In the oil and gas industry, drilling, completions and production requires and yields significant amounts of water. Sometimes, this water can be recycled/reused. Sometimes it can’t. The Water Challenge (WC) Program was created recognizing that continuous improvement is not only feasible, but also essential for both operational and environmental sustainability.
HARC’s Environmental Friendly Drilling (EFD) Systems recently demonstrated a cost effective flare gas reduction solution in the Bakken Shale, North Dakota. The 90 day pilot trial project integrated a system that provides attractive economics while providing environmental benefits associated with reduced flare emissions and on site power. HARC’s Satish Ravindran discusses the challenges in the Bakken and how the waste heat to power solution helped address the issue.
What is flaring?
Flaring is the controlled burning of natural gas that cannot be processed or sold. A gas flare, also known as a flare stack, is a gas combustion device used in industrial plants (i.e. petroleum refineries), chemical plants, natural gas processing plants, landfills and at oil and gas production sites, both offshore and onshore. Flare systems consist of a stack and pipes that feed the gas.
What does flaring do to the environment?
Natural gas is flared rather than vented without combustion for both safety and environmental reasons. Unprocessed natural gas may contain hydrocarbons that are heavier than air, such as propane and butane that can be hazardous if introduced to an ignition source. Flaring natural gas produces carbon dioxide, which, while a greenhouse gas, has a lower global warming potential than methane, the main component of natural gas. Flares can also be noisy because of the amount of gas that flows through them.
Why is the spotlight on the Bakken?
Oil drilling in the Bakken shale formation of North Dakota has resulted in associated natural gas being flared. Petroleum exploration companies find it more cost effective to burn off the gas due to the limited infrastructure in place to gather and carry the gas through pipelines. This is especially true for remote natural gas wells that are located away from pipeline networks. In the Bakken, wells flare up to 30% of the natural gas produced, while the national average for flaring is about 0.5%.
How is North Dakota dealing with the problem?
In March 2014, the North Dakota Industrial Commission (NDIC) approved a policy by the state’s Department of Mineral Resources to regulate the amount of gas flared. Oil companies are required to have a flare gas capture plan and must capture 78% of the total natural gas production for beneficial use by April 2016. The goals are then increased to 85% capture by November 2016 and 91% within next five years. Oil and natural gas producers have been given an extra two years to meet the targets owing to the low oil and natural gas prices.
HARC tests a solution to the flaring problem
HARC recently demonstrated a feasible solution to tap the flare gas to generate low emission power for onsite operations. HARC partnered with Gulf Coast Green Energy (GCGE) via a grant from the Research Partnership to Secure Energy for America (RPSEA). GCGE is a distributor for the Electratherm Inc. waste heat to power generator. Called Power+ Generator™, the technology produces electricity from any waste heat stream. Hess Inc., a leading oil and natural gas production company agreed to host the 90 day pilot trial project on one of its well pads in the Bakken. Texas A&M University’s Institute of Renewable Natural Resources (IRNR) provided an emission research study for the project.
Overview of Power+ Generator™ Technology
The Power+ Generator™ technology utilizes an Organic Rankine Cycle (ORC) system to produce electricity from waste heat. The set up consists of a Power+ Generator™ 4400 model and a low-NOx (nitrogen oxide) hot water boiler. A portion of the flared natural gas is diverted into the hot water boiler. The hot water produced, then enters a heat exchanger that excites the working fluid of the Power+ Generator™, which in turn drives a twin screw expander to create electricity. The expander creates a low pressure working fluid that is condensed to a liquid and pumped into an evaporator to start the cycle again. A water condenser loop carries heat way and air cools the working fluid in a radiator. This process is outlined in the figure below.
The ORC and the boiler equipment were installed on July 28, 2015. The final system commissioning was completed on July 29, 2015. Testing was performed through August 5, 2015. The system was left in full unmanned operation with remote monitoring and control by the project team in Nevada and Texas. Hess operators in the field were trained by the GCGE team to operate the system in case intervention was needed. The system achieved a total 89% run time, running for a total of 1,937 hours with 103,486 total cumulative kWh generated with an average of 53.4 kW electricity produced. The electricity was tied back into the utility grid.
The Texas A&M Emissions team measured an average reduction of carbon monoxide of 89%, NOx was reduced by 48.1% and VOC’s by 92.8%. The trial was a success and proved that the Power+ Generator™ solution is an economic alternative to flaring. The technology is simple to operate and can reduce flaring emissions effectively.
A link to the recent webinar hosted by GCGE and HARC about the project can be found here.