ABSTRACT

This paper is devoted to the issues related to the strategy of development of an oil-and-gas accumulation of Cenomanian age. Vanyogan field is taken as an example (West Siberia).

Results of the conducted well tests and pilot work to develop a thin and highly-viscous oil rim in PK1–2 reservoirs at Vanyogan field demonstrate that it is impossible to develop this oil accumulation without its separation from the gas cap. Gas breaks through immediately from the gas cap to the producing wells.

One of the possible ways to develop this oil rim is barrier waterflooding.

The system of development via the barrier waterflooding (water injection into the gas-oil contact) may enable conditions preventing gas coning movement towards producing wells. However, to create the water barrier will require significant overcompensation (200–250 %).

Controlled gas production from the gas cap is a possible way to produce oil reserves at immovable GOC (gas-oil contact) and lower voidage replacement ratio. Decrease in initial oil-and-gas reserves ratio by a quarter, may provide lower level of compensation (about 150%) required for barrier forming.

Based on the projected system of development (barrier waterflooding) it is possible to use thermal methods by injecting hot water into a reservoir.

Analysis of simulation results manifests a significant loss of heat during the process of barrier forming due to dominating filtration of the working agent into a gas saturated part of the reservoir that is an evidence of low efficiency of the thermal stimulation.

Results of the steam injection lab studies (fresh water) demonstrate significant swelling of clay in the rock, multiple reduction of permeability and thus impossibility of using these methods in practice.

The optimal way to retain rheological properties of oil is to inject water heated up to the reservoir temperature.

The pilot program is underway to test the barrier waterflooding at the field and assess the efficiency of the thermal method on the representative areas of the accumulation.

Implementation of the program will enable to evaluate technological efficiency of the barrier waterflooding in combination with the thermal stimulation and prepare the object for the commercial development.

Introduction

Vanyogan field is situated in the Nizhnevartovsk district of the Khanti-Mansiysk autonomous area in the Tyumen Region. The field is 100 km away from Nizhnevartovsk and 110 km from Megion on the straight. (see Fig.1).

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