Analysis of pressure and pressure derivative without type-curve matching .6. Horizontal well tests in anisotropic media

A new technique for interpreting pressure tests known as direct synthesis is proposed. This method couples the characteristic points and lines from a log-log plot of pressure and pressure derivative data with the exact analytical solution, consequently eliminating the need for multiple specialized plots or type curve matching. This paper concentrates on the interpretation of pressure tests in homogeneous and anisotropic porous media. The reservoir can be infinite or semi-infinite in areal extent and is bounded at the top and bottom boundaries. The pressure drop within the horizontal well is assumed to be negligible, i.e. infinite conductivity well condition. Step-by-step procedures to calculate reservoir parameters are presented for various pressure responses. Included are possible procedures to determine the effective horizontal wellbore length when sufficient characteristic points or lines are observed. This new technique is accurate because it uses the exact, analytical solutions to calculate reservoir parameters. Results are frequently verifiable from an independent source, e.g., another characteristic point or line. Application to pressure buildup and drawdown tests is illustrated by several examples which demonstrate the accuracy of the technique.