Application of EOR Using Water Injection in Carbonate Condensate Reservoirs in the Tarim Basin

Abstract

The largest carbonate condensate field has been found in the Tarim Basin, NW China. Different from sandstone condensate gas reservoirs, however, the conventional gas injection for pressure maintenance development is not favorable for Ordovician fracture-cave reservoirs. Based on this, in this paper, 21 sets of displacement experiments in full-diameter cores and a pilot test in 11 boreholes were carried out to study enhanced oil recovery (EOR) in complicated carbonate reservoirs. The experimental results show that the seepage channels of the gas condensate reservoirs are fractures, which are quite different from sandstone pore-throat structures. Condensate oil recovery using water injection was up to 57–88% in unfilled fractured caves and at ca. 52–80% in sand-filled fractured caves. These values are much higher than the 14–46% and 17–58% values obtained from the depletion and gas injection experiments, respectively. The water injection in 11 wells showed that the condensate oil recovery increased by 0–17.7% (avg. 3.1%). The effective EOR for residual oil replacement using water injection may be attributed to fractures, as the gas channel leads to an ineffective gas circulation and pipe flow in fracture-cave reservoirs, which is favorable for waterflood development. The complicated fracture network in the deep subsurface may be the key element in the varied and lower oil recovery rates obtained from the wells than from the experiments. This case study provides new insights for the exploitation of similar condensate gas reservoirs.

The Strike-Slip Fault Effects on the Ediacaran Carbonate Tight Reservoirs in the Central Sichuan Basin, China

“…Even so, the Ediacaran matrix reservoir is mainly of low porosity-permeability (<4% and <1 mD, respectively) (Figures 5 and 7). This is slightly higher than the Ordovician limestone reservoir in the Tarim Basin [2,6,[31][32][33] and comparable to the global deep tight reservoir [34]. Previous studies have argued that the Ediacaran reservoirs had experienced long diagenesis and occluded most primary porosity to show secondary dissolution porosity [21][22][23][24].…”

The Advances and Challenges of the Ediacaran Fractured Reservoir Development in the Central Sichuan Basin, China

“…The reliability of the fracture identification techniques requires further study and improvement. In addition, the reservoir connectivity along the fault damage zone urgently needs to be addressed during well deployment and oil/gas production [39][40][41][42][43][44]. With the complicated hydrocarbon migration and accumulation in the deep subsurface [45,46], the fracture network could be of great importance for the "sweet spot" reservoir exploitation in the petroliferous basin.…”