Redefining fluids relative permeability for reservoir sands. (Osland oil and gas field, offshore Niger Delta, Nigeria)

Redefining oil and water relative permeability for the evaluation of reservoir sands, a case study of Osland oil and gas field, Offshore Niger Delta, Nigeria has been carried out. The aim of this study is to modify water relative permeability (Kwr) and oil relative permeability (Kor) equations in sandstone units. The objectives are to provide alternative expressions for Kwr and Kor in sandstone units, use the equations as inputs in a simplified water cut (Cw) equation to predict the volume of water that will be associated with the recoverable volume of oil (VRo) in penetrated reservoirs. The relationship between porosity (Φ) and water saturation (Sw), with the relationship between porosity and hydrocarbon saturation ( Sh), were used to evaluate KWr and Kor in order to predict Cw in the selected reservoirs. Reservoir X in Well D1 shows about 2.0×106bbl  for VRo and 18.78% for Cw but in D2 it shows about 7.4×106bbl and 1.73% for VRo and Cw respectively. Similarly, in Reservoir Y, D1 has about 6.8×106bbl  of VRo and 0.034% of Cw, but in D2 it has about 9.3×106 bbl of VRo and 0.015% of Cw. The results suggest that high Φ with corresponding high Sw resulted in high associated Cw in Reservoir X. The evaluation also confirmed that the decrease in the ratio of oil relative permeability to water relative permeability (Kor/Kwr) corresponds to the increase in Cw. The total recoverable volumes of hydrocarbons from the two wells are estimated at 7.7×109cu.ft for gas and at 2.54×107bbl for oil. With the present conditions of the two reservoirs, the values of Cw in Reservoir X are low and are extremely low and negligible in Reservoir Y. Reservoir X in Well D1 has a smaller volume of VRo but the Cw is higher than others. Nonetheless, the Cw in Reservoir X is still within acceptable range.