Production rapid decline is the major problem for the tight sandstone reservoirs in Jilin oilfield. For the particular reservoir investigated in this study, production is not only subjected to the reservoir properties, but also the well completion designs especially fracturing. A comprehensive study has been conducted for multi-stage fractured horizontal wells. New fracturing improvement strategies are presented in this paper for future operations in the studied field and also those who may have similar tight sandstone reservoirs to share.
Through the integrated studies of the petrophysical characteristics, geomechanical properties and fracturing data from the fractured wells of the tight oil reservoirs in Jilin Field, numerous fracturing modeling scenarios were compared with actual fracturing monitoring data. A fully three dimension finite element simulation, associated with the analytical result from earlier production data, and the theory of interaction between fracture clusters, were built in this study. We conducted the inversing design parameters from the multi-stage hydraulic fracture with some monitoring data to improve the understanding of the reservoir properties. Additionally, a calibrated geomechanical stress model for a completed well in this field was built. At the end, the production model was presented. Data was provided to facilitate later comparison with the actual multi-stage hydraulic fracture production and valuable lessons have learned through those iteration studies.
With thoroughly trained and well calibrated model, a new fracturing strategy has been developed for the studied tight oil field. The best NPV can be achieved with the optimal fracture conductivity, fracture geometry and well performance. But first of all, the most valuable lesson we learned is that, the Effective Propped Volume (EPV) is the dominating factor for the fractured well performance, instead of the so-called Stimulated Reservoir Volume (SRV). SRV is a misinterpreted concept yet un-calculable. By adopting a numerical simulator and a proficient technology, we developed the most suitable design (perforation, fracture spacing etc.) and the fluid system (slick water, linear gel etc.) for this reservoir so that the optimal fracture geometry and fracture conductivity can be achieved. Besides that, the fracture geometry and proppant distribution were simulated. The simulated oil production data from the finite element fracture and production software is highly matched with the recorded oil production data.
An adaptability evaluation was conducted along with this study. To ensure the relevance and the authenticity of design, we analyzed the effective factors of treating material from both the laboratory and the field data in this field. A novel fracturing fluid system was applied. The fluids are more effective and leave less damage to the formation.