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Project Media:
Study Year: 2013

Executive Summary

Osage Partners, LLC. a Wyoming based operator contacted EORI and requested the institute’s assistance regarding their Muddy/Newcastle assets. The operator provided EORI with core from four wells and associated data related to the Osage field in the Powder River Basin. The operator requested that EORI characterize the clay mineralogy of the pay sands using XRD, SEM, and CEC analysis of samples from the provided core.

The purpose of performing this clay analysis was to:

• Identify clays in the formation
• Quantify clay content
• Approximate clay distribution in the formation and throughout the field
• Relate clay content to both productive and nonproductive intervals within the formation
• Determine whether or not clay inhibitors should be used (Osage Partners)
• Provide basis for SP and A/SP formulations regarding fluid rock interactions (TIORCO)
• Increase general knowledge about clays in Cretaceous Reservoirs
• Other

The results of this work are summarized in the following sections and detailed result sets are included in the appendices.

Background

The Osage field is currently producing ~120 BOPD and ~950 BWPD. The field was discovered in 1919 (Dobbin and Miller, 1941) and has since produced approximately 32.1 MMbls oil, 78.5 MMbls water and 142 MMcf gas (WOGCC ). There are up to seven separate oil bearing intervals in the Muddy / Newcastle Formation within the Osage area. The operator has contracted with TIORCO to conduct fluid studies for their reservoirs and has also moved forward on developing a water study for the Osage field. Currently the operator is injecting roughly 200 BWPD and recovering approximately 3 BOPD from three producers from the Halbouty unit. The focus of this project is the Bradley Unit of
the Osage field.

The Bradley Unit at Osage is divided into 4 separate tracts. Of interest is Tract 4, this tract is located along the western third of the unit and has produced nearly 70 percent of all Bradley production. Production in this tract began in between 1919 and 1922 and a water flood was started in 1969 and continued until 1998. The water flood was reactivated again near the end of 2000 and continued until 2009. Source water for injection is from the underlying Madison Formation. At the present it is undetermined whether or not source water was treated prior to injection. Evaluation of core analysis generated between 2006 and 2008 indicate a remaining oil resource of approximately 3 thousand bbls/acre. This determination is based on an average pay thickness of 5 feet, So of 40%, and 20% porosity.

In order to optimize their assets at Osage the operator spoke with the owner of Thompson Creek (another Muddy/Newcastle field located northeast of Osage) and learned that fluid compatibility studies should be performed prior to drilling in order to minimize reservoir damage. The operator has also expressed interest in the use of Potassium Hydroxide (KOH) as a clay inhibitor with respect to the known clays in the Newcastle Formation as they reactivate the injection in the Bradley Unit. It is important to note that the operator plans to use a portion of the Bradley Unit to identify best practices that can then be later applied to other areas within the larger Osage Field.

Project Objectives and Scope

The objective of this project was to assist Osage Partners, LLC with the characterization of the Muddy/Newcastle reservoirs at the Osage Field in the Powder River Basin (PRB), WY. The goal of this work is to provide the operator with information that may be used to enable decision making for the purpose of enhancing the recovery of oil from their Muddy/Newcastle assets (Osage, Mush Creek, etc…) in the PRB – specifically for the purpose of providing information relative to designing a water/chemical flood for the Bradley Unit of the Osage Field. Data for this project was provided to EORI by the operator and compiled from existing datasets at EORI and the Wyoming Oil and Gas Commission.

EORI conducted clay analysis on core samples from the Muddy/Newcastle Formation from four cores surrounding the Bradley Unit at the Osage Field. The analysis required compilation of available existing data, core preparation and sampling, petrographic analysis, core descriptions, and clay analysis using XRD and SEM. CEC analysis was also conducted.

This project directly supports the intended purpose and mission of EORI through the institute’s strategic objectives which include benchmarking, technology transfer and providing technical expertise to a Wyoming based operator for the purpose of developing additional resources by way of enhanced oil recovery methods.

Data overview

Core that was used for this project was originally collected between 2006 and 2008 by Rockwell Petroleum Co.. The four wells that were cored include: 21-4 (api 4529132), drilled in 2006; 18-9 (api 4529128), drilled 2007; 17-1 (api 4529141), drilled 2007; and 16-106 (api 4529202), drilled in 2008.

Of the core that was provided to EORI, only two of the wells (16-106 and 17-1) included the main pay sands of the Newcastle Formation. The pay sand intervals for wells 18-9 and 21-4 were provided to TIORCO for analysis prior to the start of this project. TIORCO was later contacted and provided samples of the pay sands from well 21-4 to EORI (note: these samples have not yet been analyzed).

Other information including field data, production data, core analysis, and log data were compiled by the operator and provided to EORI early on in the project. A literature search was conducted by EORI which resulted in a compilation of references relative to the project objectives.

The provided core analysis data were used to identify appropriate samples for clay analysis. Apart from an overall lithologic criteria, samples of similar lithogies having drastically different porosities and permeabilities were selected in order to evaluate the relative percent clay and its affect on reservoir quality.

Several factors including historic development, production, depletion, stimulation, and injection have already affected the distribution and character of clays within the Newcastle reservoir in the Osage Field. As this core was collected after primary and secondary recovery, this core is likely representative of a clay damaged reservoir.

Of the core from the four wells that was evaluated, the core from well 17-1 is most representative of the Newcastle Formation within the study area because of the completeness of the cored interval and representation of the depositional sequences that occurred within this portion of the Osage Field.

 

Acknowledgements & Credits: University of Wyoming School of Energy Resources • EORI