in one aspect , methods described herein include applying a chemical formulation to sandstone bearing at least one of oil or gas . the chemical formulation comprises a polar organic solvent , water , a fluorochemical , and a catalyst . the formulation described herein contains at least one silane of the formula i : r f so 2 — n ( r )( c n h 2n ) chz ( c m h 2m ) n ( r ′) so 2 r f ( i ) each r f is independently — c p f 2p + 1 , where p is an integer from 2 to 5 ; r is selected from the group consisting of an aryl group and c 1 to c 6 alkyl group ; m and n are each independently integers from 1 to 20 ; z is selected from the group consisting of — h and a group having the formula —( c t h 2t )— x - q - si ( y ′) w ( y ) 3 − w , in which t is an integer from 0 to 4 ; — x — is selected from the group consisting of — o —, — s — and — nh —; - q - is selected from the group consisting of — c ( o ) nh —( ch 2 ) v — and —( ch 2 )—; v is an integer from 1 to 20 ; y is a hydrolyzable group ; y ′ is a non - hydrolyzable group ; and w is an integer from 0 to 2 ; and r ′ is selected from the group consisting of r and a group represented by the formula —( ch 2 ) v — si ( y ′) w ( y ) 3 − w , with the proviso that when z is — h , r ′ is a group represented by the formula —( ch 2 ) v — si ( y ′) w ( y ) 3 − w . the perfluoroalkanesulfonamido groups ( r f so 2 n —) may be the same or different . the perfluoroalkyl groups may each contain 2 to 5 carbon atoms and may be linear , branched or cyclic . in some embodiments , each r f has 4 carbon atoms ( i . e ., p is 4 ). in formula i , m and n may each independently be integers from 1 to 20 . in some embodiments , each m and n is independently an integer from 1 to 6 . throughout this application , integer ranges from x to y are understood to include the endpoints , x and y . in some embodiments of the fluorochemical , p is 4 , r is — ch 3 , m and n are both 1 , and z is — o —( ch 2 ) 3 si ( och 3 ) 3 , — o —( ch 2 ) 3 si ( och 2 ch 3 ) 3 or — oc ( o ) nh —( ch 2 ) 3 si ( och 2 ch 3 ) 3 . in some of these embodiments , r ′ is — ch 3 . the term “ alkyl ” as used herein , refers to straight chain , branched , and cyclic alkyl . for example , c 1 to c 6 alkyl includes methyl , ethyl , propyl , isopropyl , butyl , cyclobutyl , isobutyl , and tertiary butyl . in some embodiments , each r is independently — ch 3 or — ch 2 ch 3 . in some embodiments , r and r ′ are each independently — ch 3 or — ch 2 ch 3 . in some embodiments , r and r ′ are each — ch 3 . the term “ aryl ” as used herein includes aromatic rings or multi - ring systems optionally containing one or more ring heteroatoms ( e . g ., o , s , n ). examples of aryl groups include phenyl , naphthyl , and pyridinyl . aryl groups may be unsubstituted or may be substituted by one or up to five substituents such as alkyl , as above defined , alkoxy of 1 to 4 carbon atoms , halo ( e . g ., fluoro , chloro , bromo , iodo ), hydroxyl , amino , and nitro . when substituents are present , halo and alkyl substituents are preferred . in some embodiments of formula i , v is 1 to 10 , and in some embodiments , v is 3 . the term “ hydrolyzable group ” refers to a group which either is directly capable of undergoing condensation reactions under appropriate conditions or which is capable of hydrolyzing under appropriate conditions , to yield a compound that is capable of undergoing condensation reactions . appropriate conditions include acidic or basic aqueous conditions , optionally in the presence of another condensation catalyst ( in addition to the acid or base ). the hydrolyzable groups y may be the same or different and are generally capable of hydrolyzing under appropriate conditions . appropriate conditions include , for example , acidic or basic conditions in the presence of water . hydrolysis of the y groups may allow the fluorochemical to participate in condensation reactions . the hydrolyzable groups upon hydrolysis may yield groups capable of undergoing condensation reactions , such as silanol groups . examples of hydrolyzable groups include , for instance , halogens such as chlorine , bromine , iodine , or fluorine ; alkoxy groups of the general formula — or ″ ( wherein , r ″ represents a lower alkyl group , preferably containing 1 to 6 carbon atoms , which may optionally be substituted by one or more halogen atoms ); acyloxy groups of the general formula — o ( co )— r ″ ( wherein r ″ is as indicated for the alkoxy groups ); aryloxy groups of the general formula — or ′″ ( wherein r ′″ represents an aryl moiety that may contain , for instance , 6 to 12 carbon atoms , which may further optionally be substituted by one or more substituents independently selected from halogens and c 1 to c 4 alkyl groups , the c 1 to c 4 alkyl groups optionally being substituted by one or more halogen atoms ); or poly ( oxyalkylene ) groups , in which the oxyalkylene unit in the poly ( oxyalkylene ) group preferably has 2 or 3 carbon atoms , such as — och 2 ch 2 —, — och 2 ch 2 ch 2 — and — och ( ch 3 ) ch 2 —; the oxyalkylene units can be the same , as in poly ( oxyethylene ), or present as a mixture , as in straight or branched chain or randomly distributed oxyethylene and oxypropylene units . in each of these formulae , r ″ and r ′″ may include linear , branched , and / or cyclic structures . specific examples of hydrolyzable groups include chlorine , methoxy , ethoxy , and propoxy . the non - hydrolyzable groups y ′ may be the same or different and are generally not capable of hydrolyzing under conditions for condensation reactions , ( e . g ., acidic or basic aqueous conditions where hydrolyzable groups are hydrolyzed ). the non - hydrolyzable groups y ′ may be independently a hydrocarbon group , for example an alkyl group , for instance having 1 to 6 carbon atoms , or an aryl group . the hydrocarbon group may be fluorinated or non - fluorinated . the alkyl group may be branched or unbranched . in some embodiments , y ′ is selected from the group consisting of a c 1 to c 6 alkyl group and a c 6 to c 10 aryl group . [ c 4 f 9 so 2 n ( ch 3 ) ch 2 ] 2 choch 2 ch 2 ch 2 si ( och 3 ) 3 , [ c 4 f 9 so 2 n ( ch 3 ) ch 2 ] 2 choch 2 ch 2 ch 2 si ( och 2 ch 3 ) 3 , [ c 4 f 9 so 2 n ( ch 3 ) ch 2 ] 2 choc ( o ) nhch 2 ch 2 ch 2 si ( och 3 ) 3 , [ c 4 f 9 so 2 n ( ch 3 ) ch 2 ] 2 choc ( o ) nhch 2 ch 2 ch 2 si ( och 2 ch 3 ) 3 , and c 4 f 9 so 2 n ( ch 3 ) ch 2 ch 2 ch 2 n ( so 2 c 4 f 9 ) ch 2 ch 2 ch 2 si ( och 3 ) 3 . the fluorochemicals described herein may be prepared by known methods . for example , [ c 4 f 9 so 2 n ( ch 3 ) ch 2 ] 2 choh may be made by reacting two moles of c 4 f 9 so 2 nh ( ch 3 ) with either 1 , 3 - dichloro - 2 - propanol or epichlorohydrin in the presence of base . [ c 4 f 9 so 2 n ( ch 3 ) ch 2 ] 2 choch 2 ch 2 ch 2 si ( och 3 ) 3 can be made from [ c 4 f 9 son ( ch 3 ) ch 2 ] 2 choh by alkylation with clch 2 ch 2 ch 2 si ( och 3 ) 3 or by alkylation with allyl chloride , followed by hydrosilation with hsicl 3 and methanolysis . reaction of [ c 4 f 9 so 2 n ( ch 3 ) ch 2 ] 2 choh with ocnch 2 ch 2 ch 2 si ( och 3 ) 3 yields [ c 4 f 9 so 2 n ( ch 3 ) ch 2 ] 2 choconhch 2 ch 2 ch 2 si ( och 3 ) 3 . reaction of [ c 4 f 9 so 2 n ( ch 3 ) ch 2 ] 2 choh with ocnch 2 ch 2 ch 2 si ( och 2 ch 3 ) 3 yields [ c 4 f 9 so 2 n ( ch 3 ) ch 2 ] 2 choconhch 2 ch 2 ch 2 si ( och 2 ch 3 ) 3 . without wishing to be bound by theory , it is believed that tenacious side - chains of the fluorochemical are bound to the sandstone through a condensation reaction that provides a w — si — o — si bond , wherein w represents the fluorochemical side - chain , which is ultimately covalently bonded to a si in the sandstone . the chemical formulation further comprises water , preferably in an amount effective to hydrolyze the hydrolyzable groups . in some embodiments , the amount of water will be in a range from 0 . 1 to 30 % by weight of the total chemical formulation , in particular up to 15 % by weight , up to 10 % by weight , or up to 5 % by weight . in other embodiments , water is present in an amount of at least 1 % by weight , at least 5 % by weight , or at least 10 % by weight of the total chemical formulation . in addition to water , the chemical formulation may comprise a catalyst for hydrolyzing the si — y bond . the catalyst may comprise an acid compound or an alkaline compound . when the catalyst comprises an acid compound , it may be an organic or inorganic acid . organic acids include acetic acid , citric acid , formic acid , triflic acid , perfluorobutyric acid , and combinations thereof . in some embodiments , the organic acid is soluble in a polar organic solvent , also part of the chemical formulation . inorganic acids include sulfuric acid , hydrochloric acid , hydroboric acid , phosphoric acid , and combinations thereof . the acid compounds also include acid precursors that form an acid when contacted with water . combinations of any of these acids are also contemplated by the present chemical formulations . when the hydrolysis catalyst comprises an alkaline compound , examples include amines , alkali metal hydroxides , alkaline earth metal hydroxides , and combinations thereof . particular examples include sodium hydroxide , potassium hydroxide , sodium fluoride , potassium fluoride , and trimethylamine . the hydrolysis catalyst can generally be used in amounts in a range from 0 . 01 to 10 %, but may be used in amount of at least 0 . 05 %, at least 0 . 1 %, at least 1 %, or at least 5 %, and in amounts up to 8 %, up to 5 %, up to 1 %, or up to 0 . 1 %, by weight based on the total weight of the chemical formulation . the chemical formulations described herein may further comprise one or more organic solvents ( e . g ., polar organic solvents ). the organic solvent or mixture of organic solvents is capable of dissolving one or more silanes of formula i , and optionally a mixture of silanes of formula i . additionally , when an organic acid is used , the organic solvent may be chosen so that the organic acid is soluble in the organic solvent . examples of organic solvents include aliphatic alcohols , ( e . g ., methanol , ethanol , isopropanol , and butanol ); ketones ( e . g ., acetone and methyl ethyl ketone ); esters ( e . g ., ethyl acetate and methyl formate ); ethers ( e . g , diethyl ether , tetrahydrofuran ( thf ), and dipropyleneglycol monomethylether ( dpm )); nitriles ( e . g ., acetonitrile ); and formamides ( e . g ., dimethylformamide ). in some embodiments , the polar organic solvent comprises at least one of an alcohol , a ketone , a nitrile , or a formamide . in some embodiments , the polar organic solvent comprises at least one of methanol , ethanol , propanol , butanol , acetone , acetonitrile , or dimethylformamide . in some embodiments , the polar organic solvent comprises at least one of methanol , ethanol , propanol , or butanol . in some embodiments , the polar organic solvent is selected such that it has the formula y — h where y is the hydrolyzable group of the fluorochemical . the chemical formulation may be applied to sandstone bearing at least one of oil or gas . sandstone is known to comprise sio 2 . typically , sandstone contains in a range of 50 to 80 % sio 2 by weight . other components of sandstone may include : al 2 o 3 , fe 2 o 3 , mgo , cao , na 2 o , k 2 o , tio 2 , p 2 o 5 , and mno . the temperature of application may , for example , be in a range from 20 ° c . to 220 ° c . the temperature may vary from 40 ° c . and higher , 50 ° c . and higher , even 100 ° c . and higher to up to 180 ° c ., up to 150 ° c ., even up to 200 ° c . in another aspect , the method may further comprise modifying the wetting of the sandstone . wettability modification may help increase well deliverability of oil and / or gas in a sandstone formation . wettability can play a role in condensate accumulation around a wellbore . the effect of wettability on condensate accumulation in porous media can be expressed with the young - laplace equation : p c =( 2σ cos θ )/ r where the capillary pressure pc is proportional to interfacial tension ( σ ) and the cosine of the pseudocontact angle ( cos θ ), and is inversely proportional to pore size ( r ). thus , according to the young - laplace equation , decreasing the cosine of the pseudocontact angle for a given liquid will correspondingly decrease the capillary pressure and thus may increase well deliverability by decreasing condensate accumulation or water around a wellbore . in one aspect , modifying the wetting of the sandstone is selected from the group consisting of modifying the gas wetting , modifying the liquid wetting , and modifying a combination thereof . in some embodiments , the gas wetting is increased while the liquid wetting is decreased . reducing the rate of imbibition of materials such as water , oil , or both , may also improve well deliverability . in some embodiments , the method may further comprise reducing the rate of imbibition of oil in the sandstone . one convenient proxy for measuring the rate of imbibition of hydrocarbon is the measurement of the rate of imbibition of n - decane . accordingly , in yet another aspect , the method may further comprise reducing the rate of n - decane imbibition of the sandstone . in other embodiments , the method may further comprise reducing the rate of water imbibition of the sandstone . to measure the wettability effect on condensate accumulation as described above , the present method may comprise injecting a fluid into a sandstone core ( e . g ., a berea sandstone core ). this injection will produce a maximum pressure drop across the sandstone formation . the method also comprises applying a chemical treatment to the sandstone as described herein . when the wettability of the sandstone is reduced for the liquid injected into the sandstone formation , the method further comprises reducing the maximum pressure drop across the sandstone formation . the effectiveness of the treatment may be manifested as a lower measured pressure drop . the pressure drop , if any , can be 5 % or more with respect to the pressure across an untreated core , 10 % or more , 20 % or more , 30 % or more , even 50 % or more . the maximum pressure drop can be up to 95 %, up to 90 %, up to 75 %, up to 70 %, up to 50 %, or even up to 40 %. in yet another aspect , the method further comprises extracting from the sandstone formation materials selected from the group consisting of oil , gas , and combinations thereof . the method may further comprise covalently bonding the sandstone with a side - chain derived from the fluorochemical . the side - chain may be represented by the formula ii : in formula ii , each r f is independently — c p f 2p + 1 , where p is 2 to 5 . the perfluoroalkanesulfonamido groups ( r f so 2 n —) may be the same or different . the perfluoroalkyl may each contain 2 to 5 carbon atoms and may be linear , branched or cyclic . in some embodiments , each has 4 carbon atoms . also in formula ii , each r is independently selected from the group consisting of an aryl group and a c 1 to c 6 alkyl group and n is an integer from 1 to 20 . z ′ is a group of the formula —( c t h 2t )— x - q - si —( y ′) w —, in which t is an integer from 0 to 4 . in z ′, — x — is selected from the group consisting of — o —, — s — and — nh —, - q - is selected from the group consisting of — c ( o ) nh —( ch 2 ) v — and —( ch 2 ) v —, y ′ is a non - hydrolyzable group , and w is an integer from 0 to 2 . in q , v is an integer from 1 to 20 . in the side - chain defined by formula ii the si atom shares at least one covalent bond with the sandstone . this bond to the sandstone may allow the side - chain to tenaciously alter the wettability of the sandstone . in some embodiments , the bond to the sandstone provides a permanent wettability alteration . in another aspect , the present description provides a composition comprising a sandstone bearing at least one of oil or gas , and a side - chain covalently bonded to the sandstone . the side - chain is given by formula ii . this composition may allow for the expedient extraction of oil and / or gas from a sandstone or sandstone formation bearing at least one of these . advantages and embodiments of this invention are further illustrated by the following examples , but the particular materials and amounts thereof recited in these examples , as well as other conditions and details , should not be construed to unduly limit this invention . all parts and percentages are by weight unless otherwise indicated . for the following examples , single - core testing is carried out by the following procedures : liquid was injected into an air - saturated core . the liquid was either tap - water or brine at 24 ° c . or 140 ° c ., n - decane at 24 ° c . or tetradecane at 140 ° c . the air - saturated core was placed in a core - holder . liquid was injected at the inlet at a constant rate , while the outlet pressure was maintained constant ( either atmospheric pressure or 150 psi ( 1034 kpa )). liquid injection continued until steady state was achieved . the increase in pressure drop versus time ( or pore volume injection ) and the average liquid saturation at breakthrough and / or at steady state were measured . spontaneous liquid imbibition into the air - saturated cores was measured at temperatures of 24 ° c ., 60 ° c ., and 80 ° c . for water ( tap - water ), and at 24 ° c . for n - decane . the air - saturated core was placed inside the liquid while suspended under an electronic balance . the increase in weight and the average liquid saturation was plotted as a function of the time . if the core was strongly liquid wet , most of the imbibition occurred during the first 30 minutes , where a liquid saturation of more than 60 % was obtained , as is the case of untreated berea sandstone . the rate of imbibition decreased as the wettability is altered to intermediate gas - wetting . liquid saturations of less than 5 % were obtained in some cases after more than 20 hours of imbibition . two - core - parallel flow testing was performed with a tap - water or brine injection at 24 or 80 ° c ., and with decane at 24 ° c . two air - saturated cores were placed in two core - holders and liquid was injected with a constant rate at the common inlet , while the outlet was open to atmospheric pressure . both cores were under the same pressure drop . the pressure drop across the system as well as the liquid flow rates in both cores were measured and plotted against time . unless otherwise noted , all parts , percentages , ratios , etc . in the examples and the rest of the specification are by weight . preparation of [ c 4 f 9 so 2 n ( ch 3 ) ch 2 ] 2 choh a three - necked round bottom 1000 - ml flask , fitted with a stirrer , heating mantle , condenser , nitrogen inlet , dean - stark trap and thermometer was charged with c 4 f 9 so 2 n ( ch 3 ) h [ 313 grams ( g ), 1 . 00 mole ( mol )], generally made as described in u . s . pat . no . 6 , 664 , 354 ( savu et al . ), example 1 , part a , which patent is incorporated herein by reference , n , n - dimethylformamide ( 100 g ) and heptane ( 40 g ). the mixture was heated to reflux and dried by azeotropic distillation . the mixture was cooled to about 30 ° c . under nitrogen purge , and sodium methoxide ( 30 % in methanol , 180 g , 1 . 00 mol ) was added . the mixture was heated at 50 ° c . for one hour , stripping off methanol under vacuum from an aspirator . 1 , 3 - dichloro - 2 - propanol ( 65 g , 0 . 50 mol ) was added to the flask and the temperature was elevated to 80 ° c . and held overnight . the ensuing mixture was washed with deionized water ( 300 ml at 80 ° c .) three times and the remaining organic layer was separated and dried in an oven at 120 ° c . for 1 hour . vacuum distillation at 150 ° c . to 200 ° c . at 0 . 1 to 0 . 5 mmhg ( 13 to 67 pa ) resulted in 275 g of product . analysis of the resulting yellow brown solid was consistent with [ c 4 f 9 so 2 n ( ch 3 ) ch 2 ] 2 choh . preparation of [ c 4 f 9 so 2 n ( ch 3 ) ch 2 ] 2 choc ( o ) nh ( ch 2 ) 3 si ( och 2 ch 3 ) 3 a three - necked round bottom 500 ml flask fitted with a stirrer , heating mantle , condenser , nitrogen inlet , dean - stark trap and thermometer was charged with [ c 4 f 9 so 2 n ( ch 3 ) ch 2 ] 2 choh ( 204 . 6 g , 0 . 300 mol ), and methyl ethyl ketone ( 250 g ). the mixture was heated and approximately 50 g of material was removed using the dean - stark trap . the mixture was cooled to 30 ° c ., and ocn ( ch 2 ) 3 si ( och 2 ch 3 ) 3 ( 74 . 4 g , 0 . 301 mol ) and three drops of stannous octanoate were added . the mixture was heated at 75 ° c . under nitrogen for 16 hours . a clear , slightly yellow product ensued . analysis of the product was consistent with [ c 4 f 9 so 2 n ( ch 3 ) ch 2 ] 2 choc ( o ) nh ( ch 2 ) 3 si ( och 2 ch 3 ) 3 . a core of berea sandstone was treated with a chemical formulation containing 25 % by weight of a fluorochemical represented by the formula : [ c 4 f 9 so 2 n ( ch 3 ) ch 2 ] 2 choc ( o ) nh ( ch 2 ) 3 si ( och 2 ch 3 ) 3 , 5 % by weight water , 5 % by weight acetic acid , 65 % by weight ethanol . the chemical formulation was applied to the sandstone core at 140 ° c . the n - decane imbibition of an untreated berea sandstone core and that of the treated core was measured at 24 ° c . the results are shown in fig1 . a core of berea sandstone was treated with a chemical formulation containing 12 % by weight of a fluorochemical represented by the formula : [ c 4 f 9 so 2 n ( ch 3 ) ch 2 ] 2 choc ( o ) nh ( ch 2 ) 3 si ( och 2 ch 3 ) 3 , 5 % by weight water , 5 % by weight acetic acid , 73 % by weight ethanol . the chemical formulation was applied to the sandstone core at 140 ° c . the water imbibition of an untreated berea sandstone core and that of the treated core was measured at 24 ° c . the results are shown in fig2 . a treated berea sandstone core was prepared as described in example 1 . in both the treated and untreated cores , n - decane was injected into the cores at a constant rate of 2 cc / min at 24 ° c . the pressure drop ( capillary pressure ) across the core was measured . the result for the treated core and untreated core are presented in fig3 as a plot of pressure drop vs . pore volumes ( pv ). a treated reservoir sandstone core was prepared as described in example 1 . water was injected across the core both before treatment and after treatment . water was injected at a rate of 7 cc / min . the pressure drop ( capillary pressure ) across the core was measured for both the treated core and the untreated core . the results for the treated core and untreated core are presented in fig4 as a plot of pressure drop vs . pore volumes ( pv ). a treated berea sandstone core was prepared as described in example 1 . in each core , nitrogen and n - decane were simultaneously injected with a fixed pressure drop of 7 psi ( 48 . 3 kpa ) at 24 ° c . the relative permeability of decane and nitrogen were measured . fig5 shows a plot of krg ( gas relative permeability ) vs . kro ( oil relative permeability ). treatment did not decrease absolute permeability . a treated berea sandstone core was prepared as described in example 1 . the contact angle was visually estimated for both water / gas and oil / gas systems . these contact angles were compared to the contact angles for systems identical except that they include an untreated , rather than treated core . the results are shown in the table , below . various modifications and alterations of the invention may be made by those skilled in the art without departing from the scope and spirit of the invention , and it should be understood that this invention is not to be unduly limited to the illustrative examples .