Abstract

Fracture behavior is an important aspect in fracturing technology. Many techniques are available for prestimulation simulations and post-stimulation analysis of fracture behavior. However, very few techniques address fracture behavior during the stimulation process itself. Various fracture behaviors, such as fracture extension, ballooning, and tip screenout are often not known to the operator until after it is too late or even after the job is completed. Therefore, it is important to create and evaluate different real-time analysis techniques that can be used to capture the critical information available from data gathered during jobs.

During the stimulation process, many types of information are available to the engineer. Pressure, flow, and temperature are basic information evaluated by many in the past. However, surface-pressure measurements are heavily influenced by friction, densities, proppant concentrations, and flow fluctuations, which makes conventional analyses difficult, if not impossible. In spite of this, analysis of dynamic pressure fluctuations has not been actively pursued. Certain changes in the downhole configuration, such as fracture extension, may send different pressure frequency spectra and wave intensities to the surface. The signature of these pressure waves is believed to carry such information to the surface. It is also believed that signal degradation due to friction may not influence the outcome of this type of analysis.

Capturing and evaluating generated and reflected pressure waves during fracturing may be a new approach to monitor what happens downhole during fracturing. This paper discusses different real-time analysis approaches, such as frequency analysis and wavelet technologies, and evaluates their results and compares them to real job data. These analysis results and the successful stimulation results are presented in this paper.

Introduction

Stimulating wells that behave nicely (e.g., wells that are easily stimulated) allows service companies and operators to follow standard procedures commonly performed on such wells. No special attention needs to be placed upon specifics, such as how the fracture behaves; all decisions and actions are based upon the experience the industry has acquired in the last five decades.1

However, as the hydrocarbon supply decreases and demand for it increases, the hunt for hydrocarbons becomes more challenging. New technologies, such as fluid chemistry and rheology, or even new stimulation techniques enter the marketplace. These techniques claim to provide better fracture creation, better conductivities, permeability modifications, and more. As these technologies are used, new methods for evaluating the effectiveness of the treatments are needed.

In the field of fracture-size development and measurement, tiltmeter technology may be one practical way to detect fracture shape and size. However, special equipment is required to capture this data and the sensitivity requirements make this process quite costly. In this paper, possible practical and economical means of observing fracture development with less elaborate schemes are investigated. Some of these methods eventually could be used for mapping the fracture in the future.

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