Semester

Spring

Date of Graduation

2012

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Petroleum and Natural Gas Engineering

Committee Chair

Samuel Ameri.

Abstract

The purpose of this study was to develop a safe and environmentally acceptable water base mud that will be able to suppress swelling and promote stability to the West Virginian Marcellus shale. The problem was approached by utilizing aluminum precipitation chemistry in the drilling fluid, unlike the traditional cation-exchange approach.;A dynamic swelling meter was designed by modifying a 0.001 mm resolution dial indicator and using a specially programmed smart cable connecting the dial indicator to a computer. The swelling data was acquired by the smart cable every six seconds. As a result, there were 14,400 measured points for each sample for the 24 hours test duration.;The Marcellus shale samples were prepared by cutting a core sample taken from a depth of 6,025 ft by a rotary saw. The original core sample was cylindrical with a diameter of 2-in. and a height of about 20-in. It was cut into smaller sections with the same diameter and a height ranging from {lcub}2.5 to 7{rcub} mm. The samples were dried in an oven at 70° C until weight was stabilized. The average moisture content of the samples was approximately 1 %.;Mud samples were prepared with Aquagel (natural clay), Soda Ash (Sodium carbonate), potassium alum (potassium double sulfate of aluminum), and Cellex polymer (Carboxymethyl cellulose sodium). All the substances used in developing the mud are biodegradable and were EC50 (half maximal effective concentration) tested. The base mud design had 10 lb/bbl Aquagel, 2 lb/bbl Cellex, and 5 lb/bbl Soda Ash. Later the potassium alum was added to the base mud with different concentrations (0.5, 1, 0.6, and 0.7) lb/bbl for a sensitivity test.;Each water/mud sample was tested on three shale specimens to confirm the results. Swelling test was first conducted with fresh water, which yielded the highest swelling percentage in an average of 5%. The base mud resulted with approximately 3 % swelling and 1.41 % swelling was observed with the 0.5 lb/bbl potassium alum. Also, 1.24 % swelling with the 0.6 lb/bbl potassium alum, and no swelling with the 0.7 and 1 lb/bbl potassium alum muds. From the sensitivity tests on swelling inhabitation performance, the 0.7 lb/bbl potassium alum mud was elected to be the best performer. An additional test on the same mud with three shale samples was carried and results were consistent with the previous one.;Rheological measurements were taken for all the mud samples with American Petroleum Institute (API) standards and were based on the Bingham fluid model. The mud density didn't change with different potassium alum concentrations and remained at 8.8 lb/gal. This was due to the small concentrations incorporated in the base mud. All the test muds showed acceptable rheological properties. The best performer mud with 0.7 lb/bbl potassium alum, had a plastic viscosity of 9 cp, apparent viscosity of 10 cp, and a yield point of 2 lb/100 ft 2.

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