A Study Of Well Test Analysis Method In Low Permeability Oil Reservoir

More and more low permeable reservoirs are being placed on production in our country. Well test plays an important role in each stage of exploration and development and can provide effective information of depicting the formation dynamic characters, which helps to develop the reservoir reasonably and effectively. However, In the established by the current low-permeability reservoir well testing models, more is to consider the single factor.Based on the detailed researches of articles about low permeability oil reservoirs and the analysis about flow and geological characteristics, mathematical models of well test interpretation of single-phase and oil-water two-phase flow in homogeneous low permeability reservoir and single-phase flow in fractured low-permeability reservoir are derived, which allow for the influence analysis of wellbore storage coefficient, skin factor, starting pressure gradient and permeability modulus. The numerical solutions of the models are obtained by finite difference method, then, the log-log curves of bottom hole pressure and pressure derivative are plotted. Parameters sensitivity analysis suggests that: In low-permeability reservoirs, due to the low-speed non-Darcy effects of fluid flow as well as the stress sensitivity of formation, pressure and pressure derivative curves will produce different degrees of upturned, while the starting pressure gradient effect on the pressure response is more sensitive than the impact of permeability modulus; About the Oil-water two-phase flow in low permeability reservoirs, oil-water viscosity ratio, oil-water relative permeability curve can lead pressure and pressure derivative curves in the mid-late period moving up or down, If the parameter changes have led to the total mobility increase, then curves down, otherwise, the curves upturned; In the fractured low-permeability reservoirs, Wellbore storage coefficient, elastic energy storage ratio, cross flow coefficient, starting pressure gradient and permeability modulus all have some impact to cross flow segment. In the actual well test data analysis, only considering geology and other aspects of the information comprehensively, can we make the right judgments.In addition, a systematic research about automatic matching well test analysis methods has been done. Well test interpretation software for low permeable reservoir is developed, in which Auto-fitting technique using genetic algorithms is incorporated. The real well test data are analyzed by the software and satisfactory result is achieved.