Squeeze Cementing Operations in a Thermal Carbonate Steamflood Pilot in the 1st Eocene reservoir, Wafra field, PZ

摘要

A Large Scale Pilot (LSP) carbonate steamflood has been on injection in a lower targeted section of the 1st Eocene reservoir since June 2009 in the Wafra field located within the Partitioned Zone between the Kingdom of Saudi Arabia and the State of Kuwait. Initial primary oil recovery under cold production in the 1st Eocene interval has been less than 5% because of reservoir heterogeneity, low-gravity viscous oil, and lack of significant aquifer support. Several thermal project tests have been conducted since the late 1990`s to further improve the thermal recovery and understanding in Wafra carbonate reservoirs. Key technical uncertainties for steamflooding the entire 1st Eocene carbonate reservoir include performance response by layer, reservoir heterogeneity, location and impact of barriers to vertical steam migration, scale deposition and corrosion due to reservoir-steam interactions. To gain thermal response information from different layers in a timely manner and reduce full field development uncertainties around the upper 1st Eocene intervals, the LSP wells were recently recompleted up hole from the “C” to “B” layer. In all, 41 wells, including both steam injectors and producers, were isolated in the “C” layer using cement squeeze operations. Given the potential for highly permeable connections or conduits within the lower targeted 1st Eocene layer occurring naturally, from rock dissolution during steam injection, or from previous large acid jobs, additional considerations were included in the cement squeeze design to minimize excessive cement losses within the thermal zone. A cement squeeze process was developed to facilitate placement in a zone approaching 425oF while eliminating the possibility of the cement flash setting in the wellbore.