Core sample testing protocol

Inactive Publication Date: 2015-06-04
CONOCOPHILLIPS CO
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0011]The method may further comprise removing one or more disc shaped plugs either from said plane face of the bulk sample or from said corresponding plane face of the slab, at a location with respect to the length of the bulk sample which corresponds to that of the cylindrical plugs, and subjecting said disc shaped plugs to Brazilian testing. Brazilian testing is another well-known and commonly used test like the triaxial test. It involves applying a compressive load to the curved surface of the sample disc, and provides a measure of tensile strength of rock. In this way, tensile strength results can be obtained from rock at the same level in the core as the triaxial plugs. At least two disc shaped plugs may be subjected to Brazilian testing in respective different directions, thereby obtaining a measure of anisotropy. It may be possible to take two or more Brazilian disc samples, arranged along the axis of the core, with both (or all) encompassed within the same length of core as the triaxial plugs.

Problems solved by technology

Despite its widespread usage, current core testing techniques can suffer from inaccuracy and poor consistency.
As a result, massive oilfield operations can be guided by incorrect data.
These issues are particularly problematic when characterizing non-conventional rocks such as shale.
Part of the problem also lies in the inadequacy of currently accepted models of rock properties and behaviors.

Method used

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Examples

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example 1

[0059]This example describes a protocol for preparing and analyzing core sample according to an embodiment of the present invention. A schematic of the sampling protocol along with the various measurements is shown in FIG. 1. A standard procedure is for a bulk sample having length 103 of 6 inches (15 cm) and diameter 104 of 4 inches (10 cm) to be cut along its axis so that a quarter 105 of the core is removed and submitted for archiving, whilst the remaining three quarter core 100 is available for testing.

[0060]The core analysis process begins when the preserved core samples arrive at the lab for testing. The preserved ¾whole core sample 100 is first CT scanned to validate the preserved rock material is suitable for core plugging and mechanical testing. This step is required to identify fractured, broken or desiccated core that might not be suitable for mechanical testing.

[0061]After the CT scan, the sample is prepared for plugging. A total of 4—1″×2″ (2.5 cm by 5 cm) plugs 101 are ...

example 2

[0072]This example illustrates some of the differences between single stage triaxial testing of an embodiment and multistage triaxial testing. FIG. 6 shows a sample graph plotting deviatory stress versus strain of multistage triaxial testing where confining pressure increased at each imminent failure point. There are at least three imminent failure points represented by the plateaus in the axial strain. Success of multistage triaxial testing is largely dependent on the experimenter's ability to determine the imminent failure point for each confining stress. It is not uncommon to misplace the appropriate termination point (imminent failure) for each loading cycle thereby introducing significant error in determining Mohr-Coulomb yield parameters. By contrast, FIG. 7 shows a sample graph plotting deviatory stress versus strain of single stage triaxial testing where confining pressure is constant throughout the entire test. No human error is introduced in the form of judging where the t...

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Abstract

The invention relates to the dividing up and testing of bulk samples from cores of rock. The method involves the extraction of several plugs for triaxial testing which are derived from exactly the same level in the core, and also Brazilian test samples and samples for compositional and textural analysis from the same level. Triaxial tests with different confining pressures may be performed to destruction on separate triaxial plugs, allowing a reliable full Mohr-Coulomb analysis to be performed. Mechanical properties may be related more reliably to composition and texture of rock. The technique is especially useful for non-conventional rock such as shale.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims the benefit of U.S. Provisional Patent Application 61 / 836,929, filed on Jun. 19, 2013, the entire contents of which are hereby incorporated by reference. This application is related to, and incorporates by reference in its entirety, U.S. patent application Ser. No. 14 / 309,390 entitled “Mechanical characterization of core samples”, filed concurrently herewith.STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT[0002]None.FIELD OF THE INVENTION[0003]This invention relates to the processing of rock core samples.BACKGROUND OF THE INVENTION[0004]For many years, scientists and engineers involved in hydrocarbon exploration and extraction fields have prepared and analyzed core samples of geological formations, which are often taken during or after drilling operations. This analysis is useful for studying the formation in-depth and possibly directing oilfield decisions in order to maximize recovery of hydrocarbon...

Claims

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Application Information

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IPC IPC(8): E21B47/00
CPCE21B47/00G01N1/04G01N1/08G01N1/286G01N2001/2873G01N2203/0256
Inventor AMENDT, DAVID VICTORBUSETTI, SETH
Owner CONOCOPHILLIPS CO
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