Maram AlSaif went to work for Saudi Aramco as a research geologist in 2018, and recently conducted graduate studies at Texas A&M University under a company sponsorship. This month, she will present research at IMAGE ‘24 on the energy industry’s most unavoidable subject:
The Permian Basin.
Bob Lindsay began working the Permian Basin area for Chevron in the 1980s. At the International Meeting for Applied Geoscience and Energy, he will discuss his three and a half decades of research and observations on the basin’s residual oil zones.
This year’s IMAGE includes multiple presentations on the Permian, from multiple points of view and angles of research. And it’s no wonder so many eyes are on this prolific, long-established hydrocarbon asset.
Now producing more than 6 million barrels per day, the Permian Basin continues to drive U.S. oil output. According to Enverus Intelligence, more than 20 billion barrels of Permian crude remain to be discovered.
Lately, research focus has shifted to the western side of the super basin to the Midland Basin and Delaware Basin areas. Presentations at IMAGE reflect that emphasis. AlSaif and fellow researchers will present “Investigating the potential of unconventional resources in the Midland Basin” in an Aug. 28 morning session.
IMAGE is convened by AAPG and the Society of Exploration Geophysicists, in conjunction with SEPM. It will be held Aug. 26-29 at the George R. Brown Convention Center in Houston.
Chemo-Stratigraphic Analysis of the Midland Basin
In the Midland Basin study, the Texas A&M researchers used high-resolution chemo-stratigraphic data integrated with core descriptions, organic richness/total organic carbon data and well log analysis to create a sequence stratigraphic framework.
By combining those findings with a detailed examination of minerals content, they then worked to identify play sweet spots and optimal well landing zones in the basin’s Cline Shale formation. They found that the Upper Cline Shale, also called the Wolfcamp-D interval, is “dominated by elevated levels of silicate minerals and siliceous mudstones.”
“The interpreted transgressive/high-stand deposits are characterized by high concentrations of phosphorous and, occasionally, calcium and divergent trace metal trends where the uranium concentration exceeds that of vanadium, suggesting suboxic conditions,” they reported.
“The highest organic matter preservation is associated with the interpreted low-stand deposits, especially in the Upper Cline,” they noted.
Optimal landing zone sites were identified in the Upper Cline based on high resistivity, total organic richness, siliceous content and other factors.
“The selected 20-foot (thickness) optimal landing zone has high TOC, HI (hydrogen index), S1 and S2 (volatile and residual hydrocarbons), high resistivity, elevated siliceous content and reduced percentage of clay minerals,” AlSaif said.
ROZ Evolution
Lindsay, principal in Lindsay Consulting LLC in Midland, Texas, is a former president of the West Texas Geological Society and president-elect of AAPG’s Southwest Section. For more than 30 years, he’s developed his views on the Permian Basin’s numerous and widespread residual oil zones.
He will describe that research in the presentation “Evolution of Residual Oil Zones in the Permian Super Basin” at IMAGE, in the Permian 6 morning session on Aug. 28.
In its earliest stages, he said, the Permian “could have been almost like the Middle East” in hydrocarbon content: It contained an enormous amount of mobile oil. But under pressure, a vast incursion of meteoric water – rain, snow, stormwater runoff – began to push the oil out.
“This idea is something that I have been working on since 1989. It shows how meteoric water entered the Permian Basin from the west, uplifted side of the basin in the Late Eocene-Early Miocene. Uplift was created by a series of igneous intrusions that formed the Trans-Pecos Magmatic Province,” Lindsay explained.
“As meteoric water entered the subsurface it passed by these igneous intrusions and was heated up. It also shows that there was such a large head of energy associated with the meteoric water that it could sweep mobile oil out of structural closures, leaving behind residual oil zones,” he noted.
When the Rio Grande Rift formed, the huge recharge area was down-faulted and destroyed, Lindsay said. As the energy head disappeared, fields resaturated or partially resaturated with mobile oil, with a lower ROZ remaining.
Those lower, below-water-contact ROZs have started to attract attention as targets for CO2-injection enhanced recovery. They offer the potential to produce billions of barrels of additional Permian oil while providing CO2 sequestration opportunities.
Last year, the U.S. Geological Survey published a report on ROZ assessment methodology based on a nine-county Permian Basin pilot project. It found significant upside for both CO2 utilization and potential incremental recovery – up to 2.6 billion barrels in the pilot area alone.
“It turned into a play because they could horizontal the ROZs. If they pumped off the water in there, oil would begin to flow,” Lindsay said.
“The play is to stay in the top (of the ROZ) where there is slightly higher oil saturation, in some cases inject CO2, or pump off water to drop pressure,” he added.
Comparing Barnett with Barnett (and Woodford)
Most Permian Basin research still involves optimizing production, but research approaches have broadened to include both more novel and more fundamental analysis, including core samples and well-log data – a result of the basin beginning to mature as an unconventional play area. Two other talks at IMAGE will illustrate the point.
In the Aug. 27 presentation, “Barnett and Woodford of the Permian Basin (USA) compared with Barnett (Fort Worth Basin) and Woodford (Oklahoma),” Daniel Allen and Jonathan Antia of Core Labs draw on large core datasets to identify similarities and differences among all three producing areas. Data came from advanced testing and analysis of more than 9,000 feet of relevant conventional core.
The researchers found that the Permian Barnett produces at lower depths and higher costs than its Fort Worth Basin equivalent, with regional increases in clay versus organic content proportion. They identified similar porosity and mineralogy between the Permian Basin and Oklahoma Woodford, but with substantial regional variations in thermal maturity.
Identifying areas where the Permian Barnett is more condensed, with less prospective reservoir dilution, and where thermal maturity is optimal in the Permian Woodword are keys to successful exploration, they reported.
Permian Prototype
Sebastian Ramiro-Ramirez of Diamondback Energy and fellow researchers from the University of Texas-Austin examine “Stratigraphic control on production in unconventional reservoirs: a Permian Basin example,” in another Aug. 27 morning presentation.
They evaluate comparatively higher-permeability layers in the Wolfcamp, Bone Spring and Spraberry formations in the Permian. These layers of siliciclastic and calciclastic sediment gravity-flow deposits are significantly more permeable than the mudstones that are the dominant lithofacies and source of most of the produced reservoir fluids.
Flow focused through the more permeable layers increases production rates compared to a mudstone-only reservoir. Understanding stratigraphy, permeability and flow behavior at the thin-bed scale is fundamental to optimizing development strategies in unconventional reservoirs, they found.
Additional Permian-related presentations at IMAGE ’24 will include a more detailed look at the basin’s Spraberry, Cisco, Strawn, San Andres, Bones Spring, Skinner Ranch and Simpson formations and groups. As long as the Permian Basin holds promise, it will continue to be a magnet for geological research, and for researchers.
“I would love to work on more studies in the Permian Basin, especially (in) that I am considering applying for PhD programs next year,” AlSaif said.