The goal of this project is to lessen formation damage and improve the success rate of stimulation treatments in low-permeability reservoirs.

Cementing Solutions, Inc.
Stim-Lab, Inc.
HEP Oil Co.

Location:
Houston, TX 77092

Many of today’s operators find that their stimulation treatments are not as successful as expected. Hydraulic fractures grow into adjacent zones or else do not reach the predicted length in the productive zone. Poor production performance can also result from the departure of the stimulation energy to the annulus and other zones because of an inadequate cement seal.

This project will develop an understanding of the relationship between cement seal effectiveness and post-stimulation production performance using baseline information on formation damage, hydraulic seals, fracture mechanics, and physical-property measurements. Physical and numerical modeling of the hydraulic seal created by a cemented annulus will be conducted and the results will be confirmed by conducting optimized application designs for the cementing and fracturing treatments on a number of candidate wells.

This project will document the importance of zone isolation when performing stimulation treatments in low-permeability formations. It has the potential to reveal critical properties of set cement that could influence the effectiveness of stimulation treatments. It will also reveal crucial issues related to cement materials or cementing techniques, the adjustment of which could greatly enhance a stimulation treatment. The results of this project will provide the industry with an understanding of the significance that incomplete mud removal, mud filter cake, zone isolation, and pressure transmission have on stimulation effectiveness, which in turn will highlight the need for industry to pay more attention to cement design and cementing techniques. This understanding could have an important impact on every stimulation treatment performed in the future. The proper recognition of the role of zone isolation in stimulation treatment effectiveness will help to modernize the way that cement jobs are designed and carried out for low-permeability reservoirs.

Results:

• Annulus Pressure Containment while Fracturing (APCF) test models were completed to test foam cement and compositions from the observed cement jobs.
• Numerical modeling was performed after completion of APCF testing to confirm accuracy of the mathematical model.
• Preliminary improved fracture treatment recommendations are complete and additional analysis of production data con-firms initial treatment analysis and recommendations.
• Initial cementing design process has been developed, based on formation characteristics, to provide optimum formation isolation and minimum damage of any productive fracture network.
• The required testing has been completed. Results are sufficient to complete initial seal integrity relationships. The complete data suite on which the relationships are based includes testing for the four laboratory-designed compositions and the cements used on the two field trials.
• The performance data for cement coupled with results of the stimulation engineering and field evaluations have formed the basis for the engineering analysis of cement seal requirements to optimize stimulation and production from the Barnett Shale. The engineering relationship was developed according to methods Cementing Solutions Inc. (CSI) developed for previous DOE and MMS-sponsored projects.
• One industry workshop on the results of this project was provided to Chesapeake Energy in Oklahoma City, Oklahoma in January 2005. A second workshop was held in Dallas, Texas in March 2005 and was attended by local operators.
• The decision matrix spreadsheet for designing cement treatments to maximize hydraulic seal has been completed. The calculations in the spreadsheet have been arranged so that if the user knows two of the three material properties (tensile strength, an elastic strain, or Young’s Modulus) required for a given cement, the third will be calculated for the user.

This project has been completed.  The final project report is available below under "Additional Information".

$490,296

$382,450

NETL - Gary Covatch (gary.covatch@netl.doe.gov or 304-285-4589) 
Cementing Solutions, Inc. - Fred Sabins (fsabins@cementingsolutions.com or 281-784-7902)

Final Report - April 2005: Increasing Production from Low-Permeability Gas Reservoirs by Optimizing Zone Isolation for Successful Stimulation  [PDF-15022KB]

Decision Matrix Spreadsheet  - [PDF - 52KB]