Abstract:
In the process of oil and gas exploration, formation fluid samples serve as critical data for reservoir evaluation and reserves declaration. The Mesozoic buried hill formations exhibit diverse lithologies, with heterogeneous pore and fracture-dominated storage spaces. High-angle fractures are commonly developed, while drilling fluid invasion is extensive. Logging fluid sampling success rates are low, and due to the unique challenges of offshore operations, DST testing is costly. Consequently, there remains a lack of rapid and economical productivity evaluation methods. This study employs integrated conventional logging, imaging logging, and array acoustic data to swiftly assess the effectiveness of buried hill reservoirs. Key evaluation indicators are quantified, and an optimal fluid sampling location method for fracture-cavity reservoirs is established, increasing sealing success rates by 30%. By refining traditional logging sampling procedures, the study develops the origin sealing sampling method and phased fluid injection techniques, enhancing sampling efficiency by 44%. For the first time, logging sampling technology is applied to buried hill productivity evaluation. Through the use of ultra-long variable span twin packers and a dual-inlet design, DST testing conditions are maximally simulated, leading to the development of a cable productivity testing methodology and the completion of China's first cable productivity test in Mesozoic buried hill formations. This technology has played a pivotal role in the discovery and evaluation of Mesozoic buried hill reserves, providing an efficient, safe, and flexible means for obtaining formation fluids and assessing productivity in these formations, with promising application prospects.