On Monday, three earthquakes struck west Texas in a sparsely populated area, the latest among dozens to hit the state in less than two weeks. The earthquakes included a magnitude 4.9 temblor that tied for the eighth-strongest earthquake in the state’s history. West Texas has now recorded over 100 earthquakes in the space of just nine days, a highly unusual phenomenon for a state that sits on a part of the country that’s not very seismically active.
The Role of Oil and Gas Extraction
Texas is famous in energy circles due to the extensive use of one Oil & Gas extraction technology: shale fracking. Texas extracts more shale gas than any other state in the United States, and the experts are now pointing fingers at hydraulic fracturing and enhanced oil recovery (EOR) as the culprits responsible for the state’s ongoing earthquake scourge.
According to Justin Rubinstein, a geophysicist with the U.S. Geological Survey in Menlo Park, California, Texas earthquakes are"almost 99% likely" to be linked to local oil fields.“We can say with confidence that these are related to oil and gas extractions," he said. State officials are not taking chances: Texas’ oil and gas regulator has idled two wells that send saltwater deep into the ground.
The Railroad Commission is now looking in the Camp Springs area, located about 10 miles east of Snyder along the Scurry-Fisher county line. “In efforts to reduce seismicity possibly caused by underground injection of produced water, several operators in the area have converted deep saltwater disposal wells to shallow saltwater disposal wells within the last year,” a spokesperson told the Reporter-Telegram on Friday.
Shale Fracking and Saltwater Disposal
Shale fracking is a newer Oil & Gas extraction technology that allows companies to drill not just down into the earth but horizontally along an oil formation. During shale fracking, drilling companies pump large quantities of water, sand and sometimes chemicals into an oil field at high pressure over a period of days or weeks.
This process creates microfractures in the rock that unlocks oil and gas from shale, sandstone, limestone, and carbonite and allows them to flow more easily. However, this process also unlocks huge quantities of ancient, highly salty water trapped in the same pore space as oil and gas that’s millions of years old. According to Rubenstein, modern shale technology is able to economically reach formations where the ratio of oil to water is much lower than it was decades ago, meaning as many as 20 barrels of salty water could accompany each barrel of crude pumped. This water, also known as oilfield brine, is considered hazardous waste because of its high salt content, hydrocarbons, and industrial compounds. The oilfield brine is then pumped back underground in a process known as salt water disposal. Currently, Texas has more than 50,000 oilfield brine disposal well sites.
Enhanced Oil Recovery (EOR)
The experts have also blamed Enhanced Oil Recovery (EOR) for Texas’ earthquakes. Crude oil production in U.S. oil fields frequently encompasses three distinct phases: primary, secondary, and tertiary (or enhanced) recovery.
During the primary recovery phase, gravity, the natural pressure of the reservoir and artificial lift techniques are used to drive oil into the wellbore. This initial phase typically recovers only about 10 percent of a reservoir's original oil in place (OOIP). Secondary recovery techniques are used to extend a field's productive life usually by injecting water or gas to displace oil and drive it to a production wellbore, typically resulting in the recovery of 20 to 40 percent of OOIP.
However, much of the easy-to-produce oil has already been recovered from U.S. oil fields, forcing producers to turn to several tertiary, or enhanced oil recovery (EOR), techniques. EOR technologies offer prospects for ultimately producing 30 to 60 percent, or more, of a reservoir's OOIP.
Three major categories of EOR are commercially successful: gas injection, chemical injection and thermal recovery. Gas injection is the most common EOR technology in the United States, accounting for nearly 60 percent of EOR production in the country. Gas injection uses gasses such as CO2, natural gas, or nitrogen that expand in a reservoir to push additional oil to a production wellbore while other gasses dissolve in the oil and help to lower its viscosity and improve its flow rate. CO2 injection has been used successfully throughout the Permian Basin of West Texas and eastern New Mexico, as well as in Kansas, Mississippi, Wyoming, Oklahoma, Colorado, Utah, Montana, Alaska, and Pennsylvania.
In Texas, Kinder Morgan (NYSE:KMI) has extensive carbon dioxide-enhanced oil recovery operations in Scurry County.
Regulatory Response and Future Challenges
It’s going to be interesting to see how regulators such as the Railroad Commission of Texas are going to deal with Texas’ oil-induced earthquakes. Over the past few years, Big Oil has been heavily investing in carbon capture and storage (CCS) technology, ostensibly to offset their CO2 emissions but are also using the CO2 for EOR. Recently, Calgary-based senior geological advisor Menhwei Zhao conducted an AAPG Bulletin study regarding the use of CCS in Enhanced Oil Recovery (EOR). By analyzing more than 22 years of production data from the Weyburn Midale oil pool in Saskatchewan, Zhao concluded that “enhanced oil recovery could extend the pool’s lifespan to 39 or even 84 more years.”
Zhao’s claims might not be an exaggeration: The Wasson Field’s Denver Unit CO2 EOR project resulted in a nearly seven-fold increase in crude production after injecting CO2.
The U.S. Department of Energy is currently researching novel techniques that could significantly improve the economic performance and expand the applicability of CO2 injection to a broader group of reservoirs. The DoE estimates that next-generation CO2-EOR has the potential to unlock over 60 billion barrels of oil that would otherwise be left trapped in the rocks.
By Alex Kimani for Oilprice.com
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