EOR-For-Shale Ideas to Boost Output Gain Traction

Abstract

Low oil prices may not be the biggest threat to the long-term sustainability of the North American shale business. Some are more concerned about the low recovery rates of horizontal shale wells, estimated to be about 7% on average— far short of the 40% achieved through primary and secondary (waterflooding) production in conventional reservoirs. Refracturing has been touted as the next big thing to improve ultimate recovery, but such operations remain relatively expensive and may only temporarily reset production to initial rates once or twice in a well’s life. To see long-term results and a doubling or tripling of current recovery rates, a number of experts say enhanced oil recovery (EOR) technologies must be developed to work in tight shale reservoirs. And due to persistently low natural gas prices, current efforts appear to be exclusively focused on oil and condensate producing wells. It is early days for this area of EOR research. There is no consensus on which approaches will work best, how much they may cost, what the most pressing challenges are, or exactly when an EOR operation should begin. “Our understanding is really small,” said Todd Hoffman, an assistant professor of petroleum engineering at Montana Tech University. “We’re coming from the conventional world where ‘this’ is how we did EOR and we may just have to throw all that out.” Hoffman is one of several researchers trying to figure out how EOR methodologies can be adapted or reinvented for the oil-rich shale fields of North Dakota, Texas, and Canada. One of the most popular ideas being studied is a huff-and-puff approach that uses a single horizontal well to alternate between producing oil and injecting natural gas or CO2 to re-pressurize the reservoir and displace oil. Another idea is to apply continuous injections into one well and use an offset well as the producer. Others are looking into flooding the wells with surfactants and possibly acid to stimulate production. In May, EOG Resources laid claim to the first economic demonstration of an injection-based EOR technology for tight oil in the US. The company said the development may have long-term production benefits and is competitive with drilling new wells. But other than making it clear that the process has been successful and uses dry gas produced in the same field, EOG is withholding key operational details such as whether it involves the huff-and-puff technique or continuous injections. A number of other innovative shale producers including Statoil, Nexen Energy, Continental Resources, and Marathon Oil have also either funded research or are known to be running pilots, but have not made their results public. As most shale producers remain silent about their EOR efforts, there are a growing number of technical papers being published by university petroleum departments and reservoir engineering consultants. They are using computer models and corefloods to test their theories and have produced promising numbers that suggest there may be several practical ways to implement EOR strategies for shale.