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title: "Reservoir Geology Revealed: Ultradeep Wells in Onshore China"
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A new AAPG Bulletin paper examines 350 wells deeper than 7,000 meters in the Tarim and Sichuan basins. ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­    ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­  

| View in browser One of Utah’s characteristic annual events is the Shakespeare Festival in Cedar City. Once, while attending this festival, I met an aging couple who quoted a line from Shakespeare’s Othello and remarked that this line perhaps speaks for geologists: “Are there no stones in Heaven?”   I enjoyed the witty quote, but I also thought about the remarkable progress that scientists have made since Shakespeare’s time. Today, we can determine the age and chemistry of meteorites and Moon rocks.   Petroleum geoscientists with subsurface imaging and analysis skills will increasingly contribute to astrogeology and space exploration. To illustrate this point, I have selected two contrasting case studies for this edition of Core Elements: deep and old vs. shallow and young reservoir geology.   Rasoul Sorkhabi   Editor, Core Elements Reservoir Geology Revealed:10,000-meter Deep Wells Deep carbonate reservoirs in China (AAPG Bulletin, 2026) The October issue of AAPG Bulletin features a paper on ultradeep wells—deeper than 6,000 meters—drilled in onshore China.   China’s ultradeep drilling: Over the past five years, China has drilled 350 wells deeper than 7,000 meters, mainly in the Tarim and Sichuan basins.   Half of these wells are either discoveries or hydrocarbon shows.   Notable discovery cases include: The Anyue-Penglai conventional gas field (5,000-9,000 meters) in Sichuan has reserves exceeding 70 trillion cubic feet in Ediacaran (Sinian) and Cambrian strata. The Yuanshen-1 well (8,866 meters) in the Sichuan Basin discovered oil and gas in the Ediacaran-age Dengying Formation. The Eyangye 2 well (3,600 meters of vertical depth and 1,550 meters of lateral length) drilled into the Ediacaran-age Doushantuo Shale in the Sichuan Basin produces 2 million cubic feet of gas per day. The Pengshen-6 well (9,026 meters) in the Sichuan Basin discovered gas in the Permian-age Maokou Formation with a daily flow of 52 million cubic feet. The Luntan-1 well (8,260 meters) discovered a Cambrian-age oil field in the Tarim Basin. The Dabei-4 well (8,022 meters) in the Tarim Basin produces 7 million cubic feet of gas a day from the Cretaceous-age Bashijiqike Formation. The Manshen-3 well (8,010 meters) in the Tarim Basin produces 10,000 barrels of oil per day and 18 million cubic feet of gas per day from Ordovician reservoirs. The Niudong-1 well (6,027 meters) in the Bohai Bay Basin discovered condensate in the Meso-Proterozoic-age Wumishan Formation, with oil production of 4,000 barrels per day and gas production of 20 million cubic feet per day. Reservoir quality: Chinese geologists observed that the burial depth of ultradeep carbonate reservoirs is not an inhibiting factor for oil and gas production. Reservoir porosity is highly heterogeneous and ranges from 0.1 to 18 percent. Several post-burial processes contribute to the porosity and permeability of deep carbonate reservoirs, including: Early hydrocarbon charging slows diagenetic destruction of pore space. Thermal decomposition of carbonates releases carbon dioxide and sulfuric acid that corrodes strata to form secondary pores. Dolomitization increases reservoir pore space by volume contraction (dolomite is 1–4 percent smaller than calcite), dissolution during grain-to-grain replacement, and fracture widening. Geophysical imaging revealed paleo-karst carbonate caves of various sizes from 0.2 to 2 meters in diameter. Tectonic faults in rigid carbonate rocks create shattered zones and microfractures. Uplift and overburden exhumation create new fractures and pores. Go deeper: AAPG Bulletin has published several informative papers on deep Proterozoic-Paleozoic reservoirs in the Tarim and Sichuan basins, including: Jin Lai and others (2021) Jing Hu and others (2022) Yin Liu and others (2023) Cheng Zhong and others (2024) Sponsored Bringing the Heat: Indonesia’s Sorik Marapi Geothermal Field   Tapping into geothermal resources poses significant drilling challenges in one of the most extreme environments on the planet. LEARN MORE How a Niger Delta Channel-Levee Complex Evolved Evolution of a Pleistocene slope channel in Niger Delta (Interpretation, 2026)  Nigerian researchers have published a paper in Interpretation that describes the internal architecture and evolution of a shallowly buried sand channel-levee complex on the continental slopes of the Niger Delta.   What they did: The researchers used two sets of 3D seismic data and interpreted five seismic horizons to build a 3D facies model. The researchers studied a Pleistocene-age erosive-constructive channel-levee complex named Channel-1A. They mapped eight facies based on seismic reflectors and correlated the facies types with well logs. What they found: They suggested five stages for the formation of Channel-1A: Stage 1. Channel initiation by sediment bypass, erosion, and slumping Stage 2. Basal meander loops dominated by a swing of channels that resulted in lateral accretion packages Stage 3. Lateral and vertical stacking of meandering and aggrading channels and formation of internal terraces acting as levees Stage 4. Deposition in the last channel dominated by vertical stacking and aggradation, with the uppermost part of the channel filled with turbidite mud Stage 5. Deposition of hemipelagic draping over the channel Why it matters: The new study shows how seismic geomorphology can help build 3D geocellular models for characterizing facies architecture and stratigraphic evolution of oil and gas reservoirs. Get Involved: AAPG’s Astrogeology Committee TravelNerd/Shutterstock.com If talking about stars and stones interests you, I am one of the vice chairs of AAPG’s Astrogeology Committee. In this group, we discuss astrogeology as it relates to terrestrial geology, energy, and other issues.   My fellow committee member, Doug Cook, and I have also published several astrogeology articles in Explorer, including: Artemis II Mission (May 2026) Seeing Beneath Mars (May 2026) The committee also organizes astrogeology content for some AAPG events and recommends speakers on relevant topics.   You must be an AAPG member to join. Become a member here, then reply to this email with your interest if you’d like to join the astrogeology committee. Want to help AAPG grow? Consider supporting AAPG's free resources, like this one, by donating today. AAPG thanks our advertisers for their support. Sponsorship has no influence on editorial content. If you're interested in supporting AAPG digital products, reach out to Cait Williams.   You received this email because you signed up for newsletters from AAPG. To stop receiving this newsletter, unsubscribe or manage your email preferences.   AAPG  1444 S. Boulder Ave., Tulsa, Oklahoma 74119, USA (918) 584-2555 \| 1 (800) 364-2274 (US and Canada) www.aapg.org |
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