Steam assisted gravity drainage,which is a form of steam flooding that involves continuous injection of surfacegenerated steam into a horizontal injection well to reduce heavy oil viscositycause the oil to flow more easily towards a parallel drilled horizontal producerwell, is one of the most commonly used thermal stimulation technique forextracting heavy crude oil.

This technique can, however, beimproved by generating steam downhole rather than injecting surface generatedsteam. An in-situ steam generator will reduce heat loss and ensure the highquality of the steam being injected into the reservoir which makes for animproved oil recovery. Such a steam generator has been developed and a fieldstudy to evaluate the performance of the in-situ steam generator in improvingoil recovery over conventional SAGD has been carried out on an abandoned heavyshale oil field that is being rejuvenated.The results from this fieldstudy were used in a reservoir simulation model generated using Schlumberger’sEclipse Compositional Simulator for steam stimulation.

The model was historymatched to reflect the heavy shale oil field production under natural depletiondrive and steam stimulation. Several simulation runs were made to evaluate theperformance of the in-situ generator in a vertical well and for three steam-assistedgravity drainage (SAGD) well arrangements scenarios. An analysis was alsocarried out to compare the economic impact of the different simulationscenarios.The different sensitivity runs gaveoutcomes that indicated that the use of the patented in-situ steam generator inSAGD led to 360 barrels of incrementalproduction of oil per year overconventional SAGD. The simulation study show that in-situ steam generation andinjection is an effective and environment-friendly enhanced oil recoverytechnique that has the potential to replace conventional steam fieldapplications as it is a game changer.

With the in-situ steam generator,steam quality can be maintained 100% of the time throughout the life of theprocess, which leads to guaranteed faster in-situ oil heating.