Abstract

Traditionally if a multiple boundary is suspected in a hydrocarbon reservoir, it is analyzed for its location from the well and its degree of leakage if it is a single communicating fault. Although a well in multiple leaky boundaries presents a very important flow problem in conventional reservoir engineering, no comprehensive method exists in the literature to determine the location of the well relative to each of the leaky boundaries or to determine their degree of leakage and consequently pressure drop caused by these leaking faults in the reservoir.

This study presents a new analytical solution for the pressure behavior of a well near a leaky fault. An extension of the well imaging technique to model multiple leaky boundaries using the new analytical solution which is helpful to generate type curve plots. A study of the pressure and the pressure derivative behavior for a well in multiple leaky boundary systems for different boundaries such as (a) well near a single linear leaky boundary, (b) well between two intersecting leaky boundaries forming an angle of 120 °, 90 °, 60 °.

The solution obtained can be used to improve the design and analysis of both a drawdown and interference tests between the wells separated by partially communicating faults. Type curves generated by these solutions will yield separate estimates of the formation transmissibility and the transmissibility of the fault itself. An explicit solution developed for drawdown at the active well offers the possibility of deriving fault transmissibility from the drawdown and buildup behavior of the active well. This method could be used if a convenient observation well is not available for interference testing. An extension of the well imaging technique allows modeling the leaky boundaries such as two intersecting when the well is located any where between them. Pressure and pressure derivative behavior of a well located any where between two intersecting leaky boundaries for different angles shows that the finger print is unique for a determined angle, the location of the well, and the specific transmissibility ratio of the two boundaries.

An accurate correlation between the transmissibility and the maximum pressure derivative has been established and Tiab's Direct Synthesis (TDS) technique is applied to interpret the pressure and the pressure derivative response of a well near a leaky fault. New parameter, called leakage coefficient, has been introduced to describe a partially communicating fault in case of two intersecting faults. It has been found that theleakage coefficient has direct relation with the transmissibility ratio. Several analytical correlations relating reservoir parameters with the different characteristic points and straight lines in the pressure derivative curve have been developed. Several examples describing the various fault and well locations, fault properties, and angle between the faults are included to illustrate the use of the technique developed.

Introduction

Petroleum reservoir rocks are rarely homogeneous in properties such as permeability and porosity. The heterogeneity can range from as small as grain size to as large as presence of faults that may completely trap a portion of the reservoir.

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