The Investigation of SAGD Production Profile in a Naturally Fractured Reservoir (NFR)

Abstract

The steam-assisted gravity drainage (SAGD) process has been found as a promising enhanced oil recovery (EOR) process to recover bitumen and heavy oils. A few studies were done on the SAGD process in naturally fractured reservoirs. The effects of various reservoir variables and operational parameters on production profile were simulated using commercial software. The results showed that three different periods of oil production exist in SAGD process at naturally fractured reservoirs. At first, fractures depletion in the near well region (NWR) affect mainly the initial oil production rate. However, the preheated NWR matrixes cause the oil rate not to decrease suddenly. Then, due to rising of steam into upper layer fractures, oil rate increases and therefore the first flag of the oil rate pulse occurs. At third period, another flag of oil rate pulse with a reduction trend is observed due to fractures depleting and starting of oil drainage from its surrounded matrix blocks. The second and third period occur again as steam penetrates into another block in above well region (AWR). The number of oil rate pulses shifts to left by increasing preheating period and fracture density and also by decreasing well pair length. The number of pulses also increases with reduction in well pair length and fracture density. By increasing well spacing and fracture permeability and also by decreasing production bottom hole pressure and fracture density the pulses vanish.