Evaluation of development efficiency of a complex oil deposit in fractured basement at a reservoir pressure below the saturation pressure

The article presents general information about the object of research, describes the main stages of its development history. An assessment was made to understand the development efficiency of a deposit confined to fractured basement reservoirs at a reservoir pressure below the saturation pressure. Calculations were performed on a sector dynamic model using the tNavigator 22.4 simulator. The filtration model represents a macro-fracture with micro-fractures connected to it. High-resolution X-ray tomography of real core samples was used to set the geometry of the model and the main properties of micro- and macro-fractures. The selection of the optimal pressure reduction strategy for the residual oil recovery was performed in two stages. At first, the initial state of the system, washed macro-fracture and trapped oil in micro-fractures, were modeled. Secondly, the duration of the injection and depletion periods was varied to maximize oil recovery factor (ORF). The sensitivity analysis of the calculations to changes in the main parameters of the dynamic model was performed. The ranges of parameter changes were adopted according to the results of X-ray tomography of real core samples, as well as logging and well tests. Based on the result of the work, it was concluded that the highest ORF is achieved by alternating injection and depletion regimes. The main effect on the ORF value is made by the permeability of micro-fractures, as well as the value of capillary pressure.

References

1. Nelson R.A., Geologic analysis of naturally fractured reservoirs, Cambridge: Gulf Professional Publishing, 2001, 323 р.

2. Aguilera R., Naturally fractured reservoirs, Tulsa, Oklahoma: PennWell, 1995, 521 р.

3. Cosentino L., Integrated reservoir studies, Paris: TECHNIP ed., 2001, 400 p.

4. Lebedinets N.P., Vesvalo A.N., Approximate evaluation of the granitoid rocks compressibility (In Russ.), Neftyanoe khozyaystvo = Oil Industry, 2013, no. 8, pp. 30–31.

5. Wolcott D., Applied waterflood field development, Publ. of Schlumberger, 2001, 142 p.