Novel Acid-Diversion Technique Increases Production in the Cantarell Field, Offshore Mexico

Abstract

Abstract Cantarell, which is an offshore complex of fields in the Bay of Campeche, is the most important complex in Mexico and is the second-largest producing field in the world. It is comprised of five fields, with the main pay zones consisting of highly fractured, vuggy carbonate formations from Jurassic, Cretaceous and Lower Paleocene geological ages. Matrix acidizing has always been the main stimulation process used to improve production from these carbonate reservoirs and this is especially the case now that this mature complex has reached its production peak. As with all acidizing programs, a critical factor for success of the treatments is distribution of the acid between all productive zones. Since most producing wells are not homogeneous and contain layers of varying permeability, even distribution of the acid is a difficult task. In addition, the water saturation of the various zones has a major effect on the acid distribution. Since acid is an aqueous fluid, it will tend to predominantly enter the zones with the highest water saturation, in many cases resulting in increased water production. This brings with it the multitude of problems associated with high water production. This paper will present the results of approximately 55 high permeability wells ranging from 1,000 to 6,000 md, which have been acidized using a novel acid diverter based on associative polymer technology (APT). This polymer inherently reduces the formation permeability to water with little or no effect on the permeability to hydrocarbon. Data from production logs from several of the treated wells will be presented, which show excellent oil production distribution along the perforated intervals. In addition, production logs will also be shown for wells acidized with other diverters, such as foams and in-situ crosslinked acid, which showed poorer results. Introduction Cantarell Field The Cantarell field is the second-largest oilfield in the world behind the Ghawar field in Saudi Arabia. It is located offshore in the Gulf of Mexico, 47 miles northeast of Ciudad del Carmen, Campeche. The main hydrocarbon zones in Cantarell are highly fractured carbonate formations from the Jurassic, Cretaceous and Lower Paleocene geological ages (Fig. 1). The field is made up of a number of subfields or fault blocks, with the main fields being Akal, Chac, Kutz, and Nohoch. Production started in 1979 and reached a peak of 1.1 million B/D in 1981 from 40 oil wells. By 1994 the production was down to 890,000 B/D. One year later it was producing 1 million B/D due to the addition of new platforms and wells and a nitrogen injection program. This program was capable of injecting a billion ft3/day of nitrogen to maintain reservoir pressure. By 1996 the field was producing 2.1 million B/D.