Separate-layer balanced waterflooding development technology for thick and complex carbonate reservoirs in the Middle East

Based on the waterflooding development in carbonate reservoirs in the Middle East, in order to solve the problem of the poor development effects caused by commingled injection and production, taking the thick bioclastic limestone reservoirs of Cretaceous in Iran-Iraq as an example, this paper proposes a balanced waterflooding development technology for thick and complex carbonate reservoirs. This technology includes the fine division of development units by concealed baffles and barriers, the combination of multi well type and multi well pattern, and the construction of balanced water injection and recovery system. Thick carbonate reservoirs in Iran-Iraq are characterized by extremely vertical heterogeneity, development of multi-genesis ultra-high permeability zones, and highly concealed baffles and barriers. Based on the technologies of identification, characterization, and sealing evaluation for concealed baffles and barriers, the balanced waterflooding development technology is proposed, and three types of balanced waterflooding development modes/techniques are formed, namely, conventional stratigraphic framework, fine stratigraphic framework, and deepened stratigraphic framework. Numerical simulations show that this technology is able to realize a fine and efficient waterflooding development to recover, in a balanced manner, the reserves of thick and complex carbonate reservoirs in Iran and Iraq. The proposed technology provides a reference for the development optimization of similar reservoirs.