Thirty 30 Years of Steamflooding: Reservoir Management and Operational Experiences

Abstract

Abstract The Petroleum Company of Trinidad and Tobago Limited (Petrotrin) has a heavy oil reserves base of 300 million barrels of heavy oil in the southern part of the island of Trinidad. The Company, and its predecessors, first embarked on a thermal recovery program in its acreage from 1963 with cyclic/steamflooding operations. At the present time, the Company is operating eleven (11) steamfloods and is currently implementing another major project. This paper presents a case history of the Company's thirty-two years experience in steamflooding, inclusive of reservoir management and monitoring methods, innovations and operating practices. To date (1995 June), the Company has recovered a total of 77 million barrels of heavy oil from its acreage, with a current production level of 9000 BOPD. During this period, new diagnostic methods were initiated, as well as new innovations. These include cluster drilling, slimhole injectors, insulated tubing and packers, non-gravel packed injectors, high volume pumps, limited entry perforating, insulated casing completions, diverting agents, dual injectors, iso-fluid mapping and other reservoir management techniques. In summary, the Company has had extensive success in steamflooding operations and continues to utilise this method for exploitation of its heavy oil reserves. With its proven success and existing infrastructure for this type of operation, the Company still has major opportunities in heavy oil recovery. Additionally, new methods of operation, financing and project management are being pursued to exploit these reserves. Based on Trinidad's complex geology and heterogeneous reservoirs, heavy oil recovery has been a major success through the Company's scope of operations. Several innovations in reservoir management and operating strategies can be implemented in other similarly adverse environments for heavy oil recovery. Introduction Geographically, Trinidad and Tobago lies at the mouth of the Orinoco River on the north-eastern continental shelf of South America. The island's first oil well was drilled in 1857, but with only sporadic activity subsequently, the first commercial well was eventually drilled in 1901. In this regard, therefore, the country is recognized as one of the oldest oil producing provinces world wide. Following the commercial discovery at the turn of the century, several new fields were discovered. The majority of these were in the southern half of the island s land and marine holdings, with the north and north-eastern reservoirs being principally gas-bearing, both on and offshore. The majority of the land-based operations are located in the south-western peninsula, in a region where the heavy oils are predominantly concentrated. With the majority of these heavy oils occurring at relatively shallow depths (< 3,000 ft), expertise in heavy oil exploitation was developed out of necessity. Significantly, several other factors contributed to this growth, the major ones being:A ready and available supply of fresh water, from shallow aquifers and surface catchments, for the generation of steam.A cheap and reliable supply of natural gas for firing the Company's team generators, andProven success record in steamflooding: both locally and internationally.