A new temperature-resistant and salt-tolerant mixed surfactant system(referred to as the SS system)for enhancing oil recovery at the Tahe Oilfield(Xinjiang,China)was evaluated.Based on the analysis of the crude oil,the formation water and rock components in the Tahe Oilfield,the long-term thermal stability,salt tolerance and the ability to change the wettability,interfacial activity and oil washing efficiency of the mixed surfactant system were studied.The system contains the anionic surfactant SDB and another cationic surfactant SDY.When the total mass concentration of the SS solution is 0.15 wt%,m(SDB)/m(SDY)ratio is 1 to 1,and excellent efficiencies are achieved for oil washing for five kinds of Tahe Oilfield crude oils(more than 60%).In addition,after adding cationic surfactant,the adsorption capacity of the surfactant is further reduced,reaching 0.261 mg/g.The oil displacement experiments indicate that under a temperature of 150°C and a salinity of 24.6×104 mg/L,the SS system enhances the oil recovery by over 10%after water flooding.The SS anionic–cationic surfactant system is first presented in the open literature that can be successfully applied to obtain predictions of Tahe Oilfield carbonate reservoirs with a high temperature and high salinity.
Treatment of drilling wastewater from a sulfonated drilling mud system in the Shengli Oilfield, East China, was studied. The wastewater was deeply treated by a chemical coagulationcentrifugal separation-ozone catalytic oxidation combined process. The factors （i.e. pH value, chemical dosage, reaction time, etc.） influencing the treatment effect were investigated, and pH = 7 was determined as optimal for the coagulation; polymeric aluminum chloride （PAC） was selected as the optimal coagulant with a dosage of 18 g/L; cationic polyacrylamide （CPAM） with molecular weight of 8 million was selected as the optimal coagulant aid with an optimum dosage of 8 mg/L; and the optimal condition of catalytic ozonation was found to be a pH of 12 and an oxidation time of 40 min. The results showed that the combined treatment process was effective. The oil content and suspended solids content of the effluent reached the first class discharge standard according to China＇s standard GB 8978-1996 （Integrated Wastewater Discharge Standard） and the chemical oxygen demand （COD） decreased to 195 mg/L from 2.34×10^4 mg/L after coagulation process and ozone oxidation at pH = 12 for 40 min.
针对碳酸盐岩油藏具有高温、高矿化度的特点,研制出适合该类型油藏三次采油用耐温耐盐型表面活性剂BHJ-2。考察了其耐温耐盐性、界面活性、润湿性能、吸附性能、洗油效率、驱油效率等;结果表明,BHJ-2耐温达140℃,耐盐达2.33×10~5mg/L,吸附损失为0.574 mg/g油砂,可将油-地层水-岩石接触角由亲油性109.6°转变为亲水性61.4°。在140℃高温条件下老化30 d后,界面活性和洗油效率基本不变,油水界面张力为0.576 m N/m,静态洗油效率达到83.7%,可提高驱替效率36.7%,研究表明,BHJ-2可适用于高温高矿化度条件的亲油性碳酸盐岩油藏。
Many wellbores are blocked by asphaltene deposits,which lead to production problems in the oilfield development process.In this paper,methods such as elemental analysis,and solvent extraction are adopted for the study of wellbore blockages.The content of organic matter in blockages is higher than 96% and asphaltene is the main component of the organic matter with n-heptane asphaltene content of 38%.Based on the above analyses,an agent for asphaltene dispersion and removal（named as SDJ） was developed.The performance of the SDJ agent was evaluated,and it was found that the dissolution rate of asphaltene can reach 2.9 mg.mL-1.min-1 at 60 oC.SDJ agent（1wt%） was added to crude oil with a colloid instability index greater than 0.9 can effectively inhibit asphaltene deposition in the wellbore.By the viscosity method,the dissolution amount of SDJ agent was calculated,and it was found that when the viscosity of the system is around 2,000 mPa.s（the common viscosity of crude oil）,the amount of SDJ agent added to the blockage was at least 96 g per 100 g blockages.Therefore,SDJ agent has promising application for dispersion and removal of asphaltene deposition in high-asphaltene wells.
采用脂肪醇聚氧乙烯醚、Na OH、氯乙酸、醇和混合芳烃为原料,制备了一种高效复合降黏剂SDG-3。考察了其分散原油重组分能力、界面活性、乳化性能、降黏性能、耐温耐盐性和破乳性能。结果表明:SDG-3能分散超稠油中重组分,质量分数1%的SDG-3在不含水条件下使原油黏度从181 000 m Pa·s降低至81 989 m Pa·s,降低了54.7%;使地层水-超稠油的界面张力由22.00 m N/m降低至0.32 m N/m,对超稠油乳化效果优于常规水溶性降黏剂,形成的O/W乳状液平均粒径为2.5μm,对委内瑞拉、中海油、塔河超稠油降黏率均达到99.0%以上,优于常规油溶性降黏剂的降黏率(72.6%),耐盐度达2.2×105mg/L,耐高温达140℃,与油田破乳剂配伍性好。在塔河油田进行现场实验期间,日平均节约稀油率66.6%,平均提高稠油采收率14.4%。
Borehole blockage caused by asphaltene deposition is a problem in crude oil production in the Tahe Oilfield, Xinjiang, China. This study has investigated the influences of crude oil compositions, temperature and pressure on asphaltene deposition. The asphaltene deposition trend of crude oil was studied by saturates, aromatics, resins and asphaltenes （SARA） method, and the turbidity method was applied for the first time to determine the onset of asphaltene flocculation. The results showed that the asphaltene deposition trend of crude oil by the turbidity method was in accordance with that by the SARA method. The asphaltene solubility in crude oil decreased with decreasing temperature and the amount of asphaltene deposits of T739 crude oil （from well T739, Tahe Oilfield） had a maximum value at 60℃. From the PVT results, the bubble point pressure of TH 10403CX crude oil （from well TH10403CX, Tahe Oilfield） at different temperatures can be obtained and the depth at which the maximum asphaltene flocculation would occur in boreholes can be calculated. The crude oil PVT results showed that at 50,90 and 130 ℃, the bubble point pressure of TH 10403CX crude oil was 25.2, 26,4 and 27.0 MPa, respectively. The depth of injecting asphaltene deposition inhibitors for TH10403CX was determined to be 2,700 m.
CHEN ChaogangGUO JixiangAN NaREN BoLI YaguangJIANG Qingzhe
In order to improve the enhanced oil recovery of high-temperature and high-salt oilfields, a novel temperature-resistant and salt-tolerant surfactant （denoted as SDB-7） was synthesized and evaluated for the Tahe Oilfield （Xinjiang, China）, which is representative of high-temperature and high-salt oilfields. It has a central reservoir temperature of 140 ℃ and salinity of 22.6× 10^4 mg/L. The temperature-resistant and salt-tolerant performance, interfacial activity, oil displacement efficiency, aging properties, and adsorption properties of the synthesized surfactant were evaluated for Tahe Oilfield flooding. The results showed that the SDB-7 was temperature-resistant and salt-tolerant capacity of 140 ℃ and 22.6×10^4 rag/ L, respectively, oil displacement efficiency under static condition of 84%, and adsorption loss of 0.4 mg/ g （less than 1 mg/g-oil sand）. In the heat aging experiment （under the temperature of 140 ℃ for 60 days）, the oil-water interracial tension and oil displacement efficiency of SDB-7 were almost unchanged. The oil displacement experiments showed that, under the temperature of 140 ℃ and the salinity of 22.6× 10^4 mg/L, the surfactant SDB-7 can enhance oil recovery by 14.5% after water flooding,suggesting that SDB-7 has a promising application in high temperature and high salinity （HT/HS） reservoir.
