Jianwei Wang

Deep sandstone reservoirs typically exhibit complex geological characteristics, including high temperature, high pressure, and high salinity. These reservoirs are predominantly developed using a wide well spacing strategy under natural depletion and water flooding, and no mature tertiary recovery technique has yet been established. Since chemical flooding is essentially inapplicable under such extreme reservoir conditions, natural gas injection offers unique potential due to its multiple displacement mechanisms and low sensitivity to temperature and salinity. This study conducts numerical simulations of natural gas injection in deep sandstone reservoirs coupled with phase behavior to systematically evaluate its enhanced oil recovery (EOR) potential. Phase behavior matching of the reservoir fluid is performed using the PVTi module to determine key component properties, providing an accurate pressure–volume–temperature (PVT) basis for subsequent simulations. Meanwhile, the water drive characteristic curve method is employed to predict the ultimate recovery of the target reservoir under water flooding. Subsequently, based on the fitted equation of state (EOS), a numerical simulation model of the target reservoir is constructed and history-matched against field production data. The calibrated model is then applied to quantify the development potential of both gas injection and water flooding in the target reservoir. The water drive characteristic curve predicts a water flooding recovery of 59.24%. Numerical simulation results show that rich gas flooding achieves a recovery factor of 72.28%, significantly higher than the 65.21% obtained from dry gas flooding. These results provide a theoretical basis for the efficient development of similar reservoirs.

In response to the problems of deteriorating quality of newly added reserves of deep and ultra-deep shale oil, significant differences in well efficiency among similar sweet spots, and difficulty in converting resources and production capacity, a deep and ultra-deep shale oil resource conversion evaluation method is proposed based on the entire process of shale oil development. Based on the production dynamics during the initial stage of production, we establish oil well classification standards for deep and ultra-deep shale oil and obtain two types of shale oil development unit classification standards. We construct well efficiency response indicators for development units, well efficiency index and well efficiency index, quantitatively characterizing the comprehensive well efficiency response within the development unit. We construct a production capacity evaluation system for the development of sweet spots that integrates resource utilization, technological economy, and business management. We use the fuzzy comprehensive evaluation method to obtain sweet spot evaluation scores and grades and quantitatively characterize the differences in production capacity construction for the development of sweet spots. On this basis, the “Resource–Productivity Matching Five Step Method” is proposed, which couples the sweet spot evaluation results with the well efficiency index to obtain the final score and evaluation results of resource conversion. The instance application of the M development unit shows that its overall resource conversion efficiency is not high, with only one type of area being a good match and the other areas being basic matches. The evaluation results are relative. This method achieves the integration of “sweet spot advantage (comprehensive score)—well efficiency response (well efficiency index)—conversion effect (final score)” and can identify false matches, improve the objectivity and reliability of evaluation results, and provide a scientific basis and technical support for shale oil block screening, well location deployment, construction planning and other research.

Against the backdrop of global energy pattern restructuring, the advancement of dual-carbon goals and large-scale development of unconventional oil and gas, complex oil and gas fields are confronted with practical challenges including harsh geological conditions and diversified development objectives. Traditional development planning methods for oil and gas fields suffer from single evaluation dimensions, strong subjectivity in decision making and insufficient dynamic adaptability, which make them unable to meet the full-process development requirements. To realize scientific, quantitative and systematic development planning of complex oil and gas fields, a development planning evaluation method suitable for complex oil and gas fields is established by integrating multidisciplinary theories. First, a multilevel evaluation model for oil and gas field development planning is constructed according to the characteristics and difficulties of development planning evaluation for complex oil and gas fields. The model consists of five core modules: external analysis, internal analysis, corporate development strategy selection, business planning and risk assessment. Secondly, a development planning evaluation method is established through a closed-loop process including special quantitative IFE/EFE analysis, IE matrix strategic positioning, SWOT alternative strategy pool and QSPM priority ranking. Then, the strategic priority ranking is dynamically adjusted by considering the impact of stepped oil prices. Finally, combined with the analytic hierarchy process (AHP), a comprehensive risk index evaluation model is established to realize quantitative assessment and traceability of risk levels. A case application in Block M demonstrates that its strategic positioning belongs to the growth type. Under low–medium–high tiered oil prices, the strategic combinations with the highest strategic priority are W+O strategy, S+O strategy and S+O, respectively. The development risk level is moderate risk. This study fills the gap in the whole-process evaluation system of complex oil and gas fields, and realizes the transformation of development planning from qualitative analysis to quantitative decision making. It provides theoretical methods and practical references for ensuring high-quality development of complex oil and gas fields and energy security.