Inside Aera
The Big Picture Jun 17, 2019

Anatomy of an oil well

At a display in the Aera Academy in Bakersfield, Tim Zdarko explains how an oil well’s casing system works.

There’s much more to these high-tech oil operations than meets the eye.

Some say drilling an oil well is akin to sticking a straw in the ground and sucking oil from the rock.

For Tim Zdarko, it’s far more complicated than that.

Zdarko is manager of Aera’s drilling and investment recovery team operations. He’s spent more than 40 years in oil and gas production across the U.S., as well as in the Gulf of Mexico, Africa and Europe. The last 22 years have been with Aera.

Oil wells have come a long way since California drilled its first in the mid-1800s, says Zdarko. Today, they’re high-tech operations that rely on advanced geologic and engineering studies, innovative equipment and stringent safety and environmental regulations.

“Today, we use better materials and more efficient procedures,” he says. “Crew safety and groundwater protection are paramount. We monitor production with iPads. And there’s much more regulatory oversight.”

Getting to the ‘pay zone’

A well’s primary components are the wellbore and casing. The wellbore is the hole that’s drilled into the earth to create the well.

The casing consists of telescope-like layers of steel pipe placed inside the wellbore to reach what Zdarko calls the “pay zone.” That’s where the oil or gas is.

The steel casings shrink in diameter as they penetrate the earth. At Aera the outside layer of casing usually measures 9 5/8 inches in diameter and weighs a hefty 36 pounds per foot. The next casing spans 7 inches wide. The third or interior casing totals 5 1/2 inches across.

Once the system is in place, cement is pumped down the casing and then back to the surface between the wellbore and casing. When the cement hardens, it forms a bond between the walls of the wellbore and the outside of the casing. That fortified bond is what protects groundwater and oil and gas reservoirs.

During wellbore construction, the casing and cement placement are routinely tested onsite to ensure integrity.

Perforations in the casing opposite the reservoir allow oil or gas to move into the system and up to the surface.

“If the oil flows on its own, we’ll put tubing near the top of the oil reservoir where the pay zone is,” Zdarko says. “The oil then flows up through the tubing and into the collection system.”

But if the oil doesn’t flow on its own, rods are placed in the tubing and connected to a downhole pump. These solid metal rods measure less than two inches in diameter and connect the pumping-unit parts that pump the oil up to the surface. This pumping operation is what most people recognize as the horse-head equipment that moves up and down atop the wells in an oilfield.

Either way, the well is typically equipped with sensitive monitoring equipment so it can be observed 24/7 throughout its production life.

After reaching the surface, the oil is processed and shipped to market to be used as transportation fuels or made into one of the myriad petroleum-based products we touch in everyday life.

Impressive numbers

Oil and gas wells can range in depth from a few hundred feet to more than 20,000 feet. In some parts of the world, wells go as deep as 30,000 feet, Zdarko says.

Ranging from 1,000 to 2,500 feet deep, Aera’s San Joaquin Valley wells are considered shallow. It typically takes about three days to drill an oil well in the Bakersfield area. Near Ventura, however, wells can be 13,000 feet deep and take more than a month to drill.

Retiring a well

The productive life of a San Joaquin Valley oil well generally lasts ten to twenty years. Then the well is retired, or decommissioned.

“We pump cement into the well to fill it and then we seal it off,” Zdarko says. “Then, if warranted, we’ll drill a replacement well near the old one to continue recovering any remaining oil in the reservoir.”

But Zdarko and his investment recovery team don’t stop there. They recover and reuse the decommissioned well’s tubing, rods, pump and wellhead equipment. It’s an environmentally responsible process that’s not only practiced regularly by Aera but endorsed by state regulators.

California’s Division of Oil, Gas and Geothermal Resources must approve all decommissioning. DOGGR has jurisdiction over more than 228,000 oil wells throughout the state. The state agency oversees the drilling, operation and eventual permanent closure of oil, gas and geothermal wells — important steps in protecting public safety and the environment.

DID YOU KNOW? Aera Energy is named to Forbes America’s Midsize Employers List for the fourth time and is among the top midsize companies to work for in the United States.

Aera Energy