Effect of Brine Composition and Alkaline Fluid on the Permeability Damage of Limestone Reservoirs

Abstract

Secondary and tertiary recovery processes can lead to severe and permenant reductions in permeability because of interactions between injected fluids and the reservoir rock. Permeability damage was suspected as a factor contributing to post completion production declines observed during waterflooding of an unconsolidated limestone.This study summarizes the laboratory studies undertaken to evaluate and understand permeability damage in limestone reservoirs. The influence of brine composition, salinity of alkaline fluid and injection rate on permeability damage were evaluated in consolidated and unconsolidated cores. Effluent pH and Cl concentrations were measured at the outlet of the porous medium. Brines were prepared with sodium, calcium and potassium salts (NaCl, CaCl 2 , KCl). High pH values in produced water caused the permeability reduction and consequently the pores were plugged and formation damage was observed.In alkaline flooding experiments, permeability reduction was observed as a result of high pH alkaline fluids (NaOH, NaSiO 4 ). The permeability reduction was decreased using NaCl, CaCl 2 and KCl mixtures and high oil recoveries were obtained. Suspended solid particles were released and moved with injection water as a result of Cl concentration below the critical salt concentration caused the permeability reduction and the formation damage was occurred.

Measurement of Surfactant-Induced Interfacial Interactions at Reservoir Conditions

“…It is used to describe the salinity at which the lowest oil/water IFT is achieved during alkaline and/or surfactant flooding. Bagci et al (2001) reported that the IFT decreased and then increased with increasing salinity of NaOH and NaSiO 4 brines. The dilution of synthetic reservoir brine at ambient conditions also showed a decreasing and then increasing trend in IFT (Vijapurapu and Rao 2004), and the minimum IFT fell below Zisman-type critical spreading tension, resulting in the spreading of oil on the solid surface displacing brine.…”

Investigation of Slickwater Effect on Permeability of Gas Shale from Longmaxi Formation

“…The permeability reduction of shale samples and its effect on gas well production have attracted much attention in recent years. [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31]32 Song et al 33 evaluated the influence of polymer on the permeability reduction to gas and water by using shale fracture models with different fracture widths. The polymer resisted gas flow less than water flow in the microfracture.…”