Geochemical Characterization of Alteration of Saturate Fractions by Water Flooding
CHANG XiangChun;LIANG JiXue;CUI Jing;WANG Tao;Shandong Provincial Key Laboratory of Depositional Mineralization and Sedimentary Minerals,Shandong University of Science and Technology;Laboratory for Marine Mineral Resources,Qingdao National Laboratory for Marine Science and Technology;Luming Branch of Shengli Oilfield Company,Sinopec;
Based on the GC and GC-MS analysis,modification of saturate fractions in waterflooded oils from Qu9 reservoir was dynamically investigated. The results indicate that with the advance of waterflooding,saturates characterize obvious alterations during 9-months dynamic surveillance. Saturate concentration,C_(15)-RD/C_(15)-D,C_(15)8β( H)-D/C_(16)8β( H)-HD,TTs/17α-H and RS/17α-H ratios,are progressively increasing in values. Aromatic concentration ∑nC_(21)-/∑nC_(22)+and ∑nC_(14)-/∑nC_(15~+)reduce continually. Isoalkane related ratios of Pr/Ph,iC_(18)/Pr,iC_(18)/Ph,terpane related ratios of C_(21)/C_(22) TT,C_(24)/C_(23) TT,∑ C_(19-26)/∑ C_(28-29) TTs,C_(30)*/C_(29) Ts,C_(35) R/C_(34) R,Ol/C_(30) H,G/C_(31) R,C_(31)22 S/( 22 S+22 R),C_(30) M/C_(30) H,Ts/( Ts+Tm) and C_(29) Ts/( C_(29) Ts+C_(29) H),and sterane related ratios of C_(27)-DS/C_(27)-RS,C_(29)20 S/( 20 S + 20 R),C_(29)ββ/( ββ +αα) and C_(27)-rearranged sterane 20 S/( 20 S + 20 R),keep relatively unchanged. However,irregular variation of Pr/nC17 and Ph/nC_(18) shows an initial increase and subsequent decrease,or the opposite. Water washing leads to the decrease of aromatics and light/heavy alkane values,while the biodegradation results in the concentration of tricyclic terpanes and regular sterane compared to the hopanes. Although they have minor effect on the ratios respectively composed of two isoalkanes,terpanes and steranes with similar carbon numbers,they cause the increase of drimane parameters in combination. Mixed with the geo-chromatography and wettability transformation in water flooding,saturates compositions were further altered.