Sand on demand: An approach to improving productivity in horizontal wells under heavy oil primary production

The cold production recovery process, as practised in Western Canada, is successful in vertical wells. Attempts at cold production in horizontal wells have been less successful.;The results indicate that slot size selection is critical for establishing "sand on demand". For proper slot size selection, it is essential to know the grain size distribution and the sorting (uniformity coefficient) of the sand. The findings from the sand production experiments indicate that the critical pressure gradients required for initiating sand production and for maintaining continuous sand production are much lower for well-sorted sands than for poorly-sorted sands. A correlation between slot size and controlled sand production was found for well-sorted sands that should allow for the specification of appropriate slot sizes.;The critical pressure gradient required for initiating sand production and maintaining continuous sand production decreases as the slot width or confining pressure increases. When flow rates resulted in persistent sand production, channels and/or elliptical dilated zones were created that greatly enhanced the effective permeability near the slot. This observation suggests that producing at low and steady sand cuts for a long period of time might bring two benefits; a way to transport the sand out of the well and the creation of high permeability channels or zones that can improve the production of the reservoir. Continuing sand production at sand cuts less than 1.5 % was achieved if the initial flow rates were low and were later increased in small increments.;To summarize, it was found that if the appropriate slot size was combined with the right draw down rates, controlled sand production could be achieved with attendant significant increases in permeability. This suggests that radically increased oil rates could be achieved if sand production rates can be maintained at low and consistent levels.;This dissertation presents the results of research examining the possibility of controlled sand production, "sand on demand" for horizontal wells. Specifically, the effects of slot size, confining stress, fluid velocity and sand grain sorting on sand production under less aggressive production conditions have been investigated.