Cook Inlet may have more oil and gas to give, but developing it could present a challenge.

Though there is active development on oil fields in the northern Cook Inlet and one producer in the Cosmopolitan field near Anchor Point, there may be resources that are going unexplored in other parts of the inlet, particularly along the west side.

There is likely more oil deeper below the rock layers that are currently being drilled in Upper Cook Inlet.

A study conducted by geologists from the Alaska Division of Geological & Geophysical Surveys evaluated petroleum in the Jurassic layer, a stratum below the Cenozoic layer, where most Cook Inlet oil and gas is extracted.

The study looked at oil seeps in Chinitna Bay on the west side of Cook Inlet and found that the oil is in older rocks than other areas of the inlet. Chinitna Bay, located at the south end of Lake Clark National Park, shows oil-stained fault zones along the Iniskin Peninsula on the southern shore of the bay.

Oil exploration on the Iniskin Peninsula has a long history — seepages were spotted there as early as 1853, some of the first known oil explorations in Cook Inlet.

Individuals began staking claims on the peninsula as early as 1892 and wells were drilled there in the early 20th century. None of them turned up enough to make it viable.

However, the oil is literally so visible and available that surveyors can collect oil samples from the surface, said David LePain, a petroleum geologist with the Division of Geological & Geophysical Surveys.

“This is one of those locations where you have sands where if you hit them with a hammer, you smell hydrocarbons,” LePain said. “You send them off to the lab, and they can analyze hydrocarbons from this sample.”

The oil is not immediately available near the surface. From previous drilling efforts and studies, geologists have determined that most of the oil is probably migrating to the surface through fractured reservoirs — cracks in the rock that allow oil to migrate upward in small amounts.

Drilling there may be tricky and possibly not worth it for commercial producers because of the expense required to start up there. If the payoff isn’t sure, it may be difficult to develop. But that doesn’t mean it’s impossible that producers will explore there, said Paul Decker, a petroleum geologist and resource evaluation manager with the Alaska Division of Oil & Gas.

“If (developing a field is) economically challenged in general, it’s more challenged at low prices,” Decker said. “That doesn’t mean that no one is going to do anything out here.”

One of the reasons state geologists are studying the rocks there is to gather more information and make it available as they find it, not necessarily to push for commercial development, Decker said.

“We want to make sure that people know these occurrences exist,” Decker said. “It’s not that we’re purporting that there are going to be commercially viable reservoirs.”

Some commercial oil producers have eyed the region’s potential for future development. Cook Inlet Energy won the exploration rights to the area in 2014, but surrendered the license on Sept. 28, 2015. Shortly afterward, its parent company Miller Energy declared involuntary bankruptcy on Oct. 1. Hilcorp has also applied to obtain 2-D seismic data on the Iniskin Peninsula.

The study is part of a long-standing program within the Division of Geological & Geophysical Surveys to better understand the geology and oil potential of the Cook Inlet basin, LePain said.

“Our focus is to understand the oil, gas, coal and resource potential of Alaska state lands,” LePain said. “Since 2006, we’ve had a program underway to better understand the potential of the Cook Inlet basin … so that oil companies exploring in that basin have scientific information to help further their development and exploration efforts.”

The study’s authors wrote that it merits further exploration, but whether the deeper layer of Cook Inlet can support a full-blown oil production industry remains to be seen. Predicting migration pathways and identifying where the most economically significant reservoirs are remain challenges, the authors wrote.

One of the goals of the Division of Geological & Geophysical Surveys’ Cook Inlet project is to provide more information to companies seeking to explore for those fractured reservoirs, LePain said.

“If you’re trying to pull in that information and that information is out there, if you’re doing your homework, you can get it and build a geological model of that part of the basin,” LePain said. “You’re not drilling blind.”

Reach Elizabeth Earl at elizabeth.earl@peninsulaclarion.com.