TWRI grant recipient quantifies horizontal well cost-benefit, creates new modelsBy Leslie Lee
Constructing a water well begins with making several design decisions, including whether to drill the well horizontally or vertically. Ben Blumenthal, former Texas Water Resources Institute (TWRI) research assistant, investigated the use of horizontal drilling technology for groundwater production and developed mathematical models that simplify that decision-making process.
“Horizontal wells are very advantageous for petroleum production, as evidenced by their widespread use; the question going into this study was what benefits, if any, exist for groundwater production,” said Blumenthal, who graduated in December 2014 with a Master of Science degree in Geology from Texas A&M University. His research was supported by TWRI, with Mills Scholarship and U.S. Geological Survey grant funds.
Blumenthal researched the utility of horizontal groundwater wells, developed new models for groundwater flow to horizontal wells and completed a cost-benefit analysis.
“The main advantage of a horizontal well is greater wellbore contact with the aquifer when compared to a vertical well,” Blumenthal said. “Aquifers are usually much more laterally extensive than vertically thick.”
“For example, an aquifer might extend 10 feet vertically but 100 miles laterally. For this hypothetical aquifer, with a vertical well you are limited to 10 feet of wellbore-aquifer contact. However, with a horizontal well you are limited only by the horizontal drilling capabilities, perhaps 5,000 feet of wellbore-aquifer contact.”
To investigate horizontal wells’ possible production advantages, Blumenthal developed a new type of groundwater flow model. His computer model rigorously models the wellbore, taking into account friction and acceleration pressure loss within the well, he said.
“My model is an analytical model, or a ‘plug and play’ model; you can enter your information, press play and you’re done,” he said. “If you just want to sit down at your desktop and figure this out in an hour or so, my model can run many different simulations in that amount of time.”
This model is a good starting place for professionals considering drilling a horizontal well, he said, but it can also be used to simulate any kind of well – vertical, slant or horizontal. The model has a graphical user interface that is easy to use, but is also thorough, Blumenthal said.
“I designed it so that it could run on anyone’s computer,” he said. “And, it’s going to be free and accessible.”
Potential users include engineering firms, oil and gas companies, state agencies and water utilities and suppliers.
“It’s mainly a tool for front-end, theoretical groundwater planning,” he said. “This model is good for looking at one well and knowing everything there is to know about that one well. The way my model treats the well is more rigorous, and it is simpler to use than many other groundwater models.”
Blumenthal also modeled the cost of drilling both horizontal and vertical wells, using industry data to calculate total well costs.
“Our research shows that a horizontal well may cost anywhere from two to 32 times as much as a vertical well,” he said.
“While well cost estimation is inherently a site-specific task, I think our work is at least a good first look at horizontal well cost and how it varies. Our study was focused on high production rates and large diameter wells. Our cost analysis is especially geared toward large groundwater projects, such as those at the municipality level.”
Blumenthal found that compared to vertical wells, horizontal wells are most cost-competitive at greater depths.
“After combining the cost and benefit analyses, it became clear that horizontal groundwater wells have a cost-benefit advantage over vertical wells in certain hydrogeologic scenarios and not others,” Blumenthal said. “From our research, a horizontal well can produce anywhere from one to 100 times more water than a vertical well, depending on a number of factors.”
Blumenthal found several parameters that increase the benefits of a horizontal well. These parameters include nearby recharge boundaries such as a river, vertical aquifer fractures, lower aquifer permeability, and thinner aquifers, he said.
For example, he found that if the aquifer is thin, with a low permeability, has vertical fractures and a nearby recharge boundary, and the well is deep, then a horizontal well is more economical. Conversely, if the aquifer is thick with a high permeability, has no vertical fractures or nearby river, and the well is shallow, then a vertical well is more cost-effective.
“But, all of these parameters are interconnected, so it’s difficult to just go through a checklist and determine if a horizontal well should be used in a given situation,” Blumenthal said. “This is why I built the model and am providing it free of charge. Anyone could use my work and models to determine the most cost-beneficial well given their specific aquifer conditions.”
Blumenthal’s complete work may be found in his thesis, titled: “Kinetic and Friction Head Loss Impacts on Horizontal Water Supply and Aquifer Storage and Recovery Wells.”
Dr. Hongbin Zhan, Endowed Ray C. Fish Professor in Geology in the Department of Geology and Geophysics, served as Blumenthal’s advisor and described his master’s thesis work as “superior” and its quality “equivalent to some of the best doctoral dissertations we have seen.” Zhan and Blumenthal will co-author forthcoming articles based on his thesis in international journals, Zhan said.