Projects
Karaton Subdalt: Deep Exploration as a Bet on the Future
Early February brought a proof point at Karaton Subsalt. KazMunayGas confirmed that a deep well in the Atyrau Region produced a natural gas flow to the surface!
First of five
Drilling of the first exploration well to a depth of 5,750 meters was completed in December of last year. Drilling began in November 2024 and proceeded under conditions of abnormally high reservoir pressure and the presence of hydrogen sulfide (H2S). Such geological conditions require high-technology engineering solutions, reinforced industrial safety measures, and significantly increase costs. Even so, the result confirmed the fundamental viability of the chosen deep-search concept.
For the industry, this is an important confirmation of the hydrocarbon potential of deep horizons that, for a long time, were considered too complex and economically risky for practical exploration.
Under the approved work program, testing of four additional prospective oil and gas targets lies ahead. The results should provide a fuller understanding of the block’s resource potential and determine the project’s further economic feasibility.
Historical context
The study of the Karaton structure dates back to the Soviet period. In the 1970s, as part of regional oil and gas exploration programs in the Pre-Caspian Basin, large-scale geological exploration was conducted in the Karaton Sub-Salt area. From 1974 to 1977, five deep exploration wells (SG-1, SG-2, SG-3, SG-5, SG-7) were drilled to Paleozoic strata.
All wells underwent a full set of well logging; core was taken from Triassic, Permian, Carboniferous, and Devonian intervals. Total cored footage exceeded 930 meters. The core showed indirect indicators of hydrocarbon potential, such as a bituminous odor and hydrogen sulfide, but no commercial hydrocarbon inflow was obtained at that time.
CEO of KazMunayGas, Askhat Khassenov (left), inspects the progress of drilling operations
The absence of inflow in the Soviet period is explained today by several factors: tests were conducted in open hole without adequate zonal isolation; some wells may have been sited in unfavorable structural positions; and the technology of the time did not allow detailed handling of the complex geology of the subsalt complex. The structure was therefore deemed prospective but underexplored.
A new phase of work on the Karaton block began in independent Kazakhstan. In 1998–2005, 3D seismic surveys were carried out on the contract area by Tengizchevroil LLP, and the results were transferred to the state repository.
After acquiring the block, KazMunayGas Exploration Production obtained access to these materials and, in 2012–2013, commissioned PGS to reprocess and reinterpret them. As a result, structural maps were built for key reflecting horizons from the top of the Kungurian Stage to the Middle Jurassic and the Lower Cretaceous.
In 2016, PGS Kazakhstan performed additional processing and interpretation of 3D seismic (CDP method) over an area of about 150 km². Structural, dynamic, and seismic-stratigraphic interpretations were completed; prospective targets were identified in carbonate and clastic sequences; and recommendations were issued to drill 5 exploration and appraisal wells. This work significantly refined the geological model and enabled the transition from hypotheses to practical drilling.
Geological risks and characteristics of the subsalt section
Despite its high potential, the Karaton Subsalt project was initially viewed as high risk. The primary risk for many years was trap preservation. The structure sits on the margin of the Primorsky Ridge, where the salt section is locally thinned, and faulting could have led to hydrocarbon leakage after trap formation.
A second material risk concerns the presence and quality of reservoir rocks. Unlike Tengiz, where strong reservoir quality in carbonates is largely due to secondary vuggy porosity and fracturing, these processes at the Karaton structure may be more localized.