Abstract
This paper shows the evolution of the cyclic steam stimulation (CSS) process in a Colombian heavy oil field. Some challenges have been faced like: low injectivity in the first stimulation cycles, presence of swelling clays, low lateral and vertical continuity of the producing sands, steam channeling, among others.
According to the oilfield complexity some strategies are currently being implemented after previous studies of numerical simulation and lab test evaluation: diesel slug to improve injectivity, reduced steam quality in the first cycles to increase steam injectivity, using clay inhibitor during steam injection, reduced spacing in the better zones according to opportunity index map, nitrogen injection in wells with more than six stimulation cycles, high frequency cycles and changes in completion design and drilling scheme among others.
The set of lab test, numerical simulation and pilot test have resulted in the following: 1) Use of diesel slug before steam soaking clean the hole improving injectivity, allowing more steam volume injection. 2) Reduce steam quality in first stimulation cycles is useful to increase injectivity without significantly affecting steam oil ratio SOR. 3) Using an index map opportunity help to easily identify areas with the greatest potential for infill wells. 4) Injecting nitrogen with steam in wells with more than six stimulation cycles improve production results due to the pressurization of producing sands.
Key recommendations for implementing a CSS process in heavy oil reservoirs with low lateral and vertical continuity of the producing sands, swelling clays and low net to gross are presented in this article. The recommendations range from the first injection cycles to maturity of the process and the search for new production alternatives.
