Abstract
In Colombia, there are several heavy oil fields where cyclic steam stimulation have been successfully applied for over 25 years and although it is assumed that the reservoir temperature is high and the conditions are ideal for making the leap to continuous steam injection, some studies apparently show that this technique is not feasible for the reservoir; in fact, between 1992 and 1994, the implementation of a pilot did not reach the expected results.
From this fact raises the question: What are the key factors that ensure the success of a continuous steam injection pilot? To solve this question, a numerical simulation and analytical model based study was performed, showing that the performance of the technique lies in minimizing the energy losses and supplying only the necessary heat according to each stage of the process, these practices are known as heat management.
It was found that critical aspects of heat management are: reducing well spacing, selection of open thickness to injection, perforated intervals, completion design, injector well distance from generator and injection surface line conditions, as well as constant reservoir temperature monitoring, from which the energy requirements at each stage of the process is determined and avoid an excessive injection rate which goes against project economics.
For the field case it was found that: the well spacing should be reduced from 10 to 2.5 acres, the need of using selective sequential injection scheme (due the interbedded shale), the injection rate should be reduced to 46% a year after starting the process and also change the type of insulation on the surface lines. In this paper, the methodology and tools used for factor evaluation and process optimization are presented.
