Simulation of well test processes with application of packers

Abstract

The paper considers simulation of well test processes with application of packers. Based on well parameters at different times (before a well is closed and the point in time under consideration) a mathematical model is compiled. Superposition principles are used for constructing points of pressure recovery curve. Based on that, four cases of using packers are considered according to actual pressure diagrams. Processing of build-up curves helps to determine other characteristics of a formation as well. Since a bottom hole zone is broken in a number of cases and its permeability is reduced, an amount of reservoir contamination indicators is defined as an additional pressure drawdown that has to be created to overcome resistance of reduced permeability zone. It should be noted that existing works related to assessment of influence of after-inflow effect relate to either determination of its duration or adjustment of pressure build up curves by introducing correction factors. To overcome a challenge of pressure build-up taking into account an effect of pressure drop and after-inflow effect an approximate method to solve problems of nonstationary flow is used. The method of integral relations allows obtaining solutions in a simple analytical form. After a well is closed, conditions for redistribution of pressure in bottom hole area are changing. At remote sections of a formation the process continues to flow without changing as during the functioning of a well. Therefore, it is supposed that pressure wave continues to propagate according to the Says-Horner law. As it was determined during modeling of various penetration conditions, pressure distribution curves in bottom hole area have clear straight horizontal sections after well closure. The length of sections increases with the increase of bottom hole pressure. If the cause and nature of build-up curves are known full information about pressure change after well shut will be used. So, it will help to determine parameters of distant and bottom hole area of reservoir more accurately.

Keywords

• well test
• packer
• formation
• inflow
• reservoir pressure
• flow resistance
• bottom hole area
• interpacker space
• pressure build-up curves
• after-inflow effect
• permeability of bottom hole area of formation
• productivity index
• potential rate
• contamination
• drilling process