Solar-Powered Diaphragm Pumps Enhance Shale Gas Profitability
Tom OíDonnell, Product Manager, Neptune Chemical Pump Co
Ravi Prasad, Director of Sales Pump Solutions Group (PSG) India

India, the fourth-largest energy consumer in the world behind the United States, China and Japan, faces significant energy challenges that have forced it to examine alternate ways to meet its increasing energy demands. One method that continues to increase in popularity worldwide is the extraction of natural gas trapped witjhin shale formations below the Earth's surface. The article talks about the new diaphragm pump technology which provides enhanced chemical injection solutions designed to optimise shale well production.

India has identified six basins that hold shale gas potential viz Cambay (Gujarat);Assam-Arakan (Northeast); Gondawana (Central India); KG onshore (Andhra Pradesh); Cavery onshore and Indo Gangatic. The Oil Ministry of India sees dependence on foreign oil decreasing by 50 percent in 2020 and 75 percent by 2025, due in part to its plans to explore and exploit untapped reserves. India currently imports as much as 79 per cent of its oil.

While it has been known for many years that natural shale gas and oil reserves were trapped in deposits of shale formed from ancient sea basins millions of years ago, technology wasn't available to economically extract those resources until recently. Various technologies play a prominent role in efficient shale-gas extraction, including the pumps that must be used to inject chemicals into shale wells during the production process known as hydraulic fracturing, or fracking.

Unlocking shale formations through horizontal drilling and hydraulic fracturing initiates the gas recovery process from producing zones deep beneath the surface; a process that often results in more than 20-years of production from a single well. During the production years, gas operators face additional significant challenges to provide low cost energy to the world's population. Water and sand entering the well bore, corrosion of steel piping and harsh environmental conditions constantly work against the efforts of those striving to reclaim natural gas.

A resourceful industry soon discovered introducing specific chemicals into the contained well bore counteracted many of the detrimental effects of this harsh environment. Anti-corrosion inhibitors enhance the life of the steel tubing used to conduct the gas stream from the underground reservoir to the surface. Surfactants break the surface tension of water that enters the well bore, effectively reducing the water column pressure on the gas moving toward the surface. With reduced downward pressure exerting by the water column, more gas is extracted from the formation. In cold weather environments, methanol is often used to lower the freezing point of liquid moving through surface transportation piping.

Introducing production-enhancing chemicals into the well is most commonly accomplished with a pump at the surface. The pumpís primary purpose is to consistently and accurately inject a user-selectable type and volume of chemicals into the well, without discharging harmful gases into the environment. Many may argue that the large number of variables in a well disqualify the need for injected chemical volumes to be consistent. However, astute operators know a consistent, repeatable volume of chemical injected into the well enables a predictable outcome - including the monthly usage, and thus cost, of the chemicals injected, the corrosion rate of down-hole steel tubing and, in some cases, even the volume of gas produced.

Equipment reliability and remote monitoring capabilities are additional key requirements of chemical injection pumps located at remote gas well locations. Pumps requiring frequent maintenance create unpredictable down -hole outcomes resulting from a reduction in injected chemical volume. Additional costs are incurred as skilled technicians are deployed to diagnose and resolve the pump problems. Remote monitoring serves as "eyes on the ground" for busy gas well operators. Traditional once -per-day pump knowledge is augmented by the pump controller's ability to automatically contact the operator when an anomaly occurs. Gas well operators benefit on many levels by reducing the time between actual problem occurrence and problem detection at remote well sites.

To function at maximum efficiency, a chemical-injection system must employ a pump that consistently injects an accurate, user-selectable chemical volume into the well bore. Much of the pump technology currently utilised for this application falls short of that objective. Root causes include inconsistent injection rates, seal failures, chemical leakage, gaseous discharge to the environment and increased maintenance requirements.

At present, the two most prevalent pump styles used to inject chemicals into a well bore are gas-powered (pneumatic) and solar-powered reciprocating piston pumps. Despite the widespread usage, these pump technologies are prone to recurring issues that may cause significant problems for natural gas producing companies.

Although low-cost, comparatively simple to operate gas-powered pumps are popular among natural gas producers, they are now being phased out due to a heightened focus by governmental regulating entities on the potential harmful effects of greenhouse gases. As a part of the pumpís normal cycle, gas-powered pumps vent natural gas (methane) and other compounds (such as carbon dioxide and hydrogen sulfide) into the air. A typical gas-powered pump emits from 250 to 650 standard cubic feet per day (SCFD) of dry gas into the atmosphere. Some of the escaping gaseous compounds are potentially harmful to the environment and can be dangerous to personnel working around the well site.

Gas-powered pumps often experience uneven performance in their principal function - to consistently deliver an accurate, user-selected volume of chemical into the well bore. Gas-powered pumps are powered by the wellís pressure, which can vary significantly. Regulators are used to provide a constant pressure to these pumps, thus adding another piece of equipment that must be maintained, properly set and function correctly to ensure desired pump performance. Any variation in the pressure supplied to the pump can result in a variance in the amount of chemical injected into the well bore. Frequently, gas well operators are compelled to dispatch service personnel to remote well locations to check and adjust dosing rates.

As gas-powered pumps are phased out for this application, many natural gas producers have begun using solar-powered reciprocating piston pumps that feature a timer to control pump cycles. Reciprocating piston pumps typically utilise an eccentric cam connected to the motor shaft to convert the motor's rotational motion to the axial motion required by the piston. The faster the motor cycles (i.e. revolutions per minute), the faster mechanical connection points between the eccentric cam and reciprocating rod wear and require replacement. However, these pumps contain dynamic seals, which tend to degrade over time. Dynamic seals form a barrier between a moving part (such as a piston or reciprocating rod) and a stationary part (such as the pump housing). As these seals wear, liquid chemical intended for the contained well bore may leak into the environment.

V-packing is a type of dynamic seal common on reciprocating piston pumps. Some of these seals are designed to be tightened at regular intervals. If V -packing seals are over-tightened, they can grip the reciprocating rod too hard, causing undue stress on the motor and additional drain on the battery. Maintaining optimal pump effectiveness requires gas producers to regularly dispatch service personnel to the well.

With gas-powered pumps on their way out, and many solar-powered reciprocating piston pumps not living up to expectations, natural gas producers are in need of a new and innovative solar chemical injection system that incorporates a different type of pumping technology. Increasingly, they are turning to an innovative solar-powered chemical injection pump that features diaphragm metering technology.

Diaphragm metering pumps are highly durable and resistant to various chemicals. Featuring few moving parts and no dynamic seals, diaphragm metering pumps are more reliable and easier to maintain than gas-powered and reciprocating piston pumps. The diaphragm completely separates the chemical side from the hydraulic-fluid side. Regardless of the type of chemical to be injected, seal materials do not require changeout. On the hydraulic-fluid side, there are no O-rings in the pressurising piston sleeve, which means less wear on the piston rod.

Diaphragm metering pumps feature all stainless-steel components in contact with the injected chemical (such as the pump head and check valves), and a chemicalresistant PTFE-coated diaphragm. This robust design helps extend the life of the pump, while preventing chemical leaks and reducing the cost of maintenance.

One of the top monthly operational expenses incurred by many shale gas producers is the cost of the chemical that is injected into the well bore. Frequently, chemicalinjection pumps will be set at a higher dosing rate than prescribed for the well. This common practice is necessary to counteract pump inefficiencies associated with the current technology (gas-powered and reciprocating piston). Diaphragm metering pumps address this concern by consistently injecting user-selected chemical volumes into the well bore with extreme accuracy.

When speaking specifically about chemical-injection systems that utilise diaphragm metering pumping technology, Neptuneô Chemical Pump Company, North Wales, PA, USA, in collaboration with sister Dover Corporation company Ferguson Beauregard, recently created the Solar Dô Chemical Injection Pump. Relying on the resources and expertise of one of the most trusted names in the energy and chemical-dosing industries, the Solar D pump solves many of the problems experienced with other chemical-injection systems, thereby optimising productivity and enhancing profitability.

The Solar D pump is based on proven Neptune diaphragm metering pump technology that has been used in industrial chemical-dosing applications for years. The diaphragm metering pump features a brushless motor, paired with a digital controller for precise, accurate injection rates. Over the pressure range of 300 to 1,200 psi (21 to 83 bar), tests show that the Solar D pump has a dramatically smaller deviation of injection rate within a 95 percent confidence interval. The result: the need to inject a greater volume of chemical than that prescribed for the well is greatly reduced - resulting in real savings for operators.

At 1,200 psi, other solar chemical-injection pumps can vary their injection rate as much as 2.8 percent (over 4 gallons a month per well - assuming 5 gallons injected per day). By comparison, the pump's injection rate varies only as much as 0.9 per cent (less than 1.5 gallons per month per well). Its reliability means fewer technician trips to the well in conjunction with the additional chemical cost savings for operators. Solar D diaphragm metering pump injection rates are easily adjustable from 0 to 45 gallons per day (0 to 170 L/day). The pump's digital controller allows users to cycle the pump for exact amounts of time to ensure highly accurate daily injection rates. An onboard calculation routine enables users to run a common rate test, record the results of that test and plug the values into the controls, thereby allowing the pump to be calibrated to the specific well conditions. The operator is than able to key in the prescribed chemical volume and the controller automatically sets the required cycle times. The pump can also be easily configured to allow remote monitoring via cell phone or interface with existing SCADA systems.

In summary, the Solar D chemical injection system offers numerous benefits previously unavailable to shale gas producers.
  • Environmentally friendly, emitting no atmospheric gases
  • Utilises a seal-less, low-maintenance, diaphragm metering pump technology
  • Consistently injects accurate user-selectable chemical volumes, enabling lower chemical consumption and corresponding costs, while enabling predictable down-hole benefits.
When considering all of these features and weighing the ownership costs associated with previous pumping alternatives, the new Solar Dô Sola-Powered Chemical Injection Pump provides an efficient solution for overcoming the harsh realities of natural gas production from shale formations.