Development of Gas-Condensate Reservoirs by Directional Intracontour Waterflooding

Abstract

Abstract This paper presents an overview of some of the advanced water-flooding technologies developed for gas-condensate reservoirs (GCR) in the former Soviet Union. Although developed in the 1970's and since then successfully applied in the field, there are no published accounts of this technology being applied elsewhere. This technology is based on both the block structure of most gas-condensate reservoirs and the " block reservoir structure" of major fields. In both case areas of low permeability connect seemingly separate reservoirs or field zones. These areas of low permeability act in a manner similar to semi-permeable membranes. The flow of water through low permeability areas, especially those containing clay deposits, takes place only if the pressure gradient exceeds some initial value (initial gradient). Such phenomenon also occurs for gas flow, but the values of the initial pressure gradient for gas (Gg) are much lower than for water. As a result, injected water cannot flow through these areas of low permeability and move from one highly-permeable zone to another. However, at the same time gas can flow freely from block to block provided the pressure gradient is higher than Ggi. The properties of gas-saturated rocks prevent water invasion into the "dry" blocks, until the blocks with injection wells are almost totally saturated by water (at Sgres). By utilizing this phenomena, greater gas and condensate recoveries can be achieved than by using water injection schemes which disregard the intrinsic heterogeneity of reservoirs. An experimental laboratory program verifying the phenomenon of initial pressure gradient was performed in the TIPM Laboratory in 1999. This work is ongoing.