Analysis of Pressure Buildup Data Following a Short Flow Period

Abstract

Methods for analyzing buildup data following a short flow period are presented, discussed, and illustrated. A new type curve for uniform-flux and infiniteconductivity vertically fractured wells is presented. By matching buildup data with this new type curve, we can determine the dimensionless flowing time before shut-in. A method for converting buildup data to equivalent drawdown data is discussed. This method can be used to combine buildup and drawdown data to obtain a longer band of data for type-curve matching. This method can be used for constant-rate production, constant-pressure production, and for the case where both pressure and rate vary during production.

Some Applications of Pressure Derivative Analysis Procedure

“…Consider the match of the fractured well response discussed in Ref. 2 Although not documented here, computations suggest that Eq. 7 is also valid for this wellbore condition.…”

Analysis of Short-Time Buildup Data for Finite-Conductivity Fractures

“…The curves corresponding to different values of t DX/U fD 2 are similar in shape, and multiple matches The major problem with this type curve is that we must be sure that the drawdown portion of the test is dominated by the bilinear flow period. We offer the following suggestion to ensure that this requirement is 5x10-8 5.48 x 10-9 11 1x10- 7 1.10 x 10-8 11 3x10- 7 3.29x10-8 11 1 x 10- 6 1.09x 10-9 11 3 x 10-s 3.22x 10-7 11 1 x 10- 5 1.09x10-s 11 3 x 10- 5 3.26x10-s 11 1 x 10- 4 1.09 x 10-5 11 3 x 10- 4 3.30 x 10-5 11 1 x 10- 3 1.16 x 10-4 12 3x10- 3 3.57 x 10-4 12 1 x 10- 2 1.27 x 10-3 13 OCTOBER 1982 satisfied. If the agreement between the two values of t is reasonable, the value of t Dx /a jD 2 obtained from the match can be used together J"ith the value of PwD (Fig.…”

“…2 can be converted to drawdown data and thus that the drawdown type curves can be used directly. This is the most accurate procedure available since it involves a minimum number of assumptions, but it does require that drawdown data be available unless Atlt::50.1 or Atlt ~ I.…”

“…The principal objectives of this paper are (l) to show that the normal form of the drawdown type curves 4 for finite-conductivity fractured wells is inadequate to analyze buildup data following a short flow period, (2) to present a modified version of these curves to analyze short-time data (drawdown or buildup), (3) to present a buildup type curve suitable for analyzing data measured after a short production period, (4) to discuss the strengths and limitations of the equivalent-time method, and (5) to establish a theoretical basis for this procedure and to explain the empirical findings of Agarwal. 3 The buildup type curve presented here can be used to analyze tests in fractured wells when the response during the flow period is dominated by the bilinear flow regime.…”

A Unified Approach for Falloff and Buildup Tests Analysis Following a Short Injection/Production Time

“…Additionally, it is common to design pressure tests considering short flow periods because of operative difficulties, mainly when surface facilities for transporting produced or injection fluids are not available. Raghavan et al (1982) proposed a method to analyze pressure buildup data following a short flow period, their method converts buildup data into equivalent drawdown data, in such a way that they can be analyzed with type-curve matching or by using conventional semi-log methods. Soliman (1986) introduced an analysis technique for impulse tests (pressure buildup or falloff tests preceded for a short injection or production period) and concluded that a log-log plot of pressure change as a function of total test time yields a straight line whose slope is a function of flow type, while the intercept is a function of reservoir permeability.…”