Abstract
The naturally fractured reservoirs play an important role in the stable output of Daqing oilfield, which is the largest field in China. But after several years’ development, many wells are becoming to be low efficient wells, the production rate is sharply declining and watercut increased greatly. To improve current development effect, research on how to improve the waterflood effect was carried out, and a pilot test was implemented.
The geological study and the multidisciplinary investigation were first performed. Sourceless microseismic fracture monitoring technique shows that there are natural fractures. The statistics results of sourceless microseismic testing of 36 wells indicate that the total number of fractures is 94, among them, there are 23 east-west fractures, occupying 24.15%, 11 north-east fractures(11.17%), 33 east-west fractures(35.11%), and 27 north-south fractures(28.17%). Also pressure buildup cure shows that there exist inflexion points, which indicates that there are natural fractures. Based on the above research results, integrating detailed reservoir description with reservoir numerical simulation, the injection-production adjustment plan and infill drilling were designed. A field test was carried out: the high watercut wells and low production wells on injection line are converted to injection to form a line drive pattern.
This field test in the Daqing field is an excellent opportunity to: (1) demonstrate the method to improve the development effect of mature naturally fractured reservoir, (2) show that this should be of reference value to improve the development effect of field.
