Abstract

At the state oil company of Trinidad and Tobago, (Petrotrin) and its predecessor companies, Field Rejuvenation has evolved through time from single well targets to the more highly detailed and complex field reservoir characterization project currently underway.

Initially single well target selection would be done by individual engineers operating their specific field. Generally, the benefit of these actions were not long term and did not significantly affect or arrest the declining production trends. At a more formal level there were studies undertaken in the process of the implementation a secondary or enhanced oil recovery project. This had the effect of arresting field declines and improving overall recoveries in the target fields.

The foregoing activities were carried out by the operating companies of the day. In the late eighties because of limited capital resources, a program of leasing blocks of idle wells to small independent local operators was initiated. This program proved successful in increasing indigenous oil production from idle assets as well as generating positive cash flows. It was therefore expanded and has since included farmouts and joint-venture arrangements with foreign companies participating also.

Currently Petrotrin is concluding a detailed field reservoir characterization study of one of its most mature fields on land which began production in 1913. The preliminary results have demonstrated the crucial role of reservoir characterization in evaluating the true potential of mature fields, and its potential for increasing production even from these fields.

Introduction

Trinidad has a long history of oil exploration and production. Oil was discovered in 1867 but commercial production only began from 1908. All the major land oilfields are found in the southern half of the island. The state oil company of Trinidad and Tobago, PETROTRIN, began as an entity in 1993 with the merger of two other state companies, Trintoc and Trintopec. Prior to this several major international oil companies have been producing the leases, and included: United British Oilfield of Trinidad (UBOT), Shell Trinidad Ltd., Kern Trinidad Ltd., Texaco Trinidad Ltd., and British Petroleum. This paper will deal with the efforts of Petrotrin and its two predecessor state companies.

The philosophy of rejuvenation was to increase production through the reactivation of idle wells. Initially this was not a coordinated process and it was left up to individual engineers operating the lease to determine which wells would be acted upon. This approach focused on the well as an entity, and hardly ever considered its relation to the overall management of the reservoir. During field development and subsequent surveillance, it became apparent that some fields were amenable to secondary recovery. In these cases some sort of injection would be initiated with the injectant being water, steam, CO2, or microbes. Because of the recent success of detailed reservoir characterization in similar fields, Petrotrin initiated a project to evaluate the feasibility of this method in their environment.

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