Determining skin zone properties from injectivity tests in single- and multilayer reservoirs

Abstract

This work proposes an interpretation technique for injectivity tests that provides a new estimation for skin zone permeability and radius in single-layer reservoirs. A means to compute the reservoir skin factor in multilayer commingled reservoirs is also presented. Under the assumption that layer flow-rates are decoupled, the suggested method was extended to compute individual layer permeabilities and skin factors. The results indicate that this hypothesis is valid in reservoirs where layer skin factors are similar.

Performance Analysis of Hydrocarbon Wells Based on the Skin Zone

“…Thus, the normal type of reservoirs includes carbonate rocks, the grains of which consist largely of shells, grain fragments and oolites. The cement of sandstone is very diverse (marl, calcareous, clay, siliceous, ferruginous and so on) [9][10][11]. The cementing material may be both primary, deposited with the sand grains and chemically deposited as a result of the diagenetic process between and around the grains, and secondary, deposited from aqueous solutions that have penetrated the rock after deposition.…”

Pressure Transient Analysis for Injectivity Tests in Multilayer Reservoirs

“…During injection, pressure derivative attains negative values between t 0.009 h and t 0.2 h. This behavior consists of a characteristic signature of a reservoir with formation damage [10,32]. After the flood front overcomes the damaged region, pressure derivative rises again and, hence, pressure increases.…”

“…Reservoirs with Multilateral Horizontal Wells 17 This Chapter presents the extension of the analytical solutions developed by Peres and Reynolds [10] and Peres et al [11] for injectivity tests in single-layer reservoirs so that they can be applied in multilayer reservoirs with multilateral horizontal wellbores. It should be noted that models for predicting pressure transient responses during the injection and falloff periods in multilayer reservoirs with a vertical well have already been developed [12,16,32].…”

“…In this Section, their solutions will be introduced and, then, extended to multilayer stratified reservoirs. The main insight is to split the bottom hole pressure in two terms: one that encompasses the single-phase oil flow and another that derives from the mobility contrast between oil and water [12,16,32].…”

“…As the injection goes on, the flood front propagates. In reservoirs with formation damage, eventually the flood front overcomes the skin zone radius, yielding a characteristic shift in pressure derivative [32]. During this blunt shift, pressure derivative may even attain negative values [10].…”