The goal is to enhance the operational flexibility of the nation's natural gas storage system by developing an effective remediation treatment for gas storage well damage resulting from hydrocarbons, organic residues, and production chemicals (HOPS) that uses the application of carbon dioxide as the primary fluid.
Advanced Resources International – project management and research product
Stim-Lab, Inc. – laboratory testing, protocol development
Arlington, Virginia 22201
HOPS damage can occur in almost any gas storage well environment, either as a result of fluids introduced from the surface or from naturally occurring hydrocarbons within the reservoir (oil and/or condensate). Such naturally occurring hydrocarbons are present in many storage reservoirs since most storage facilities were originally oil or gas fields that were later converted to gas storage use. The introduction of HOPS from the surface can also occur at any storage facility and in some cases, such as with corrosion inhibitor squeeze treatments, the damaging materials are injected into wells intentionally. The interaction between the introduced fluids and reservoir fluids, formation wetability, and the reservoir's temperature are important contributing factors to the creation of HOPS damage.
The project successfully demonstrated that damage to the two storage fields studied was a result of HOPS; specifically, native oil, compressor oil, and asphaltene precipitation. Although the laboratory testing of supercritical CO2 for the removal of damage typical in the Huntsman field was successful, no treatment methods for removal of damage typical in the Overisel field was found. Efficient, cost-effective alternatives to current remediation techniques still need to be investigated.
In this project, materials and information necessary to recreate the HOPS damage observed in several major gas storage fields were collected. This included field historical and operational data and fluid samples. Appropriate core specimens were then assembled to conduct laboratory experiments. Using this data, a basis was formed for identifying the potential sources of HOPS damage and the probable events and timing of the introduction of HOPS damage.
In-line flow-stream monitoring devices were installed in order to collect HOPS particles during injection and withdrawal cycles. These particles were used to identify the HOPS responsible for causing damage in the subject fields. Next, methods to reduce the negative impact of HOPS were examined along with the costs and effective life of current HOPS remediation treatments. Past HOPS treatments were evaluated using available deliverability and cost information. A comparison was made between these factors and the estimated costs and effective life of the remediation treatment concepts developed by this project.
Laboratory studies were then conducted using reservoir rock samples and identified suspected damaging fluid samples from the subject gas storage fields. Core flooding experiments were conducted to evaluate and substantiate field-observed damage. Remediation steps were performed in an effort to remove observed damage using various treatment techniques and chemicals, including the application of supercritical carbon dioxide. Testing conditions were aimed at simulating field application conditions, with the objective of developing treatments that were realistic both logistically and economically.
Although the project was successful in the laboratory demonstration of the application of CO2 for the removal of damage typical in one of the subject fields, it was not successful in finding any treatment method that successfully removed the damage typical of the other fields. The knowledge gained through the laboratory investigations with the successful field did not significantly advance the understanding of CO2's remedial benefits due to the wealth of existing knowledge from enhanced recovery activities. As a result, the project was ended and did not progress to Phase 2.
This project is complete and all deliverables have been received.
Final Report [PDF 3.0MB] - July, 2004