Unconventional Gas Fracture Logging Method and Apparatus

Abstract

A method for logging slick water hydraulic frac well includes the steps of: Perforating the well bore; Pumping fresh water into the reservoir; Running a high resistivity measurement tool down the hole to measure the resistance of the reservoir at selected intervals along the hole; Logging the resistance measurements; and Comparing the resistance of the reservoir strata with the resistance of the fresh water pumped into the reservoir to map the fracture. It is desirable but not necessary to run a high resistivity tool down the hole prior to the perforation step and measure the resistance of the reservoir to provide base line logging data, whereby the base line logging data may be compared with the water frac logging resistance measurements.

Description

BACKGROUND[0001]1. Field of the Invention[0002]The subject invention is generally related to logging systems for data logging oil and gas wells and is specifically directed to a method and apparatus for logging wells employing slick water hydraulic fracturing.[0003]2. Discussion of the Prior Art.[0004]Hydraulic fracturing, or fracing, is used to initiate production in low-permeability reservoirs and re-stimulate production in older producing wells. In hydraulic fracing, a fluid is injected into a well at pressures so intense that the structure ‘cracks,’ or fractures. Fracing is used both to open up fractures already present in the formation and create new fractures.[0005]Fracture fluid can be oil-based, water-based, acid-based or gel. However, water fracs are the most common and least expensive. Slick water frac jobs are the primary technique used for developing tight-gas reservoirs. In order to retrieve gas at a commercially profitable rate, most tight-gas reservoirs need to be fra...

AI Technical Summary

Benefits of technology

"The invention is about a way to measure the resistivity of water used in fracturing oil wells. This helps to better understand the structure of the fracture network and make the well more economically viable. The method involves running a high resistivity tool down the hole to measure the resistance of the reservoir, logging the resistance measurements, and comparing them with the resistance of the fresh water pumped into the reservoir to map the fracture. This can be done in a cased, cemented hole. The invention makes it possible to use logging data from slick water fracs in many reservoirs where gel fracing was previously required. The method can also help to map the fracture network created by the slick water frac."

Problems solved by technology

However, water fracs are the most common and least expensive.

Although excellent for transporting proppant, these gels often damaged the fracture, usually generated high-net fracturing pressures and were expensive.

Microseismic imaging has shown that water fracs can create very long fractures.

However, since water is less efficient than gels at carrying proppant, the effective fracture half-lengths may vary significantly, depending on proppant concentration and placement effectiveness.

The use of little or no proppant in a water frac may also result in low fracture conductivities.

As a result, under prior art methods, effective fracture conductivities are often difficult to predict when little or no proppant is used.

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