Dean, Dean and More Dean: Dawson Wells Reach 15 MMbbl Milestone

For her thesis in 2018, Colorado School of Mines geosciences grad student Brittany Abbuhl took a look at the tight-sandstone Dean Formation in the northern Midland Basin.

Dr. Stephen Sonnenberg, a past American Association of Petroleum Geologists president and longtime Mines professor, was her adviser.

In particular, Abbuhl focused on Dawson County, Texas, as well as the adjacent Borden County, finding the northern Midland’s Dean up to 200 ft thick with roughly 10% porosity—similar to the overlying Spraberry where permeability is less than 1 millidarcy.

While volumes of research had been done on the Permian Basin, some have focused on the Spraberry and Wolfcamp “but fewer yet have studied the Dean Formation,” she wrote.

Thus, the purpose of her work.

Among her conclusions: The productivity of Dawson County’s Dean was worth a closer look.

Beginning in 2020, operators have done that and, to date, made more than 15 MMbbl from just a few dozen Dean wells in Dawson ranging from 59 months old to just 4, according to an Oil and Gas Investor analysis of Railroad Commission of Texas (RRC) files.

On a boe basis, the Dawson Dean gives up a 90%-plus oil weighting.

The output from the 43 wells’ total 486,000 feet of lateral has averaged 32,739 bbl per 1,000 feet.

Average production from their combined 952 months online is 527 bbl/d.

‘Dean, Dean and more Dean’

Raymond James analyst John Freeman couldn’t have been more emphatic about the hot new play this spring, while taking a 41-page dive into what’s working in the Midland Basin in 2025.

“Dean, Dean and more Dean,” he wrote about Birch Resources’ whopper wells in the fine-grained, low-permeability, siliciclastic rock that overlies the Wolfcamp’s calcareous mudstones.

The privately held Houston-based operator made 7.34 MMbbl through January from 16 Dean wells in Dawson in a combined 286 months beginning in July 2022, according to the OGI analysis.

Per day, Birch’s wells have averaged 851 bbl. The average output to date per 1,000 ft of the wells’ combined 176,101 ft of lateral is 41,666 bbl.

Freeman wrote that Birch’s newest wells in Dean “were among the Midland Basin’s most productive wells during 2024.”

They include Birch’s Hot Pie, Lady Stoneheart and Ghost wells, all in southeastern Dawson.

First-24-hour IPs ranged from 1,785 to 2,668 bbl, according to completions reports.

On an IP-180 basis, the Birch wells averaged 1,189 bbl/d, “far above the Midland average IP-180 of 615 bbl/d,” Freeman reported.

Each lateral is about 10,300 ft, according to RRC data. First-11-month production from the two Hot Pie wells was 955,000 bbl; two Lady Stoneheart wells, 869,000 bbl in their first 13 months; and two Ghost wells, 519,000 bbl, also in 13 months.

“The Dean has been the biggest development since our last deep-dive report on the basin a few years ago,” Freeman wrote.

In 2024 productivity throughout the Midland, the “Dean leads the pack,” he found.

“During 2024, Dean wells were 33% more productive than Wolfcamp A wells and 31% more productive than Wolfcamp B.”

Dawson operators

Opening the Dawson Dean play was privately held, Midland-based Reliance Energy with its Caballo Azul 28-33 #2884DN that IP’ed 375 bbl from a 9,930-ft lateral and came online in March 2020, according to RRC data.

It produced 310,644 bbl through January 2025.

Following Reliance, EOG Resources, disguised as CGS Operating, brought online the Santorini #M2H in May 2020 that IP’ed 471 bbl from a 10,416-foot lateral and produced 501,602 bbl through this past January, according to well files.

EOG had picked up its Dawson County property in April 2020 from J. Cleo Thompson; prior owners had been Occidental Petroleum, Three Rivers Operating II and Pioneer Natural Resources, according to RRC data.

Piñon Operating followed in September 2020 with its Chocolate Lab 40-33 #1H that IP’ed 1,004 bbl from a 7,429-foot lateral and produced 359,128 bbl through this past January.

In 2021, EOG and Reliance each brought two more Dean wells online. In 2022, Birch Resources joined with two, while EOG made three, and Reliance and Piñon each made one.

Dean A&D

Leaseholds with Dean rights began to change hands in Dawson in July 2023 when SM Energy bought the Reliance property totaling 20,750 contiguous acres for $93.5 million, including five Dean wells that had already produced 1.5 MMbbl and have gone on to make another 751,811 bbl to date.

Some of Reliance’s property was picked up from White Rock Oil & Gas in August 2021, a couple months after the E&P put it on the market.

Fully operated and 100% HBP, White Rock described the contiguous 1,417 gross and net acres as low-decline and 100% oil, according to the PetroDivest sales flyer.

In addition to the Middle Spraberry, “the offering includes potential in the Lower Spraberry and Dean formations, providing additional near-term development targets,” PetroDivest added.

It also noted that the southwestern Dawson position was surrounded by CGS’ (EOG’s) Santorini #2H that had been permitted in February 2021 and a Reliance well, Trigger 19-18 #1MS, that had been permitted in January 2021.

Also in 2023, Ike Operating entered, buying out Piñon that October, picking up its three wells that had already produced 1.35 MMbbl and have made 1.92 MMbbl through this past January in their first 108 months combined online.

Hibernia Resources IV entered in 2024 and put five wells in Dean, adding to 14 new Dean holes made by Birch, EOG, Ike and SM, according to RRC data through January.

Among the county’s 111 operators in January, the five drilling for Dean pay produced 810,489 bbl of Dawson’s total 951,312 bbl that month.

In contrast, the county’s production totaled 336,706 bbl from all formations in January 2018, according to RRC files.

Where oil was found before

Calvin (Dean) Field was discovered in 1965 at the central Reagan-Glasscock border, producing 44.4 MMbbl by 1994; in January 1995, it produced a total of only 61,000 bbl from more than 100 wells and was shut in before yearend.

Meanwhile, Dawson County fields that target the Dean specifically by name produced 17.6 MMbbl and 12.6 Bcf of casinghead gas from January 1993 through January 2025 according to the RRC. Those records from the 1990s are the RRC’s oldest digitized production data.

The largest is the Ackerly (Dean Sand) Field, giving up 16.2 MMbbl in those 31 years and 10.7 Bcf at Dawson’s southeastern border with Borden, Howard and Martin counties.

The Ackerly was discovered in 1954 by Stanolind Oil and Gas when putting the vertical J.Y. Graves #A-1 in Dean at about 8,000 feet.

The field is flanked on the west by the Tex-Hamon (Dean) Field in south-central Dawson that produced 1.3 MMbbl and 1.8 Bcf in the past 31 years.

Dean geology

In the past century, formations above and below the Permian period were economically produced, while the Leonardian-epoch Spraberry, Dean and upper Wolfcamp series resisted giving up much of their oil.

Discovered in 1949, Spraberry Trend was known to be steeped in oil and gas but considered “the world’s largest uneconomic oil field” well into this century as little oil could be pried from the rocks without horizontals and modern fracture stimulations.

The Dean, underlying Spraberry and overlying Wolfcamp, was deposited about 275 million years ago as what are now South America and North America collided in platedrift, wrote Li Liu, a University of Oklahoma geosciences master’s graduate with a University of Texas Ph.D., along with William A. Ambrose, a senior geosciences researcher, in 2022.

The Dean, they found, is a “laterally continuous, largescale sheet” of sandstone that is some 300 feet thick in the northern Midland Basin and 100 feet south.

In the Delaware Basin, the deposit’s age equivalent is Third Bone Spring overlying Wolfcamp.

But the Dean’s appearance and its depositional setting are more similar to the younger, sandy, silty, Guadalupian-epoch Bell, Cherry and Brushy canyons in the Delaware Mountain Group, wrote C. Robertson Handford in a 1981 paper published in “AAPG Bulletin.”

He found them to be indistinguishable from each other.

Upper, lower Dean

In studying Dawson Dean cores, Mines’ Abbuhl found an upper and a lower Dean separated by a cemented carbonate, making them “mineralogically unique from one another and, consequently, contain different reservoir properties.”

The Lower Dean has more quartz, kerogen and clay; the Upper Dean, more calcite, dolomite and aragonite.

The cement likely acts as a seal, preventing the Lower Dean’s oil from seeping into the Upper Dean, “thus explaining why there are no hydrocarbon indicators within the Upper Dean.”

The upper layer also has single-digit porosity, she added, while the Lower Dean’s is up to 12%.

“Overall, the Upper Dean contains a higher percentage of authigenic and detrital carbonate minerals that are prone to occlude porosity and restrict permeability, while the Lower Dean has higher silica content, lower authigenic and detrital carbonate content, and higher overall porosity and permeability,” she found.

The Lower Dean also contains less water, more total organic carbon and more natural fracturing, resulting in “better reservoir quality and prospectivity than the Upper Dean.”

As the northern Midland Basin’s Dean is thickest than elsewhere in the basin, it’s likely due to sediment drifting from the Horseshoe Atoll, she added.

D&C intervention

When Handford’s 1981 report—the most often cited research on the Dean Formation—was published, oil was $32/bbl or an inflation-adjusted $112/bbl today.

Operators were in the money.

At that price, he expected Sprayberry and Dean “will undoubtedly become an increasingly important objective for the development of enhanced oil recovery [EOR] techniques in fine-grained, low-permeability, low-pressure reservoirs.”

He concluded, “Large quantities of producible hydrocarbons undoubtedly remain in the Dean and Spraberry formations.”

But otherwise, making much more out of the Dean than EOR would surface would require some type of breakthrough, he concluded.

“Other remaining hydrocarbons include what is undiscovered and will remain [undiscovered] unless an accident intervenes or where sedimentologic aspects are integrated into future exploration strategies.”

Forty years later, the Dean intervention arrived in Dawson County: fracture-stimulated horizontals.

Hibernia, SM, EOG, Birch Results

Hibernia put online four Robyn Lee laterals in Dean in September and October with IPs averaging 2,015 bbl each from laterals averaging 16,000 feet, according to the RRC data.

Combined production in their average first 4.5 months online through January totaled 802,840 bbl, according to RRC data.

Meanwhile, in the 19 months through January since buying the Reliance property in Dawson, SM Energy has produced 1.3 MMbbl.

Its JB Books #1382DN IP’ed 1,359 boe/d, 95% oil, from an 11,632-foot lateral in Dean in October, averaging 117 bbl per 1,000 ft, reported Arun Jayaram, analyst for J.P. Morgan Securities.

A companion well, JB Books #1381DN, IP’ed 1,338 boe/d, 96% oil, from an 11,629-foot lateral, averaging 115 bbl per 1,000 ft.

“One of the interesting takeaways from our Midland Basin Scorecard was that Dawson County had the highest well productivity on a [per]-lateral-foot-adjusted basis in 2024,” Jayaram wrote in the February analysis, while also noting that the sample pool of wells was small: 27.

While SM has discussed its Dean work with investors, “EOG has provided very little detail on its Dawson County program aside from highlighting a robust portfolio of domestic exploration activity,” Jayaram noted.

At the time of his report, though, he found EOG was running one rig in the county, based on Enverus data.

EOG’s results in southwestern Dawson haven’t been great, though.

“State data show nine EOG wells in Dawson … with first production in 2024, all of which are underperforming the average Midland Basin well,” Jayaram wrote.

Six-month cumulative output among nine wells for which Jayaram had data was 6,200 bbl per 1,000 ft, “which is 37% below the Midland Basin average in 2024.”

When removing the poorest two performers, the EOG wells’ output is 26% below the Midland average from all formations, he added.

Meanwhile in the Dean, Birch Resources is the “leader in the clubhouse,” Raymond James’ Freeman wrote, among Midland Basin operators’ 2024 well productivity improvements.

“Birch’s productivity increased over 70% on an oil basis year over year,” mostly from focusing 75% of its D&C in the Dean versus 21% in 2023, Freeman wrote.

Dean in Howard County

SM put two Dean wells in western Howard County about 35 miles south of the Dawson play in its six-well Guitar North multi-formation development that also has a well each in Jo Mill, Middle Spraberry, Lower Spraberry and Wolfcamp A.

Guitar North #2883DN IP’ed 1,805 bbl from a 10,156-foot lateral, according to the RRC file.

A second Dean well, Guitar North #2885DN IP’ed 1,451 bbl from a 10,352-foot lateral.

Nearby and also in Howard County, Oxy’s 18-well Santana development near Big Springs and about 40 miles south of the Dean hotspot in Dawson included four landed in Dean that IP’ed between 1,162 and 1,775 bbl/d each.

The other wells were landed in Sprayberry, Wolfcamp A and Wolfcamp B.

Beginning in 2000, Santana #2430D made 325,000 bbl in its first 57 months online after IP’ing 1,162 bbl from a 10,876-foot lateral, according to the RRC files.

Santana #2436D made 320,000 bbl after IP’ing 1,775 bbl from a 12,011-foot lateral.

Another well, Santana #2432D, made 340,000 bbl after IP’ing 1,727 from a 11,137-foot lateral.

More prolific, Santana #2938D made 760,000 bbl in just under five years after IP’ing 1,343 bbl from a 12,500-foot lateral.

Through January, the 18-well package made 4.6 MMbbl and 15.1 Bcf, according to RRC data.

Dean in Martin County

Diamondback Energy has been landing Dean wells in Martin County just across the Howard border from the SM and Oxy wells.

Its 12-well Grantham West 50-48 unit, with three in Dean, about 25 miles south of the Dawson hotspot, doesn’t include per-well production data in the RRC files.

But the unit made 1.6 MMbbl and 3.4 Bcf its first 10 months online through January.

Separately, it put two Dean wells in the seven-well Tomcat 23-24 pad in Martin County nearer to the Dawson hotspot.

Tomcat C made 276,000 bbl and 331 MMcf of casinghead gas in its first 10 months through January, while Tomcat D made 226,000 bbl and 271 MMcf.

Freeman found that Diamondback’s 2024 productivity was 9% greater than in 2023.

And the “Dean Formation was a primary driver of the productivity increase,” he added, contributing to Diamondback making the highest-return Midland Basin wells in 2024, along with joining ConocoPhillips.

He also found that Oxy switched to landing more often in Dean rather than Jo Mill in 2024, contributing to 22% better wells than in 2023.

“More Dean—the most productive zone—and less Jo Mill, the least productive zone, was a nice recipe for better overall [Oxy] well performance,” he reported.

New Core Inventory

The Dean results are great news in a well-mowed Midland Basin, according to Freeman’s analysis.

He found 32% of Dean acreage in the northern Midland Basin works at $50 oil and $2.50 gas, which is a price point he deems “core,” while 49% works at $70 and $3.50.

The new Dean wells’ results are picking up where the heavily drilled Wolfcamp A and B inventory is losing after posting 67% of Midland Basin wells in 2019 but 47% in 2024, Freeman reported.

“As core inventory in the Wolfcamp A and B are increasingly played out, we expect operators to seek new core locations in the Wolfcamp C/D, Dean and Jo Mill, which have more fragmented acreage quality and offer less consistent returns.”

Jo Mill sits between the Middle Spraberry and Lower Spraberry, while Wolfcamp C and D underlie Wolfcamp B.

Operators are also working to make core of more Pennsylvanian rock underlying Wolfcamp D and of the yetdeeper Devonian-age Woodford.

Freeman counted 59 Lower Pennsylvanian and Woodford wells that came online in 2024 and 46 in 2023.

The Dean play won’t last forever, though, while the average includes “the monster wells drilled by Birch in Dawson County.

“So, we anticipate productivity in the bench to fall moving forward. That core area of the Dean that Birch has been drilling has nearly been exhausted.”

Herb Vogel, SM Energy president and CEO, told investors earlier this year that SM is seeing variability in the formation. The team is “focusing in ‘OK, where are the best ones going to be and where are the other ones going to be?’ It’s going to be pad-dependent.”

But the Dean has shown that, “because of the productivity, it’s really competitive,” he added.

That is, “as long as you select the right locations for it.”