An integrated, form-driven package which performs both conventional and type curve transient pressure analysis of multiphase reservoirs with single, dual or triple-porosity behavior has been developed.
The single or dual-porosity reservoir can be hydraulically fractured and thus the early behavior might be characterized by a 1/2 or 1/4 slope on a log-log crossplot of pressure difference vs. time depending on the finite or infinite conductivity of the hydraulic fracture. The early time behavior might be dominated by wellbore storage effects in which case the log-log plot will yield a straight line with a slope equal to 1.0.
In the case of dual and tripleporosity systems the shape of the transition period is dependent on the assumption of restricted (pseudo steady state) or unrestricted (unsteady state) interporosity flow.
The reservoirs can be infiniteacting, sealead or with constant pressure at the outer boundaries.
Some of the key parameters calculated from the analysis include transmissibility, skin, wellbore storage, omega, lambda, matrix storage. fracture storage, number of fractures intercepting the wellbore, size of the matrix blocks. fracture aperture, hydraulic fracture half-length, and distance to reservoir boundary.
The package analyzes drawdowns, buildups, isochronal and falloff tests. It is complemented with specialized analyses and plots including Horner, superposition, MDH, reservoir limit test, triple porosity, linear flow, and a Cartesian plot of pressure difference vs. time to evaluate wellbore storage effects.
The basic equations for generating this package are presented together with various typical crossplots.
The analysis of naturally fractured reservoirs has been the object of intensive studies during the last few years which have summarized 'in four books on the subject. 1 - 4 WELLTEST-NFR was particularly designed to assist in the identification and quantification of naturally fractured reservoirs. but it also operates at the same high level of performance in analyzing conventional and hydraulically fractured reservoirs.
The purpose of WELLTEST-NFR is to provide engineers with an easy to use computer program capable of handling most of the well testing methods currently available.
This package has three programs:
FILTER is a pre-processor which reads pressure data from a floppy disk or a file in the hard disk and generates an 1nput data file for WELLTESTNFR.
WELLTEST-NFR is the main body of the package which analyzes the test data.
J. OUTPUT is a post-processor which generates a report out of the output file from WELLTESTN, NFR.
WELLTEST-NFR is composed of four different modules:
Input data editing module creates an input data file or edits the existing file in such a way that the file contains all the input data required for interpreting test data.
Program control module steamlines the overall operation to allow multiple analyses with the same data set.
Typecurve analyses module performs various typecurve interpretations depending upon the type of reservoir and analysis technique.
Specialized analyses module handles a variety of conventional interpretation techniques specifically designed for reservoir parameter calculations. A flow chart of the program overview