IMPACT OF WETTABILITY ALTERATION ON RELATIVE PERMEABILITY IN SANDSTONE FOR GAS-CONDENSATE APPLICATION

Abstract

Gas condensate reservoirs can experience severe production losses once the bottom-hole flowing pressure drops below the dew point pressure, where condensate starts to form near the wellbore. During production under these conditions, liquid hydrocarbons start to accumulate forming a condensate bank near the wellbore which adheres to the surface of the rock and reduces or completely blocks the mobility of the gas. In addition to condensate, water accumulation could gather near the wellbore and negatively affect the relative permeability of gas in that region. A novel approach to overcome this condensate banking and water damage behavior is by altering the wettability of the rock from liquid-wet to gas-wet or intermediate-gas-wet using chemical treatment. The aim of this study is to experimentally examine the effectiveness of the chemical treatment to optimize the wettability and enhance gas relative permeability to increase the gas well productivity. The experiments were conducted on Grey Berea sandstone core samples with length ranging between 1 and 6 inches. The average porosity and permeability of the rock samples used in the treatment were 20% and 100 mD, respectively. Different weight percentages of the surfactant were mixed with different combinations of solvents and were injected into the core sample then aged at a temperature of 180o F. After that, the sample was tested for spontaneous decane imbibtion, contact angle, and gas relative permeability to figure out the optimum combination and optimum weight percentage that altered the rock wettability. We were able to correlate the enhancement in relative permeability characteristics with the observed variation in spontaneous imbibition plots. This is a new and important contribution to the literature in the field.