Research and application of complex fluid identification and effectiveness rapid evaluation for deep low porosity and permeability reservoir: taking Huizhou 19-6 million-ton oilfield in Pearl River Mouth Basin (eastern) as an example

With the continuous deepening of exploration work in the Pearl River Mouth Basin (eastern), the exploration to low porosity and permeability reservoirs has become the main battlefield for increasing oil and gas reserves and production. However, deep reservoirs are affected by factors such as complex lithology, poor physical properties, and diverse fluid types, resulting in a series of severe challenges in exploration operations, including difficulties in distinguishing critical hydrocarbon reservoirs, identifying low-contrast oil layers, and characterizing reservoir effectiveness. It is difficult to distinguish critical oil and gas, to identify low-contrast oil layers, and to characterize reservoir effectiveness. Based on core, PVT analysis test data, FLAIR fluid logging, digital core and test data, using PVT analytical data for calibration, the consistency of PVT data between surface gas logging and underground reservoir was clarified for the first time, and the WH and BH parameters of gas logging were optimized to build the identification chart of condensate gas and light oil. In addition, using the calibration based on core oil-bearing data, we found that the contents of FLAIR “heavy hydrocarbon components” (C₄, C₅, C₆, C₇, C₈) were positively correlated with reservoir oil-bearing property. At last, using sampling and test data for calibration, a low-contrast oil layer identification method of C₄₊₅ and C₆₊ was constructed. The macro and micro evaluation parameters of digital core were optimized via big-data analysis, and a new classification standard of reservoir effectiveness based on macro permeability of digital core, micro micron pore connectivity, and micron median pore throat radius was established. The field application showed that the accuracy of critical fluid, low contrast reservoir identification, and reservoir effectiveness evaluation in Huizhou 19-6 Oilfield was more than 95% through multi-technology integration and complementary advantages of different data, which will effectively guide and support the rapid operation decision-making and operation plan formulation, greatly improve the efficiency of well site operation and reduce the operation cost.