Continental mixed shale oil reservoirs are characterized by strong lithological heterogeneity, complex reservoir architecture, and highly variable hydraulic fracture propagation, making it difficult to simultaneously maximize hydrocarbon recovery and economic performance. Existing optimization methods generally emphasize either production enhancement or economic evaluation, while lacking an integrated framework that quantitatively couples geological characterization, hydraulic fracturing design, production forecasting, and techno-economic optimization. To address this limitation, this study proposes a geology–engineering integrated workflow based on EUR–IRR response-surface co-optimization. Geological and engineering sweet spots were first identified through integrated core observations, well-log interpretation, and mineralogical analyses. A three-dimensional hydraulic fracture propagation model was subsequently established and calibrated using field production data to optimize key fracturing parameters, including cluster number, pumping rate, fluid intensity, and proppant intensity. Based on the optimized fracturing design, a series of development scenarios with different lateral lengths and well spacings were evaluated. The corresponding 15-year project-level estimated ultimate recovery (EUR) and internal rate of return (IRR) were quantitatively coupled through interpolation-based response-surface modeling, enabling identification of the optimal development window under the economic constraint of IRR ≥ 6%. The results indicate that the maximum EUR (7.215 × 10⁵ m³) is achieved with a 5000 m lateral length and a 50 m well spacing; however, the corresponding IRR is only 5.8%, indicating that maximizing production alone does not ensure economic viability. The recommended development scheme consists of a 3500 m lateral length and a 150 m well spacing, yielding a 15-year project EUR of 4.238 × 10⁵ m³ and an IRR of 12.5%, representing the optimal balance between production efficiency and economic return. Sensitivity analysis under ±10% oil price fluctuations further demonstrates the robustness of the optimized development strategy. The proposed workflow establishes a quantitative framework that integrates geological characterization, hydraulic fracture simulation, production prediction, and techno-economic evaluation. It provides an effective decision-support methodology for fracturing design and well pattern optimization in highly heterogeneous continental mixed shale oil reservoirs and can be readily extended to similar unconventional reservoirs.

This investigation ventures into the nuanced porosity traits of shallow shale gas reservoirs, pinpointing the critical determinants of their gas content with a nuanced touch. By harnessing sophisticated microscopy and analytical methods, we embarked on an exploration into the porosity architecture of shale, identifying the distinct pore spaces that harbor shale gas and applying gas adsorption techniques to evaluate its storage potential. Noteworthy is our utilization of diverse adsorption mechanisms and models to accurately fit methane adsorption data while carefully considering the influence of marine shallow shale’s pore structure peculiarities, total organic carbon (TOC) content, and clay mineral content on its adsorption prowess. We introduce a refined model for appraising gas adsorption volumes, an innovative stride toward bolstering the precise estimation of reserves in marine dam shallow shale gas and shedding light on accurate gas adsorption volume calculations in analogous shallow shale gas scenarios. This manuscript offers profound insights into the sophisticated interplay between shale porosity and gas storage, enriching our understanding and enabling more accurate future resource estimations.

Hero Ridge shale oil reservoirs are characterized by stacked pay boxes, strong vertical heterogeneity, rapid variations in lithology and in situ stress, and significant well-to-well interference during platform-scale three-dimensional development. Conventional fracturing design methods that focus mainly on single-well stimulation are insufficient to simultaneously address fracture propagation, reservoir contact and development economics. Taking the 1H platform and representative wells in the upper member of the Xiaganchaigou Formation (E₃², Boxes 5-6) as examples, this study establishes a workflow integrating reservoir-engineering dual-quality evaluation, single-well parameter optimization, platform-coordinated fracturing, dynamic pore-pressure-stress updating, and EUR-IRR response-surface analysis. Results show that Box 6 has better reservoir quality and fracability than Box 5, with average porosity, oil saturation and brittle-mineral content of 7.6%, 50.9% and 67.6%, respectively. Well 1H6-1, with a 1500 m lateral, penetrated Class I + II sweet spots for 90.6% of the horizontal interval, providing a geological basis for efficient volume stimulation. For conventional sweet-spot wells, the optimal single-well design includes eight clusters per stage, a pumping rate of 18 m³/min, a fluid intensity of 35 m³/m and a proppant intensity of 3.25 m³/m. For 200 m-spaced wells, the pumping rate and fluid intensity should be reduced to 16 m3/min and 32 m³/m, respectively, with 100 m³ of prepad gel to mitigate fracture overlap and stress interference. Further response-surface analysis based on actual EUR-IRR data shows that the highest EUR occurs at a lateral length of 4000 m and well spacing of 50 m (EUR = 566,261 m³), but the IRR is -27.1%. By contrast, the best IRR point is at a lateral length of 4000 m and well spacing of 600 m (IRR = 14.5%), with EUR of 377,500 m³. This demonstrates that the production-optimal and economics-optimal schemes are not coincident. The expanded pilot scheme has an after-tax IRR of 9.31%, after-tax NPV of RMB 131.38 million and payback period of 5.93 years. The results indicate that fracturing optimization in Hero Ridge should move from single-well engineering maximization to integrated decision-making that combines single-well design, platform coordination, lateral-length/well-spacing optimization and techno-economic evaluation.