Chihuahua Basin

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The Chihuahua basin, also known as the Chihuahua-Pedregosa basin, is located in parts of southwestern New Mexico, southeastern Arizona, and northern Mexico. Mexico is a country with high production rates of crude oil. As of 2010, it ranked seventh in the world ahead of Norway, the United Kingdom, Venezuela, Iraq, and Brazil. It produces more oil than it consumes. It exports the rest, which is obviously important for its economy. But it ranks only 17th in the world in total oil reserves.[1] The Pedregosa area lies within the structurally complex Basin and Range province and has been subjected to intense tectonism and igneous activity from Laramide time onward. Around the few plutonic intrusive masses the sedimentary section has been metamorphosed, but most zones of alteration extend less than a few feet around the hypabyssal intrusive masses [2]


The basin is characterized by four main depositional cycles, which are separated by major hiatuses and erosional truncation. The oldest cycle is Ordovician through Mississippian and is dominated carbonate deposition. Both conventional and unconventional plays are attractive targets in this sequence of rocks[3] The second depositional cycle is Pennsylvanian through Permian age. This cycle exhibits the most attractive opportunities in the Pedregosa Basin in the Pernio - Penn sequence which was deposited in a dramatically smaller basin than the previous cycle. Large well developed reef tracks, depositional onlap, depositional terminations and erosional truncations characterize the Permo-Penn cycle in the Hueco South Unit area. The third depositional cycle is early Cretaceous in age and duration and appears as a thin veneer of sediments that were deposited across the basin with an extraordinarily thick sequence of rocks being deposited in the U-Bar syncline. The syncline is a deep basinal trough, which trends from northwest to southeast through southwest New Mexico and into Mexico. Rich source beds and good reservoir units are expected in the U-Bar formation, which may exceed 3500' in total thickness in syncline. The eastern margin of the unit is at the western edge of the U-Bar syncline. The fourth and final depositional cycle is the Tertiary and Quaternary age sequence of rocks. These units were deposited as lacustrine, marginal lacustrine and fluvial sediments in the Playas and Hachita Valleys. They form a relatively thin veneer and do not hold significant hydrocarbon value. In addition both intrusive and extrusive rocks were emplaced at this time but it appears the overall effect of volcanic activity in the area is limited since most of the wells in the area are not thermally altered.[3]

                                                                                                                                                                                               Mexico Basin Map .png 

Petroleum Systems

Source Rock

In the Chihuahua-Pedregosa basin, major reservoir objectives include the Ordovician El Paso ( = Ellenburger) and Montoya carbonate rocks, Silurian Fusselman dolomites, Pennsylvanian to Permian shelf and reef carbonate rocks and basin-fill sandstones, and Lower Cretaceous shelf limestones and sandstones. Important source units of petroleum include the Devonian Percha (= Woodford) shales, Mississippian to Permian basin limestones and shales, Jurassic shales, and Lower Cretaceous limestones. [2]

Eight hundred feet of porous Silurian Fusselman dolomite, present in the Franklin Mountains, was eroded by Middle Devonian uplift and erosion in the Big Hatchet Mountains area (Kottlowski and Pray, 1967) . The eroded scarp was covered by sapropelic shale and dark cherts of the Upper Devonian. Similar conditions on the eastern shelf and central basin platform of the Permian basin of West Texas and southeastern New Mexico produce structural and stratigraphic oil.[4]

Trap and Seal

On the assumption that some of the reported Cenozoic shows are valid, the possibility exists that the source of the hydrocarbons noted was a paleo accumulation in Cretaceous or Paleozoic rocks that was destroyed subsequently by diastrophic events. There are porous sands, conglomerates, and possibly igneous rocks in the Cenozoic section that, with adequate trapping conditions, could contain petroleum accumulations escaped from older destroyed pools. There is also the possibility that traps in pre-Cenozoic rocks beneath the pediment surfaces extending outward from the mountains into the valleys could contain undisturbed paleo accumulations or accumulations escaped from older pools. [5]


The two major reservoir units in this cycle are the Ordovician El Paso dolomites and the Montoya dolomite. The El Paso is equivalent to the Ellenburger Formation in the Midland and Delaware basins. These pays are expected primarily on structural highs such as those observed in the Hueco South Unit area.[3]

Geologic Risk and Uncertainties

One of the biggest uncertainties for this basin is the fair play from different governments. This region may be called the Cuatro Fronteras, as it includes four major political boundaries—the international boundary between the United States and Mexico, and three boundaries between states, Arizona-New Mexico, New Mexico- Texas, and Sonora-Chihuahua. Any regional study of stratigraphic or structural geology, and especially an evaluation of petroleum potential, requires an exchange of surface and subsurface data across these boundaries.[6]


The Pedregosa basin has been subjected to extensive tectonic activity throughout its history creating major concerns about maintaining trap integrity. Our analysis which includes the use of seismic data, demonstrates the existence of undisturbed basinal sequences in the Hueco South Unit area where the sediment packages (of the Permo-Penn and Cretaceous age sequences) remain in tack. These packages are highly prospective over the targeted unit area.[3]

Evidence for early Paleozoic tectonism is scant, except for the middle Ordovician departure of Cuyania, which occupied the region east of the La Babia zone. Four distinct episodes of late Paleozoic tectonism can be identified in the region.

The first three events were first identified in the Marathon thrust belt:

1) Mississippian-Pennsylvanian deformation in the hinterland of the thrust belt (Meramecian-Atokan with a pause during Morrowan)

2) Pennsylvanian orogeny (Desmoinesian-Missourian)

3) Pennsylvanian-Permian folding and thrusting (Virgilan-Early Wolfcampian.)

4) Permain (Late Wolfcampian-Leonardian-Guadalupian) erosion/truncation and subsequent tilting [7]

Future Potential

A show of gas in the Epitaph was found in the No. 1 Espia and may be an equivalent of the gas zone in the Humble No. 1 State "BA"; however, the show could not be tested because of mechanical difficulties. Other indications of petroleum on electric logs and in samples are being evaluated as part of a regional study to be completed before additional drilling is considered in Chihuahua. Many of the Pemex wells were drilled on the uplifts to minimize the depths to Paleozoic and Mesozoic objectives. The few wells drilled in the bolson valleys have reached only Mesozoic and Upper Paleozoic rocks. Thus the Middle and Lower Paleozoic objectives lying at great depths would be some of the best targets for future exploration.[6]

With such potential, the Pedregosa area deserves continued exploration. Although there have been no discoveries of commercial production, some good shows of oil and gas have been encountered. Favorable areas are open to leasing.

Wells Drilled.jpg

Production Facilities


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  2. 2.0 2.1 Greenwood, E., Kottlowski, F. E., & Thompson, S. (n.d.). Petroleum Potential and Stratigraphy of Pedregosa Basin: Comparison witli Permian and Orogrande Basins’. 22.
  3. 3.0 3.1 3.2 3.3 Kornegay, G. (2007). Hueco.pdf. Dan A. Hughes Company, L.P.
  4. Greenwood, E. (n.d.). Oil and gas possibilities in the Pedregosa Basin. 2.
  5. Aiken, C. L. V., & Sumner, J. S. (1974). A Geophysical and Geological Investigation of Potentially Favorable Areas for Petroleum Exploration in Southeastern Arizona. OGCC Report of Investigation RI-3.
  6. 6.0 6.1 Thompson, S., Tovar R, J. C., & Conley, J. N. (1978). Oil and gas exploration wells in the Pedregosa Basin. NMGS Fall Field Conference.
  7. Haenggi, W. T. (2001). Tectonic history of the Chihuahua trough, Mexico and adjacent USA, Part I: The pre-Mesozoic setting. Boletín de La Sociedad Geológica Mexicana, 54(1), 28–66.
  8. Whaley, J., 2017, Oil in the Heart of South America,], accessed November 15, 2021.
  9. Wiens, F., 1995, Phanerozoic Tectonics and Sedimentation of The Chaco Basin, Paraguay. Its Hydrocarbon Potential: Geoconsultores, 2-27, accessed November 15, 2021;
  10. Alfredo, Carlos, and Clebsch Kuhn. “The Geological Evolution of the Paraguayan Chaco.” TTU DSpace Home. Texas Tech University, August 1, 1991.