Development of a Successful Chemical Treatment for Gas Wells with Water and Condensate Blocking Damage

Abstract

Significant productivity loss occurs in gas condensate reservoirs due to condensate and water accumulation near the production well. Our experimental study shows that gas relative permeability decreases by more than 95% due to liquid blockage (high water saturation along with condensate accumulation) and the reduction is even more pronounced in presence of mobile water. Significant advances have been made during this study to develop and extend a chemical treatment to reduce the damage caused by liquid blocking in gas condensate reservoirs. The treatment is composed of a non-ionic polymeric fluorochemical in a glycol/alcohol or glycol ether/alcohol solvent mixture. The chemical treatment alters the wettability of water-wet sandstone to neutral wet and increases the gas relative permeability. It also reduces the liquid trapping in pores, which increases the relative permeability to oil or condensate and makes the removal of water blockage from treated zone easier. Selection of solvents to deliver the fluorochemical to the rock surface is critical to the success of the treatment, especially in the presence of high water saturation and high salinity brine. The treatment improved the gas and condensate relative permeabilities by a factor of about 2–4 on liquid blocked outcrop and reservoir sandstone rocks. The improvement in relative permeability after chemical treatment was quantified by performing coreflood experiments at reservoir conditions. The treatment also shows good durability against flowing gas, condensate, brine and solvent. We have developed a chemical treatment that shows great potential to increase production from liquid blocked gas wells with relatively small treatment volumes since only the near-well region needs to be treated. Introduction In gas condensate reservoirs a significant loss in the well productivity is observed when the bottomhole pressure in flowing wells falls below the dew point pressure of the fluid. The buildup of a condensate bank around the well impedes the flow of gas to the well and thus reduces its productivity. Water blocking can cause additional reduction in well deliverability of gas condensate wells. Water can be introduced into the formation during drilling, completion, or workover operations. Water can also flow into a gas-bearing zone from a high-pressure aquifer or a water-bearing zone. Liquids, including both condensate and water, are trapped in pores by capillary forces causing a significant reduction in gas relative permeability and this reduces well productivity. The loss in productivity can be even more pronounced in low permeability reservoirs as very high liquid saturations can be trapped in these reservoirs because of high capillary forces. The reduction in well productivity for gas condensate wells is generally a function of fluid phase behavior and the reduction in relative permeabilities in the near wellbore region. Both phenomena are complex and difficult to predict their effects under reservoir conditions, therefore a great deal of effort has been put into the study of both. Kokal et al. (2000), Pederson and Milter (2004) and Bang et al. (2006a) have studied the effect of water on the phase behavior of gas condensate fluids under reservoir conditions. Relative permeability studies have been done over a wide range of conditions with synthetic fluids (Henderson et al., 2000; Kumar, 2006; Ayyalasomayajula et al., 2003; Bang et al., 2006b) as well as with reservoir fluids (Nagarajan et al., 2004; Mott et al., 2000). Effect of various parameters such as capillary number, non-Darcy effects, fluid composition and rock type on gas relative permeability have been investigated.

Mitigation of the Effects of Condensate Banking: A Critical Review

“…Al-Anazi et al (2005a) mentioned that methanol treatments, as a solvent injection method, displaced the liquid bank (liquid hydrocarbon or water) by the multicontact-miscible technique. Bang et al (2010a) mentioned that adding methanol to a mixture of water and condensate reduced the dewpoint, and hence, retards the phenomenon of condensate dropout. Different solvents and alcohols were investigated; among these chemicals are methanol, isopropyl alcohol (IPA), and ethanol.…”

Wettability alteration of carbonate rocks from liquid-wetting to ultra gas-wetting using TiO 2 , SiO 2 and CNT nanofluids containing fluorochemicals, for enhanced gas recovery

“…The contact angle of water on the rocks treated with these three reference nanofluids was obtained ˃160 ° while 150 ° is the best result for water contact angle on the rock reported until now [5,6]. It is worth noting that the reference nanofluids also could interestingly create coatings with self-cleaning property on the rock samples which fluoro-polymers/surfactants [2][3][4][5][6][7][8][9][10][11][12][13][14] and fluorinated nanosilica solutions [35] were not able to do.…”

“…10c Compared with previous chemicals, one can see the water and n-decane contact angle on surface of the rocks samples treated with nanofluids a, b and c is obviously higher. Accordingly, wettability of the rock changed from strongly liquid-wetting to ultra gas-wetting (both superhydrophobic and superoleophobic) state showing contact angles of about 150° and higher for both water and n-decane (previous works [2][3][4][5][6][7][8][9][10][11][12][13][14]35] shows contact angle of ˂100° for ndecane).…”

“…As a result, they demonstrated that wettability alteration had substantial effect on improving liquid mobility and gas productivity of treated rocks. Several other experimental studies have been also performed on wettability alteration of different rock types (to gas-wetness) using surfactants or fluoro-chemical polymers/surfactants [8][9][10][11][12][13][14]. However, some of these chemicals declared not to be cost-effective or environmentally friendly.…”

Preparation of the modified limestone possessing higher permeability of gas well based on fluorinated silica: Effect of catalyst

“…This can reveal that the wettability alteration can be effective in high reservoir pressure and temperature as it has good effect at room temperature. Since the density and viscosity of gases change with pressure change, we may apply Darcy's law by pseudo pressure method to achieve more accurate calculations [23]. For single phase:…”