Hydrocarbon viability prediction of some selected reservoirs in Osland Oil and gas field, Offshore Niger Delta, Nigeria

Abstract

Abstract An alternative approach involving the use of modified expressions for the free fluid index (FFI) permeability (K), reservoir quality index (RQI) and flow zone indicator (FZI), was used to predict the viability of hydrocarbon in some selected reservoirs. The aim of this work is to predict flow units, transmissibility and primary recovery through porosity (Ф) derived from wire-line logs. In the absence of core data, Ф values derived from the density log (RHOB) were optimised herein. Alternative expressions for the FFI, K, RQI, and FZI were suggested. A simplified approach with the use of only porosity dependent expressions for these parameters (FFI, K RQI, and FZI) that lies within the scope of the study was used for the evaluation of the reservoirs. Quick-look models for the prediction of RQI an FZI based on these the redefined equations were presented. Drudgery and computational errors that may come with the use of a range of other dependent parameters [irreducible water saturation (Swirr), formation factor (F), tortuosity factor (a) and cementation exponent (m)] were avoided. The reservoir, in well D1, is about 90 ft (27 m) thick, with the upper 30 ft (9 m) occupied by gas, the next 28 ft (8.5 m) is filled with oil and the remaining 32 ft (9.8 m) is water filled. The reservoir, in well D2, is about 110 ft (33.5 m) thick and it is oil saturated. Within D1 reservoir, average Ф, FFI, K, RQI, and FFI are 0.2, 0.18, 1256mD, 2.5 μm and 10.1 μm respectively. Within D2 reservoir, average Ф, FFI, K, RQI, and FFI are 0.25, 0.23, 5166mD, 4.5 μm and 13.5 μm respectively. Significant transmissibility and good rates of hydrocarbons recoveries are anticipated within the evaluated reservoirs.