![]() c also equals to reservoir initial pressure pi.Ĭonstant-Rate Buildup Test (Finite-acting analysis): Two methods (1) Nonlinear regression to fit with equation: pws = c + m * log(t) + m_star * t, find m, m_star, and c simultaneously, (2) Slider's plot of pws - m_star * delta_t vs log(delta_t) if m_star is known. m is used to calculate k and c to calculate s. Multirate Buildup Test: Normal plot of pws vs sigma(log((t - t_j-1)/(t - t_j) to find m and c. c also equals to reservoir initial pressure pi. m is used to calculate k and c to calculate s.Ĭonstant-Rate Buildup Test (Infinite-acting analysis): Horner plot of shut-in pressure pws vs log((tp+delta_t)/delta_t) to identify wellbore-storage period or the ETR, find m and c. m is used to calculate k and c to calculate s.Ĭonstant-Pressure Flow Test: Normal plot of 1/q vs log(time) to find m and c. Multirate Drawdown Test: Normal drawdown plot of (pi-pwf)/qn vs Fp to find slope m and intercept c. Slope m is used to calculate k**, intercept c to calculate s**, and slope m* to calculate reservoir size Constant-Rate Buildup Test (Finite-acting analysis): flow is shut-in at time t, q=0, pressure builds up (opposite of Constant-Rate Drawdown Test), flow in finite-acting conditionĬonstant-Rate Drawdown Test: Semilog drawdown plot of pressure vs time to find slope m and intercept c of MTR region and Normal drawdown plot of pressure vs time to find slope m*.Multirate Buildup Test: shut-in is preceded by multirate flow.Constant-Rate Buildup Test (Infinite-acting analysis): flow is shut-in at time t, q=0, pressure builds up (opposite of Constant-Rate Drawdown Test), flow in infinite-acting condition.Constant-Pressure Flow Test: rate changes.Multirate Drawdown Test: pressure declines as rate changes.Constant-Rate Drawdown Test: pressure declines as rate is constant.Reservoir initial pressure pi (from shut-in well test).Reservoir size re and reservoir pore volume vp (from constant-rate drawdown test and multirate buildup test).Pressure drop delta_ps due to skin damage.Skin factor is the measure of how damaged the well is. Permeability k or permeability-thickness factor kh.The purposes of well-test analysis are to determine the following by analyzing the pressure-transient response. Late-time region (LTR): where well behaves finite-acting, reservoir boundary effects dominate (see Chapter 7.2).Middle-time region (MTR): where well behaves infinite-acting (determined from semilog plot, see Chapter 7.2).Early-time region (ETR): the wellbore-storage period (determined from Horner plot of shut-in well test, see Chapter 7.5).The pressure-transient response is divided into 3 regions: The basis of well-test analysis is understanding of single-phase-flow in porous media concepts. ![]()
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