Assessing Helium and Methane Enrichment in Buried Hill Reservoirs Through Pulsed Neutron Logging Techniques

Abstract Helium is a rare, non-renewable resource crucial for scientific research, medical applications, and high-tech industries. With rising global demand, evaluating helium resources has become a key focus for geological studies. Buried hill reservoirs are particularly significant targets for helium exploration. Thus, developing methods to locate helium in these reservoirs is an urgent area of scientific research. A novel evaluation method has been developed to determine the dual gas saturation of helium and methane in buried hill reservoirs using advanced pulsed neutron logging technology. This approach employs dual detectors to measure inelastic and capture gamma counts, enabling precise assessment of gas saturation levels. The ratio of inelastic gamma counts is used to calculate water saturation, establishing a baseline for fluid presence. Meanwhile, the capture gamma counts ratio differentiates between helium and methane, providing essential insights into the gas composition. This method enhances the efficiency and accuracy of exploration efforts in these significant geological formations. Our research investigates how lithology and fracture angle affect gas saturation calculations. The results reveal that lithology is the primary factor influencing gas saturation, while the fracture angle has a minimal impact on the calculations. In addition, we developed several saturation calculation models specifically designed for both simple and complex lithologies. Our findings demonstrate that the proposed method can control saturation error within a 13% margin, effectively satisfying saturation calculation requirements even in instances where the fracture equivalent porosity is low. This level of precision is essential for reliable resource evaluation, particularly in challenging reservoir conditions. By accurately accounting for lithological variations, our models provide a more nuanced understanding of gas saturation and enhance the overall effectiveness of exploration efforts in complex geological environments. This research contributes significantly to optimizing resource management strategies and improving decision-making processes in the extraction of helium and methane from buried hill reservoirs. Looking ahead, future research will focus on varying the distribution of fractures and the types of borehole mud used during drilling. By exploring these factors, we aim to enhance the applicability of our method, ultimately optimizing the exploration and recovery of helium and methane in buried hill reservoirs.