DEA-161 – A Proposal to Develop an Improved Methodology for Wellbore Stability Predictiona

DEA Project Summary

To download the presentation of DEA Project 161 in PDF format, click here.
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To download the brochure for DEA Project 161 in PDF format, click here.

Date Submitted: August 31, 2006
Technical Area: Exploration
Sponsor: Marathon Oil Company/John Jones/Advanced Senior Drilling Engineer/
Title: A Proposal to Develop an Improved Methodology for Wellbore Stability Prediction
Submitted by: Knowledge Systems Inc./William Standifird/Senior Vice President/
Principal Investigator(s): William Standifird, Officer in charge,; AJ Rizvi, Project Manager,; Dr. Jon Zhang, Chief Project Geoscientist,; Dr. Xinpu Shen, Geomechanics Specialist,; Dr. Joel Gevirtz, Modeling Specialist,; Dr. Martin D. Matthews, Modeling Specialist,
Business Impact: Loss of wellbore stability is the major source of non-productive time while drilling, causing an estimated $8 billion in world-wide losses each year. A clear goal of this project is to identify practical methods that will reduce or eliminate the incidence of unstable wellbores at a fraction of the cost of remediation.

Specifically, this project is intended to increase the effectiveness of drilling engineers in planning for wellbore stability such that the business of the project participants will be improved in the following ways:

* Reduced well construction time and cost
o Reduced casing related costs
o Reduced mud costs
o Reduced dependence on contingency casing designs
* Improve quality of formation evaluation data
* Maintain hole integrity for maximum production

Technical Objectives: The objective of the project is the identification and development of best practices for practical wellbore stability analysis. The resulting methodologies should be readily applicable by drilling engineers.

There are five essential ingredients that form the basis for this proposed project:

1. A detailed wellbore stability analysis of a significant number of wells (~50 per geographic area) using all available data to include seismic, wireline, drilling and pressure test data such as MDT’s, mini-frac’s and LOT’s.
2. A multi-disciplinary team that includes engineering and geoscience specialists to study the results of these analyses and formulate the improved methodology.
3. The improved methodologies will be blind-tested rigorously and completely documented to validate the performance improvements.
4. The results of all the analyses will be aggregated, sorted and distilled into best practices for practical wellbore stability analysis.
5. The best practices will be delivered via workshops to ensure operations personnel receive maximum benefit from the study and improved methodologies.

It is anticipated that this improved methodology will include some combination of possible new wellbore stability analysis models and/or guidelines for applying existing ones. New tools for defining and constraining rock strength may include temperature effects, a streamlined workflow, or the use of stochastic modeling to constrain highly unknown parameters.

Implementation of the methodology will be accomplished by a combination of technical forums, training courses, reference manuals, an electronic or “smart” manual and an internet web page for keeping the methodology updated.
Methodology: Research of Current Practices
We will conduct a thorough review of industry wellbore stability analysis practices, then use the results to select the most promising modeling methods. From available sources, gather the necessary data to test the selected models on a representative sampling of wells.

Data Gathering, Quality Control and Validation
An assessment will be made to determine the relative priority of data types. Based on the assessment, data will be acquired from available resources and organized within a project database.

Determination of in-situ stress and rock strength
Assumptions regarding in-situ stress and rock strength parameters are key factors in developing and validating wellbore stability models. A best practice will be developed and validated against available rock strength data from core samples, and used to provide consistent inputs to the wellbore stability models.

Wellbore Stability Analysis
For each of the selected wellbore stability modeling methods, an analytical wellbore stability prediction will be generated for the selected wells, using the information available pre-drill. Similarly, we will analyze how these predictions could have been modified using information available while drilling.

Separately, a definitive wellbore stability diagnosis will be prepared for each well using the best practices previously identified. The analyses will be correlated to known wellbore instability indicators like deformation, cavings and pack-offs.

Under certain geomechanical conditions analytical methods may not produce reliable results. Numerical methods for modeling wellbore failure mechanisms, like finite element analysis, will be considered as an alternative, provided that such methods are practical and efficient.

These predictions will be rigorously compared to the actual well diagnoses to determine the best practices for wellbore stability estimation both pre-drill and while drilling.

Documentation and Communication of Findings
Project findings will be documented and distributed among participants using appropriate methods, including manuals, expert systems, workshops and training courses.

The final scope of work will be agreed by the project participants.
Deliverables: This project will produce the following deliverables to the participants:

1. Monthly project status reports and more detailed interim project progress reports every six months during the project.
2. Based on a study of the analysis results from this project, an improved methodology will be determined for the prognosis of wellbore stability. This methodology is anticipated to be some combination of methods, models, data and procedures that result in an improved prognosis. It may include new models that better fit the analysis results, recommendations for different approaches for generating velocity data from surface seismic data, and/or recommended well planning procedures.
3. Any new models, algorithms and/or methods for wellbore stability analysis that are developed as a result of this project will be distributed to each participant in digital programmatic form such that they can be directly used in DrillWorks Expert as a User Defined Method or User Defined Program, or, alternatively they can be built into other software by the participant. Each participant will be able to distribute unlimited copies of such new methods within the participant’s company.
4. The methodology will be documented and described in a Wellbore Stability Prognosis Manual. It is anticipated that the manual will be in the range of 100 to 200 pages. Each participant will receive five copies of the manual. Additional copies will be available at cost.
5. The methodology will also be provided in electronic manual form, using a rule-based expert system structure that runs under Windows. Each participant will receive a corporate license to the electronic manual that allows unlimited copies within participant’s corporation.
6. A Wellbore Stability School specifically designed for drilling engineers will be held in each of the project’s geographic areas (five proposed). The course will be 3 days in length and cover the practical aspects of wellbore stability modeling and the associated best practices.
7. The data and analysis results will be maintained in digital form in a relational database such that it will be available for future research and study to include testing new models and methods.
8. A Wellbore Stability website will be created and maintained that contains project results, available data and updated information. This website will require password access and each project participant will be provided with a password that will be updated periodically. It will also include an FTP site that will permit downloading of data in digital form as the owners of the data provide permission for disclosure.

Startup Date: January 1, 2007
Project Cost: 1,470,000.00
Cost per Participant: 98,900.00

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