Abstract

Being Cantarell Complex the most important oil field on Mexico and the sixth largest in the world, Pemex Exploration y Production (PEP) initiated a comprehensive program to increase reserves, through pressure maintenance by nitrogen injection. This will be an overview paper describing th process followed to select the new development program fo Cantarell Field, based on geological, reservoir simulation and economical studies; a review of the original field development in late 1970´s and early 1980´s, and the current short term and long term development projects. A description is made of existing production and export facilities as well as existing wellhead platforms, production complexes and gas treating facilities. Several short term development projects are currently applied to debottleneck existing facilities, reduce gas flaring, increase storage capacity and export berths using Floating Storage and Offloading vessels (FSO). Those projects are based on engineering studies, reviews of oil/gas separation and gas compression facilities. Finally, some long term projects were established to increase production handling capability and oil storage and exports. These projects cover a program to drill additional development wells, new wellhead platforms, new production complexes and new pipelines.

Introduction

Cantarell Field has four blocks called Akal, Nohoch, Chac and Kutz being Akal block the most important containing 91.4 % of the 35 billion barrels of initial oil in place of the field. 1 Currently the field is producing 42 % of national production and contents 25.7% of Mexico oil reserves. The oil produced from this field is Maya type from 19 to 22 API degrees.

The field production started on June, 1979 reaching a production pike of 1.157 MMBPD on April, 1981 through 40 wells. This production level was sustained until early 1996 through the drilling of 139 development wells, using gas lift and reducing back pressure restrictions (Fig. 1).

A well productivity decline was observed as reservoi pressure was falling. The initial well productivity of 30,000 bpd falls to 7,000 bpd while the reservoir pressure declined from 270 Kg/cm2 to 113 Kg/cm2.

The pressure declining occurs due to fluids extraction even with the natural water influx through the south edge of the field. As a result of pressure declining to levels below the bubble point pressure a secondary gas cap exists now in the reservoir.

Project Objective

Considering the remarkable reservoir pressure declining which in turn has reduced well productivity to one fourth of its initial value, but mostly due to the fact that the water encroaching through the south flank has a lower displacement efficiency leaving behind approximately 19% more oil trapped in the reservoir than the gas expansion, a comprehensive program to maintain reservoir pressure by nitrogen injection has been established with the objective of maximize the economical value of the field.

Geology

The Cantarell Complex is located in the Continental Shelf inside the Gulf of Mexico about 75 Km. NNW from Ciudad del Carmen, Campeche. (Fig. 2) It was discovered en 1976 when the well Chac-1 was completed as producer well.

The complex is formed by several blocks bounded by faults (Figs. 3). The structure is a big anticline oriented NW-SE, its geological configuration resulted from tectonic processes originated by the rupture and interaction of the tectonic plates in the Pacific Coast.

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