Cyclic Steam Injection With Additives: Laboratory and Field Test Results of Steam/Foam and Steam/Solvent Processes

Abstract

Abstract Cyclic steam injection is the most commonly used method to produce the heavy oil reservoirs in the Bolivar Coast in Western Venezuela. The efficiency of this method in this field, as measured by the oil to steam ratio, is remarkably high, mainly due to compaction drive. Nevertheless, later cycles show a natural decline in the efficiency of the process. In order to improve the efficiency, and to extend the application of cyclic steam injection in the field, different types of additives are being tested. Laboratory study, and field tests were conducted in order to study the possible merits of the addition of small amounts of solvent as part of the injection process. On the other hand, due to the massive sand bodies, and shale intercalations that exist in the heavy oil reservoirs of the Bolivar Coast, foam was used in order to improve the vertical sweep efficiency of steam injection during huff 'n' puff. After the conduction of laboratory experiments with steam/foam, a set of 16 wells we re selected in order to test the injection of two commercial foaming agents (LTS and BBS). In this work, the field results of these pilot test of foam injection are analyzed, and correlated with several variables. Four wells were stimulated with steam injection with solvent. The solvent used was an industrial diesel. As in the previous case, field results were analyzed. The merits of the process are obtained by comparing the response of the wells, with neighboring wells with similar characteristics. Prior to the field tests, laboratory experiments were carried out, in order to obtain the operating conditions. Introduction The main heavy oil reservoir of the Bolivar Coast area in western Venezuela (Bachaquero, Laguna, Lower Lagunillas and Tia Juana) contain an estimated initial oil-in-place of 36,000 MMSTB, of crudes of gravity between 9 to 15 degrees API, with in-situ oil viscosity between 100 to 100,000 cp. The field is of younger tertiary age (Miocene), the major oil-bearing sands are located in the Lower Lagunillas Formation, which are unconsolidated in nature, and contain numerous shale intercalations. These reservoirs were produced under primary depletion, and after 1959, under cyclic steam injection. Recovery under cyclic steam injection is estimated at 23%. P. 71^