A New Self-Generating Foam Workover Fluid for Low Pressure Reservoirs

An offshore normal temperature low pressure low permeability low water cut reservoir needed to be worked over, the workover fluid can cause contamination and hence damage the reservoir. To deal with this problem, a cleaning low density self-generating foam workover fluid was developed based on an anti-water-block water-based workover fluid. A self-generating foaming agent ZSP and a wettability alteration agent FZJ etc. were used in formulating the new workover fluid. The workover fluid was evaluated for its general properties, and it was found that the workover fluid has good basic performance, its density can be adjusted between 0.5 g/cm³ and 0.9 g/cm³. The workover fluid is well compatible with the formation waters, natural cores after treatment with this workover fluid can have their wetting phase damage near the wellbore being removed, thereby improving the permeability of the oil phase in a disguised way. This cleaning low density foam workover fluid has been successfully used on three wells (well CH33 etc.), no downhole troubles occurred during operation. Two days after the workover operation, the three wells regained their normal production rates, indicating that this new workover fluid has satisfied the requirements of workover operations on offshore reservoirs with low pressure, low permeability and low water cut.