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Method for Cement Evaluation with Acoustic and Nuclear Density Logs

a cement and density log technology, applied in the field of oil or gas production, can solve the problems of fluid contaminated cement, less than ideal, fluid filled channels within the cement sheath,

Inactive Publication Date: 2014-02-20
GUO PINGJUN +1
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  • Abstract
  • Description
  • Claims
  • Application Information

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Benefits of technology

The patent describes a method for evaluating the quality of cement in a cased well using a density logging tool and an acoustic logging tool. The method involves obtaining density logs and acoustic logs, inverting the acoustic logs to create an updated medium model, and then using this updated model to evaluate the quality of the cement. The main technical effect of this method is to provide a more accurate way to evaluate the quality of cement in cased wells, which can help to improve well construction and prevent damage to the well.

Problems solved by technology

Less than ideal cementing can result in fluid filled channels within the cement sheath and fluid contaminated cement due to incomplete replacement or sweep of drilling mud with cement slurry.

Method used

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  • Method for Cement Evaluation with Acoustic and Nuclear Density Logs
  • Method for Cement Evaluation with Acoustic and Nuclear Density Logs
  • Method for Cement Evaluation with Acoustic and Nuclear Density Logs

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[0041]The present inventive method is tested using an ultrasonic modeling software program that simulates the acoustic waveforms 52. A well with fully cemented casing and free pipe was selected to mock up for the modeling study. Actual acoustic data from the subject well was also obtained. The modeling code essentially predicts the field measurements that would result in an actual experiment. The modeled and field ultrasonic waveform data are in good agreement as shown in FIGS. 10 and 11, proving that the modeling code works well. For FIG. 10, a fully cemented well with a good cement bond was modeled and also measured experimentally. FIG. 13 shows a wellbore model with a good cement bond that is very similar to the model in the calculation. For FIG. 11, free pipe (no cement at all) was modeled and measured. FIG. 14 shows a wellbore model with fluid behind casing that is not far off the model used in the FIG. 11 calculation. The waveforms in FIGS. 10 and 11 depict the cement bond qua...

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Abstract

Method for evaluating cement quality in a cased well. A density log of the well is obtained using, for example, a GammaRay sources and detectors (51). The detector count rates are inverted to provide initial estimates of cement density and thickness (53). Acoustic waveform data are obtained from the well using an acoustic logging tool (52). The acoustic data are inverted (54-56), using the initial estimates of cement density and thickness obtained from the density logs, and an updated density log is inferred. Cement images are obtained from the updated density log, and cement bond quality can be estimated (57).

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]This application claims the benefit of U.S. Provisional Patent Application 61 / 683,528, filed Aug. 15, 2012, entitled METHOD FOR CEMENT EVALUATION WITH ACOUSTIC AND NUCLEAR DENSITY LOGS, the entirety of which is incorporated by reference herein.FIELD OF THE INVENTION[0002]This invention relates generally to the field of production of oil or gas, and more particularly to well drilling. Specifically, the invention is a method for evaluating cement density in cementing around well casings.BACKGROUND OF THE INVENTION[0003]When a well is drilled and steel casing is placed, cement slurry is pumped into the annular space between casing and formations. The primary objectives of cementing are to provide mechanical support for the steel casing string and zonal isolation between earth strata or formations. Multiple-stage casing and cementing operations are common procedures to establish pressure barriers during drilling a well. It allows the use of he...

Claims

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Application Information

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IPC IPC(8): E21B47/00
CPCE21B47/00E21B47/005
Inventor GUO, PINGJUNSMITH, RICHARD J.
Owner GUO PINGJUN
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