Riphean anisotropic cavernous-fissured carbonate reservoirs of oilfield at East Siberia area – one of the most problematic objects of oil and gas production described in this article. Here is discussed geological substantiation and first result of new technology involving in drilling of Riphean carbonate reservoirs with "Controlled pressure technology" by recovery wells with horizontal bottom at the oil-gas condensate field in Evenki Region. Comparison results of conventional drilling and "MPD" (Managed Pressure Drilling) technology.
Riphean reservoirs drilling process could be provided in two options.
The first one – horizontal conventional drilling. As far as the bit penetrates into the reservoir we are seeing SPP (Stand Pipe Pressure) decrease which means we have total lost circulation. There was only one means for resolving this problem – using LCM (Lost Circulation Material). Due to complicated geology and high parameter of gas factor in Riphean reservoirs (losses while circulation/ gains while static), LCM was insufficient solution.
The second is to perform drilling process using MPD (Managed Pressure Drilling) technology. We have the advantage using lower mud weight compared with conventional drilling. MPD technology corresponds with geological conditions of Riphean reservoirs and can be more profitable in future production from these wells.
MPD technology with closed loop circulation system showed that we can "manage" BHP (Bottom Hole Pressure) and it really works in temperature conditions of 45 Celsius below zero in Evenki Region (East Siberia). In practice we have seen, that it was possible to achieve more gentle management of BHP than with conventional drilling using LCM. Also with "MPD" system in this oilfield we were able to drill the first ERD (Extended Reach Drilling) well. However, even with such extended horizontal section (1000 meters), a significant reduction of losses was achieved without using LCM. Total results of MPD technology we will see after DST (Drill Stem Test) of drilled wells.
New technology showed that it was a right choice to use close loop system and MPD. Also for drilling new wells in this Riphean carbonate reservoirs of this oilfield area we will use this experience. Best way to reduce catastrophic losses in abnormally low pressure reservoir conditions is reduce and control the ECD and details how to achieve it we have considered in this article.
The results: Reduced interval construction time. From 31 days to 24 days.Reduced fluid loss during drilling. From 2000 m3 to 1200 m3.Improved the operational safety by closing the loop and real time early kick and loss detection.
