Controlling factors on the effectiveness of turbidite fan reservoir of the Meishan Formation, Qiongdongnan Basin

The turbidite fan of Miocene Meishan Formation in Qiongdongnan Basin is one of the main contributors of natural gas in the area. To increase the natural gas reserve and production in this area, the sedimentary mechanism, the controlling factors and prediction methods were studied. According to a large number of DST, geological fluid sampling, core and rotary sidewall coring measured data, and relevant enterprise standards, the turbidite fan reservoir of the could be divided into four levels of grade: high-quality, good, effective, and tight. The four levels correspond to high production, commercial production capacity, merely productive capacity, and dry layer. Results show that the type of turbidite fans and its internal composition, bottom current reformation, and reservoir effectiveness are key factors on reservoir prediction success. Fault-terrace basin floor fans, basin floor fans cut by canyon, and integral basin floor fans are three types of relatively good reservoirs; and bottom current reworking is important to improve the reservoir of middle fan and outer fan in open flow environment. For the basin floor fan cut by canyon, the lithological side seal needs to be focused in the future. For the integral basin floor fans, the reservoir pinch out shall be considered too. At present, the rate of reservoir prediction of the Meishan turbidite fans in this area is very low. The methods developed in this study shall be of great value to improve the success rate of reservoir prediction.