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A new approach for interpreting a pressure transient test after a massive acidizing treatment
Abstract
Interpreting a pressure transient test from an acidized well in the framework of the thin skin concept is not straightforward for several reasons. First, the effect of stimulation cannot be considered to be localized in an infinitesimal region near the wellbore. Second, even if an equivalent skin factor can be defined, it will not be constant during the transient period. Third, the negative skin factor does not allow for a rigorous solution of the transient problem in the presence of wellbore storage, and hence, type curves can be generated only using "equivalent" fractured well models. In this paper we introduce a theoretically rigorous approach for the case when the effect of stimulation or damage can be represented using a power-law model to represent the reservoir permeability (as a function of the radial distance from the well). The well-reservoir system is described using three parameters-the areal average permeability, the power-law exponent (positive for damaged and negative for stimulated wells) and the wellbore storage coefficient. To our knowledge, this is the first time this problem has been addressed in the technical literature. The model is solved rigorously in the Laplace domain. We used numerical inversion of the Laplace domain solution to generate type curves. Two sets of type curves are presented for interpreting pressure transient tests from nonstimulated wells and stimulated (acidized) wells. From a practical point of view- however, the newly developed type curve for nonstimulated wells do not provide any substantial advantages over the existing methods, and in fact, this case is simply a reproduction of the Bourdet, et al. type curve for an infinite-acting homogenous reservoir. On the other hand, our new type curve for a stimulated well differs from any previous results discussed in the literature and constitutes the substantive contribution of this work. Data analyses verify that the new generated type curves can be implemented as a new interpretation methodology-particularly for the stimulated well case. An apparent disadvantage of the new type curves is that the drainage radius is a component of the type curve "family parameter," and hence, the concept of an "infinite-acting" reservoir is not applicable. Ideally, practicing engineers need to have a good understanding of the drainage area to obtain a realistic value of the power-law exponent (of the permeability profile). The proposed methodology may be particularly attractive for the evaluation of nontraditional "reservoir stimulation" treatments (e.g., high-rate water fracturing without proppant), where the geometric containment of the stimulation effect is not known.
Description
Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to digital@library.tamu.edu, referencing the URI of the item.Includes bibliographical references (leaves 40-45).
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Citation
Mursal (2002). A new approach for interpreting a pressure transient test after a massive acidizing treatment. Master's thesis, Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /ETD -TAMU -2002 -THESIS -M873.
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