Rejuvenation of a Mature Tight Sandstone Oil Reservoir through Multistage Hydraulic Fracturing: A Case Study of a North African Basin

Development of mature oil fields has been increasingly attractive in recent years as a significant amount of world oil and gas production is being extracted from these formations. Hydraulic fracturing (either as a selective corrective stimulation method or as a preliminary completion approach) is a well-established technique in mature oil field rejuvenation to improve productivity and deliverability of such a diminishing field. After many years of successful production in A۱ and A۲ reservoirs, A۳ and A۴ reservoirs were developed with only one hydraulically fractured vertical well (Well #۱). As the production from well #۱ in A۳/A۴ reservoirs was below the expectation, the well was shut down after ۳ years of production. Therefore, the main objective of this research paper is to investigate re-development options for A۳/A۴ reservoirs due to the low deliverability and productivity of the vertical well #۱. Sensitivity analysis for history matching, critical conductivity, and optimum dimensionless fracture conductivity (Cfd) was performed followed by forecasting and multistage hydraulic fracturing. Numerical results showed that there is a critical conductivity beyond which production is insensitive to the conductivity, for a specific propped length and production time. Results also showed that critical conductivity increased with propped length and decreased with production time. After ۲۵ years of forecasting, the recovery factor for the ۹۰۰m lateral with eight fractures and ۱۱۰m spacing was the highest at ۲.۶۵%. The corresponding values for the ۳۰۰m and ۶۰۰m laterals were ۲.۳۷% and ۲.۴۲%. Therefore, the study suggests that horizontal wells with a longer length and optimized number of fractures and spacing will provide maximum well recovery.

Keywords:

Unconventional Resources , Mature Field , Tight Sandstone , Multistage Hydraulic Fracturing , Fracture Conductivity