Remedial Cementing at High Temperatures (Case Study: Oilfields of Rosneft-Stavropolneftegaz)

Abstract

Oilfields of Rosneft-Stavropolneftegaz have basic distinctions, such as high reservoir temperatures, up to 1600C, and low depths, down to 3,500m, and old casing strings, where cement sheath is often absent, which require application of special technologies and compounds to be efficient for these conditions. In prior years all remedial cementing in Rosneft-Stavropolneftegaz, irrespectively of water trouble sources, were executed with cement slurry only. We have selected technologies and compiled application matrices for elimination of behind-the-casing flow (reverse cementing) and flow string leaks (flow string leak repair) in high temperature environment. In 2008-2009 the laboratory and pilot testing of technologies was performed, and new process was tested during water inflows elimination in the wells with high injection capacity. The risks are determined for planning and execution of remedial cementing, and the ways of finding solutions are offered. In general the total success of remedial cementing in 2009 in Rosneft-Stavropolneftegaz amounted to 70%, which twice exceeds this index for the year 2008. The average growth of flow rate for 11 wells amounted to 24 tones/day. It was possible owing to: Correct selection of candidate wells;Opportunity to select various plugging materials for specific task, i.e. using materials other than cement slurry;Selection of optimal flow charts for cementing process execution. The successfully tested technologies are potentially applicable within the Company in 130 wells in the fields of Rosneft- Stavropolneftegaz, Grozneftegaz and Dagneft.