Abstract

The Cantarell field, discovered in 1976, is one of the largest oil fields in the world. This oil giant is a mature field and has produced over 7,800 million barrels of oil during 22 years of exploitation. It is made up of four blocks: Akal, Nohoch, Chac, and Kutz. Heavy oil and gas from Upper Cretaceous carbonate breccia is produced from 223 wells using primary and secondary recovery methods.

The possibility of the existence of a prospective hydrocarbon trap located below the Cantarell Field was recognized in 1990. Through various studies, this new reservoir was explored and defined. The new discovery, Sihil, surpasses all previous predictions regarding the quantity of oil reserves, thereby making the discovery of the fifth block in the Cantarell Field the most important discovery in the last decade.

Sihil allows Pemex Exploration and Production (PEP) to establish a strategic plan to add even more hydrocarbon reserves using data provided by investigation of other underlying blocks.

Introduction to the Cantarell Field

Cantarell Field, discovered in 1976 offshore Campeche, Mexico, is the sixth largest oil field in the world. It is located on the continental shelf in the southern part of the Gulf of Mexico and within the east-central part of the Bay of Campeche, 80 kilometers (km) northwest of Ciudad del Carmen, Campeche, Mexico (see Figure 1: Location of Cantarell Oil Field).

This petroleum giant is considered to be a mature field. It has produced approximately 7,861 million barrels (bbl) of oil during 22 years of production and exploitation. Prior to discovering Sihil, the Cantarell field was known to be composed of four blocks: Akal, Nohoch, Chac, and Kutz (see Figure 2: Map of Akal, Nohoch, Chac, and Kutz fields). The most important block is Akal, which contains over 90 percent of Cantarell's oil reserves.

The Cantarell field currently produces approximately 1.4 million barrels per day (mmbpd) and production is expected to increase upon completion of a major expansion and modernization program conducted by Pemex. Hydrocarbons produced from this field are oils with an API of 20° to 24°. Production comes from 205 wells using primary and secondary recovery methods.

The Sihil Reservoir, located in a thrust block below the Akal field, was discovered in 1998 and is the fifth block of the Cantarell field. This technical paper will concentrate on the assumptions and challenges that led to the discovery of Sihil Reservoir.

Geologic History of the Cantarell Field

The regional tectonic model proposed by R.R. Rojas (Reference 1) provides insight into the Akal and Sihil structures. Typical Cretaceous and Jurassic structure in the region is the result of normal faulting during the Early Cretaceous, though some authors claim that the process started in the continental part of the Jurassic Late Tithonian.

This system shows a decollement level that corresponds to the Middle Jurassic salts, with the development of salt rollers.

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