Abstract
Water production management is a common concern for oil fields adopting water flooding. Water shut-off (WSO) technologies: both mechanical and chemical methods have been investigated to mitigate increasing water production. Mechanical methods like cementing or shut-off by completion types work within the wellbore. Crosslink polymer gels as chemical method penetrate by maximum 10 ft from the wellbore in most cases. Hence, the crossflow inside the reservoir is considered as a potential risk to deteriorate the WSO impact on production improvement. This paper focuses on an advanced nano-chemical WSO technology, which is emulsion system with supercharged nanoparticles (ESN®). The ESN® has unique features to overcome several difficulties which conventional chemical methods face frequently. Furthermore, the ESN® has a strong advantage that can selectively block water zone and penetrate in maximum 50 ft from the wellbore.
A pilot test of chemical water shut off using ESN® is planned in an offshore carbonate oil field (Field-A) in Abu Dhabi. The Field-A has been developed under continuous water injection more than 25 years and suffers from the resultant high water production. Well-1 was selected as a candidate well for pilot test because this well had been unable to flow due to high water cut.
As the first step of pilot preparation, the effectiveness of ESN® was evaluated using the numerical simulation model compared with conventional WSO methods. In the simulation model, local grid refinement (LGR) was applied at the grids including wellbore to replicate the penetration feature of each WSO. According to this model, the ESN® expected significant benefit on the well life extension by water cut reduction and increase in oil production compared with the conventional gels.
For further detailed evaluation by the numerical model, the uncertainty of reservoir properties affecting crossflow was evaluated through sensitivity study. In the upper part of reservoir in the Field-A, there is high permeability streak which acts as a main flow path for injected water from injectors to producers. For vertical and deviated oil producers, the perforation was conducted below the high permeability streak to avoid early water breakthrough. With consideration of these specifications, a sensitivity study of vertical permeability and high permeability streak was conducted. As a result of sensitivity study, improvement of well performance by ESN® was expected with consideration of parameter uncertainty range, though incremental oil production is dependent on parameter value.
As the next step of pilot preparation, this sensitivity study outcomes were also utilized to select such pilot well which can expect maximum incremental recovery by applying this technology.
