Question: Which American multinational oil field service company has been testified against in Congress by Bunny Greenhouse in 2005?

Context paragraphs:
Tweneboa Enyenra Ntomme Oil Field: The Tweneboa Enyenra Ntomme Oil Field is an oil field within Ghana's territorial waters and the country's second major oil field after the Jubilee Oil Field.  It is popularly known as the TEN oil field, an acronym formed from the three drilling fields that it comprises.  Coincidentally, the exploration for oil in the basin also started with ten pre-first oil wells.

South Belridge Oil Field: The South Belridge Oil Field is a large oil field in northwestern Kern County, San Joaquin Valley, California, about forty miles west of Bakersfield.  Discovered in 1911, and having a cumulative production of over 1500 Moilbbl of oil at the end of 2008, it is the fourth-largest oil field in California, after the Midway-Sunset Oil Field, Kern River Oil Field, and Wilmington Oil Field, and is the sixth-most productive field in the United States.  Its estimated remaining reserves, as of the end of 2008, were around 494 Moilbbl , the second-largest in the state, and it had 6,253 active wells.  The principal operator on the field was Aera Energy LLC, a joint venture between Royal Dutch Shell and ExxonMobil.  Additionally, the field included the only onshore wells in California owned and operated by ExxonMobil.

Summerland Oil Field: The Summerland Oil Field (and Summerland Offshore Oil Field) is an inactive oil field in Santa Barbara County, California, about four miles (6 km) east of the city of Santa Barbara, within and next to the unincorporated community of Summerland.  First developed in the 1890s, and richly productive in the early 20th century, the Summerland Oil Field was the location of the world's first offshore oil wells, drilled from piers in 1896.  This field, which was the first significant field to be developed in Santa Barbara County, produced 3.18 million of barrels of oil during its 50-year lifespan, finally being abandoned in 1939-40.  Another nearby oil field entirely offshore, discovered in 1957 and named the Summerland Offshore Oil Field, produced from two drilling platforms in the Santa Barbara Channel before being abandoned in 1996.

Bunny Greenhouse: Bunnatine (Bunny) H. Greenhouse is a former chief contracting officer Senior Executive Service (Principal Assistant Responsible for Contracting (PARC)) of the United States Army Corps of Engineers.  On June 27, 2005, she testified to a Congressional panel, alleging specific instances of waste, fraud, and other abuses and irregularities by Halliburton with regard to its operations in Iraq since the 2003 invasion.  She described one of the Halliburton contracts (secret, no-bid contracts awarded to Kellogg, Brown and Root (KBR)—a subsidiary of Halliburton) as "the most blatant and improper contract abuse I have witnessed during the course of my professional career".

Round Mountain Oil Field: The Round Mountain Oil Field is a large oil and gas field in the foothills of the Sierra Nevada, about 10 mi northeast of Bakersfield, California, United States.  It is east of the giant Kern River Oil Field, one of the largest in the United States, and also close to the Mount Poso Oil Field and Kern Front Oil Field.  With a cumulative total recovery of more than 110 Moilbbl of oil, it is the 48th largest oil field in California, but remains relatively productive with still about ten percent of its reserves remaining in the ground, according to the California Department of Oil, Gas, and Geothermal Resources (DOGGR).

Stratagraph: Stratagraph is an oil field service company headquartered in Lafayette, Louisiana.  The primary focus of the business is providing mud logging, geosteering and well site geology services to petroleum exploration and production companies.

Bu Hasa oil field: The Bu Hasa Oil Field is an oil field 84 km north west of Abu Dhabi Islands.  It was discovered in 1962 and developed by Abu Dhabi Petroleum Company.  The oil field is owned by Abu Dhabi National Oil Company and operated by Abu Dhabi Company for Onshore Oil Operations.  The total proven reserves of the Bu Hasa oil field are around 6.52 billion barrels (1450×10tonnes), and production is centered on 600000 oilbbl/d .

Halliburton: The Halliburton Company, an American multinational corporation.  One of the world's largest oil field service companies, it has operations in more than 70 countries.  It owns hundreds of subsidiaries, affiliates, branches, brands, and divisions worldwide and employs approximately 50,000 people.

Šamac oil field: The Šamac oil field is an oil field located in Šamac.  It was discovered in 2004 and developed by Energopetrol.  The total proven reserves of the Šamac oil field are around 3.6 billion barrels (500×10tonnes), and production is supposed to be centered on 200000 oilbbl/d .  If the information regarding this oil field is correct than it is the largest onshore oil field in Europe.

Kern River Oil Field: The Kern River Oil Field is a large oil field in Kern County in the San Joaquin Valley of California, north-northeast of Bakersfield in the lower Sierra foothills.  Yielding a cumulative production of close to 2 Goilbbl of oil by the end of 2006, it is the third largest oil field in California, after the Midway-Sunset Oil Field and the Wilmington Oil Field, and the fifth largest in the United States.  Its estimated remaining reserves, as of the end of 2006, were around 476 Moilbbl , the second largest in the state.  It had 9,183 active wells, the second highest in the state.  The principal operator on the field is Chevron Corporation

Supporting paragraphs: Bunny Greenhouse Halliburton
Answer: Halliburton