss. Standard, enhanced-power frames also make the impellers an estimated 33 percent stronger than other pumps.
Maintenance
The centrifugal pumps’ simple operation also means that they will consistently operate at their full capabilities, provided that a routine regime of preventive and protective maintenance is followed. This maintenance routine should include:
- The monitoring of bearing and lubricant conditions
- Examining the shaft seal condition
- Monitoring pump vibration
- Checking for changes in discharge pressures
These actions can be conducted on a simple quarterly or annual maintenance schedule. Maintenance checks should be performed more often if the pump is used in severe- service conditions, such as those commonly found in oil and gas applications.
Growth for the Future
With the boom in oil and gas production in the U.S., many production companies complete a new well every other day. The opportunities for production companies in this new era of oil and natural gas exploration and production are limitless. The ability to access oil and gas reserves that were once thought out of reach will help the U.S. lead the global oil and gas market in the future, but only if producers can efficiently, reliably, safely and cost effectively remove commodities from the ground and transport them to the end user.
To meet this lofty standard, oil and gas producers must identify the technologies that can best satisfy their needs and then use them as part of a cohesive system that is beneficial not only to them but to all the players along the production and supply chain. Centrifugal pump technology has stepped up in a number of areas that are crucial to the success of any oil and gas production operation. These pumps, which adhere to strict ANSI standards for operation that were put into place 35 years ago, can aid any production operation in meeting its actual production quotas and its regulatory, environmental safety and self-imposed cost and efficiency requirements.
Pumps & Systems, April 2012